Polishing apparatus
A polishing apparatus according to the present invention has a polishing surface (101), a top ring (1) for holding a semiconductor wafer (W), and a top ring shaft (11) for pressing the top ring (1) against the polishing surface (101). The top ring (1) has a retainer ring (3) for holding a peripheral portion of the semiconductor wafer (W), a housing (2) substantially in a form of a disk which is connected to the top ring shaft (11), a sliding contact joint (4, 5, 6, 2b) interconnecting the retainer ring (3) and the housing (2) in a state such that the retainer ring (3) and the housing (2) are brought into sliding contact with each other.
The present invention relates to a polishing apparatus, and more articularly to a polishing apparatus for polishing a workpiece to be polished, such as a semiconductor wafer, by holding the workpiece and pressing the workpiece against a polishing surface.
BACKGROUND ARTIn recent years, semiconductor devices have become more integrated, and structures of semiconductor elements have become more complicated. Further, the number of layers in multilayer interconnections used for a logical system has been increased. Accordingly, irregularities on a surface of a semiconductor device are increased, so that step heights on the surface of the semiconductor device tend to be large. This is because, in a manufacturing process of a semiconductor device, a thin film is formed on a semiconductor device, then micromachining processes, such as patterning or forming holes, are performed on the semiconductor device, and these processes are repeated to form subsequent thin films on the semiconductor device.
When the number of irregularities is increased on a surface of a semiconductor device, the following problems arise. When a thin film is formed on a semiconductor device, the thickness of the film formed at portions having a step becomes small. Further, an open circuit may be caused by disconnection, or a short circuit may be caused by insufficient insulation between interconnection layers. As a result, good products cannot be obtained, and the yield tends to be lowered. Further, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use. At the time of exposure in a lithography process, if the irradiation surface has irregularities, then a lens unit in an exposure system is locally unfocused. Therefore, if the irregularities on the surface of the semiconductor device are increased, then it becomes problematically difficult to form a fine pattern itself on the semiconductor device.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In a chemical mechanical polishing, while a polishing liquid containing abrasive particles such as silica (SiO2) therein is supplied onto a polishing surface such as a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing surface, so that the substrate is polished.
This type of polishing apparatus includes a polishing table having a polishing surface formed by a polishing pad and a top ring for holding a semiconductor wafer. When a semiconductor wafer is polished with such a polishing apparatus, the semiconductor wafer is held and pressed against the polishing table under a predetermined pressure by the top ring. At that time, the polishing table and the top ring are moved relative to each other to bring the semiconductor wafer into sliding contact with the polishing surface, so that the surface of the semiconductor wafer is polished to a flat mirror finish.
The polishing pad is so elastic that pressing forces applied to a peripheral edge portion of the semiconductor wafer tend to be non-uniform. Accordingly, the semiconductor wafer may excessively be polished only at the peripheral edge portion to thus cause edge rounding. In order to prevent such edge rounding, as shown in
In the aforementioned conventional top ring, since the retainer ring 600 and the housing 620 are rigidly connected to each other, as shown in
Specifically, in order to improve a polishing performance, a portion for pressing a workpiece W to be polished tends to have a complicated structure. Since the top ring has a complicated pressing mechanism, a portion at which the retainer ring 600 is attached to the housing 620 is separated from an outer peripheral edge of the workpiece W in a circumferential direction so as to form an overhanging portion in view of structural mechanics. A bending moment M0 produced by the overhanging deforms the retainer ring 600 as shown in
Thus, in the aforementioned polishing apparatus, the retainer ring 600 for holding a peripheral portion of the workpiece W is required to have a function to uniformly press the polishing surface 610 of the polishing table in addition to a function to hold the workpiece W.
DISCLOSURE OF INVENTIONThe present invention has been made in view of the above drawbacks. It is, therefore, a first object of the present invention to provide a polishing apparatus which can prevent or reduce partial wear of a retainer ring during polishing so as to conduct highly accurate polishing.
A second object of the present invention is to provide a polishing apparatus which can reduce cost for expendables and environment loads, enhance reliability, and shorten a period of time required to conduct dummy polishing after a new retainer ring is attached to a housing.
A third object of the present invention is to provide a retainer ring which allows dummy polishing, which has been required to be performed on a polishing apparatus, to be performed on a separate dedicated apparatus or machine tool.
In order to attain the first object, according to a first aspect of the present invention, there is provided a polishing apparatus having a polishing surface, a top ring for holding a workpiece to be polished, and a top ring shaft for pressing the top ring against the polishing surface. The top ring has a retainer ring for holding a peripheral edge portion of the workpiece, a housing substantially in a form of a disk which is connected to the top ring shaft, and a sliding contact joint interconnecting the retainer ring and the housing in a state such that the retainer ring and the housing are brought into sliding contact with each other.
With such an arrangement, when the top ring is pressed against the polishing surface, the retainer ring and the housing are brought into sliding contact with each other. Accordingly, even if the top ring shaft applies a load to a central portion of the housing, only a vertical component of the load is transmitted to the retainer ring while no bending moment is applied to the retainer ring because the housing and the retainer ring slide with respect to each other. As a result, the retainer ring is not tilted due to a bending moment. Thus, it is possible to prevent partial wear from being caused on a lower surface of the retainer ring.
The sliding contact joint may comprise a free joint, preferably a ball joint, to bring the retainer ring and the housing into sliding contact with each other.
According to a second aspect of the present invention, there is provided a polishing apparatus having a polishing surface, a top ring for holding a workpiece to be polished, and a top ring shaft for pressing the top ring against the polishing surface. The top ring has a retainer ring for holding a peripheral edge portion of the workpiece, a housing substantially in a form of a disk which is connected to the top ring shaft, and a joint interconnecting the retainer ring and the housing. The joint has a sufficient high rigidity in horizontal and vertical directions and a low flexural rigidity.
Thus, since the rigidity of the joint is increased in the horizontal and vertical directions, a load can reliably be transmitted from the top ring shaft to the retainer ring. Further, since the flexural rigidity of the joint is lowered, a bending moment due to a load applied to a central portion of the housing can be absorbed by the joint to reduce a bending moment applied to the retainer ring. Accordingly, it is possible to prevent inclination of the retainer ring and reduce partial wear of the lower surface of the retainer ring.
It is desirable that the joint is disposed outside of a center of a radial width of the retainer ring. When the joint is disposed outside of the center of the radial width of the retainer ring, a load of the top ring shaft is applied to a portion located outside of the center of the radial width of the retainer ring. Accordingly, a bending moment is produced with respect to the center of the width of the retainer ring. This bending moment cancels a bending moment produced by a load applied to the central portion of the housing. Thus, a bending moment applied to the retainer ring 3 can further be reduced. Accordingly, it is possible to reduce partial wear of the lower surface of the retainer ring more effectively. The joint may have a cross-section constricted at a vertically central portion thereof.
According to a third aspect of the present invention, there is provided a polishing apparatus having a polishing surface, a top ring for holding a workpiece to be polished, and a top ring shaft for pressing the top ring against the polishing surface. The top ring has a retainer ring for holding a peripheral edge portion of the workpiece and a housing substantially in a form of a disk which is connected to the top ring shaft. A rigidity of the housing is increased so that an inclination of a lower surface of the retainer ring is reduced with respect to the polishing surface when the top ring is pressed against the polishing surface.
For example, the housing may be made of a material having high strength and rigidity, such as metal or ceramics, and thickened so as to have a high rigidity. Thus, when the housing has a high rigidity, a bending moment becomes unlikely to be applied to the retainer ring even if a load is applied to the central portion of the housing by the top ring shaft. Accordingly, it is possible to prevent partial wear of the retainer ring.
In order to attain the second object, according to a fourth aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece to be polished, such as a semiconductor wafer, to a flat mirror finish. The polishing apparatus has a polishing surface and a top ring for holding a workpiece to be polished. The top ring has a retainer ring for holding a peripheral edge portion of the workpiece. The retainer ring has a first ring member made of resin, a second ring member made of metal or ceramic, and a fastening tool for fastening the first ring member and the second ring member in a manner such that the first ring member and the second ring member can be detached as two layers in a vertical direction.
With such an arrangement, it is possible to enhance the reliability of fastening the first ring member and the second ring member. Further, the retainer ring can be regenerated merely by replacement of a worn first ring member. Accordingly, it is possible to reduce cost for expendables. Furthermore, when the retainer ring is attached to a lower surface of a peripheral portion of the housing by a detachable fastening tool, a clamp stress is received by the second ring member such as metal or ceramics, which has a high rigidity. Thus, the retainer ring is prevented from being deformed. Therefore, it is possible to shorten a period of time, i.e., downtime, required for a dummy polishing process.
It is desirable that the first ring member is brought into contact with the polishing surface. It is also desirable that the first ring member includes particles serving as abrasive particles when the first ring member is scraped. In this case, particles scraped from the first ring member of the retainer ring serve as abrasive particles. Thus, abrasive particles are supplied from the retainer ring by supplying, e.g., pure water to the polishing surface.
It is desirable that the retainer ring further includes an engagement portion to fit the first ring member and the second ring member into each other. With such an arrangement, it is possible to facilitate assembling the retainer ring and further enhance the reliability of fastening the first ring member and the second ring member.
The retainer ring is preferably configured such that the retainer ring can be regenerated only by replacement of the first ring member. Since the retainer ring can be regenerated merely by replacement of the first ring member, it is possible to reduce cost for expendables and environment loads.
It is desirable that the fastening tool comprises a bolt. When a bolt is used as the fastening tool, it is possible to facilitate fastening, assembling, and disassembling the first ring member and the second ring member.
In order to attain the third object, according to a fifth aspect of the present invention, there is provided a retainer ring for holding a peripheral edge portion of a workpiece to be polished, which is held on a substrate holding surface of a top ring. The retainer ring has a first ring member made of resin, a second ring member made of metal or ceramic, and a fastening tool for fastening the first ring member and the second ring member in a manner such that the first ring member and the second ring member can be detached as two layers in a vertical direction. The first ring member is polished to have flatness.
Thus, the first ring member and the second ring member can be fastened by a detachable fastening tool to form a retainer ring having a two-layer structure in the vertical direction. Then, the first ring member can be polished so as to have flatness. Accordingly, it is not necessary to conduct dummy polishing on the polishing apparatus which has heretofore been required.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of a polishing apparatus according to the present invention will be described below with reference to
Various kinds of polishing pads are available on the market. For example, some of these are SUBA800, IC-1000, and IC-1000/SUBA400 (two-layer cloth) manufactured by Rodel Inc., and Surfin xxx-5 and Surfin 000 manufactured by Fujimi Inc. SUBA800, Surfin xxx-5, and Surfin 000 are non-woven fabrics bonded by urethane resin, and IC-1000 is made of hard rigid foam polyurethane (single layer). Foam polyurethane is porous and has a large number of fine recesses or holes formed in its surface.
The top ring 1 is connected to a top ring shaft 11 via a universal joint 10, and the top ring shaft 11 is coupled to a top ring air cylinder 111 fixed to a top ring head 110. The top ring 1 has a housing 2 (flange portion) substantially in the form of a disk, which is coupled to a lower end of the top ring shaft 11, and a retainer ring 3 disposed at a peripheral portion of the housing 2.
The top ring air cylinder 111 is connected to a pressure adjustment unit 120 via a regulator R1. The pressure adjustment unit 120 serves to adjust a pressure by supply of a pressurized fluid such as pressurized air from a compressed air source or by evacuation with pump or the like The air pressure of the pressurized air to be supplied to the top ring air cylinder 111 is adjusted via the regulator R1 by the pressure adjustment unit 120. The top ring air cylinder 111 moves the top ring shaft 11 vertically to raise and lower the whole top ring 1 and press the retainer ring 3 attached to the housing 2 against the polishing table 100 under a predetermined pressing force.
The top ring shaft 11 is coupled to a rotary sleeve 112 by a key (not shown). The rotary sleeve 112 has a timing pulley 113 disposed at a peripheral portion thereof A top ring motor 114 is fixed to the top ring head 110. The timing pulley 113 is connected to a timing pulley 116 mounted on the top ring motor 114 via a timing belt 115. Accordingly, when the top ring motor 114 is energized for rotation, the rotary sleeve 112 and the top ring shaft 11 are rotated in unison with each other via the timing pulley 116, the timing belt 115, and the timing pulley 113 to thereby rotate the top ring 1. The top ring head 110 is supported on a top ring head shaft 117 rotatably supported on a frame (not shown).
The top ring 1 will be described in greater details.
As shown in
As shown in
As described above, the top ring shaft 11 is disposed above a central portion of the housing 2, and the housing 2 is coupled to the top ring shaft 11 by the universal joint 10. The universal joint 10 has a spherical bearing mechanism by which the housing 2 and the top ring shaft 11 are tiltable with respect to each other, and a rotation transmitting mechanism for transmitting rotation of the top ring shaft 11 to the housing 2. These mechanisms transmit a pressing force and a rotating force from the top ring shaft 11 to the housing 2 while allowing the housing 2 and the top ring shaft 11 to be tilted with respect to each other.
The spherical bearing mechanism includes a hemispherical recess 11a defined centrally in a lower surface of the top ring shaft 11, a hemispherical recess 2c defined centrally in an upper surface of the housing 2, and a bearing ball 12 made of a highly hard material such as ceramics and interposed between the recesses 11a and 2c. As shown in
Meanwhile, the rotation transmitting mechanism includes engagement pins 9 fixed to the housing 2 near the top ring shaft 11 and engagement holes 11c formed in the top ring shaft 11. Even if the housing 2 is tilted with respect to the top ring shaft 11, the engagement pins 9 remain in engagement with the engagement holes 11c while contact points are displaced because the engagement pins 9 are vertically movable through the engagement holes 11c. Thus, the rotation transmitting mechanism reliably transmits rotational torque of the top ring shaft 11 to the housing 2.
The housing 2 and the retainer ring 3 have a space defined therein, which accommodates therein an elastic pad 20 brought into contact with the semiconductor wafer W held by the top ring 1, an annular holder ring 21, and a chucking plate 22 substantially in the form of a disk for supporting the elastic pad 20. The elastic pad 20 has a radially outer edge clamped between the holder ring 21 and the chucking plate 22 fixed to a lower end of the holder ring 21 and covers a lower surface of the chucking plate 22. Thus, a pressure chamber 30 is defined between the elastic pad 20 and the chucking plate 22. The elastic pad 20 is made of a highly strong and durable rubber material such as ethylene propylene rubber (EPDM), polyurethane rubber, or silicone rubber.
An opening 22a is formed at a central portion of the chucking plate 22. A fluid passage 40 comprising tubes and connectors communicate with the opening 22a, which is connected to the pressure adjustment unit 120 via a regulator R2 provided on the fluid passage 40. Specifically, the pressure chamber 30 between the elastic pad 20 and the chucking plate 22 is connected to the pressure adjustment unit 120 via the regulator R2 provided on the fluid passage 40.
A pressurizing sheet 23 comprising an elastic membrane extends between the holder ring 21 and the housing 2. The pressurizing sheet 23 has one end clamped by a pressurizing sheet support 2d mounted to a lower surface of the housing 2 and another end clamped between an upper end portion 21a and a stopper portion 21b of the holder ring 21. The housing 2, the chucking plate 22, the holder ring 21, and the pressurizing sheet 23 jointly define a pressure chamber 31 in the housing 2. As shown in
The pressure chamber 30 between the chucking plate 22 and the elastic pad 20 and the pressure chamber 31 above the chucking plate 22 are respectively supplied with pressurized fluids such as pressurized air, released to an atmospheric pressure, or evacuated, via the fluid passages 40 and 41 connected to the pressure chambers 30 and 31. Specifically, as shown in
Further, the chucking plate 22 has inner suction portions 24 and outer suction portions 25 projecting downward outside of the opening 22a. The inner suction portions 24 have communication holes 24a communicating with a fluid passage 42, which comprises tubes and connectors. The inner suction portions 40 are connected to the pressure adjustment unit 120 via a regulator R4 provided on the fluid passage 42. Similarly, the outer suction portions 25 have communication holes 25a communicating with a fluid passage 43, which comprises tubes and connectors. The outer suction portions 25 are connected to the pressure adjustment unit 120 via a regulator R5 provided on the fluid passage 43. Negative pressures can be developed at opening ends of the communication holes 24a and 25a of the suction portions 24 and 25 by the pressure adjustment unit 120, thereby attracting a semiconductor wafer W to the suction portions 24 and 25. The suction portions 24 and 25 have elastic sheets, such as thin rubber sheets, attached to their lower ends, to thereby softly attract and hold the semiconductor wafer W.
As shown in
In the polishing apparatus thus constructed, when a semiconductor wafer W to be delivered, the entire top ring 1 is moved to a transferring location of the semiconductor wafer. Then, the communication holes 24a and 25a of the suction portions 24 and 25 are connected to the pressure adjustment unit 120 via the fluid passages 42 and 43. The semiconductor wafer W is attracted under vacuum to the lower ends of the suction portions 24 and 25 by suction effect of the communication holes 24a and 25a. While the semiconductor wafer W is attracted to the suction portions, the entire top ring 1 is moved to a position above the polishing table 100 having the polishing surface (polishing pad 101) thereon. The outer circumferential edge of the semiconductor wafer W is held by the retainer ring 3 so that the semiconductor wafer W is not removed from the top ring 1.
For polishing, the attraction of the semiconductor wafer W by the suction portions 24 and 25 is released, and the semiconductor wafer W is held on the lower surface of the top ring 1. Simultaneously, the top ring air cylinder 111 connected to the top ring shaft 11 is actuated to press the retainer ring 3 fixed to the lower end of the top ring 1 against the polishing surface on the polishing table 100 under a predetermined pressing force. In such a state, a pressurized fluid having a predetermined pressure is supplied to the pressure chamber 30 to thereby press the semiconductor wafer W against the polishing surface on the polishing table 100. The polishing liquid supply nozzle 102 supplies a polishing liquid Q onto the polishing pad 101 in advance, so that the polishing liquid Q is held on the polishing pad 101. Thus, the semiconductor wafer W is polished with the polishing liquid Q being present between the (lower) surface, to be polished, of the semiconductor wafer W and the polishing pad 101.
When a pressurized fluid is supplied to the pressure chamber 30, an upward force is applied to the chucking plate 22. Accordingly, in the present embodiment, a pressure fluid is supplied to the pressure chamber 31 through the fluid passage 41 to prevent the chucking plate 22 from being lifted by forces from the pressure chamber 31.
As described above, the pressing force applied by the top ring air cylinder 111 to press the retainer ring 3 against the polishing pad 101 and the pressing force applied by the pressurized air supplied to the pressure chamber 30 to press the semiconductor wafer W against the polishing pad 101 are appropriately adjusted to polish the semiconductor wafer W. When the polishing of the semiconductor wafer W is finished, the semiconductor wafer W is attracted to the lower ends of the suction portions 24 and 25 under vacuum. At that time, the supply of the pressurized-fluid into the pressure chamber 30 to press the semiconductor wafer W against the polishing surface is stopped, and the pressure chamber 30 is vented to the atmosphere. Accordingly, the lower ends of the suction portions 24 and 25 are brought into contact with the semiconductor wafer W. The pressure chamber 31 is vented to the atmosphere or evacuated to develop a negative pressure therein. If the pressure chamber 31 is maintained at a high pressure, then the semiconductor wafer W is strongly pressed against the polishing surface only in areas brought into contact with the suction portions 40.
After attraction of the semiconductor wafer W, the entire top ring 1 is moved to a transferring position of the semiconductor wafer W, and then a fluid (e.g., compressed air or a mixture of nitrogen and pure water) is ejected to the semiconductor wafer W via the communication holes 24a and 25a of the suction portions 24 and 25 to release the semiconductor wafer W from the top ring 1.
As described above, in the present embodiment, when the top ring 1 is pressed against the polishing surface, the retainer ring 3 and the housing 2 are brought into sliding contact with each other by the ball joints 4. Accordingly, even if the top ring shaft 11 applies a load to the central portion of the housing 2, only a vertical component of the load is transmitted to the retainer ring 3 while no bending moment is applied to the retainer ring 3 because the housing 2 and the retainer ring 3 slide with respect to each other. As a result, the retainer ring 3 is not tilted due to a bending moment. Thus, it is possible to prevent partial wear from being caused on a lower surface of the retainer ring 3.
Here, the aforementioned bending moment can also be prevented from being applied to the retainer ring 3 by enhancing a rigidity of the housing 2. For example, the housing 2 may be made of a material having high strength and rigidity, such as metal or ceramics, and thickened so as to have a high rigidity. Thus, an inclination of the lower surface of the retainer ring 3 with respect to the polishing pad 101 is reduced when the top ring 1 is pressed against the polishing pad 101. When the housing 2 has a high rigidity, a bending moment becomes unlikely to be applied to the retainer ring 3 even if a load is applied to the central portion of the housing 2 by the top ring shaft 11. Accordingly, it is possible to prevent partial wear of the retainer ring 3.
In the present embodiment, the aforementioned sliding contact joints can eliminate bending moments applied to the retainer ring 3. Accordingly, it is not necessary to enhance the rigidity of the housing 2 to prevent generation of bending moments. Thus, as shown in
In the present embodiment, since the rigidity of the joint 50 is increased in the horizontal and vertical directions, a load can reliably be transmitted from the top ring shaft 11 to the retainer ring 3. Further, since the flexural rigidity of the joint 50 is lowered, a bending moment due to a load applied to the central portion of the housing 2 can be absorbed by the joint 50 to reduce a bending moment applied to the retainer ring 3. Accordingly, it is possible to prevent inclination of the retainer ring 3 and reduce partial wear of the lower surface of the retainer ring 3. In the present embodiment, the housing 2, the joint 50, and the upper member 3a of the retainer ring 3 are formed integrally with each other. However, the present invention is not limited to this example.
As described above, the joint 50 having a low flexural rigidity can reduce a bending moment applied to the retainer ring 3. As shown in
In the present embodiment, one end of a pressurizing sheet 23 is clamped between the upper member 3a of the retainer ring 3 and a pressurizing sheet support 3d provided radially inward of the upper member 3a but may be fixed to the housing 2 as with the first embodiment.
The top ring shaft 311 is disposed above a central portion of the housing body 302a of the housing 302, and the housing 302 is coupled to the top ring shaft 311 by the universal joint 310. The universal joint 310 has a spherical bearing mechanism by which the housing 302 and the top ring shaft 311 are tiltable with respect to each other, and a rotation transmitting mechanism for transmitting rotation of the top ring shaft 311 to the housing 302. These mechanisms transmit a pressing force and a rotating force from the top ring shaft 311 to the housing 302 while allowing the housing 302 and the top ring shaft 311 to be tilted with respect to each other.
The spherical bearing mechanism includes a hemispherical recess 311a defined centrally in a lower surface of the top ring shaft 311, a hemispherical recess 302c defined centrally in an upper surface of the housing body 302a, and a bearing ball 312 made of a highly hard material such as ceramics and interposed between the recesses 311a and 302c. Meanwhile, the rotation transmitting mechanism includes drive pins (not shown) fixed to the top ring shaft 311 and driven pins (not shown) fixed to the housing body 302a. Even if the housing 302 is tilted with respect to the top ring shaft 311; the drive pins and the driven pins remain in engagement with each other while contact points are displaced because the drive pin and the driven pin are vertically movable relative to each other. Thus, the rotation transmitting mechanism reliably transmits rotational torque of the top ring shaft 311 to the housing 302.
The housing 302 and the retainer ring 303 attached to the housing 302 have a space defined therein, which accommodates therein an elastic pad 304 brought into contact with a semiconductor wafer W, to be polished, held by the top ring 301, an annular holder ring 305, annular elastic pad supports 309 and 313 for supporting the elastic pad 304, and a chucking plate 306 substantially in the form of a disk for supporting the elastic pad supports 309 and 313. The elastic pad 304 has a radially outer edge clamped between the chucking plate 306 and the elastic pad supports 309 and 313 and covers lower surfaces of the elastic pad supports 309 and 313.
A pressurizing sheet 307 comprising an elastic membrane extends between the holder ring 305 and the housing 302. The pressurizing sheet 307 has one end clamped between the housing body 302a of the housing 302 and the pressurizing sheet support 302b and another end clamped between an upper end portion of the holder ring 305 and the chucking plate 306. The housing 302, the chucking plate 306, the holder ring 305, and the pressurizing sheet 307 jointly define a pressure chamber 314 in the housing 302.
An end of a fluid passage 315 such as a pipe is opened to the pressure chamber 314. The fluid passage 315 is connected to a compressed air source via a selector valve or a regulator, which is not shown. Ends of fluid passages 316 and 319 such as pipes are opened to a lower surface of the chucking plate 306. The fluid passages 316 and 319 are connected to the compressed air source via a selector valve or a regulator, which is not shown. Further, fluid passages 317 and 318 such as pipes are opened to lower surfaces of the elastic pad supports 309 and 313. The fluid passages 317 and 318 are connected to a vacuum source and the compressed air source via a selector valve or a regulator, which is not shown.
By depressurizing the lower surfaces of the elastic pad supports 309 and 313 via the fluid passage 318, a semiconductor wafer W is attracted to and held on the lower surfaces of the elastic pad supports 309 and 313. While the top ring 301 is rotated, the semiconductor wafer W attracted to and held on the lower surface of the housing 302 is pressed against the polishing surface (the upper surface of the polishing pad) 321 on the rotating polishing table 320. Thus, the semiconductor wafer W is polished by relative movement between the semiconductor wafer W and the polishing surface 321. At that time, compressed air is supplied to the pressure chamber 314 and between the lower surface of the chucking plate 306 and the semiconductor wafer W via the fluid passages 315, 316, 317, 318, and 319. Pressing forces to press the semiconductor wafer W against the polishing surface 321 on the polishing table 320 are adjusted by adjustment of pressures.
An annular groove 332a is formed in the lower surface of the second ring member 332. The first ring member 331 has an annular projection 331a formed on its upper surface which can fit into the groove 332a.
Specifically, the retainer ring 303 has an engagement portion to engage the first ring member 331 and the second ring member 332 with each other. This arrangement facilitates attachment of the first ring member 331 to the second ring member 332 and strengthens fastening of these members. Such an engagement portion may be eliminated. Instead of the engagement portion, a pin may be used to fix the first ring member 331 and the second ring member 332 to each other.
Polyetheretherketone (PEEK), polyphenylene sulfide (PPS), full aromatic polyimide resin, which is refractory plastics, or polycarbonate resin can be used as the resin for the first ring member 331 of the retainer ring 303. It is desirable that the first ring member 331, which is brought into contact with the polishing surface 321, contains particles serving as abrasive particles when being scraped or particles that cause no damage to a semiconductor wafer. The second ring member 332 is made of metal such as titanium or stainless, or ceramics such as alumina so as to achieve good heat transfer from the first ring member 331. Preferably, the bolts 333, which fasten the first ring member 331 and the second ring member 332, may be made of a material having a thermal expansion coefficient close to that of resin of the first ring member 331 or metal (titanium or stainless) or ceramics of the second ring member 332.
In order to achieve good heat transfer from the first ring member 331 to the second ring member 332, it is desirable to enlarge a contact area at the interface. A material having a high thermal expansion coefficient may preferably be used for the bolts 333. Further, as shown in
When the top ring 301 including the retainer ring 303 having a structure shown in
Since the retainer ring 440 formed integrally of resin is deformed by fastening forces of the bolts attached to the housing 302, it is necessary to perform a dummy polishing process to remove irregularities on its surface due to deformation after the retainer ring 440 is newly attached to the housing 302. Such a dummy polishing process increases a downtime of the apparatus.
Further, when the top ring 401 including the retainer ring 440 having a structure shown in
Here, in order to prevent partial wear of the retainer ring, a ring member made of stainless (or titanium, ceramics) and a ring member made of resin may be bonded to each other by an adhesive to form a two-layer structure. Such a retainer ring having a two-layer structure should be discarded due to wear of the ring member made of resin. Accordingly, such a retainer ring suffers high cost for expendables and large environmental loads. Further, aged deterioration of the adhesive or separation due to insufficient adhesion is caused so as to lower the reliability.
In the present embodiment, as shown in
Further, the retainer ring 303 is configured such that the first ring member 331 is fastened to the lower surface of the second ring member 332 by the assembly bolts 333. Accordingly, when the retainer ring 303 is fastened and fixed to the lower surface of the peripheral portion of the housing 302 by the bolts 308 as shown in
In the present embodiment, the first ring member 331 and the second ring member 332 forming the retainer ring 303 are fastened to each other by the bolts 333. However, means for fastening the first ring member 331 and the second ring member 332 to each other is not limited to this example. Various detachable fastening tools may be employed. For example, one of the ring members 331 and 332 may have a step portion having a small outside diameter, and the other of ring members 332 and 331 may have a recess having a large inside diameter. Externally threaded grooves may be provided in an outer circumferential surface of the step portion having a small outside diameter while internally threaded grooves may be provided in an inner circumferential surface of the recess having a large inside diameter. Thus, the first ring member 331 and the second ring member 332 may be fastened to each other by screwing the externally threaded grooves and the internally threaded grooves on each other. Further, other mechanical fastening tools may be employed.
When the lower surface of the retainer ring is brought into uniform contact with the polishing surface, the retainer ring may block polishing slurry to be supplied from the exterior of the retainer ring so as to make it difficult to supply polishing slurry sufficiently to a workpiece to be polished, which is present inside of the retainer ring. Accordingly, slits may be formed in the lower surface of the retainer ring to supply polishing slurry therethrough to a workpiece to be polished, which is present inside of the retainer ring. However, when slits are formed in a sliding contact surface of the retainer ring, polishing properties vary in a circumferential direction between portions having the slits and portions having no slits. A retainer ring according to the following embodiments can prevent such drawbacks.
As shown in
With the notch 512a extending radially inward on the outer circumferential surface of the retainer ring 512, the rigidity in the vertical direction with respect to the lower surface of the retainer ring 512 can gradually be reduced toward its periphery. Thus, an area having a low surface pressure is disposed at a peripheral portion of the lower surface of the retainer ring 512. Specifically, a range in which the top ring has a low pressing force is provided. Accordingly, polishing slurry can readily be introduced into an inner side of the retainer ring 512. Once the polishing slurry has been introduced into the inner side of the retainer ring 512, it does not flow out of the retainer ring 512 with ease. Thus, it is possible to increase the amount of polishing slurry supplied to a workpiece held inside of the retainer ring 512.
As shown in
Further, as shown in
An elastic member such as rubber may be filled into the non-contact portion 512a provided between the lower surface of the housing 511 and the upper surface of the retainer ring 512 as shown in
For example, the extended portion 512c shown in
A material used for a portion of the retainer ring 512 which is brought into contact with the polishing surface may be different from a material used for a portion of the retainer ring 512 which is brought into contact with the housing 511.
In this case, as shown in
In the embodiment shown in
In the examples shown in
Accordingly, the semiconductor wafer W to be polished and the lower surface of the retainer ring 512 are brought into sliding contact with the polishing surface 522 between the rotating top ring 510 and the polishing surface 522 on the rotating and/or revolving polishing pad 522. Polishing slurry supplied to a central portion of the polishing pad 522, which is not shown, or a portion of the polishing pad 522 near a peripheral portion of the retainer ring 512 from a nozzle is introduced between the lower surface of the retainer ring 512 and the polishing surface of the polishing pad 522 from the peripheral portion of the retainer ring 512 which has a low surface pressure. Thus, the polishing slurry can readily be supplied to the interior of the retainer ring 512. Specifically, polishing slurry can be supplied uniformly to the interior of the retainer ring by provision of a portion having a low surface pressure along the perimeter of the retainer ring 512. Accordingly, polishing slurry can be supplied uniformly to the entire surface of the semiconductor wafer W to be polished. Thus, uniform polishing properties can be obtained.
When polishing slurry is supplied to an upper surface (polishing surface) of the polishing pad 522 from a rear face of the polishing pad 522 through one or more openings provided in at least portions of the polishing pad 522 which are brought into contact with the semiconductor wafer W, used polishing slurry can satisfactorily be discharged from the surface of the semiconductor wafer W toward the peripheral portion of the retainer ring 512 by effect of the retainer ring 512 having the notch 512a as described above. Accordingly, since new polishing slurry is continuously supplied uniformly to the entire surface of the surface of the semiconductor wafer W to be polished, uniform polishing properties can be obtained. Such a method of supplying polishing slurry is suitable for a revolving polishing pad (having a radius e) or a case in which the top ring 510 passes through a central portion of a rotating polishing pad 522.
Further, a slit having a size and a shape such that it does not cancel the aforementioned surface pressure gradient effect of the retainer ring 512 due to the notch 512a may be provided in a sliding contact surface of the retainer ring so as to promote uniform supply of slurry to the surface to be polished.
According to the embodiments, polishing slurry can readily be supplied uniformly to the interior of a retainer ring, which holds a peripheral edge of a workpiece to be polished. Thus, there can be provided a polishing apparatus which has good polishing properties over the entire surface of a surface of a workpiece to be polished.
In the above embodiments, the present invention can be applied to any top ring which holds a peripheral edge portion of a workpiece and bring the workpiece into sliding contact with a polishing surface. Thus, the present invention is not limited to examples in which the top ring is rotated while the polishing table is rotated. For example, the present invention can be applied to an example in which the top ring holds a workpiece to be polished and make a translational orbital movement with respect to the polishing surface.
The polishing table is employed in the above embodiments. However, the present invention is not limited to a polishing apparatus having a polishing table. The present invention can be applied to any polishing apparatus as long as the polishing apparatus holds a workpiece to be polished by a top ring, presses the workpiece against the polishing surface, and provides a relative movement between the workpiece and the polishing surface to polish the workpiece.
Although certain preferred embodiments of the present invention have been described above, it should be understood that the present invention is not limited to the above embodiments. As a matter of course, various changes may be made therein without departing from the scope of the present invention.
INDUSTRIAL APPLICABILITYThe present invention is suitably used for a polishing apparatus for polishing a workpiece to be polished, such as a semiconductor wafer, by holding the workpiece and pressing the workpiece against a polishing surface.
Claims
1. A polishing apparatus comprising:
- a polishing surface;
- a top ring for holding a workpiece to be polished; and
- a top ring shaft for pressing said top ring against said polishing surface, said top ring including: a retainer ring for holding a peripheral edge portion of the workpiece, a housing substantially in a form of a disk, said housing being connected to said top ring shaft, and a sliding contact joint interconnecting said retainer ring and said housing in a state such that said retainer ring and said housing are brought into sliding contact with each other.
2. The polishing apparatus as recited in claim 1, wherein said sliding contact joint comprises a free joint to bring said retainer ring and said housing into sliding contact with each other.
3. The polishing apparatus as recited in claim 2, wherein said free joint comprises a ball joint.
4. A polishing apparatus comprising:
- a polishing surface;
- a top ring for holding a workpiece to be polished; and
- a top ring shaft for pressing said top ring against said polishing surface, said top ring including: a retainer ring for holding a peripheral edge portion of the workpiece, a housing substantially in a form of a disk, said housing being connected to said top ring shaft, and a joint interconnecting said retainer ring and said housing, said joint having a sufficient high rigidity in horizontal and vertical directions and a low flexural rigidity.
5. The polishing apparatus as recited in claim 4, wherein said joint is disposed outside of a center of a radial width of said retainer ring.
6. The polishing apparatus as recited in claim 4, wherein said joint has a cross-section constricted at a vertically central portion thereof.
7. A polishing apparatus comprising:
- a polishing surface;
- a top ring for holding a workpiece to be polished; and
- a top ring shaft for pressing said top ring against said polishing surface, said top ring including: a retainer ring for holding a peripheral edge portion of the workpiece, and a housing substantially in a form of a disk, said housing being connected to said top ring shaft,
- wherein a rigidity of said housing is increased so that an inclination of a lower surface of said retainer ring is reduced with respect to said polishing surface when said top ring is pressed against said polishing surface.
8. A polishing apparatus comprising:
- a polishing surface; and
- a top ring for holding a workpiece to be polished, said top ring including a retainer ring for holding a peripheral edge portion of the workpiece,
- wherein said retainer ring includes: a first ring member made of resin; a second ring member made of metal or ceramic; and a fastening tool for fastening said first ring member and said second ring member in a manner such that said first ring member and said second ring member can be detached as two layers in a vertical direction.
9. The polishing apparatus as recited in claim 8, wherein said first ring member is brought into contact with said polishing surface.
10. The polishing apparatus as recited in claim 9, wherein said first ring member includes particles serving as abrasive particles when said first ring member is scraped.
11. The polishing apparatus as recited in claim 8, wherein said retainer ring further includes an engagement portion to fit said first ring member and said second ring member into each other.
12. The polishing apparatus as recited in claim 8, wherein said retainer ring is configured such that said retainer ring can be regenerated merely by replacement of said first ring member.
13. The polishing apparatus as recited in claim 8, where said fastening tool comprises a bolt.
14. A retainer ring for holding a peripheral edge portion of a workpiece to be polished in a top ring for pressing the workpiece against a polishing surface and bringing the workpiece into sliding contact with the polishing surface, said retainer ring comprising:
- a first ring member made of resin;
- a second ring member made of metal or ceramic; and
- a fastening tool for fastening said first ring member and said second ring member in a manner such that said first ring member and said second ring member can be detached as two layers in a vertical direction.
Type: Application
Filed: Jul 14, 2004
Publication Date: Jun 15, 2006
Inventors: Osamu Nabeya (Tokyo), Tetsuji Togawa (Tokyo)
Application Number: 10/562,877
International Classification: B24B 29/00 (20060101);