Plating apparatus, plating method and substrate processing apparatus
The present invention provides a plating apparatus which uses an insoluble anode and which can perform plating of a substrate stably while preventing oxygen gas, generated due to the use of the insoluble anode, from causing defects in the substrate. The plating apparatus includes: a substrate holder for holding a substrate; a cathode section including a seal ring for contacting a peripheral portion of a surface, to be plated, of the substrate held by the substrate holder to seal the peripheral portion water-tightly, and a cathode for contacting the substrate to supply current to the substrate; a vertically-movable electrode head provided above the cathode section, including an anode chamber housing an anode made of an insoluble material and having a bottom opening closed with a water-permeable porous member; a plating solution injection section for injecting a plating solution between the anode and the surface, to be plated, of the substrate held by the substrate holder; a power source for applying a plating voltage between the cathode and the anode; and a gas discharge line for discharging a gas from the anode chamber.
1. Field of the Invention
The present invention relates to a plating apparatus and a plating method, and more particularly to a plating apparatus and a plating method used for filling a fine circuit pattern formed in a substrate, such as a semiconductor substrate, with metal (interconnect material) such as copper so as to form interconnects.
The present invention also relates to a substrate processing apparatus for use as a substrate holding apparatus in the above plating apparatus, in an etching apparatus for etching away at least part of a thin film or the like formed on or adhering to the surface of a substrate, or in a polishing apparatus for mirror-polishing the surface of a substrate, or the like, and also to a substrate processing method.
2. Description of the Related Art
Recently, there has been employed a circuit forming method comprising forming fine recesses for interconnects, such as interconnect trenches (trenches) or fine holes (via holes) in a circuit form, in a semiconductor substrate, embedding the fine recesses with copper (interconnect material) by copper plating, and removing a copper layer (plated film) at portions other than the fine recesses by means of CMP or the like.
A plating apparatus having the following configuration has been known as this type of plating apparatus used for plating to form fine interconnects having high aspect ratios. A substrate is held in such a state that a surface (surface to be plated) of the substrate faces upward (in a face-up manner). A cathode is brought into contact with a peripheral portion of the substrate so that the surface of the substrate serves as a cathode. An anode is disposed above the substrate. While a space between the substrate and the anode is filled with a plating solution, a plating voltage is applied between the substrate (cathode) and the anode to plate a surface (surface to be plated) of a substrate (for example, see Japanese laid-open patent publication No. 2000-232078).
In a plating apparatus in which a substrate is held and plated in single wafer processing while a surface of the substrate faces upward, a distribution of a plating current can be made more uniform over an entire surface of the substrate to improve uniformity of a plated film over the surface of the substrate. Generally, the substrate is transferred and subjected to various processes in such a state that a surface of the substrate faces upward. Accordingly, it is not necessary to turn the substrate at the time of plating.
It is widely practiced with such a plating apparatus to use a soluble anode made of, for example, copper (phosphor-containing copper) containing 0.03 to 0.05% of phosphor so as to form a collagenous black film comprising a compound of phosphor and chlorine, called black film, on the surface of the anode, thereby suppressing the generation of monovalent copper ions (slime) from the anode.
In the case of using a soluble anode, however, when monovalent copper ions generated from the anode are deposited excessively on the surface of a black film formed on the anode, the black film detaches from the anode and the monovalent copper ions easily become copper. The detached black film itself can cause particles in the plating solution.
It may therefore be considered to use an insoluble anode. When an insoluble anode is used, however, oxygen gas is generated at the anode surface. The oxygen gas, when having reached a substrate, can cause defects in the substrate. Further, the liquid level of plating solution can change due to the pressure of the oxygen gas acting on the surface of the plating solution, making it impossible to carry out stable plating.
On the other hand, as shown in
In CMP processing of a plated film, however, a larger thickness of the plated film requires a larger polishing amount, leading to a prolonged processing time. An increase in the CMP rate to avoid the processing prolongation can cause dishing in broad trenches during the CMP processing.
In order to solve these problems, it is necessary to make a thickness of a plated film as thin as possible, and eliminate raised portions and recesses in the plated film even when narrow trenches and broad trenches are co-present in the surface of the substrate to thereby enhance the flatness. At present, however, when carrying out electroplating using, for example, an electrolytic copper sulfate bath, it is not possible to simultaneously decrease raised portions and recesses solely by the action of the plating solution or an additive.
In-plane uniformity of a thickness of a plated film is a measure for evaluating the plating performance of plating carried out on a semiconductor substrate. It is desirable that the thickness of a plated film formed on a surface of a substrate be uniform over the entire surface, i.e. from the center to the periphery, of a substrate.
According to a common standard., for example, the error range of the diameter of a substrate, such as a 300 mmφ semiconductor wafer, is about ±0.2 mm (300±0.2 mm). It is, therefore, necessary to provide a substrate holding apparatus for holding such a substrate with a mechanism that can absorb about the 0.4 mm error.
A plurality of seats 24, each having a step portion 24a on the inner side, is provided in the peripheral portion of the substrate holder 12 at a given pitch along the circumferential direction. The step portion 24a is to make contact with a peripheral portion of the lower surface of a substrate W so as to place thereon and support the substrate W, and is configured to absorb, for example, about 0.4 mm error when holding a 300 mmφ substrate W, as described above. A hooked chuck 26 at its center in the length direction is rotatably supported to the seat 24, and at the lower end is rotatably coupled to the upper end of a pressing rod 30 which is biased downwardly by a helical spring 28.
When the pressing rod 30 moves downwardly by the elastic force of the helical spring 28, the chuck 26 rotates such that it closes inwardly, so that a peripheral portion of the substrate W, placed and supported on the step portion 24a of the seat 24, is nipped between the step portion 24a and the front end of the chuck 26. The substrate W is thus held mechanically. When the pressing rod 30 moves upwardly against the elastic force of the helical spring 28, the chuck 26 rotates such that it opens outwardly, so that the nipping of the peripheral portion of the substrate W, placed on the step portion 24a of the seat 24, between the step portion 24a and the front end of the chuck 26 is released.
A plurality of support posts 32 is mounted on the peripheral portion of the rotating disk 16 at a given pitch along the circumferential direction. Cathodes 34, which comprise six parts, for example, and a ring-shaped seal ring 36 covering the upper surface of the cathodes 34 are mounted to the top ends of the support posts 32. The seal ring 36 has a downwardly-extending tapered inner peripheral portion which inclines inwardly and downwardly.
As shown in
An extensible bellows 38 is disposed between the substrate holder 12 and the rotating disk 16 to prevent the plating solution from intruding into the mechanism side where the spline shaft 10, etc. are present.
According to the substrate holding apparatus, when the substrate holder 12 is lowered to a position (substrate transfer position) as shown in
When the substrate holder 12 is somewhat raised to a position (cleaning position) as shown in
When the substrate holder 12 is further raised to a position (plating position) as shown in
The seal ring 36 is generally made of a rubber, and may be formed from, for example, a fluorocarbon rubber, a silicone rubber or a variety of elastomers. The seal ring 36 maybe mounted to a metal or resin holder for use.
As described above, according to the conventional substrate holding apparatus, a substrate is fixed by the mechanical chucks on the seats of the substrate holder which are designed in consideration of the maximum tolerance for the diameter of the substrate in order to absorb the dimensional error of the substrate diameter. Accordingly, the absorbed dimensional error of the diameter of a substrate W directly leads to an error in positioning of the substrate W with respect to the substrate holder. For example, when holding a substrate W having a diameter of 299.8 mm (diametrical error: −0.2 mm) with the substrate holding apparatus to process the substrate W, there occurs an error of about 0.4 mm at the maximum in the contact points between the cathodes 34 and the substrate W and in the contact portion between the seal ring 36 and the substrate W in terms of the distances from the edge of the substrate W. When a substrate is held in a substrate holding apparatus with such an inaccurate positioning and brought into contact with cathodes and a seal ring disposed, for example, above the substrate, variation (error) occurs in the contact position between the substrate and the cathodes and in the contact position between the substrate and the seal ring.
Such a variation (error) in the contact position between a substrate and cathodes/seal ring, when the substrate is a next-generation substrate having a thin-film seed layer with a narrow interconnect width or when the substrate is plated with a plating apparatus with a vary small distance between the substrate and the cathodes, makes the flow of electric current at the substrate surface non-uniform, thereby producing a significant difference in the thickness of the plated formed on the surface of the substrate between the central portion and the peripheral portion of the substrate.
On the other hand, with respect to the seal ring 36, as shown in
Though a substrate holding apparatus for a plating apparatus has been described hereinabove, the same problems are involved in substrate holding apparatuses for other electrolytic processing apparatuses, such as an electrolytic etching apparatus, or for a polishing apparatus, etc.
SUMMARY OF THE INVENTIONThe present invention has been made in view of the above situation in the related art. It is therefore a first object of the present invention to provide a plating apparatus which uses an insoluble anode and which can perform plating of a substrate stably while preventing oxygen gas, generated due to the use of the insoluble anode, from causing defects in the substrate.
It is a second object of the present invention to provide a plating apparatus and a plating method which can deposit a metal plated film, such as a copper plated film, selectively in interconnect trenches and fine holes formed in the surface of a substrate.
It is a third object of the present invention to provide a substrate processing apparatus and method which can hold a substrate in a substrate holder with accurate positioning of the substrate with respect to the substrate holder, without being influence by a diametrical error of the substrate, and can perform various processing processes such as electroplating.
In order to achieve the above object, the present invention provides a plating apparatus comprising: a substrate holder for holding a substrate; a cathode section including a seal ring for contacting a peripheral portion of a surface, to be plated, of the substrate held by the substrate holder to seal the peripheral portion water-tightly, and a cathode for contacting the substrate to supply current to the substrate; a vertically-movable electrode head provided above the cathode section, including an anode chamber housing an anode made of an insoluble material and having a bottom opening closed with a water-permeable porous member; a plating solution injection section for injecting a plating solution between the anode and the surface, to be plated, of the substrate held by the substrate holder; a power source for applying a plating voltage between the cathode and the anode; and a gas discharge line for discharging gas from the anode chamber.
The use of an anode made of an insoluble material can avoid the need for a change of anode and, in addition, obviate the generation of particles due to the peeling of a black film which would occur when using a soluble anode. Further, oxygen gas generated at the surface of the insoluble anode during plating can be introduced into the anode chamber, and the oxygen gas in the anode chamber can then be discharged so that the oxygen gas will not reach the substrate.
Preferably, the plating apparatus further comprises a control section for controlling an amount of the gas discharged through the gas discharge line.
By controlling the amount of the gas discharged through the gas discharge line with the control section so as to keep the pressure in the anode chamber constant, the liquid surface level of the plating solution in the anode chamber can be prevented from changing, enabling stable plating.
In a preferred embodiment of the present invention, the plating apparatus further comprises a pressure sensor for detecting the pressure in the anode chamber, and the control section controls the amount of the gas discharged through the gas discharge line based on an output of the pressure sensor.
By detecting the pressure in the anode chamber with the pressure sensor and performing a feedback control by, for example, operating a vacuum pump in proportion to the detected pressure, the pressure in the anode chamber can be kept constant.
In a preferred embodiment of the present invention, the plating apparatus further comprises an integrator for integrating an electric current flowing between the cathode and the anode, and the control section controls the amount of the gas discharged through the gas discharge line based on an output of the integrator.
The amount of oxygen gas generated at the anode surface during plating is proportional to the electric current flowing between the substrate (cathode) connected to the cathode and the anode. Accordingly, by integrating the electric current and performing a feedforward control by, for example, operating a vacuum pump in proportion to the integrated current value, the pressure in the anode chamber can be kept constant.
The present invention also provides a plating method comprising: providing in a plating cell an anode and a plating solution impregnated material disposed above the anode, and filing a plating solution into the plating cell until the plating solution reaches to above the plating solution impregnated material; bringing a downwardly-facing surface, to be plated, of a substrate into contact with the plating solution above the plating solution impregnated material; and applying a voltage between the anode and the surface to be plated of the substrate, thereby carrying out plating of the surface, to be plated.
By interposing the plating solution impregnated material, which serves as a high-resistance structure, between the substrate and the anode, it becomes possible to effect uniform plating over the entire surface, to be plated, of the substrate. Further, by holding the substrate with its surface, to be plated, facing downwardly (face down), and providing the plating solution impregnated material on the anode side, the diametrical size of the plating solution impregnated material can be easily made large relative to the diametrical size of the substrate, ensuring uniform plating. Further, the plating solution impregnated material can prevent a so-called black film, which can be formed on the anode during plating, from moving to the substrate side.
In a preferred embodiment of the present invention, a contact member is provided on the upper surface of the plating solution impregnated material, and plating is carried out while keeping the surface, to be plated, of the substrate in contact with the upper surface of the contact member.
By thus carrying out plating while keeping the surface, to be plated, of the substrate in contact with the upper surface of the contact member, the plating solution can be supplied preferentially into interconnect trenches and fine holes formed in the surface, to be plated, of the substrate, thus making it possible to preferentially (selectively) deposit a metal plated film, such as a copper plated film, on the surfaces of the interconnect trenches and fine holes. In particular, when plating is carried out by allowing a contact member, having such fine through-holes as to permit passage of the plating solution, in contact with an electrical conductor layer on the surface, to be plated, of the substrate, the plating solution flows into interconnect trenches and fine holes, but it little flows between the flat portion of the substrate and the contact member, resulting in preferential deposition of a metal on the surfaces of the interconnect trenches and the fine holes.
Preferably, the operation of applying a voltage between the surface, to be plated, of the substrate and the anode while keeping the surface, to be plated, in contact with the upper surface of the contact member and the operation of detaching the surface, to be plated, of the substrate from the upper surface of the contact member are repeated.
When the surface, to be plated, of the substrate is detached from the upper surface of the contact member, a fresh plating solution can flow into interconnect trenches and fine holes on the substrate more easily, thus facilitating selective metal plating onto the surfaces of the interconnect trenches and the fine holes.
Preferably, the substrate is allowed to rotate or make a scroll movement while the surface, to be plated, of the substrate is kept in contact with the plating solution.
By allowing the substrate to rotate or make a scroll movement, plating can be effected move uniformly over the entire surface, to be plated, of the substrate. The rotation or scroll movement of the substrate may be carried out either when the substrate is in contact with the contact member or when the substrate is apart from the contact member.
In a preferred embodiment of the present invention, the plating solution is supplied into the plating cell from below the plating solution impregnated material, and the plating solution is passed through the plating solution impregnated material and supplied to above the plating solution impregnated material.
Even when the plating solution is supplied from below to above the plating solution impregnated material, because of the plating solution impregnated material (and the upper contact member) that functions as a filter, particles, such as those coming from a black film, produced on the anode side can be prevented from moving to above the plating solution impregnated material (and the upper contact member).
It is also possible to supply the plating solution from above the plating solution impregnated material onto the upper surface of the plating solution impregnated material.
This makes it possible to easily control the composition (amounts of ions, amounts of additives and composition of additives) of the plating solution on the anode side and the composition of the plating solution above the plating solution impregnated material and for use in plating respectively at the optima (the two compositions may be identical).
The present invention also provides another plating apparatus comprising: an anode disposed in a plating cell; a plating solution impregnated material disposed above the anode; a plating solution supply section for supplying and filling a plating solution into the plating cell until the plating solution reaches to above the plating solution impregnated material; and a substrate holder for holding a substrate with its surface, to be plated, facing downwardly; wherein the surface, to be plated, of the substrate held by the substrate holder is brought into contact with the plating solution above the plating solution impregnated material to carry out plating of the surface, to be plated.
In a preferred embodiment of the present invention, the plating apparatus further comprises a contact member having a flat upper surface as a contact surface, provided above the plating solution impregnated material, and a holder drive mechanism for repeating the operation of bringing the surface, to be plated, of the substrate held by the substrate holder into contact with the contact surface of the contact member and the operation of detaching the surface, to be plated, from the contact surface of the contact member.
Preferably, the holder drive mechanism includes a mechanism for vertically moving the substrate holder, and a mechanism for allowing the substrate holder to rotate or make a scroll movement.
The plating solution supply section may include a plating solution supply pipe for supplying the plating solution into the plating cell from below the anode, and a plating solution supply pipe for supplying the plating solution to above the plating solution impregnated material.
Preferably, a filter is provided between the anode and the plating solution impregnated material.
The present invention also provides a substrate processing apparatus comprising: a vertically-movable substrate holder for supporting a substrate in a horizontal position and detachably holding the substrate; and a positioning guide disposed such that it surrounds the circumference of the substrate holder; wherein the positioning guide has a tapered surface which, when the substrate supported horizontally by the substrate holder is lowered or raised, contacts the peripheral end surface of the substrate to position the substrate with respect to the substrate holder.
According to this substrate processing apparatus, positioning of a substrate with respect to the substrate holder is performed by bringing the peripheral end surface as a reference into contact with the tapered surface of the positioning guide. In this positioning, the center position of the substrate does not change regardless of the diameter of the substrate, i.e., regardless of any dimensional error in the diameter. Thus, positioning of the substrate with respect to the substrate holder can be performed with accuracy without being influenced by the diametrical size of the substrate. In particular, when there is a dimensional error in the diametrical size of a substrate, though the height position of the substrate with respect to the positioning guide changes upon contact of the substrate in a horizontal position with the tapered surface of the positioning guide, the center position of the substrate with respect to the guide does not change. Accordingly, when the substrate is attracted and held by the substrate holder, for example, by means of a vacuum chuck, the center of the substrate can coincide with the center of the substrate holder.
In a preferred embodiment of the present invention, the positioning guide is formed in a cylindrical shape, and the tapered surface contacts the peripheral end surface of the substrate over substantially the entire circumference of the peripheral end surface to position the substrate with respect to the substrate holder.
According to this embodiment, substantially the entire circumference of the peripheral end surface of a substrate can be utilized as a reference. This enables a more accurate positioning of the substrate with respect to the substrate holder. The positioning guide in a cylindrical shape may have a cut-off portion e.g. for handling.
Preferably, an electrode for contacting a peripheral portion of the substrate held by the substrate holder to supply current to the substrate and a seal ring for pressure-contacting a peripheral portion of the substrate to seal the peripheral portion are provided above the substrate holder.
The substrate pressing apparatus, when employed in a plating apparatus, enables accurate positioning of a substrate held by the substrate with respect to the cathode and the seal ring. Thus, the distances of the contact positions of the substrate with the cathode and the seal ring from the peripheral end of the substrate can be made uniform, whereby the in-plane uniformity of the thickness of plated film can be enhanced for substrates of various diametrical sizes.
The seal ring is preferably composed of a composite material comprising a metal covered with a rubber.
The seal ring composed of such a material has an enhanced rigidity and improved shape stability. When a substrate is sealed with such a seal ring, the deformation of the seal ring can be small enough to securely prevent a leak of plating solution, etc. Further, because of the high dimensional accuracy of the seal ring, the distance of the sealing boundary from the peripheral end surface of the substrate can be made substantially equal constantly.
The substrate holder is preferably designed to hold the substrate by vacuum attraction.
The use of such a substrate holder can avoid the need to provide an outwardly-projecting holding member, such as a mechanical chuck, and can securely hold a substrate supported by the positioning guide.
Preferably, a temperature control section for controlling the temperature of the substrate holder is provided within the substrate holder.
By controlling not only the temperature of a chemical liquid, such as a plating solution, but also the temperature of the substrate holder and a substrate held by the holder at a constant temperature, the effect of a chemical liquid, which is supplied to the substrate upon processing of the substrate, can be maximized. The temperature control section may be comprised of, for example, an electric heater, a Peltier device or a thermocouple.
The temperature control section, for example, comprises a fluid flow passage for allowing a temperature-controlled heat medium to flow therein.
A heating medium or a cooling medium is used as a heat medium.
The present invention also provides a substrate processing method comprising: lowering or raising a substrate supported horizontally by a substrate holder and bringing a peripheral end surface of the substrate into contact with a tapered surface of a positioning guide, disposed such that it surrounds the substrate holder, to position the substrate with respect to the substrate holder; and holding the substrate by the substrate holder.
Preferably, the tapered surface of the positioning guide is brought into contact with the peripheral end surface of the substrate over substantially the entire circumference of the peripheral end surface to position the substrate with respect to the substrate holder.
The substrate held by the substrate holder may be raised so as to bring an electrode into contact with a peripheral portion of the substrate to supply current to the substrate, and bring a seal ring into pressure contact with a peripheral portion of the substrate to seal the peripheral portion.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will be described below with reference to the drawings. The following embodiments show examples in which copper as an interconnect material is embedded in fine recesses for interconnects formed in a surface of a substrate such as a semiconductor wafer so as to form interconnects composed of a copper layer. However, it is of course possible to use other kinds of interconnect materials instead of copper.
An example of forming copper interconnects in a semiconductor device will be described with reference to
Then, as shown in
Then, as shown in
The apparatus frame 812 is shielded so as not to allow a light to transmit therethrough, thereby enabling subsequent processes to be performed under a light-shielded condition in the apparatus frame 812. Specifically, the subsequent processes can be performed without irradiating the interconnects with a light such as an illuminating light. By thus preventing the interconnects from being irradiated with a light, it is possible to prevent the interconnects of copper from being corroded due to a potential difference of light that is caused by application of light to the interconnects composed of copper, for example.
An annular vacuum attraction groove 504b communicating with a vacuum passage 504a provided in the substrate holder 504 is formed in a peripheral portion of an upper surface of the substrate holder 504. Seal rings 508 and 510 are provided on inward and outward sides of the vacuum attraction groove 504b, respectively. With the above structure, the substrate W is placed on the upper surface of the substrate holder 504, and the vacuum attraction groove 504b is evacuated through the vacuum passage 504a to attract the peripheral portion of the substrate W, thereby holding the substrate W.
An elevating/lowering motor (not shown) comprising a servomotor and a ball screw (not shown) are used to move the swing arm 500 vertically, and a swinging motor (not shown) is used to rotate (swing) the swing arm 500. Alternatively, a pneumatic actuator may be used instead of the motor.
In this embodiment, the cathode section 506 has the cathodes 512 comprising six cathodes, and the annular seal member 514 disposed above the cathodes 512 so as to cover upper surfaces of the cathodes 512. The seal member 514 has an inner circumferential portion which is inclined inwardly and downwardly so that a thickness of the seal member 514 is gradually reduced. The seal member 514 has an inner circumferential edge portion extending downwardly. With this structure, when the substrate holder 504 is moved upwardly, the peripheral portion of the substrate W held by the substrate holder 504 is pressed against the cathodes 512, thus flowing current to the substrate W. At the same time, the inner circumferential edge portion of the seal member 514 is held in close contact with the upper surface of the peripheral portion of the substrate W to seal a contact portion in a watertight manner. Accordingly, a plating solution that has been supplied onto the upper surface (surface to be plated) of the substrate W is prevented from leaking from the end portion of the substrate W, and the cathodes 512 are thus prevented from being contaminated by the plating solution.
In this embodiment, the cathode section 506 is not movable vertically, but is rotatable together with the substrate holder 504. However, the cathode section 506 maybe designed to be movable vertically so that the seal member 514 is brought into close contact with the surface, to be plated, of the substrate W when the cathode section 506 is moved downwardly.
The electrode head 502 comprises a rotatable housing 520 and a vertically movable housing 522 which have a bottomed cylindrical shape with a downwardly open end and are disposed concentrically. The rotatable housing 520 is fixed to a lower surface of a rotating member 524 attached to a free end of the swing arm 500 so that the rotatable housing 520 is rotated together with the rotating member 524. An upper portion of the vertically movable housing 522, on the other hand, is positioned inside the rotatable housing 520, and the vertically movable housing 522 is rotated together with the rotatable housing 520 and is moved relative to the rotatable housing 520 in a vertical direction. The vertically movable housing 522 defines an anode chamber 530 by closing the lower open end of the vertically movable housing 522 with a porous member 528 so that a circular anode 526 is disposed in the anode chamber 530 and is dipped in a plating solution which is introduced to the anode chamber 530.
In this embodiment, the porous member 528 has a multi-layered structure comprising three-layer laminated porous materials. Specifically, the porous member 528 comprises a plating solution impregnated material 532 serving to hold a plating solution mainly, and a porous pad 534 attached to a lower surface of the plating solution impregnated material 532. This porous pad 534 comprises a lower pad 534a adapted to be brought into direct contact with the substrate W, and an upper pad 534b disposed between the lower pad 534a and the plating solution impregnated material 532. The plating solution impregnated material 532 and the upper pad 534b are positioned in the vertically movable housing 522, and the lower open end of the vertically movable housing 522 is closed by the lower pad 534a.
As described above, since the porous member 528 has a multi-layered structure, it is possible to use the porous pad 534 (the lower pad 534a) which contacts the substrate W, for example, and has flatness enough to flatten irregularities on the surface, to be plated, of the substrate W.
The lower pad 534a is required to have the contact surface adapted to contact the surface (surface to be plated) of the substrate W and having a certain degree of flatness, and to have fine through-holes therein for allowing the plating solution to pass therethrough. It is also necessary that at least the contact surface of the lower pad 534a is made of an insulator or a material having high insulating properties. The surface of the lower pad 534a is required to have a maximum roughness (RMS) of about several tens μm or less.
It is desirable that the fine through-holes of the lower pad 534a have a circular cross section in order to maintain flatness of the contact surface. An optimum diameter of each of the fine through-holes and the optimum number of the fine through-holes per unit area vary depending on the kind of a plated film and an interconnect pattern. However, it is desirable that both the diameter and the number are as small as possible in view of improving selectivity of a plated film which is growing in a recess. Specifically, the diameter of each of the fine through-holes may be not more than 30 μm, preferably in the range of 5 to 20 μm. The number of the fine through-holes having such diameter per unit area may be represented by a porosity of not more than 50%.
Further, it is desirable that the lower pad 534a has a certain degree of hardness. For example, the lower pad 534a may have a tensile strength ranging from 5 to 100 kg/cm2 and a bend elastic constant ranging from 200 to 10000 kg/cm2.
Furthermore, it is desirable that the lower pad 534a is made of hydrophilic material. For example, the following materials may be used after being subjected to hydrophilization or being introduced with a hydrophilic group by polymerization. Examples of such materials include porous polyethylene (PE), porous polypropylene (PP), porous polyamide, porous polycarbonate, and porous polyimide. The porous PE, the porous PP, the porous polyamide, and the like are produced by using fine powder of ultrahigh-molecular polyethylene, polypropylene, and polyamide, or the like as a material, squeezing the fine powder, and sintering and forming the squeezed fine powder. These materials are commercially available. For example, “Furudasu S (tradename) “manufactured by Mitsubishi Plastics, Inc, “Sunfine UF (trade name)”, “Sunfine AQ (trade name)”, both of which are manufactured by Asahi Kasei Corporation, and “Spacy (trade name)” manufactured by Spacy Chemical Corporation are available on the market. The porous polycarbonate may be produced by passing a high-energy heavy metal such as copper, which has been accelerated by an accelerator, through a polycarbonate film to form straight tracks, and then selectively etching the tracks.
The lower pad 534a may be produced by a flattening process in which the surface, to be brought into contact with the surface of the substrate W, of the lower pad 534a is compacted or machined to a flat finish for thereby enabling a high-preferential deposition in the fine recesses.
On the other hand, the plating solution impregnated material 532 is composed of porous ceramics such as alumina, SiC, mullite, zirconia, titania or cordierite, or a hard porous member such as a sintered compact of polypropylene or polyethylene, or a composite material comprising these materials. The plating solution impregnated material 532 maybe composed of a woven fabric or a non-woven fabric. In case of the alumina-based ceramics, for example, the ceramics with a pore diameter of 30 to 200 μm is used. In case of the SiC, SiC with a pore diameter of not more than 30 μm, a porosity of 20 to 95%, and a thickness of about 1 to 20 mm, preferably 5 to 20 mm, more preferably 8 to 15 mm, is used. The plating solution impregnated material 532, in this embodiment, is composed of porous ceramics of alumina having a porosity of 30%, and an average pore diameterof 100 μm. Theporous ceramic plate per se is an insulator, but is constructed so as to have a smaller conductivity than the plating solution by causing the plating solution to enter its inner part complicatedly and follow a considerably long path in the thickness direction.
In this manner, the plating solution impregnated material 532 is disposed in the anode chamber 530, and generates high resistance. Hence, the influence of the resistance of the copper layer 7 (see
The electrode head 502 has a pressing mechanism comprising an air bag 540 in this embodiment for pressing the lower pad 534a against the surface (surface to be plated) of the substrate W held by the substrate holder 504 under a desired pressure. Specifically, in this embodiment, a ring-shaped air bag (pressing mechanism) 540 is provided between the lower surface of the top wall of the rotatable housing 520 and the upper surface of the top wall of the vertically movable housing 522, and this air bag 540 is connected to a pressurized fluid source (not shown) through a fluid introduction pipe 542.
Thus, the swing arm 500 is fixed at a predetermined position (process position) so as not to move vertically, and then the inner part of the air bag 540 is pressurized under a pressure of P, whereby the lower pad 534a is uniformly pressed against the surface (surface to be plated) of the substrate W held by the substrate holder 504 under a desired pressure. Thereafter, the pressure P is restored to an atmospheric pressure, whereby pressing of the lower pad 534a against the substrate W is released.
A plating solution introduction pipe 544 is attached to the vertically movable housing 522 to introduce the plating solution into the vertically movable housing 522, and a pressurized fluid introduction pipe (not shown) is attached to the vertically movable housing 522 to introduce a pressurized fluid into the vertically movable housing 522. A number of pores 526a are formed within the anode 526. Thus, a plating solution Q is introduced from the plating solution introduction pipe 544 into the anode chamber 530, and the inner part of the anode chamber 530 is pressurized, whereby the plating solution Q reaches the upper surface of the plating solution impregnated material 532 through the pores 526a of the anode 526, and reaches the upper surface of the substrate W held by the substrate holder 504 through the inner part of the plating solution impregnated material 532 and inner part of the porous pad 534 (the upper pad 534b and the lower pad 534a).
The anode 526 is composed of an insoluble metal, such as platinum, titanium, etc., or of an insoluble electrode comprising a metal base plated or coated with a metal, such as platinum, for example, an electrode comprising a titanium base and an iridium coating. The use of the anode 526 composed of an insoluble material (insoluble electrode) can avoid the need for a change of the anode 526 and, in addition, obviate the generation of particles due to the peeling of a black film which would occur when using a soluble anode. However, oxygen gas is generated at the surface of the anode 526 during plating. The oxygen gas, when it reaches the surface of the substrate W, can cause defects in the substrate. In view of this, the plating apparatus of this embodiment has the following construction.
A gas discharge port 564 is mounted to the top wall of the vertically movable housing 522 that defines the anode chamber 530, and a gas discharge line 570, provided with a shut-off valve 566 and a vacuum pump 568, is connected to the gas discharge port 564. In carrying out plating, the shut-off valve 566 is opened and the vacuum pump 568 is driven to vacuum-evacuate the anode chamber 530, so that oxygen gas generated at the surface of the anode 526 passes through the pores 526a of the anode 526 and reaches the top of the anode chamber 530, and is discharged through the gas discharge line 570. In this manner, the oxygen gas is prevented from reaching the surface of the substrate W.
The plating apparatus of this embodiment is provided with a pressure sensor 572 for detecting the pressure in the anode chamber 530. A signal from the pressure sensor 572 is inputted into a control section 574. Based on an output signal from the control section 574, the operation of the vacuum pump 568 is feedback-controlled so that the pressure in the anode chamber 530 is kept constant. By thus controlling the amount of gas discharged through the gas discharge line 570 so as to keep the pressure in the anode chamber 530 constant, the liquid surface level of the plating solution in the anode chamber 530 can be prevented from changing, enabling stable plating.
As shown in
The amount of oxygen gas generated at the surface of the anode 526 during plating is proportional to the electric current flowing between the substrate (cathode) W connected to the cathodes 512 and the anode 526. Accordingly, by integrating the electric current and performing a feedforward control by operating the vacuum pump 568 in proportion to the integrated current value, the pressure in the anode chamber 530 can be kept constant.
The cathodes 512 and the anode 526 are electrically connected to the cathode and the anode of the plating power source 550, respectively.
The operation of the plating apparatus in carrying out plating will now be described. First, a substrate W is held, by vacuum attraction, on the upper surface of the substrate holder 504, and the substrate holder 504 is raised to bring a peripheral portion of the substrate W into contact with the cathodes 512 so as to place the substrate in an electricity-passable condition. The substrate holder 504 is further raised to bring a peripheral portion of the upper surface of the substrate W into pressure contact with the seal ring 514 to water-tightly seal the peripheral portion of the substrate W.
The electrode head 502, on the other hand, is moved from a position (idling position) at which idling is performed for replacement and removal of bubbles of the plating solution to a predetermined position (processing position) while the plating solution is kept held in the electrode head 502. In particular, the swing arm 500 is raised and then swung to move the electrode head 502 to a position right above the substrate holder 504. Thereafter, the electrode head 502 is lowered and is stopped when it has reached the predetermined position (processing position). The anode chamber 530 is internally pressurized so as to emit the plating solution, held in the electrode head 502, from the lower surface of the porous pad 534. Thereafter, pressurized air is introduced into the air bag 340 to press on the lower pad 534a downwardly.
Thereafter, the electrode head 502 and the substrate holder 504 are respectively rotated while the entire surface of the porous member 528 (lower pad 534a) is kept in contact with the surface to be plated of the substrate W at a uniform pressure.
Next, the cathodes 512 are connected to the cathode of the plating power source 550 and the anode 526 is connected to the anode of the plating power source 550, thereby effecting plating of the surface to be plated of the substrate W. During the plating, the shut-off valve 566 of the gas discharge line 570 is opened and the vacuum pump 568 is operated while it is controlled so that the pressure in the anode chamber 530 is kept constant, thereby discharging gas from the anode chamber 530. This prevents oxygen gas generated at the surface of the anode 526 during plating from reaching the substrate W and also prevents the liquid surface level of the plating solution in the anode chamber 530 from changing.
After carrying out plating for a predetermined time, the cathodes 512 and the anode 526 are disconnected to the plating power source 550, and the shut-off valve 566 is closed to return the internal pressure of the anode chamber 530 to atmospheric pressure. The internal pressure of the air bag 540 is also returned to atmospheric pressure to thereby release the pressure of the lower pad 534a on the substrate W. Thereafter, the electrode head 502 is raised.
The above operation is repeated a number of times, according to necessity, so as to form a copper layer 7 (see
The plating solution, which has flowed into the reservoir 604, is introduced into the plating solution regulating tank 608 by operating a pump 606. This plating solution regulating tank 608 is provided with a temperature controller 610, and a plating solution analyzing unit 612 for sampling the plating solution and analyzing the sample solution. Further, component replenishing pipes 614 for replenishing the plating solution with components which are found to be insufficient by an analysis performed by the plating solution analyzing unit 612 are connected to the plating solution regulating tank 608. When a pump 616 is operated, the plating solution in the plating solution regulating tank 608 flows in the plating solution supply pipe 618, passes through the filter 620, and is then returned to the plating solution tray 600.
In this manner, the composition and temperature of the plating solution is adjusted to be constant in the plating solution regulating tank 608, and the adjusted plating solution is supplied to the electrode head 502 of the plating apparatus 818. Then, by holding the adjusted plating solution by the electrode head 502, the plating solution having constant composition and temperature at all times can be supplied to the electrode head 502 of the plating apparatus 818.
The substrate holder 422 is coupled to an upper end of a spindle 426 which is rotated at a high speed by energization of a spindle rotating motor (not shown). Further, a cleaning cup 428 for preventing a treatment liquid from being scattered around is disposed around the substrate W held by the clamp mechanism 420, and the cleaning cup 428 is vertically moved by actuation of a cylinder (not shown).
Further, the cleaning and drying apparatus 820 comprises a chemical liquid nozzle 430 for supplying a treatment liquid to the surface of the substrate W held by the clamp mechanism 420, a plurality of pure water nozzles 432 for supplying pure water to the backside surface of the substrate W, and a pencil-type cleaning sponge 434 which is disposed above the substrate W held by the clamp mechanism 420 and is rotatable. The pencil-type cleaning sponge 434 is attached to a free end of a swing arm 436 which is swingable in a horizontal direction. Clean air introduction ports 438 for introducing clean air into the apparatus are provided at the upper part of the cleaning and drying apparatus 820.
With the cleaning and drying apparatus 820 having the above structure, the substrate W is held by the clamp mechanism 420 and is rotated by the clamp mechanism 420, and while the swing arm 436 is swung, a treatment liquid is supplied from the chemical liquid nozzle 430 to the cleaning sponge 434, and the surface of the substrate W is rubbed with the pencil-type cleaning sponge 434, thereby cleaning the surface of the substrate W. Further, pure water is supplied to the backside surface of the substrate W from the pure water nozzles 432, and the backside surface of the substrate W is simultaneously cleaned (rinsed) with the pure water ejected from the pure water nozzles 432. Thus cleaned substrate W is spin-dried by rotating the spindle 426 at a high speed.
The width of movement L of the edge nozzle 926 is set such that the edge nozzle 926 can be arbitrarily positioned in a direction toward the center from the outer peripheral end surface of the substrate, and a set value for L is inputted, according to the size, usage, or the like of the substrate W. Normally, an edge cut width C is set in the range of 2 mm to 5 mm. In the case where a rotational speed of the substrate is a certain value or higher at which the amount of liquid migration from the backside to the face is not problematic, the copper layer, and the like within the edge cut width C can be removed.
Next, the method of cleaning with this bevel etching and backside cleaning apparatus 822 will be described. First, the substrate W is horizontally rotated together with the substrate holder 922, with the substrate being held horizontally by the spin chucks 921 of the substrate holder 922. In this state, an acid solution is supplied from the center nozzle 924 to the central portion of the face of the substrate W. The acid solution may be a non-oxidizing acid, and hydrofluoric acid, hydrochloric acid, sulfuric acid, citric acid, oxalic acid, or the like is used. On the other hand, an oxidizing agent solution is supplied continuously or intermittently from the edge nozzle 926 to the peripheral edge portion of the substrate W. As the oxidizing agent solution, one of an aqueous solution of ozone, an aqueous solution of hydrogen peroxide, an aqueous solution of nitric acid, and an aqueous solution of sodium hypochlorite is used, or a combination of these is used.
In this manner, the copper layer, or the like formed on the upper surface and end surface in the region of the edge cut width C of the substrate W is rapidly oxidized with the oxidizing agent solution, and is simultaneously etched with the acid solution supplied from the center nozzle 924 and spread on the entire face of the substrate, whereby it is dissolved and removed. By mixing the acid solution and the oxidizing agent solution at the peripheral edge portion of the substrate, a steep etching profile can be obtained, in comparison with a mixture of them which is produced in advance being supplied. At this time, the copper etching rate is determined by their concentrations. If a natural oxide film of copper is formed in the circuit-formed portion on the face of the substrate, this natural oxide is immediately removed by the acid solution spreading on the entire face of the substrate according to rotation of the substrate, and does not grow anymore. After the supply of the acid solution from the center nozzle 924 is stopped, the supply of the oxidizing agent solution from the edge nozzle 926 is stopped. As a result, silicon exposed on the surface is oxidized, and deposition of copper can be suppressed.
On the other hand, an oxidizing agent solution and a silicon oxide film etching agent are supplied simultaneously or alternately from the back nozzle 928 to the central portion of the backside of the substrate. Therefore, copper or the like adhering in a metal form to the backside of the substrate W can be oxidized with the oxidizing agent solution, together with silicon of the substrate, and can be etched and removed with the silicon oxide film etching agent. This oxidizing agent solution is preferably the same as the oxidizing agent solution supplied to the face, because the types of chemicals are decreased in number. Hydrofluoric acid can be used as the silicon oxide film etching agent, and if hydrofluoric acid is used as the acid solution on the face of the substrate, the types of chemicals can be decreased in number. Thus, if the supply of the oxidizing agent is stopped first, a hydrophobic surface is obtained. If the etching agent solution is stopped first, a water-saturated surface (a hydrophilic surface) is obtained, and thus the backside surface can be adjusted to a condition that will satisfy the requirements of a subsequent process.
In this manner, the acid solution, i.e., etching solution is supplied to the substrate W to remove metal ions remaining on the surface of the substrate W. Then, pure water is supplied to replace the etching solution with pure water and remove the etching solution, and then the substrate is dried by spin-drying. In this way, removal of the copper layer in the edge cut width C at the peripheral edge portion on the face of the substrate, and removal of copper contaminants on the backside are performed simultaneously to thus allow this treatment to be completed, for example, within 80 seconds. The etching cut width of the edge can be set arbitrarily (from 2 to 5 mm), but the time required for etching does not depend on the cut width.
The gas introduction pipe 1010 is connected to a mixed gas introduction line 1022 which in turn is connected to a mixer 1020 where a N2 gas introduced through a N2 gas introduction line 1016 containing a filter 1014a, and a H2 gas introduced through a H2 gas introduction line 1018 containing a filter 1014b, are mixed to form a mixed gas which flows through the line 1022 into the gas introduction pipe 1010.
In operation, the substrate W, which has been carried in the chamber 1002 through the gate 1000, is held on the elevating pins 1008 and the elevating pins 1008 are raised up to a position at which the distance between the substrate W held on the lifting pins 1008 and the hot plate 1004 becomes about 0.1 to 1.0 mm, for example. In this state, the substrate W is then heated to e.g. 400° C. through the hot plate 1004 and, at the same time, the antioxidant gas is introduced from the gas introduction pipe 1010 and the gas is allowed to flow between the substrate W and the hot plate 1004 while the gas is discharged from the gas discharge pipe 1012, thereby annealing the substrate W while preventing its oxidation. The annealing treatment may be completed in about several tens of seconds to 60 seconds. The heating temperature of the substrate may be selected in the range of 100 to 600° C.
After the completion of the annealing, the elevating pins 1008 are lowered down to a position at which the distance between the substrate W held on the elevating pins 1008 and the cool plate 1006 becomes 0 to 0.5 mm, for example. In this state, by introducing cooling water into the cool plate 1006, the substrate W is cooled by the cool plate 1006 to a temperature of 100° C. or lower in about 10 to 60 seconds. The cooled substrate is transferred to the next step.
In this embodiment, a mixed gas of N2 gas with several percentages of H2 gas is used as the above antioxidant gas. However, N2 gas may be used singly.
As shown in
Linear guides 176, which extend vertically and guide vertical movement of the movable frame 154, are mounted to the fixed frame 152, so that by the actuation of a head-elevating cylinder (not shown), the movable frame 154 moves vertically by the guide of the linear guides 176.
Substrate insertion windows 156a for inserting the substrate W into the housing portion 156 are formed in the circumferential wall of the housing portion 156 of the processing head 160. Further, as shown in
On the other hand, a substrate fixing ring 186 is fixed to a peripheral portion of the lower surface of the substrate holder 158. Columnar pushers 190 each protrudes downwardly from the lower surface of the substrate fixing ring 186 by the elastic force of a spring 188 disposed within the substrate fixing ring 186 of the substrate holder 158. Further, a flexible cylindrical bellows-like plate 192 made of e.g. Teflon (registered trademark) is disposed between the upper surface of the substrate holder 158 and the upper wall of the housing portion 156 to hermetically seal therein.
When the substrate holder 158 is in a raised position, a substrate W is inserted from the substrate insertion window 156a into the housing portion 156. The substrate W is then guided by a tapered surface 182a provided in the inner circumferential surface of the guide frame 182, and positioned and placed at a predetermined position on the upper surface of the seal ring 184a. In this state, the substrate holder 158 is lowered so as to bring the pushers 190 of the substrate fixing ring 186 into contact with the upper surface of the substrate W. The substrate holder 158 is further lowered so as to press the substrate W downwardly by the elastic forces of the springs 188, thereby forcing the seal ring 184a to make pressure contact with a peripheral portion of the front surface (lower surface) of the substrate W to seal the peripheral portion while nipping the substrate W between the housing portion 56 and the substrate holder 58 to hold the substrate W.
When the head-rotating servomotor 162 is driven while the substrate W is thus held by the substrate holder 158, the output shaft 164 and the vertical shaft 168 inserted in the output shaft 164 rotate together with via the spline 166, whereby the substrate holder 158 rotates together with the housing portion 156.
At a position below the processing head 160, there is provided an upward-open treatment tank 100 comprising an outer tank 100a and an inner tank 100b which have a slightly larger inner diameter than the outer diameter of the processing head 160. A pair of leg portions 104, which is mounted to a lid 102, is rotatably supported on the outer circumferential portion of the treatment tank 100. Further, a crank 106 is integrally coupled to each leg portion 106, and the free end of the crank 106 is rotatably coupled to the rod 110 of a lid-moving cylinder 108. Thus, by the actuation of the lid-moving cylinder 108, the lid 102 moves between a treatment position at which the lid 102 covers the top opening of the treatment tank 100 and a retreat position beside the treatment tank 100. In the surface (upper surface) of the lid 102, there is provided a nozzle plate 112 having a large number of jet nozzles 112a for jetting outwardly (upwardly), electrolytic ionic water having reducing power, as described below, for example.
Further, as shown in
By lowering the processing head 60 holding the substrate so as to cover or close the top opening of the treatment tank 100 with the processing head 60 and then jetting a chemical liquid from the jet nozzles 124a of the nozzle plate 124 disposed in the inner tank 100b of the treatment tank 100 toward the substrate W, the chemical liquid can be jetted uniformly onto the entire lower surface (surface to be processed) of the substrate W and the chemical liquid can be discharged out from the discharge pipe 126 while preventing scattering of the chemical liquid to the outside. Further, by raising the processing head 60 and closing the top opening of the treatment tank 100 with the lid 102, and then jetting a rinsing liquid from the jet nozzles 112a of the nozzle plate 112 disposed in the upper surface of the lid 102 toward the substrate W held in the processing head 60, the rinsing treatment (cleaning treatment) is carried out to remove the chemical liquid from the surface of the substrate. Because the rinsing liquid passes through the clearance between the outer tank 100a and the inner tank 100b and is discharged through the drainpipe 127, the rinsing liquid is prevented from flowing into the inner tank 100b and from being mixed with the chemical liquid.
According to the pretreatment apparatus 828, the substrate W is inserted into the processing head 160 and held therein when the processing head 160 is in the raised position, as shown in
The lowermost position of the processing head 160 may be adjusted to adjust the distance between the substrate W held in the processing head 160 and the nozzle plate 124, whereby the region of the substrate W onto which the chemical liquid is jetted from the jet nozzles 124a of the nozzle plate 124 and the jetting pressure can be adjusted as desired. Here, when the pretreatment liquid such as a chemical liquid is circulated and reused, active components are reduced by progress of the treatment, and the pretreatment liquid (chemical liquid) is taken out due to attachment of the pretreatment liquid to the substrate. Therefore, it is desirable to provide a pretreatment liquid management unit (not shown) for analyzing composition of the pretreatment liquid and adding insufficient components. Specifically, a chemical liquid used for cleaning is mainly composed of acid or alkali. Therefore, for example, a pH of the chemical liquid is measured, a decreased content is replenished from the difference between a preset value and the measured pH, and a decreased amount is replenished using a liquid level meter provided in the chemical liquid storage tank. Further, with respect to a catalytic liquid, for example, in the case of acid palladium solution, the amount of acid is measured by its pH, and the amount of palladium is measured by a titration method or nephelometry, and a decreased amount can be replenished in the same manner as the above.
As shown in detail in
The suction head 234 and the substrate receiver 236 are operatively connected to each other by a splined structure such that when the substrate receiver drive cylinders 240 are actuated, the substrate receiver 236 vertically moves relative to the suction head 234, and when the substrate rotating motor 238 is energized, the output shaft 242 thereof is rotated to rotate the suction head 234 and the substrate receiver 236 in unison with each other.
As shown in detail in
The substrate receiver 236 is in the form of a downwardly open, hollow bottomed cylinder having substrate insertion windows 236a defined in a circumferential wall thereof for inserting therethrough the substrate W into the substrate receiver 236. The substrate receiver 236 also has an annular ledge 254 projecting inwardly from its lower end, and an annular protrusion 256 disposed on an upper surface of the annular ledge 254 and having a tapered inner circumferential surface 256a for guiding the substrate W.
As shown in
Further, at the top opening of the plating tank 200, there is provided an openable/closable plating tank cover 270 which closes the top opening of the plating tank 200 in a non-plating time, such as idling time, so as to prevent unnecessary evaporation of the plating solution from the plating tank 200.
As shown in
Particularly, in this embodiment, by controlling the plating solution supply pump 304, the flow rate of the plating solution which is circulated at a standby of plating or at a plating process can be set individually. Specifically, the amount of circulating plating solution at the standby of plating is in the range of 2 to 20 litter/minute, for example, and the amount of circulating plating solution at the plating process is in the range of 0 to 10 litter/minute, for example. With this arrangement, a large amount of circulating plating solution at the standby of plating can be ensured to keep a temperature of the plating bath in the cell constant, and the flow rate of the circulating plating solution is made smaller at the plating process to form a protective film (plated film) having a more uniform thickness.
The thermometer 266 provided in the vicinity of the bottom of the plating tank 200 measures a temperature of the plating solution introduced into the plating tank 200, and controls a heater 316 and a flow meter 318 described below.
Specifically, in this embodiment, there are provided a heating device 322 for heating the plating solution indirectly by a heat exchanger 320 which is provided in the plating solution in the plating solution storage tank 302 and uses water as a heating medium which has been heated by a separate heater 316 and has passed through the flow meter 318, and a stirring pump 324 for mixing the plating solution by circulating the plating solution in the plating solution storage tank 302. This is because in the plating, in some cases, the plating solution is used at a high temperature (about 80° C.), and the structure should cope with such cases. This method can prevent very delicate plating solution from being mixed with foreign matter or the like unlike an in-line heating method.
Further, on the outer surface of the peripheral wall of the cleaning tank 202 and at a position above the jet nozzles 280, there is provided a head cleaning nozzle 286 for jetting a cleaning liquid, such as pure water, inwardly and slightly downwardly onto at least a portion, which was in contact with the plating solution, of the head portion 232 of the substrate head 204.
In operating the cleaning tank 202, the substrate W held in the head portion 232 of the substrate head 204 is located at a predetermined position in the cleaning tank 202. A cleaning liquid (rinsing liquid), such as pure water, is jetted from the jet nozzles 280 to clean (rinse) the substrate W, and at the same time, a cleaning liquid, such as pure water, is jetted from the head cleaning nozzle 286 to clean at least a portion, which was in contact with the plating solution, of the head portion 232 of the substrate head 204, thereby preventing a deposit from accumulating on that portion which was immersed in the plating solution.
According to this electroless plating apparatus 830, when the substrate head 204 is in a raised position, the substrate W is held by vacuum attraction in the head portion 232 of the substrate head 204 as described above, while the plating solution in the plating tank 200 is allowed to circulate.
When plating is performed, the plating tank cover 270 of the plating tank 200 is opened, and the substrate head 204 is lowered, while the substrate head 204 is rotating, so that the substrate W held in the head portion 232 is immersed in the plating solution in the plating tank 200.
After immersing the substrate W in the plating solution for a predetermined time, the substrate head 204 is raised to lift the substrate W from the plating solution in the plating tank 200 and, as needed, pure water (stop liquid) is immediately jetted from the jet nozzle 268 toward the substrate W to cool the substrate W, as described above. The substrate head 204 is further raised to lift the substrate W to a position above the plating tank 200, and the rotation of the substrate head 204 is stopped.
Next, while the substrate W is held by vacuum attraction in the head portion 232 of the substrate head 204, the substrate head 204 is moved to a position right above the cleaning tank 202. While rotating the substrate head 204, the substrate head 204 is lowered to a predetermined position in the cleaning tank 202. A cleaning liquid (rinsing liquid), such as pure water, is jetted from the jet nozzles 280 to clean (rinse) the substrate W, and at the same time, a cleaning liquid, such as pure water, is jetted from the head cleaning nozzle 286 to clean at least a portion, which was in contact with the plating solution, of the head portion 232 of the substrate head 204.
After completion of cleaning of the substrate W, the rotation of the substrate head 204 is stopped, and the substrate head 204 is raised to lift the substrate W to a position above the cleaning tank 202. Further, the substrate head 204 is moved to the transfer position between the transfer robot 816 and the substrate head 204, and the substrate W is transferred to the transfer robot 816, and is transported to a next process by the transfer robot 816.
As shown in
The plating solution management unit 330 has a dissolved oxygen densitometer 332 for measuring dissolved oxygen in the plating solution held by the electroless plating apparatus 830 by an electrochemical method, for example. According to the plating solution management unit 330, dissolved oxygen concentration in the plating solution can be controlled at a constant value on the basis of indication of the dissolved oxygen densitometer 332 by deaeration, nitrogen blowing, or other methods. In this manner, the dissolved oxygen concentration in the plating solution can be controlled at a constant value, and the plating reaction can be achieved in a good reproducibility.
When the plating solution is used repeatedly, certain components are accumulated by being carried in from the outside or decomposition of the plating solution, resulting in lowering of reproducibility of plating and deteriorating of film quality. By adding a mechanism for removing such specific components selectively, the life of the plating solution can be prolonged and the reproducibility can be improved.
The polishing power of the polishing surface of the polishing cloth 840 decreases with a continuation of a polishing operation of the CMP apparatus 832. In order to restore the polishing power, a dresser 848 is provided to conduct dressing of the polishing cloth 840, for example, at the time of replacing the substrate W. In the dressing, while rotating the dresser 848 and the polishing table 842 respectively, the dressing surface (dressing member) of the dresser 848 is pressed against the polishing cloth 840 of the polishing table 842, thereby removing the polishing liquid and chips adhering to the polishing surface and, at the same time, flattening and dressing the polishing surface, whereby the polishing surface is regenerated. The polishing table 842 may be provided with a monitor for monitoring the surface state of the substrate to detect in situ an end point of polishing, or with a monitor for inspecting in situ the finish state of the substrate.
During reversing of the substrate W, the mounting base 355 waits at a position, indicated by solid lines, below the substrate W. Before or after reversing, the mounting base 355 is raised to a position indicated by dotted lines to bring the film thickness sensors S close to the substrate W gripped by the reversing arms 353, 353, thereby measuring a film thickness.
According to this embodiment, since there is no restriction such as the arms of the transfer robot, the film thickness sensors S can be installed at arbitrary positions on the mounting base 355. Further, the mounting base 355 is adapted to be movable upward and downward, so that the distance between the substrate W and the sensors S can be adjusted at the time of measurement. It is also possible to mount plural types of sensors suitable for the purpose of detection, and change the distance between the substrate W and the sensors each time measurements are made by the respective sensors. However, the mounting base 355 moves upward and downward, thus requiring certain measuring time.
An eddy current sensor, for example, may be used as the film thickness sensor S. The eddy current sensor measures a film thickness by generating an eddy current and detecting the frequency or loss of the current that has returned through the substrate W, and is used in a non-contact manner. An optical sensor may also be suitable for the film thickness sensor S. The optical sensor irradiates a light onto a sample, and measures a film thickness directly based on information of the reflected light. The optical sensor can measure a film thickness not only for a metal film but also for an insulating film such as an oxide film. Places for setting the film thickness sensor S are not limited to those shown in the drawings, but the sensor may be set at any desired places for measurement in any desired numbers.
Next, a sequence of processing for forming copper interconnects on the substrate having the seed layer 6 shown in
First, the substrate W having the seed layer 6 formed in its surface is taken out one by one from a transfer box 810, and is carried in the loading/unloading station 814. The substrate W, which has carried in the loading/unloading station 814, is transferred to the thickness measuring instrument 824 by the transfer robot 816, and an initial film thickness (film thickness of the seed layer 6) is measured by the thickness measuring instrument 824. Thereafter, if necessary, the substrate is inverted and transferred to the plating apparatus 818. In the plating apparatus 818, as shown in
Then, the substrate W having the copper layer 7 formed thereon is transferred to the cleaning and drying apparatus 820 by the transfer robot 816, and the substrate W is cleaned by pure water and spin-dried. Alternatively, in a case where a spin-drying function is provided in the plating apparatus 818, the substrate W is spin-dried (removal of liquid) in the plating apparatus 818, and then the dried substrate is transferred to the bevel etching and backside cleaning apparatus 822.
In the bevel etching and backside cleaning apparatus 822, unnecessary copper attached to the bevel (edge) of the substrate W is removed by etching, and at the same time, the backside surface of the substrate is cleaned by pure water or the like. Thereafter, as described above, the substrate W is transferred to the cleaning and drying apparatus 820 by the transfer robot 816, and the substrate W is cleaned by pure water and spin-dried. Alternatively, in a case where a spin-drying function is provided in the bevel etching and backside cleaning apparatus 822, the substrate W is spin-dried in the bevel etching and backside cleaning apparatus 822, and then the dried substrate is transferred to the heat treatment apparatus 826 by the transfer robot 816.
In the heat treatment apparatus 826, heat treatment (annealing) of the substrate W is carried out. Then, the substrate W after the heat treatment is transferred to the film thickness measuring instrument 824 by the transfer robot 816, and the film thickness of copper is measured by the film thickness measuring instrument 824. The film thickness of the copper layer 7 (see
As shown in
In the pretreatment apparatus 828, a pretreatment before plating comprising at least one of attachment of Pd catalyst to the surface of the substrate and removal of oxide film attached to the exposed surface of the substrate, for example, is carried out. Then, the substrate after this pretreatment, as described above, is transferred to the cleaning and drying apparatus 820 by the transfer robot 816, and the substrate W is cleaned by pure water and spin-dried. Alternatively, in a case where a spin-drying function is provided in the pretreatment apparatus 828, the substrate W is spin-dried (removal of liquid) in the pretreatment apparatus 828, and then the dried substrate is transferred to the electroless plating apparatus 830 by the transfer robot 816.
In the electroless plating apparatus 830, as shown in
After the electroless plating, the substrate W is transferred to the cleaning and drying apparatus 820 by the transfer robot 816, and the surface of the substrate is cleaned by a chemical liquid, and cleaned (rinsed) with pure water, and then spin-dried by rotating the substrate at a high speed. After the spin-drying, the substrate W is returned into the transfer box 810 via the loading/unloading station 814 by the transfer robot 816.
In this embodiment, copper is used as an interconnect material. However, besides copper, a copper alloy, silver, a silver alloy, and the like may be used.
As described in detail hereinabove, according to the present invention, the use of an anode made of an insoluble material can avoid the need for a change of anode and, in addition, obviate the generation of particles due to the peeling of a black film which would occur when using a soluble anode. Further, oxygen gas generated at the surface of the insoluble anode during plating can be introduced into the anode changer, and the oxygen gas in the anode chamber can then be discharged so that the oxygen gas will not reach the substrate. This can prevent the oxygen gas from causing defects in the substrate.
The plating cell 710 is formed in the shape of an upwardly-open container, and an overflow tank 711 is provided around the upper portion of the outer circumferential surface of the plating cell 710. The lower chamber, partitioned by the filter 740, in the plating cell 710 constitutes an anode chamber 713 in which the anode 720 is disposed.
The anode 720 may be composed of the same metal as the metal to be plated, or an insoluble metal such as platinum, titanium, etc., or an insoluble electrode comprising a metal base plated with e.g. platinum. As with the preceding embodiment, because of no necessity for a change, etc., an insoluble metal or an insoluble electrode is preferred. The anode 720 is housed in an anode cup 721, and is to be connected to the anode of a plating power source 797. Though the anode 720 of this embodiment is tabular, it is also possible to house a plurality of ball-shaped anodes in the anode cup 721.
The plating solution impregnated material 730 may be composed of the same material as the plating solution impregnated material 532 (see e.g.
A membrane filter having numerous fine holes (holes with a diameter of e.g. about 0.1 μm), an ion-exchange resin membrane, a filter composed of PP or PE fibers compressed into the form of a sheet, etc. may be used as the filter 740. The filter 740 has a function of passing the plating solution Q therethrough, but blocking passage of particles, such as those coming from a so-called black film.
The plating solution supply section includes a plating solution supply pipe 751 that passes through the center of the bottom of the plating cell 710 and penetrates through the center of the anode 720, and is inserted centrally into the plating solution impregnated material 730, a plurality of plating solution supply pipes 753 for supplying the plating solution Q from the bottom of the plating cell 710 into the plating cell 710 on the side below the anode 720, and a plating solution supply pipe 755 for supplying the plating solution Q from above the contact member 760 provided in an upper position in the plating cell 710. Thus, the plating solution supply pipe 751 supplies the plating solution Q directly into the plating solution impregnated material 730, the plating solution supply pipes 753 supply the plating solution Q into the anode chamber 713 of the plating cell 710, and the plating solution supply pipe 755 supplies the plating solution Q directly onto the upper surface of the contact member 760. The plating solution Q, supplied into the plating cell 710 via the plating solution supply pipes 751, 753, 755, is discharged out of the plating cell 710 via a plurality of discharge pipes 757, provided in the sidewall of the plating cell 710, and the overflow tank 711 and is circulated.
With respect to the contact member 760, as with the lower pad 534a (see e.g.
The material of the contact member 760 that meets the above requirements may be the same as the above-described lower pad 534a.
The substrate holder 770 holds the substrate W with its front surface (surface to be plated) facing downwardly. According to this embodiment, the substrate holder 770 attracts and holds the substrate W by vacuum-attracting or electrostatically attracting the back surface of the substrate W. In a peripheral portion of the lower surface of the substrate holder 770 is provided a cathode 771 for feeding electricity from the peripheral bevel portion of the substrate W to the electrical conductor layer of the surface to be plated of the substrate W. The cathode 771 is to be connected to the cathode of the plating power source 796.
The holder drive mechanism 790 includes a rotational drive shaft 791 connected to the center of the upper surface of the substrate holder 70, a scroll drive shaft 793 for causing the rotational drive shaft 791 to make a scroll movement, and a drive section 795 for rotationally driving the shafts 791, 793 and driving the substrate holder 770 to move vertically. With the provision of the holder drive mechanism 790, it is possible to rotate or scroll-rotate the substrate W, held by the substrate holder 770, by the drive section 795, and lower the substrate holder 770 so as to bring the surface to be plated of the substrate W into contact with the plating solution Q over the upper surface of the contact member 760 or bring the surface to be plated into pressure contact with the upper surface of the contact member 760.
The plating power source 796 is to apply a plating voltage between the anode 720 and the electrical conductor layer of the surface to be plated of the substrate W, as described above, and generally applies a positive potential to the anode 720 and a negative potential to the substrate W. Depending upon the manner of using the plating apparatus 700, the plating power source 796 may be designed to be able to switch between positive potential application and negative potential application.
A method for metal-plating the surface to be plated of the substrate W by the plating apparatus 700 having the above-described construction will now be described.
First, the plating solution Q is supplied from the plating solution supply pipes 753 into the plating cell 710, the plating solution Q is supplied from the plating solution supply pipe 751 into the plating solution impregnated material 730 and the contact member 760, and the plating solution Q is also supplied from the plating solution supply pipe 755 onto the upper surface of the contact member 760. At the same time, the plating solution Q is discharged out of the plating cell 710 via the discharge pipes 757 and the overflow tank 711. The discharged plating solution Q, after removing impurities from it by, for example, passing it through a filter, is returned into the plating cell 710 via the plating solution supply pipes 751, 753, 755. In this manner, the plating solution Q is circulated.
Since the interior of the plating cell 710 is partitioned by the plating solution impregnated material 730, the plating solution Q supplied from the plating solution supply pipes 753 mainly fills the anode chamber 713, the plating solution Q supplied from the plating solution supply pipe 751 mainly fills the interior of the plating solution impregnated material 730 and the interior of the contact member 760, and the plating solution Q supplied from the plating solution supply pipe 755 mainly fills the space above the contact member 760. The plating solution Q in each of the above regions can pass through the filter 740, the plating solution impregnated material 730 and the contact member 760 into the other region. However, the amount of such transferring plating solution is small. Accordingly, it is easily possible to vary the compositions of the respective plating solutions Q to be supplied from the plating solution supply pipes 751, 753, 755 so as to meet the intended uses of the respective regions.
In particular, with respect to the plating solution Q to be supplied from the plating solution supply pipe 755, a plating solution may be used which contains a suitable additive for embedding a plating metal into the interconnect trenches and fine holes of the substrate W. With respect to the plating solution Q to be supplied from the plating solution supply pipes 551, 553, a plating solution not containing the above additive or a plating solution having a different composition from that of the above plating solution may be used. Instead of the supply of the plating solution Q onto the upper surface of the contact member 760 via the plating solution supply pipe 755, it is also possible to omit the plating solution supply pipe 755 and supply the plating solution Q from the plating solution supply pipes 751, 753 through the plating solution impregnated material 730 and the contact member 760 onto the upper surface of the contact member 760.
Next, while circulating the plating solution Q in the above-described manner, the substrate holder 770, holding the substrate W face down on the lower surface of the holder 770, is lowered by the holder drive mechanism 790 to bring the surface to be plated of the substrate W into contact with the plating solution Q. A voltage is applied from the plating power source 796 to between the anode 720 and the electrical conductor layer of the substrate W to pass electric current therebetween, thereby effecting plating (e.g. copper plating) onto the electrical conductor layer of the substrate surface. During the plating, the surface to be plated of the substrate W is allowed to be in contact with the contact member 760 in the below-described manner.
According to this embodiment, plating is carried out while keeping the surface to be plated of the substrate W in contact with the contact member 760. While the surface to be plated of the substrate W is kept in contact with the contact member 760, it is possible to rotationally drive the substrate holder 770 so as to slide the surface to be plated of the substrate W on the surface of the contact member 760. It is also possible to repeat the contact and non-contact between the contact member 760 and the surface to be plated of the substrate W at appropriate time intervals during plating.
By thus carrying out plating while keeping the surface to be plated of the substrate W in contact with the contact member 760, it becomes possible to supply the plating solution Q preferentially into the interconnect trenches and fine holes of the substrate W, thereby depositing the metal preferentially onto the surfaces of the interconnect trenches and the fine holes.
When application of current is started in the state shown in
If the contact and non-contact between the contact member 760 and the substrate W are repeated during plating, a fresh plating solution Q favorably can enter the fine recesses W1 more easily when the contact member 760 and the substrate W are apart.
In some cases, it is possible to carry out ordinary plating in the plating solution Q while keeping the substrate W apart from the contact member 760 before, after or during plating carried out by allowing the substrate W to be in contact with the contact member 760. For example, after carrying out plating for a short time while keeping the surface to be plated of the substrate W apart from the contact member 760, the surface to be plated is brought into contact with the contact member 760 to carry out the above-described plating.
According to this embodiment, because of the presence of the plating solution impregnated material 730 as a high-resistance structure between the substrate W and the anode 720, uniform plating over the entire surface to be plated of the substrate W can be effected whether plating is carried out while keeping the substrate W in contact with the contact member 760 or while keeping the substrate W apart from the contact member 760. In particular, electricity is fed to the peripheral bevel portion of the substrate W. Without the plating solution impregnated material 730, since the electric resistance of the electrical conductor layer increases with the distance from the periphery of the substrate W, potential variation is produced in the surface of the substrate W, resulting in variation of the plating rate. The presence of the plating solution impregnated material 730, which has such a large resistance as to make the electric resistance difference in the surface of the substrate W negligible, can equalize the plating rate. Further according to this embodiment, the substrate W is held face down, and the plating solution impregnated material 730 is provided on the plating cell 710 side. Accordingly, the diametrical size of the plating solution impregnated material 730 can be made larger than the diametrical size of the substrate W with ease, whereby more uniform plating can be effected.
Further, by rotating or scroll-rotating the substrate W in this embodiment, even more uniform plating becomes possible over the entire surface to be plated of the substrate W. The rotation or scroll movement of the substrate W may be performed either when plating is carried out while keeping the substrate W in contact with the contact member 760 or when plating is carried out while keeping the substrate W apart from the contact member 760.
During plating, a so-called black film produced at the anode 720 floats in the plating solution Q in the anode chamber 713. However, the plating solution impregnated material 730 and, according to this embodiment, also the contact member 760 and the filter 740 can prevent the movement of the black film to the substrate W side.
As described above, since the anode chamber 713 is defined by the filter 740 (or by the plating solution impregnated material 730 in case of not providing the filter 740) in the plating apparatus 700, it is possible to easily control the composition (amount of ions, amounts of additives and composition of additives) of the plating solution Q in the anode chamber 713 and the composition of the plating solution Q above the contact member 760 for use in plating of the substrate W respectively at the optima (the two compositions may be identical).
As another method to promote the growth of plated film in the fine recesses W1, it is possible to employ a method which involves a repetition of the contact and non-contact between the contact member 760 and the substrate W, and an intermittent power supply in accordance with the contact/non-contact, in particular a method which comprises supplying a power only when the substrate W is in contact with the contact member 760 (or a method which comprises supplying a higher power when the substrate W is in contact with the contact member 760).
In electroplating, when there is a plenty of fresh plating solution over a portion to be plated, the plating solution contains metal ions in a large amount and thus has a low electric resistance. Accordingly, a high electric current flows in the plating solution. However, if the supply of plating solution is insufficient, the resistance of the plating solution increases with the consumption of the metal ions in the plating solution, whereby the electric current decreases. The amount of plating solution differs greatly between the space surrounded by the surface portion of the substrate W and the surface of the contact member 760 and the space surrounded by the fine recesses W1 and the surface of the contact member 760, and therefore there is a difference in the time at which the resistance of plating solution begins to increase. Thus, the current value begins to decrease at an earlier time (a1) in the surface portion of the substrate W, while the current value begins to decrease at a considerably later time (a2) in the fine recesses W1. The respective currents become constant after the times (b1, b2) at which the supply and consumption of the metal ions (copper ions) become balanced. The time at which the current becomes constant and the constant current value vary depending upon the width, the hole size, the number, etc. of the fine recesses W1. In the case of a constant current control, a rise in the voltage occurs in response to the above current decrease.
By applying a voltage or electric current in a pulsed manner (i.e. on/off or decrease/increase of voltage/current in a pulsed manner) in synchronization with the cycle of contact/non-contact between the contact member 760 and the substrate W, it becomes possible to further promote the growth of plated film in the fine recesses W1 compared to the surface portion of the substrate W. In this case, it is most effective to make the pulse width equal to the time period (a2) until the current begins to decrease in the fine recesses W1. Further, since a fresh plating solution is supplied into the fine recesses W1 upon the contact/non-contact operation, there is no need to make the current density small for the purpose of ensuring the film quality, hence there is no significant lowering of the throughput. In order to improve the in-plane film thickness distribution of the plated film formed on the substrate W, it is possible to change the relative position between the contact member 760 and the substrate W by the holder drive mechanism 790 during the non-contact time, as described above.
As yet another method to promote the growth of plated film in the fine recesses W1, instead of the repetition of contact/non-contact between the contact member 760 and the substrate W (or in combination with the contact/non-contact between the contact member 760 and the substrate W), it is possible to employ a method which comprises changing the pressure of the substrate W on the contact member 760 upon contact from a relatively high pressure to a low pressure and, at the same time, changing the voltage application condition according to the change in pressure. The change of the voltage application condition includes an intermittent voltage application, an increase/decrease of applied voltage (repetition of high voltage and low voltage), etc. The voltage application may be application of a simple direct-current voltage, application of a pulse voltage as a group of pulses, or application of a sine-wave voltage. A method of carrying out plating by employing the change of the voltage application condition in association with a change of pressing condition of the substrate W on the contact member 760 may be carried out in the following two manners:
The first manner relates to the case where the change of the pressing condition is a change of the intensity of the pressure of the surface to be plated of the substrate W on the contact member 760 and the change of the voltage application condition is an intermittent voltage application. According to this manner, for example, a voltage is applied when the above pressure is relatively high to carry out plating, whereas a voltage is not applied when the pressure is relatively low to stop plating and a fresh plating solution is supplied between the fine recesses W1 of the substrate W and the contact member 760.
The second manner relates to the case where the change of the pressing condition is a change of the intensity of the pressure of the surface to be plated of the substrate W on the contact member 760 and the change of the voltage application condition is a change of the intensity of applied voltage. According to this manner, for example, a high voltage is applied when the above pressure is relatively high to carry out plating, whereas a low voltage is applied when the pressure is relatively low and a fresh plating solution is supplied to replace the plating solution in the fine recesses W1 which was consumed upon the high voltage application.
As a method for solving the above-described problem illustrated in
When carrying out electroplating by the plating apparatus 700 shown in
When carrying out electrolytic etching, on the other hand, the positive and the negative of the plating power source 796 are reversed so as to make the electrical conductor layer of the substrate W an anode and change the anode 720 to a cathode. Thereafter, the holder drive mechanism 790 is driven to lower the substrate holder 770 so as to press the surface to be plated of the substrate W on the contact member 760 at a predetermined pressure while the substrate holder 770 is rotated, thereby etching the surface to be plated of the substrate W while rubbing the surface to be plated with the surface of the contact member 760. By thus performing electrolytic etching during plating and carrying out the electrolytic etching while pressing the surface to be plated of the substrate W on the surface of the contact member 760 and moving the both surfaces relative to each other, it becomes possible to selectively etch away raised portions of the plated film formed over narrow trenches on the surface to be plated of the substrate W, thereby improving the flatness of the plated film. Thus, the above-described problem illustrated in
The transfer robot 303 takes a substrate W before plating out of a substrate cassette set in one of the loading/unloading sections 301 and places the substrate W on the temporary substrate storage stage 311. The other transfer robot 305 takes the substrate W on the temporary substrate storage stage 311 and transfers it to one of the plating apparatuses 700, where plating of the substrate W is carried out in the above-described manner. After completion of the plating, the substrate W is taken by the transfer robot 305 out of the plating apparatus 700 and transferred to the bevel and back surface cleaning unit 307, where the substrate W is cleaned. The substrate W is then transferred by the transfer robot 303 to the spin-drying unit 309, where the substrate W is dried. Thereafter, the substrate W is transferred by the transfer robot 303 to a substrate cassette set in one of the loading/unloading sections 301 and is housed in the cassette, whereby a series of plating processes of the substrate W is completed.
As described in detail hereinabove, the present invention makes it possible to plate a substrate uniformly over the entire surface to be plated of the substrate. Further, a metal plated film, such as a copper plated film, can be deposited selectively in interconnect trenches and fine holes formed in a substrate surface.
As shown in
The use of the substrate holder 12, which holds a substrate W by vacuum attraction, can avoid the need to provide an outwardly-projecting holding member, such as a mechanical chuck, and can securely hold the substrate which is supported by a positioning guide, as will be described later.
A fluid flow passage 12b as a temperature control section for allowing a heat medium to flow in it so as to control the temperature of the substrate holder 12 at a constant temperature is provided within the substrate holder 12. The fluid flow passage 12b communicates at one end with one fluid flow passage 10b that vertically penetrates the spline shaft 10 and at the other end with the other fluid flow passage 10c that vertically penetrates the spline shaft 10. The fluid flow passage 10b is connected to a heat medium supply line 50 extending from a heat medium supply source 48, and the fluid flow passage 10c is connected to a heat medium discharge line 52 extending from the heat medium supply source 48. A heat medium, which may be a heating medium or a cooling medium, whose temperature is controlled by the heat medium supply source 48, is thus supplied into the fluid flow passage 12b within the substrate holder 12 and flows in one direction along the fluid flow passage 12b in a circulative manner, thereby controlling the temperature of the substrate holder 12 and also the temperature of the substrate W held by the substrate holder 12 at a constant temperature.
By thus controlling not only the temperature of a chemical liquid, such as a plating solution, but also the temperature of the substrate holder 12 and a substrate W held by the substrate holder 12 at a constant temperature, the effect of a chemical liquid, which is supplied to the substrate W upon processing of the substrate, can be maximized. Though in this embodiment the temperature control section is comprised of the fluid flow passage 12b, the temperature control section may also be comprised of, for example, an electric heater, a Peltier device or a thermocouple.
On the upper surface of a rotating disk 16 coupled to the upper end of a main shaft 14, a positioning guide 54, which is generally cylindrical and has a downwardly-tapering tapered surface 54a, is provided concentrically with the substrate holder 12 such that it surrounds the circumference of the substrate holder 12. The diameter D1 of the upper end opening of the tapered surface 54a of the positioning guide 54 is set to be larger than the sum of the diameter of a substrate W to be held by the substrate holder 12 and the maximum error for the substrate W. In particular, in the case of a φ300 mm substrate, the diameter D1 is larger than the sum of 300 m and the maximum error +0.2 mm, i.e. 300.2 mm. Thus, with a necessary margin added to the sum, the diameter D1 is set at e.g. about 302 to 310 mm. The diameter D2 of the lower end opening of the tapered surface 54a is set to be smaller than the sum of the diameter of the substrate W to be held by the substrate holder 12 and the minimum error for the substrate W. In particular, in the case of a φ300 mm substrate, the diameter D2 is smaller than the sum of 300 mm and the minimum error −0.2 mm, i.e. 299.8 mm. Thus, with a necessary margin added to the sum, the diameter D2 is set at e.g. about 290 to 299 mm. The inclination angle θ of the tapered surface 54a is set at e.g. 5 to 30°.
As the substrate holder 12 descends, as described below, the substrate W supported on the substrate holder 12 enters smoothly into the inside of the positioning guide 54 without interfering with the positioning guide 54. As the substrate holder 12 further descends, the substrate W comes to be supported by the positioning guide 54, without falling off the positioning guide 54, and only the substrate holder 12 continues to descent.
The positioning guide 54, in consideration of chemical resistance, low friction, strength, processibility, etc., is formed of a PEEK material. Other resin materials, such as PTFE, PCTFE, PVC, PP, etc., may also be employed. A metal material, such as a stainless steel or titanium, is of course usable as a material for the positioning guide 54. The positioning guide 54 is subjected to water cleaning, cleaning with a chemical and spin-drying after the completion of plating, and therefore is desirably of a well-drained shape. Further, it is desirable that water cleaning or chemical cleaning of the substrate W and the positioning guide 54 be carried out while they are positioned such that the distance between them is smallest.
The positioning guide 54 rotates together with the substrate holder 12 by the rotation of the main shaft 14. The positioning guide 54 is not provided with a movable member for positioning, and positioning of the substrate W with respect to the substrate holder 12 is completed merely by placing the substrate W on the surface of the positioning guide 54.
Support posts 32 are mounted on the peripheral portion of the rotating disk 16, and at the top of the support posts 32 are provided, as shown in
The seal ring 36 composed of such a composite material comprising a metal covered with a rubber has an enhanced rigidity and improved shape stability. When the substrate W is sealed with the seal ring 36, as shown in
When attracting and holding the substrate W by the substrate holding apparatus 40, the substrate W is first placed on the upper surface of the substrate holder 12, which is in a somewhat raised position, so that the substrate W is supported horizontally on the upper surface. The substrate W is in a condition to be movable horizontally along the upper surface of the substrate holder 12. While keeping the substrate W in a horizontal position, the substrate holder 12 is lowered to bring the peripheral end surface of the substrate W into contact with the tapered surface 54a of the positioning guide 54 over substantially the entire circumference of the peripheral end surface, as shown in
According to necessity, the substrate holder 12 is again raised so as to horizontally support and raise the substrate W which has been supported by the tapered surface 54a of the positioning guide 54, and the substrate holder 12 is then lowered so as to shift the support of the substrate W by the substrate holder 12 to the support of the substrate W by the tapered surface 54a of the positioning guide 54. This operation may be repeated one or more times.
Next, while keeping the substrate holder 12 in a condition to attract and hold the substrate W, i.e. while vacuuming the vacuum passage 12a provided within the substrate holder 12 via the vacuum source 44, the substrate holder 12 is raised and when the upper surface of the substrate holder 12 contacts the substrate W supported by the tapered surface 54a of the positioning guide 54, the substrate W is attracted and held on the upper surface of the substrate holder 12, as shown in
According to this embodiment, positioning of the substrate W with respect to the substrate holder 12 is thus performed by bringing the peripheral end surface of the substrate W as a reference into contact with the tapered surface 54a of the positioning guide 54. In this positioning, the center position of the substrate W does not change regardless of the diameter of the substrate W, i.e., regardless of any dimensional error in the diameter. Thus, positioning of the substrate W with respect to the substrate holder 12 can be performed with accuracy without being influenced by the diametrical size of the substrate W. In particular, when there is a dimensional error in the diametrical size of the substrate W, though the height position of the substrate W with respect to the positioning guide 54 changes (substrate W with a larger diameter is supported in an upper position by the tapered surface 54a) upon contact of the substrate W in a horizontal position with the tapered surface 54a of the positioning guide 54 to hold the substrate W, the center position of the substrate W with respect to the guide 54 does not change. Accordingly, when the substrate W is attracted and held by the substrate holder 12, for example, by means of a vacuum chuck, the center of the substrate W can coincide with the center of the substrate holder 12.
Further according to this embodiment, the positioning guide 54 has a cylindrical shape, and the tapered surface 54a contacts the peripheral end surface of the substrate W over substantially the entire circumference of the peripheral end surface to position the substrate W with respect to the substrate holder 12. This enables a more accurate positioning of the substrate W with respect to the substrate holder 12. The cylindrical positioning guide 54 may have a cut-off portion e.g. for handling.
The electrode head 42 includes a housing 62 mounted to a vertically-movable support plate 60, and a high-resistance structure 64 disposed such that it closes the bottom opening of the housing 62. The housing 62 has at its bottom an inwardly-projecting portion 62a and the high-resistance structure 64 has at its top a flange portion 64a. The high-resistance structure 64 is held by the housing 62 with the flange portion 64a caught on the inwardly-projecting portion 62a. A hollow plating solution chamber 66 is thus defined inside the housing 62.
The high-resistance structure 64 of this embodiment is composed of the same material as the plating solution impregnated materials 532 (see e.g.
The provision of the high-resistance structure 64, which exhibits a high electric resistance, makes it possible to make the influence of the resistance of e.g. the seed layer 6 (see
An anode 68 is disposed in the plating solution chamber 66, and a plating solution introduction pipe (not shown) for introducing a plating solution 70 into the plating solution chamber 66 is mounted to the housing 62. The plating solution 70, introduced from the plating solution supply pipe into the plating solution chamber 66, immerses the anode 68, passes through the high-resistance structure 64 and reaches to below the high-resistance structure 64.
In the case of performing copper plating, for example, in order to suppress the formation of slime, the anode 68 may be composed of copper (phosphor-containing copper) containing 0.03 to 0.05% of phosphor. The anode 68 may also be composed of an insoluble metal such as platinum, titanium, etc., or an insoluble electrode comprising a metal base plated with e.g. platinum. Because of no necessity for a change, an anode composed of an insoluble metal or an insoluble electrode is preferred. Further, because of permeability to plating solution, the anode 68 may have a net form.
The cathode 34 and the anode 68 are to be electrically connected to the cathode and the anode of a plating power source, respectively.
The operation of the plating apparatus in carrying out plating will now be described.
First, after performing accurate positioning of a substrate W in the above-described manner, the substrate W is attracted and held by the substrate holder 12. The substrate W is raised to a raised portion (plating position) as shown in
In this state, the gap between the substrate W and the high-resistance structure 64 is filled with the plating solution 70 in an amount of e.g. not more than about 10 cc, and the cathodes 34 and the anode 68 are electrically connected to the cathode and the anode of the plating power source, respectively, thereby performing plating of the surface of the substrate W. During plating, the main shaft 14 is rotated, according to necessity, to rotate the substrate holder 12 at a rotational speed of e.g. 1-40 min−, thereby reducing localized plating on the substrate which would be caused by electric field concentration due to the shape of the electrode and enhancing the in-plane uniformity of the film thickness of the plated film formed. Further, according to necessity, a heat medium (heating medium or cooling medium) is allowed to flow in the fluid flow passage 12b during plating so as to control (by heating or cooling) the temperature of the substrate holder 12 and the substrate W held by the substrate holder 12 at a constant temperature, as described above, thereby enhancing the plating performance. After completion of the plating, the electrode head 42 is raised and is moved to a retreat position.
Next, the plating solution 70 remaining on the substrate W is recovered, for example, by means of an aspirator nozzle, which is movable over the substrate W, until the amount of the residual liquid becomes e.g. about several cc. After the recovery of plating solution, the aspirator nozzle is returned to a retreat position.
Thereafter, while rotating the substrate holder 12 by rotating the main shaft 14, pure water is supplied to the surface of the substrate W to clean the surface of the substrate W with pure water. During the cleaning, the several cc of plating solution remaining on the surface of the substrate W is cleaned off with pure water, falling off the periphery of the seal ring 36 by centrifugal force. In order to minimize scattering of the diluted plating solution, the rotational speed of the substrate holder 12 is preferably controlled at several tens to a hundred and several tens min−1.
Next, the substrate holder 12 is lowered to a position (cleaning position) as shown in
After the completion of water cleaning, the supply of pure water is stopped, and the rotational speed of the substrate holder 12 is increased to spin-dry the substrate W and the positioning guide 54.
After the spin-drying of the substrate W, the rotation of the substrate holder 12 is stopped, and the substrate holder 12 is lowered to a position (substrate transfer position) as shown in
Next, the substrate holder 12 is raised to support horizontally and raise the substrate W which has been supported by the tapered surface 54a of the positioning guide 54, and the substrate W is sent to the next process step.
In this embodiment, the substrate processing apparatus according to the present invention is employed as a substrate holding apparatus in the electroplating apparatus. The substrate processing apparatus, when thus used as a substrate holding apparatus in an electroplating apparatus, can make the contact positions of a substrate, held by the substrate holder, with a cathode and a seal ring more accurate and can enhance the in-plane uniformity of the thickness of plated film regardless of an error in the diameter of the substrate. Further, margins that have conventionally been allowed for cathode contact position and seal ring contact position can be made smaller, for example, from 2.5 mm to 2.0 mm, thus making it possible to enlarge the effective area of a substrate.
The substrate processing apparatus can be employed as a substrate holding apparatus in an electrolytic etching apparatus by reversing the above-described anode and cathode, and using an etching liquid instead of a plating solution. It is, of course, possible to use the substrate processing apparatus as a substrate holding apparatus in a polishing apparatus.
According to the substrate processing apparatus of the present invention, the accuracy of positioning of a substrate with respect to a substrate holder can be enhanced without being influenced by a dimensional error in the diameter of the substrate. Thus, the substrate processing apparatus, when used as a substrate holding apparatus in an electroplating apparatus, can make the contact positions of a substrate, held by the substrate holder, with a cathode and a seal ring more accurate and can therefore enhance the in-plane uniformity of the thickness of plated film regardless of an error in the diameter of the substrate. Further, margins that have conventionally been allowed for cathode contact position and seal ring contact position can be made smaller, for example, from 2.5 mm to 2.0 mm, thus making it possible to enlarge the effective area of a substrate. This will contribute much to increasing the product yield now and in future years when the diametrical sizes of substrates are becoming increasingly large.
Claims
1. A plating apparatus comprising:
- a substrate holder for holding a substrate;
- a cathode section including a seal ring for contacting a peripheral portion of a surface, to be plated, of the substrate held by the substrate holder to seal the peripheral portion water-tightly, and a cathode for contacting the substrate to supply current to the substrate;
- a vertically-movable electrode head provided above the cathode section, including an anode chamber housing an anode made of an insoluble material and having a bottom opening closed with a water-permeable porous member;
- a plating solution injection section for injecting a plating solution between the anode and the surface, to be plated, of the substrate held by the substrate holder;
- a power source for applying a plating voltage between the cathode and the anode; and
- a gas discharge line for discharging gas from the anode chamber.
2. The plating apparatus according to claim 1, further comprising:
- a control section for controlling an amount of the gas discharged through the gas discharge line.
3. The plating apparatus according to claim 2, further comprising:
- a pressure sensor for detecting the pressure in the anode chamber;
- wherein the control section controls the amount of the gas discharged through the gas discharge line based on an output of the pressure sensor.
4. The plating apparatus according to claim 2, further comprising:
- an integrator for integrating an electric current flowing between the cathode and the anode;
- wherein the control section controls the amount of the gas discharged through the gas discharge line based on an output of the integrator.
5. A plating method comprising:
- providing in a plating cell an anode and a plating solution impregnated material disposed above the anode, and filling the plating cell with a plating solution so that the plating solution impregnated material is immersed in the plating solution;
- bringing a downwardly-facing surface, to be plated, of a substrate into contact with the plating solution on the plating solution impregnated material; and
- applying a voltage between the anode and the surface, to be plated, of the substrate, thereby carrying out plating of the surface, to be plated.
6. The plating method according to claim 5, wherein a contact member is provided on the upper surface of the plating solution impregnated material, and plating is carried out while keeping the surface, to be plated, of the substrate in contact with the upper surface of the contact member.
7. The plating method according to claim 6, wherein the operation of applying a voltage between the surface, to be plated, of the substrate and the anode while keeping the surface, to be plated, of the substrate in contact with the upper surface of the contact member, and the operation of detaching the surface, to be plated, of the substrate from the upper surface of the contact member are repeated.
8. The plating method according to claim 5, wherein the substrate is allowed to rotate or make a scroll movement while the surface, to be plated, of the substrate is kept in contact with the plating solution.
9. The plating method according to claim 5, wherein the plating solution is supplied into the plating cell from below the plating solution impregnated material, and the plating solution is passed through the plating solution impregnated material and supplied to above the plating solution impregnated material.
10. The plating method according to claim 5, wherein the plating solution is supplied from above the plating solution impregnated material onto the upper surface of the plating solution impregnated material.
11. A plating apparatus comprising:
- an anode disposed in a plating cell;
- a plating solution impregnated material disposed above the anode;
- a plating solution supply section for supplying and filling a plating solution into the plating cell until the plating solution reaches to above the plating solution impregnated material; and
- a substrate holder for holding a substrate with its surface, to be plated, facing downwardly;
- wherein the surface, to be plated, of the substrate held by the substrate holder is brought into contact with the plating solution above the plating solution impregnated material to carry out plating of the surface, to be plated.
12. The plating apparatus according to claim 11, further comprising:
- a contact member having a flat upper surface as a contact surface, provided above the plating solution impregnated material; and
- a holder drive mechanism for repeating the operation of bringing the surface, to be plated, of the substrate held by the substrate holder into contact with the contact surface of the contact member and the operation of detaching the surface, to be plated, from the contact surface of the contact member.
13. The plating apparatus according to claim 12, wherein the holder drive mechanism includes a mechanism for vertically moving the substrate holder, and a mechanism for allowing the substrate holder to rotate or make a scroll movement.
14. The plating apparatus according to claim 11, wherein the plating solution supply section includes a plating solution supply pipe for supplying the plating solution into the plating cell from below the anode, and a plating solution supply pipe for supplying the plating solution to above the plating solution impregnated material.
15. The plating apparatus according to claim 11, wherein a filter is provided between the anode and the plating solution impregnated material.
16. A substrate processing apparatus comprising:
- a vertically-movable substrate holder for supporting a substrate in a horizontal position and detachably holding the substrate; and
- a positioning guide disposed such that it surrounds the circumference of the substrate holder;
- wherein the positioning guide has a tapered surface which, when the substrate supported horizontally by the substrate holder is lowered or raised, contacts the peripheral end surface of the substrate to position the substrate with respect to the substrate holder.
17. The substrate processing apparatus according to claim 16, wherein the positioning guide is formed in a cylindrical shape, and the tapered surface contacts the peripheral end surface of the substrate over substantially the entire circumference of the peripheral end surface to position the substrate with respect to the substrate holder.
18. The substrate processing apparatus according to claim 16, wherein an electrode for contacting a peripheral portion of the substrate held by the substrate holder to supply current to the substrate, and a seal ring for pressure-contacting a peripheral portion of the substrate to seal the peripheral portion are provided above the substrate holder.
19. The substrate processing apparatus according to claim 18, wherein the seal ring is composed of a composite material comprising a metal covered with a rubber.
20. The substrate processing apparatus according to claim 16, wherein the substrate holder is designed to hold the substrate by vacuum attraction.
21. The substrate processing apparatus according to claim 16, wherein a temperature control section for controlling the temperature of the substrate holder is provided within the substrate holder.
22. The substrate processing apparatus according to claim 21, wherein the temperature control section comprises a fluid flow passage for allowing a temperature-controlled heat medium to flow therein.
23. A substrate processing method comprising:
- lowering or raising a substrate supported horizontally by a substrate holder and bringing a peripheral end surface of the substrate into contact with a tapered surface of a positioning guide, disposed such that it surrounds the substrate holder, to position the substrate with respect to the substrate holder; and
- holding the substrate by the substrate holder.
24. The substrate processing method according to claim 23, wherein the tapered surface of the positioning guide is brought into contact with the peripheral end surface of the substrate over substantially the entire circumference of the peripheral end surface to position the substrate with respect to the substrate holder.
25. The substrate processing method according to claim 23, wherein the substrate held by the substrate holder is raised so as to bring an electrode into contact with a peripheral portion of the substrate to supply current to the substrate, and bring a seal ring into pressure contact with a peripheral portion of the substrate to seal the peripheral portion.
26. The substrate processing method according to claim 25, wherein the seal ring is composed of a composite material comprising a metal covered with a rubber.
27. The substrate processing method according to claim 23, wherein the substrate is held by the substrate holder by vacuum attraction.
28. The substrate processing method according to claim 23, wherein the temperature of the substrate is controlled.
29. The substrate processing method according to claim 28, wherein the temperature of the substrate holder is controlled by allowing a temperature-controlled heat medium to flow within the substrate holder.
Type: Application
Filed: Jun 4, 2004
Publication Date: Feb 3, 2005
Inventors: Tsutomu Nakada (Tokyo), Junji Kunisawa (Tokyo), Hiroyuki Kanda (Tokyo), Mizuki Nagai (Tokyo), Satoru Yamamoto (Tokyo), Koji Mishima (Tokyo), Shinya Morisawa (Tokyo), Seiji Katsuoka (Tokyo), Natsuki Makino (Tokyo), Yukio Fukunaga (Tokyo)
Application Number: 10/860,115
