Planting process and manufacturing process for semiconductor device thereby, and plating apparatus
An objective of this invention is to reliably form a plating film. The following two steps are sequentially conducted: step 101 of connecting a film-formation surface of a wafer 109 to a cathode electrode 107, making the film-formation surface inclined from the surface of a plating solution 103 and immersing the wafer 109 into the plating solution 103 with applying a first current between the cathode electrode 107 and an Cu anode electrode 105 disposed in the plating solution 103, and step 103 of, after immersing the film-formation surface in the plating solution 103, applying a second current between the cathode electrode 107 and the Cu anode electrode 105 to form a metal film on the film-formation surface by electrolytic plating. In step 101, the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface.
This application is based on Japanese patent application NO. 2005-125782, the content of which is incorporated hereinto by reference.
BACKGROUND1. Technical Field
This invention relates to a plating process for forming a conducting film by electrolytic plating and a process for manufacturing a semiconductor device by the plating process, as well as a plating apparatus.
2. Related Art
A damascene process is one of processes for forming a Cu multilayer interconnection in an LSI. In a damascene process, a monolayer or multilayer insulating film is formed on an Si wafer with a transistor, and the insulating film is selectively removed to form a trench of an interconnection pattern and a hole called as a via for electrical connection between multilayer interconnection layers. Next, a material containing a high-melting metal called as a barrier metal is deposited by chemical vapor deposition or physical vapor deposition. Then, a Cu film called as a seed is deposited by chemical vapor deposition or physical vapor deposition. Cu is grown on the seed by electrolytic plating using the seed as a cathode to fill the trench and the hole with Cu. Subsequently, the barrier metal, the seed Cu and the plated Cu outside the trench and the hole are removed by chemical mechanical polishing. These steps are repeated to form a Cu multilayer interconnection.
In a damascene process, defective burying must be avoided in a Cu film burying process by Cu electrolytic plating.
A plating apparatus 200 shown in
Since a growth rate in electrolytic plating is proportional to a current, film formation is conducted at a constant current in the light of film-thickness controllability. Since the plating solution 203 dissolves the Cu seed 211, a negative potential is applied between the Cu anode 205 and the cathode electrode 207 before and during immersing the wafer for preventing the Cu seed 211 from being dissolved in the plating solution. As shown in
As a method for controlling a current in horizontal bath immersion, Japanese Patent Application No. 2004-218080 has disclosed that constant-voltage and constant-current control is conducted before and after placing a plating solution. The application has described that defective burying can be thus prevented during plating a copper film over a semiconductor wafer.
However, the wafer 209 is actually immersed into the plating solution 203 with the surface of the plating solution 203 waves. Since the wafer 209 is put into the bath horizontally to the surface of the plating solution 203, the whole surface of the wafer 209 does not come into contact with the plating solution 203 at one time due to a wave as shown in
In order to solve the problem, Japanese Patent Application No. 2001-32094 has disclosed that during a period from the initial contact of a surface to be plated with a plating solution to complete contact of the whole surface with the solution, a voltage is kept constant until the complete contact with the solution for preventing variation in a current density due to fluctuation in a liquid-contact area caused by a wave. The reference has described that the technique allows for plating with improved uniformity and appearance when plating a wafer with a metal seed.
However, since the wafer 209 is inserted horizontally to the liquid surface in the plating apparatus 200, bubbles may adhere to the interface between the surface of the wafer 209 and the plating solution 203.
Attempting to solve the problem, Japanese Patent Application No. 2003-129297 has disclosed that a semiconductor wafer is immersed into a plating solution at an predetermined angle to the horizontal direction and in an immersion step, is applied a voltage equal to that applied in a film forming step after the immersion. The reference has described that immersion of the wafer at a given angle can prevent bubbles from being trapped by a hole in the wafer. Herein, immersing a wafer surface to be film-formed into a plating bath at an angle to the surface of a plating solution is called “inclined insertion” as appropriate.
SUMMARY OF THE INVENTIONHowever, after investigating the method described in Japanese Patent Application No. 2003-129297, the present inventors have found that stable film formation is difficult in spite of prevention of bubble adherence by inclined insertion of a wafer.
The present inventors have intensely investigated a cause of defective plating in inclined insertion of a wafer, and finally have found that the cause of defective plating is an increase in a current density unique to the particular insertion style, inclined insertion, which will be detailed below.
In the plating apparatus 220, a current density is increased in an area in contact with the liquid in the wafer 209 at an angle to the liquid surface of the plating solution 223, so that a Cu film excessively grows in this area. For solving the problem, lowering a voltage at the time of contacting with the liquid may be conceived, but when the wafer 209 is inclined-inserted, a current density varies in the course of immersion even under control for lowering a voltage in contrast to horizontal insertion. In inclined insertion, as the wafer 209 is immersed deeper, an area contacting with the liquid in the wafer 209 increases. If a resistance in the system decreases in inverse proportion to increase in an area contacting with the liquid, a current density is kept constant, but actually, they are not in such inverse relationship because of a fixed resistance of a part such as a cable in the machine and further because a seed (not shown in
The wafer 209 is generally immersed into the plating solution 223 with being rotated. Therefore, when it is rotated at an adequate rate, a current density in an initial plating stage is lower at a position closer to the center of the wafer 209. The dotted line in
After intense investigation for preventing fluctuation in a current density newly generated during inclined insertion of a wafer in a plating solution, the present inventors have found that fluctuation in a current density can be prevented by controlling a current on the basis of an inclination angle of the wafer from the liquid surface of the plating solution in the course of immersing a wafer, finally achieving this invention.
According to an aspect of this invention, there is provided a plating process comprising
a first step of connecting a film-formation surface of a wafer to a cathode electrode, inclining the wafer to the surface of a plating solution and immersing the wafer into the plating solution with applying a first current between the cathode electrode and an anode electrode placed in the plating solution, and
a second step of, after immersing the film-formation surface in the plating solution, applying a second current between the cathode electrode and the anode electrode to form a metal film on the film-formation surface by electrolytic plating,
wherein in the first step, the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface.
In the first step of the plating process of this invention, the wafer is inclined-inserted with applying the first current between the cathode electrode and the anode electrode and controlling the first current depending on an inclination angle of the surface between the plating solution and the film-formation surface of the wafer. Thus, it can effectively prevent fluctuation in a current density generated in the initial plating stage during the inclined insertion. It can, therefore, improve stability in the formation of a metal film and improve an yield of producing a plated film.
In the first step in the plating process of this invention, the first current applied between the anode electrode and the cathode electrode may be controlled, taking factors other than an inclination angle into account. For example, in the first step, the current may be controlled in the light of, in addition to an inclination angle, a speed in the direction of the normal line in the film-formation surface of the wafer and an elapsed time after the wafer contacts with the liquid. It can further reliably prevent fluctuation in a current density in the first step. Furthermore, in the first step, the first current may be controlled, neglecting fluctuation in an inclination angle within a given range.
According to another aspect of the present invention, there is provided a process for manufacturing a semiconductor device having a metal film, comprising
forming the metal film on the wafer by the plating process as described above.
In the manufacturing process of this invention, a metal film is formed on a wafer by the plating process as described above, so that even when forming a fine metal film pattern in a semiconductor device, defective burying of the metal film and local increase in a film thickness can be prevented, resulting in stable film formation. Thus, an yield in manufacturing a semiconductor device can be improved.
According to another aspect of the present invention, there is provided a plating apparatus, comprising
a plating bath to be filled with a plating solution,
a wafer holding unit whereby a film-formation surface of a wafer is held at an angle to the surface of the plating solution,
a wafer moving unit whereby the wafer held by the wafer holding unit is immersed into the plating solution,
a cathode electrode feeding a current to the wafer when it comes into contact with the wafer,
an anode electrode placed in the plating bath such that it faces the wafer holding unit,
a power source for applying a current between the anode electrode and the cathode electrode, and
a controller controlling a current intensity applied between the anode electrode and the cathode electrode on the basis of an inclination angle of the film-formation surface from the liquid surface.
The plating apparatus according to this invention has a configuration where the wafer holding unit holds the film-formation surface at an inclined angle to the liquid surface and the controller controls a current intensity on the basis of the inclination angle. Thus, the configuration can effectively prevent fluctuation in a current density generated during inclined insertion with allowing for stably inclined-inserting the wafer.
Any combination of these elements and any variation of this invention interconverted between a process and an apparatus are also effective as aspects of this invention.
According to this invention, a plated film can be stably grown by inclining the wafer to the surface of a plating solution, immersing the wafer into the plating solution with applying the first current between a cathode electrode and an anode electrode and controlling the first current on the basis of an inclination angle of the film-formation surface from the liquid surface.
BRIEF DESCRIPTION OF THE DRAWINGSThe above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purpose.
Embodiments of this invention will be described with reference to the drawings, using formation of a Cu film on a silicon wafer by electrolytic plating as an example. In all of the drawings, a common element is indicated by an identical symbol, and a common explanation is appropriately not repeated in the following description. In the following embodiments, a wafer may be a semiconductor substrate such as silicon, gallium and arsenic or an insulating substrate such as a glass substrate and a resin substrate. The wafer may be a substrate itself or a substrate on which are formed some elements such as semiconductor elements and interconnections.
Embodiment 1
a plating bath 101 to be filled with a plating solution 103,
a wafer moving unit (a driving unit, not shown) whereby a wafer 109 held by a cathode electrode 107 is immersed into the plating solution 103,
the cathode electrode 107 feeding a current to the wafer 109 when it comes into contact with the wafer 109,
an anode electrode (Cu anode electrode 105) disposed in the plating bath 101 such that it faces the cathode electrode 107,
a power source 115 for applying a current between the Cu anode electrode 105 and the cathode electrode 107, and
a controller 117 controlling a current intensity applied between the Cu anode electrode 105 and the cathode electrode 107 on the basis of an inclination angle of the film-formation surface from the liquid surface (
The plating apparatus 110 further has a current adjusting unit 129 (
The plating apparatus 110 also has a wafer position controller 133 (
There will be further described the configuration of the plating apparatus 110.
The plating apparatus 110 has the plating bath 101; the Cu anode electrode 105 disposed in the plating bath 101; the cathode electrode 107 disposed over the plating bath 101 and holding the wafer 109; the power source 115 applying a current between the Cu anode electrode 105 and the cathode electrode 107; and the controller 117 for controlling movement of the cathode electrode 107. The plating bath 101 is filled with the plating solution 103. The cathode electrode 107 holds the wafer 109 at an angle to the liquid surface of the plating solution 103, and is rotatable and movable to directions toward and away from the Cu anode electrode 105. The cathode electrode 107 holds the wafer 109 such that it is electrically connected to the Cu seed 111 as a seed metal layer formed on the wafer 109.
Although being not shown, the plating bath 101 may be disposed in the course of a circulating path for the plating solution 103. For example, the machine has a configuration where the plating solution 103 is discharged from the plating bath 101 and then received by another plating solution chamber (not shown), where it is then controlled to a desired temperature, filtrated by, for example, a filter and again introduced into the plating bath 101 from an inlet (not shown).
A current applied between the Cu anode electrode 105 and the cathode electrode 107 is controlled by a controller (not shown in
The data memory 135 stores data on an immersion process for the wafer 109 and data on a current applied between the Cu anode electrode 105 and the cathode electrode 107. The data on an immersion process for the wafer 109 may include an inclination angle θ between the wafer 109 and the liquid surface of the plating solution 103, and a speed of immersing the wafer 109. The data on a current may include a table of a current intensity I associated with an elapsed time after the wafer contacts with the liquid. The current intensity I meets the relation of formula (1) described later.
The timer 139 measures an elapsed time from immersion initiation, assuming that t=0 when the wafer 109 comes into contact with the plating solution 103.
The controller 117 has a current controller 131 and a wafer position controller 133.
The wafer position controller 133 acquires the data on a lowering speed of the cathode electrode 107 stored in the data memory 135 and the data on an inclination angle between the wafer 109 and the liquid surface of the plating solution 103, and controls operation of a driving unit for the cathode electrode 107 (not shown). Controlling the operation of the cathode electrode 107 by the wafer position controller 133 results in controlling a lowering speed of the wafer 109 and an inclination angle of the wafer 109. Although both inclination angle and lowering speed are constant (invariable) in this embodiment, they may be variable; for example, their data may be stored in the data memory 135 as data associated with a time. When an inclination angle is variable, the wafer position controller 133 controls the position of the wafer 109. This case will be described later in Embodiment 3.
The current controller 131 controls the intensity of a current I applied between the Cu anode electrode 105 and the cathode electrode 107 with acquiring an elapsed time measured by the timer 139 and current data associated with a time stored in the data memory 135.
The current adjusting unit 129 adjusts a current from the power source 115 to a given intensity and applyies it between the Cu anode electrode 105 and the cathode electrode 107. The power source 115 may, for example, supply a given constant current.
The wafer position data detector 137 detects a liquid contact time, that is, an immersion initiation time (t=0) by detecting a position of the wafer 109, specifically a height from the plating solution 103. Alternatively, the wafer position data detector 137 may detect a position of the wafer 109, specifically its inclination angle to the liquid surface.
Here, an immersion initiation time and an inclination angle of the wafer 109 to the liquid surface of the plating solution 103 can be, for example, detected by measuring a step number of a driving unit specifically a motor for the cathode electrode 107 (not shown). The step number until the wafer 109 contacts the plating solution 103 or becomes the predetermined inclining angle is acquired by preliminary measurement. The data memory 135 stores the measured step number. Then, when the step number detected by the wafer position data detector 137 reaches the step number stored in the data memory 135 in the course of plating, the wafer position controller 133 judges that the wafer 109 contacts with the plating solution 103 or becomes predetermined inclining angle and controls a current applied between the electrodes. Furthermore, a weak voltage can be applied before contacting with the plating solution 103 and a position and an angle at the moment of current flow can be determined as a position and an angle when the wafer 109 contacts with the plating solution 103, respectively.
There will be described a plating process according to this embodiment.
The plating process of this embodiment has the following steps:
step 101 (the first step): the film-formation surface of the wafer 109 is connected to the cathode electrode 107, the wafer 109 is inclined to the surface of the plating solution 103 and immersed into the plating solution 103 with applying a first current between the cathode electrode 107 and the Cu anode electrode 105 placed in the plating solution 103; and
step 103 (the second step): after immersing the film-formation surface in the plating solution 103, a second current is applied between the cathode electrode 107 and the Cu anode electrode 105 to form a metal film on the film-formation surface by electrolytic plating.
In step 101, the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface. The metal film is, for example, a copper-containing metal film.
In step 101 (the first step), the wafer 109 is gradually immersed with keeping the film-formation surface at a given angle θ to the plating solution 103 until the wafer 109 is completely immersed in the plating solution 103. In this embodiment, step 103 (the second step) is performed after immersing the whole film-formation surface in the plating solution 103 while a substantially constant current I is applied between the Cu anode electrode 105 and the cathode electrode 107. In this embodiment, a current intensity is controlled in each step.
In step 101, a liquid-contact area in the wafer 109 takes an inclination angle as a variable and the first current varies depending on the liquid-contact area. Here, a liquid-contact area in the wafer 109 is an area of the plating surface of the wafer 109 under the liquid surface of the plating solution 103 in the direction to the bottom of the plating bath 101. In step 101, specifically, the first current is varied in proportion to a liquid-contact area as in the following equation:
I(t)=I0/πr2×S(t)
wherein I(t) is a current intensity at a time t which is applied between the electrodes in step 101 and I0 is a current intensity in the second step, S(t) is a liquid-contact area in the film-formation surface at time t and r is a radius of the wafer 109. S and I are functions of t.
In step 101 in this embodiment, the inclination angle θ is substantially constant and the wafer 109 is immersed into the plating solution 103 at a substantially constant speed. As used herein, the term “substantially constant” means that θ or v is kept constant such that variation in a current density i caused by fluctuation in θ or v is negligible, and thus an inclination angle or a speed may be somewhat varied within the range.
In step 101, the wafer position controller 133 drives the wafer 109 to move down in the direction vertical to the liquid surface with holding the wafer 109 at an angle to the liquid surface of the plating solution 103, and to immerse the wafer 109 into the plating solution 103 at a constant speed. Here, the wafer 109 is immersed with being rotated around the central axis.
In step 101, the current controller 131 controls ON/OFF of the power source 115 and the operation of the current adjusting unit 129. The current controller 131 controls the power source 115 and the current adjusting unit 129 to apply a current I with an intensity represented by equation (1). Where θ is an inclination angle between the wafer 109 and the liquid surface of the plating solution 103, r is a radius of the wafer 109, v is a lowering speed of the wafer 109 which is herein a speed in a direction of the normal line of the liquid surface of the plating solution 103, t is an elapsed time after the wafer 109 contacts with the plating solution 103 of the wafer 109, and I0 is a current in step 103, a current represented by equation (1) is applied between the Cu anode electrode 105 and the cathode electrode 107 in step 101.
I=(I0/πr2)×S=I0(φ−cos φ sin φ)/π (1)
wherein I0 is the intensity of the second current and 2φ is an angular aperture of the liquid-contacting part to the wafer center, that is, the angle of an ark of the outer edge of the wafer 109 not contacting with the plating solution 103. As shown in
Furthermore, in this embodiment, φ and t meet the conditions: cos φ=(r−vt/sin θ)/r, 0≦t≦2r sin φ/v. In this embodiment, v is substantially constant.
There will be described effects of this embodiment.
In this embodiment, the wafer 109 is immersed at a constant angle θ from the liquid surface of the plating solution 103. Then, a current intensity until the completion of the immersion is controlled by the controller, taking an inclination angle θ, an immersion speed v and an elapsed time t after the wafer 109 contacts with the plating solution 103 into consideration. Thus, the following advantages can be achieved.
First, local increase in a current density can be prevented in the plated surface of the wafer 109.
In contrast, in step 101 in this embodiment, a current between the both electrodes from the power source 115 is controlled such that an area of the liquid-contacting surface in the wafer 109 is proportional to a current intensity between the Cu anode electrode 105 and the cathode electrode 107, taking an inclination angle θ, an immersion speed v and an elapsed time t from contacting with the plating solution 103 into consideration. Thus, as indicated by a solid line in
Because a current represented by equation (1) is applied until completion of the immersion, and a current intensity is controlled to be, at the completion of the immersion, identical to the constant current intensity I0 applied between the electrodes in step 103, the transition from the immersion step to the film formation step can be stably conducted.
Secondly, immersing the wafer 109 with inclining to the liquid surface can prevent bubbles from adhering to the surface of the wafer 109, so that local defective formation of a plating film due to bubble adhesion and local increase in a film thickness can be prevented, resulting in reliable growth.
Thirdly, since inclined insertion is employed in step 101, adhesion of bubbles to the surface of the wafer 109 can be prevented and even when there is a wave generated in the plating solution 103, deterioration in burying properties in the plating film can be prevented because of the following reason. In the initial immersion stage where a liquid-contacting area is small, an immersion position of the wafer is at the end of the plating apparatus where the wave is smaller than at the center and thus influence of the wave is negligible. When the wafer 109 is immersed in the center where a wave of the plating solution 103 is bigger, a liquid-contacting area of the wafer 109 is already adequately large, so that influence of the wave is also negligible. Therefore, burying properties in the center of the wafer 109 can be comparable to those in its end.
Embodiment 2This embodiment relates to another process for controlling a current applied between a cathode electrode and an anode electrode in electrolytic plating using the plating apparatus 110. In embodiment 1, a current intensity applied between a cathode electrode and an anode electrode is controlled in accordance with the above equation (1) in step 101 in forming a plating film. In this embodiment, the wafer 109 is immersed into the plating solution at a substantially constant speed while a current intensity applied between the electrodes is varied in proportion to an elapsed time t after the wafer 109 contacts with the plating solution 103 in step 101.
Specifically, in step 101 described above in embodiment 1, a current intensity I represented by the following equation (2) instead of equation (1) is applied.
I=I0t/t0 (2)
wherein I0 is an intensity of the second current and t0 is a time of completion of the first step.
More specifically, in this embodiment, θ is constant and a current intensity I represented by equation (3) is applied in step 101.
wherein I0 is an intensity of the second current, r is a radius of the wafer 109, θ is an inclination angle and v is a lowering speed of the wafer 109 in the direction of the normal line of the liquid surface. In this embodiment, v is substantially constant and 0≦t≦2r sin θ/v.
This embodiment relates to another process for controlling a current applied between a cathode electrode and an anode electrode in electrolytic plating using the plating apparatus 110. Although there has been described immersion with a constant inclination angle θ of the wafer 109 from the plating solution 103 in embodiments 1 and 2 as examples, an inclination angle θ may be a time-dependent variable.
As shown in
There will be described the plating process of this embodiment with reference to FIGS. 9 to 13.
The wafer position controller 133 rotates the wafer holding part 127 at an angular rate ω around O. Then, as shown in
As the wafer holding part 127 is further rotated, an immersed area 121 gradually increases while an inclination angle θ gradually decreases (
Then, at a given time t, the whole surface of the wafer 109 is immersed in the plating solution 103, where an inclination angle is θ1 (
Then, the wafer holding part 127 continues to rotate until θ=0. At θ=0, a distance between the liquid surface and the wafer 109 is d (
Among these operations, the statuses in
L sin θ+R−d=R cos θ+a sin θ,
a={L sin θ+R(1−cos θ)−d}/sin θ.
Thus, in equation (1), that is,
I=(I0/πr2)×S=I0(φ−cos φ sin φ)/π (1),
cos φ=a/r={L sin θ+R(1−cos θ)−d}/r sin θ,
θ=θ0−ωt, 0≦t≦(θ0−θ1)/ω,
R cos θ0+(−L+r) sin θ0=R−d,
R cos θ1+(−L−r) sin θ1=R−d.
According to this embodiment, even when an inclination angle θ varies depending on t, local increase in a current density and fluctuation in a plating film thickness can be prevented as in embodiment 1, because a current is controlled in proportion to a contact area of the wafer 109 with the plating solution 103.
Embodiment 4In step 101 in the above embodiments, immersion of the wafer 109 may be initiated with applying a given voltage between the Cu anode electrode 105 and the cathode electrode 107. Specifically, before the wafer 109 comes into contact with the plating solution 103, a constant voltage of higher than 0 V to 0.1 V or lower is applied. Applying a voltage higher than 0 V may allow a current intensity in step 101 to be more reliably controlled. Applying a voltage of 0.1 V or lower may result in further stable film formation in step 101.
Thus, even when accurate monitoring of liquid-contact timing of the wafer 109 is difficult based on a lowering speed of the wafer 109 alone, a current between the Cu anode electrode 105 and the cathode electrode 107 can be monitored. Such monitoring of the current intensity can allow a current intensity in step 101 to be more reliably controlled.
In step 101, instead of making the power source 115 ON at t=0, that is, the time when the wafer 109 contacts with the plating solution 103, and then increasing a current from 0 A, a current may be applied from an initial intensity corresponding to 0.1 V. Thus, step 103 can be initiated correspondingly earlier, resulting in further reduction in a time required for a plating process.
Embodiment 5This embodiment relates to a semiconductor device manufactured using the plating apparatus or the plating process described in any of the above embodiments.
There will be further described about the interconnection structure and a process for manufacturing it with reference to an interconnection structure in a dot-line enclosure 116 in
The manufacturing process according to this embodiment has the step of forming a metal film on the wafer 109 by the plating process as described in any of the above embodiments. The manufacturing process of this embodiment has the step of preparing the wafer 109 in which a transistor is formed on a circular silicon wafer, wherein the step of forming a metal film is included in the process for forming a conductive pattern made of a metal film over the transistor.
The first copper interconnection 22a has a tantalum-containing barrier metal film 24a and a copper film 26a. A connection plug 28 connected to the upper surface of the first copper interconnection 22a is formed in the silicon oxide film 18. The connection plug 28 consists of a tantalum-containing barrier metal film 30 and a copper film 32. The second copper interconnection 22b connected to the upper surface of the connection hole is formed in the second stacked film 14b. The second copper interconnection 22b has a tantalum-containing barrier metal film 24b and a copper film 26b. A first Cu silicide film 34a and a second Cu silicide film 34b are formed on the upper surfaces of the first copper interconnection 22a and the second copper interconnection 22b, respectively.
There will be described a process for manufacturing the interconnection structure shown in
Next, a tantalum-containing barrier metal film 24a as a multilayer of Ta and TaN is formed over the whole surface of the substrate by sputtering and reactive sputtering (
Then, as shown in
Then, the excessive copper film 26a and the excessive tantalum-containing barrier metal film 24a formed outside the interconnection trench are removed by chemical mechanical polishing (CMP) with leaving the copper film 26a and so forth only within the interconnection trench to form the first copper interconnection 22a (
Next, a second SiCN film 16 and a silicon oxide film 18 are deposited (
Then, a tantalum-containing barrier metal film 30 and a copper film 32 are sequentially formed such that they fill the inside of the connection hole 40 (
Then, a third SiCN film 20 and a second stacked film 14b are deposited over the connection plug 28 (
Thus, the interconnection structure shown in
In this embodiment, when forming a copper interconnection, the plating process described in any of the above embodiments is used to form a Cu film grown in the interconnection trench. Thus, fluctuation in a current density during forming the Cu film can be prevented, resulting in reduction in variation in a thickness of the plating film on a substrate. Therefore, the Cu film constituting the copper interconnection can be stably formed. Thus, the semiconductor device according to this embodiment can be manufactured in an improved yield.
The present invention has been described with reference to some embodiments. It will be understood by those skilled in the art that these embodiments are merely illustrative and that there may be many variants and these variations are also within the scope of the present invention.
For example, although there has been described a case where a Cu film is formed in the above embodiments, a plating film may be, instead of a Cu film, another metal film such as an Al film and an Ni film, or an alloy film containing at least one of Cu, Al and Ni.
Furthermore, in the above embodiments, the data memory 135 may store a plurality of controlling equations for a current intensity applied between the Cu anode electrode 105 and the cathode electrode 107 in step 101, so that a controlling method for a current intensity can be selected in the controller 117.
Although there has been described a case where a current intensity is controlled on the basis of a given inclination angle, a lowering speed and an elapsed time after the wafer contacts with the liquid in the above embodiments, a lowering speed of the wafer 109 may be controlled on the basis of a given inclination angle and a current intensity.
It is apparent that the present invention is not limited to the above embodiment, that may be modified and changed without departing from the scope and spirit of the invention.
Claims
1. A plating process comprising
- a first step of connecting a film-formation surface of a wafer to a cathode electrode, inclining the wafer to the surface of a plating solution and immersing the wafer into the plating solution with applying a first current between the cathode electrode and an anode electrode placed in the plating solution, and
- a second step of, after immersing the film-formation surface in the plating solution, applying a second current between the cathode electrode and the anode electrode to form a metal film on the film-formation surface by electrolytic plating,
- wherein in the first step, the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface.
2. The plating process as claimed in claim 1, wherein in the first step, a liquid-contact area in the wafer is a function of an inclination angle as a variable and the first current varies depending on the liquid-contact area.
3. The plating process as claimed in claim 2, wherein in the first step, the first current is varied in proportion to the liquid-contact area.
4. The plating process as claimed in claim 1, wherein the first current is represented by the following equation (1): I=I0(φ−cos φ sin φ)/π (1)
- wherein I0 is an intensity of the second current and 2φ is an angle made by straight lines passing through the wafer center and intersections of outer edge of the wafer with the surface of the plating solution.
5. The plating process as claimed in claim 1, wherein the first current is represented by the following equation (2): I=I0t/t0 (2)
- wherein I0 is an intensity of the second current and to is a time of completion of the first step.
6. The plating process as claimed in claim 1, wherein in the first step, the inclination angle is substantially constant.
7. The plating process as claimed in claim 6, wherein the wafer is immersed into the plating solution at a substantially constant speed.
8. The plating process as claimed in claim 7, wherein the first current is represented by the following equation (1): I=I0(φ−cos φ sin φ)/π (1)
- wherein I0 is an intensity of the second current; 2φ is an angle made by straight lines passing through the wafer center and intersections of outer edge of the wafer with the surface of the plating solution; φ meets the condition: cos φ=(r−vt/sin θ)/r; r is a radius of the wafer; θ is the inclination angle; v is a moving speed of the wafer in the direction of the normal line in the liquid surface; and 0≦t≦2r sin θ/v.
9. The plating process as claimed in claim 7, wherein the first current is represented by the following equation (3): I=vI0t/2r sin θ (3)
- wherein I0 is an intensity of the second current; r is a radius of the wafer; θ is the inclination angle; v is a moving speed of the wafer in the direction of the normal line of the liquid surface; and 0≦t≦2r sin θ/v.
10. The plating process as claimed in claim 1, wherein in the first step, immersion of the wafer is initiated with applying a given voltage between the anode electrode and the cathode electrode.
11. The plating process as claimed in claim 1, wherein in the second step, the second current is substantially constant.
12. The plating process as claimed in claim 1, wherein the metal film is a copper-containing metal film.
13. A process for manufacturing a semiconductor device having a metal film, comprising forming the metal film on a wafer by the plating process as claimed in claim 1.
14. The process for manufacturing a semiconductor device as claimed in claim 13,
- comprising preparing the wafer in which a transistor is formed on a silicon wafer,
- wherein said forming a metal film is included in a process for forming a conductive pattern made of the metal film over the transistor.
15. A plating apparatus, comprising:
- a plating bath to be filled with a plating solution,
- a wafer holding unit whereby a film-formation surface of a wafer is held at an angle to the surface of the plating solution,
- a wafer moving unit whereby the wafer held by the wafer holding unit is immersed into the plating solution,
- a cathode electrode feeding a current to the wafer when it comes into contact with the wafer,
- an anode electrode placed in the plating bath such that it faces the wafer holding unit,
- a power source for applying a current between the anode electrode and the cathode electrode, and
- a controller controlling a current intensity applied between the anode electrode and the cathode electrode on the basis of an inclination angle of the film-formation surface from the liquid surface.
16. The plating apparatus as claimed in claim 15, further comprising a current adjusting unit which adjusts a current intensity applied from the power source and then applies the current between the anode electrode and the cathode electrode,
- wherein the controller controls the current adjusting unit on the basis of the inclination angle.
17. The plating apparatus as claimed in claim 15, wherein a liquid-contact area in the wafer is a function of the inclination angle as a variable and the controller varies the first current depending on the liquid-contact area.
18. The plating apparatus as claimed in claim 15, wherein the controller has a wafer position controller which controls the inclination angle and a lowering speed of the wafer.
Type: Application
Filed: Apr 21, 2006
Publication Date: Oct 26, 2006
Inventors: Akira Furuya (Kanagawa), Yasuaki Tsuchiya (Kanagawa)
Application Number: 11/408,172
International Classification: C25D 5/00 (20060101);