Polishing head assembly having recess and cap - Patents.com

Abstract

A polishing head assembly for polishing semiconductor wafers includes a polishing head and a cap. The polishing head has a top and a recess along a bottom. The recess has a concave surface. A hole extends from the top through the concave surface. A cap is disposed within the recess, the cap having an annular wall and a floor extending across the annular wall. The annular wall has an opening corresponding to the hole. The floor is spaced from the concave surface to form a chamber between the concave surface and the floor. The polishing head assembly includes a band surrounding a portion of the annular wall. The hole and the corresponding opening receive a fastener for releasably securing the annular wall to the concave surface.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 202827, filed June 25, 2021, the disclosure of which is incorporated by reference in its entirety into this application.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to polishing semiconductor wafers, and more particularly to a polishing head assembly having a recess and a cap. [Background technology]

[0003] Semiconductor wafers are typically used to manufacture integrated circuit (IC) chips onto which circuits are printed. First, the circuits are printed in miniaturized form on the surface of the wafer. The wafer is then separated into circuit chips. This miniaturized circuitry requires that the front and back surfaces of each wafer be extremely flat and parallel to ensure proper printing of the circuit on all sides of the wafer.

[0004] To achieve this, grinding and polishing processes are typically used to improve the flatness and parallelism of the front and back surfaces of the wafer after it has been cut from the ingot. A particularly good finish is required when the wafer is polished in preparation for printing miniaturized circuits onto the wafer by electron beam lithography or photolithography processes (hereafter "lithography"). The surface of the wafer onto which the miniaturized circuits are printed needs to be flat.

[0005] A polisher typically includes a circular or annular polishing pad mounted on a turntable or platen for rotational drive about a vertical axis passing through the center of the pad, and a mechanism for holding the wafer and forcing the wafer into the polishing pad. The wafer is typically attached to a polishing head, for example, using the surface tension of a liquid or vacuum / suction. A polishing slurry, which typically contains chemical abrasives and abrasive particles, is applied to the pad to increase the polishing interaction between the polishing pad and the surface of the wafer. This type of polishing operation is commonly referred to as chemical mechanical polishing (CMP).

[0006] During operation, the pad rotates and the wafer is brought into contact with and pressed against the pad by the polishing head. The polishing head is typically assembled using an epoxy adhesive. However, failure of the epoxy adhesive joints during the life of the polishing head can cause undesirable effects such as loose parts, air leaks, damaged wafers, and reduced yields. Repairing these polishing heads is difficult because the head must be heated to remove the remaining epoxy resin so that the head can be completely disassembled. After heating removal, little of the existing parts of the head assembly can be salvaged. Thus, there is a need for an improved polishing head assembly.

[0007] This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to better understand the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0008] In one aspect, a polishing head assembly for polishing semiconductor wafers includes a polishing head and a cap. The polishing head has a top and a recess along a bottom. The recess has a concave surface. A hole extends from the top through the concave surface. The cap is disposed within the recess, the cap having an annular wall and a floor extending across the annular wall. The cap is made of a structural material. The floor has a bottom surface and a top surface and is spaced from the concave surface to form a chamber between the concave surface and the top surface. The annular wall has an opening corresponding to the hole. The polishing head assembly includes a band surrounding a portion of the annular wall. The hole and the corresponding opening receive a fastener for releasably securing the annular wall to the concave surface.

[0009] In another aspect, a polishing head assembly for polishing semiconductor wafers includes a polishing head and a cap. The polishing head has a top and a downwardly extending annular member defining a recess along a bottom. The recess has a concave surface. A hole extends from the top through the concave surface. The cap is disposed within the recess, the cap having an annular wall and a floor extending across the annular wall. The cap is made of a structural material. The floor is spaced from the concave surface to form a chamber between the concave surface and the floor. The annular wall has a first portion and a second portion. The first portion of the annular wall has an opening corresponding to the hole. The second portion of the annular wall extends downwardly from the first portion. The polishing head assembly includes a unitary integral band surrounding the second portion of the annular wall. The hole and the corresponding opening receive a fastener that removably secures the first portion of the annular wall of the cap to the concave surface of the polishing head. The first portion of the annular wall has a first O-ring that forms a seal when the first portion and the concave surface are seated together.

[0010] Various refinements exist in the features described in relation to the above-mentioned aspects. Likewise, further features may be incorporated into the above-mentioned aspects. These refinements and additional features may exist individually or in any combination. For example, various features described below in relation to any of the illustrated embodiments may be incorporated into any of the above-mentioned aspects, alone or in any combination. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a partial and schematic front view of a polishing apparatus. [Diagram 2] FIG. 2 is a cross-sectional view of an example of the polishing head assembly of the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of an example of a polishing head assembly according to the second embodiment. [Figure 4] FIG. 4 is a cross-sectional view of an example of a polishing head assembly according to the third embodiment. [Diagram 5] FIG. 5 is a perspective view of the polishing head assembly illustrated in FIG. 2 including a template and a wafer held by the template. [Figure 6] FIG. 6 is a partial cross-sectional view of the polishing head assembly illustrated in FIG. 5 with the wafer omitted.

[0012] Like reference numbers in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Generally, and in embodiments of the present disclosure, suitable substrate "wafers" (also referred to as "semiconductor wafers" or "silicon wafers") include monocrystalline silicon wafers, such as silicon wafers obtained by dicing wafers from monocrystalline silicon ingots formed by the Czochralski or float zone processes. Each wafer includes a central axis, a front surface, and a rear surface parallel to the front surface. The front and rear surfaces are generally perpendicular to the central axis. The front and rear surfaces are joined by a periphery. The wafers may be of any diameter suitable for use by one of ordinary skill in the art, including, for example, 200 millimeter (mm), 300 mm, greater than 300 mm, or 450 mm diameter wafers.

[0014] In one embodiment, the wafer is pre-rough polished, and the wafer with rough front and back surfaces is first subjected to an intermediate polishing operation in which the front surface of the wafer is polished but not the back surface to improve flatness parameters or to smooth the front surface and remove handling scratches. To perform this operation, the wafer is placed against the polishing head assembly. In this embodiment, the wafer is held in place against the polishing head assembly by surface tension. The wafer is placed on the turntable of the polisher with the front surface of the wafer in contact with the polishing surface of the polishing pad.

[0015] A polishing head assembly mounted on the polisher is capable of moving vertically along an axis extending through the wafer. While the turntable rotates, the polishing head assembly moves relative to the wafer and urges the wafer toward the turntable, forcing the front surface of the wafer into abrasive engagement with the polishing surface of the polishing pad.

[0016] A conventional polishing slurry containing abrasive particles and a chemical etchant is applied to the polishing pad. The polishing pad acts on the surface of the wafer to remove material from the front side of the wafer, resulting in a surface with improved smoothness. As an example, the intermediate polishing operation preferably removes less than about 1 micron of material from the front side of the wafer.

[0017] The wafer is then subjected to a finish polishing operation, in which the front surface of the wafer is finish polished to remove fine or "micro" scratches caused by large size colloidal silica, such as Syton® from DuPont Air Products Nanomaterials, in the intermediate step, to produce a highly reflective and damage-free front surface of the wafer. The intermediate polishing operation generally removes more of the wafer than the finish polishing operation. The wafer may be finish polished on the same polisher used to intermediate polish the wafer as described above. However, a separate polisher may be used for the finish polishing operation. The finish polishing slurry is typically ammonia-based, with a low concentration of colloidal silica injected between the polishing pad and the wafer. The polishing pad applies the finish polishing slurry to the front surface of the wafer to remove any remaining scratches and haze, leaving the front surface of the wafer generally highly reflective and damage-free.

[0018] 1, a portion of a polishing apparatus is shown diagrammatically and generally designated 100. The polishing apparatus 100 may be used to polish the front side of a semiconductor wafer W. It is contemplated that other types of polishing apparatus may be used.

[0019] The polishing apparatus 100 includes a wafer holding mechanism, e.g., a template having a backing film 110 and a retaining ring 120, a polishing head assembly 130, and a turntable 140 having a polishing pad 150. The backing film 110 is disposed between the polishing head assembly 130 and the retaining ring 120 that receives a wafer W. The retaining ring 120 has at least one circular opening that receives the wafer W to be polished.

[0020] The wafer W in this embodiment is attached and held to the polishing head assembly 130 by surface tension. To create the surface tension, a wet saturated backing film 110 is attached to the polishing head assembly 130 with a pressure sensitive adhesive. The backing film 110 and the retaining ring 120 form a template or "wafer retaining template." The backing film 110 is typically a soft polymer pad or other suitable material.

[0021] The wafer W is then pressed against the wet saturated backing film 110 to remove or squeeze out most of the water or other suitable liquid. As the water is squeezed out, the wafer is held onto the backing film 110 by surface tension and atmospheric pressure acting on the exposed surface of the wafer. As the water is squeezed out, the wafer is attached to the polishing head assembly 130.

[0022] Portions of the polishing head assembly 130 are flexible enough to deform in response to changes in pressure acting on the polishing head assembly 130, yet rigid enough not to deform when the wafer is pressed into the wet saturated template. Surface tension provides a constant holding force on the surface of the wafer. This constant holding force ensures that any deformation of the polishing head assembly 130 adjacent to the wafer is directly translated into a proportional deformation of the wafer.

[0023] Holding the wafer W by surface tension works differently than other known mechanisms that use a flexible membrane or vacuum to hold the wafer against the polishing head assembly. The flexible membrane, as known in the art, deforms to create spaces or vacuum pockets between the wafer and the flexible membrane when the wafer is pressed onto it. These vacuum pockets allow the membrane to pick up the wafer. Other membranes have vacuum holes that are connected to a vacuum to create a low pressure area for picking up the wafer.

[0024] The polishing apparatus 100 applies forces to the polishing head assembly 130 to move the polishing head assembly 130 vertically, raising or lowering the polishing head assembly 130 relative to the wafer W and the turntable 140. An upward force raises the polishing head assembly 130, and a downward force lowers the polishing head assembly 130. As described above, downward vertical movement of the polishing head assembly 130 relative to the wafer W applies a polishing pressure to the wafer to urge the wafer against the polishing pad 150 of the turntable 140. As the polishing apparatus 100 increases the downward force, the polishing head assembly 130 moves vertically downward to increase the polishing pressure.

[0025] A portion of the polishing head assembly 130, the polishing pad 150, and the turntable 140 rotate at a selected rotational speed by a suitable drive mechanism (not shown) as known in the art. The rotational speeds of the polishing pad and the turntable may be the same or different. In some embodiments, the polishing apparatus includes a controller (not shown) that allows an operator to select the rotational speed of both the polishing head assembly 130 and the turntable 140, and the downward force applied to the polishing head assembly.

[0026] 2, an example of a polishing head assembly 200 for use in the polishing apparatus 100 is shown. The polishing head assembly 200 includes a polishing head 210, a cap 240, and a band 270. The polishing head assembly 200 may include a template with a backing film and a retaining ring, such as the backing film 110 and the retaining ring 120 (shown in FIG. 1). The polishing head 210 has a top 212 and a bottom 214 that are substantially parallel to each other. The polishing head 210 has a platform 216 provided on the top 212 and a hole 218 extending from the platform 216 through the bottom 214.

[0027] The polishing head 210 has an annular member 220 extending downward from a platform 216 to a bottom 214. The annular member 220 has an inner surface 222 and an outer surface 224. The outer surface 224 forms a periphery of the polishing head 210. The annular member 220 defines a recess along the bottom 214, the recess having a concave surface 226 extending between the annular member 220. In this embodiment, the hole 218 extends from the platform 216 through the concave surface 226. As will be described in more detail below, a portion of the annular member 220 may have inlets 272, 278 formed in the outer surface 224 and inner surface 222, respectively, at the bottom 214 that fit the shape of the band 270.

[0028] The cap 240 is disposed within a recess defined by the annular member 220. The cap 240 includes a floor 242 surrounded by an annular wall 250 that extends upwardly from the floor 242. The floor 242 has a top surface 244 and a bottom surface 246. In this embodiment, the bottom surface 246 extends outwardly beyond the annular wall 250 to a tab 248. As will be described in more detail below, the tab 248 may be shaped to mate with a band 270. In other embodiments, the bottom surface 246 may not extend beyond the annular wall 250 such that the annular wall 250 defines the outermost periphery of the cap 240.

[0029] The annular wall 250 has an inner surface 252, an outer surface 254, a top portion 256, and a bottom portion 258. The top portion 256 has a top edge 260 and an opening 259 formed therein. The opening 259 extends into the top portion 256 and corresponds to the hole 218. The hole 218 and the corresponding opening 259 receive a fastener 290 (e.g., a screw) for removably securing the annular wall 250 to the concave surface 226, thereby removably securing the cap 240 to the polishing head 210. The top edge 260 of the annular wall 250 contacts the concave surface 226 when the annular wall 250 is secured thereto. The top portion 256 may have an O-ring 262 at the top edge 260 that forms a seal when the annular wall 250 is secured to the concave surface 226.

[0030] 2, the annular wall 250 has a greater thickness at the top 256 than at the bottom 258. The thinner wall at the bottom 258 allows the bottom 258 to function as a hinge that allows the floor 242 to temporarily flex without permanently deforming relative to the polishing head 210. For example, the floor 242 may temporarily flex upward toward the polishing head 210 in response to downward vertical movement of the polishing head assembly 200 that brings the cap 240 into contact with a wafer (such as wafer W shown in FIG. 1). The inner surface 252 of the annular wall 250 may be angled at the top 256 relative to the outer surface 254 such that the thickness of the top 256 is greatest at the top edge 260 and tapers downward toward the bottom 258.

[0031] At least a portion of the outer surface 254 abuts the inner surface 222 of the annular member 220 when the cap 240 is secured to the polishing head 210. Preferably, the outer surface 254 is substantially parallel to the inner surface 222. In this embodiment, the height of the annular wall 250 is greater than the downward extension of the annular member 220, and the inner surface 222 of the annular member 220 surrounds the top 256 of the annular wall 250. In other embodiments, the annular member 220 may surround a greater or lesser portion of the annular wall 250.

[0032] The floor 242 is spaced apart from the concave surface 226 when the cap 240 is secured to the polishing head 210. Thus, the annular wall 250, the top surface 244 of the floor 242, and the concave surface 226 define the chamber 205 when the cap 240 is secured to the polishing head 210. The height of the chamber 205 is determined by the height of the annular wall 250, since the top edge 260 contacts the concave surface 226 when the annular wall 250 is secured to the concave surface 226. In some embodiments, the chamber 205 is pressurized with a pressurized medium or fluid. The chamber 205 may be connected to a pressure source (not shown) for supplying a pressurized medium or fluid to the chamber 205. As discussed above, the floor 242 may be able to temporarily flex relative to the polishing head 210 without permanently deforming. For example, the pressure in the chamber 205 may be adjusted to increase or decrease the flexure of the floor 242. In embodiments in which an O-ring 262 is used, the seal formed by the O-ring 262 between the top edge 260 and the concave surface 226 can prevent leakage of pressurized medium or fluid from the chamber 205, thereby maintaining a predetermined pressure within the chamber 205.

[0033] The polishing head 210 and cap 240 may be made from a structural material such as steel, aluminum, ceramic, or other suitable material. In some embodiments, the polishing head 210 and cap 240 are made from cast aluminum (e.g., MIC6® aluminum cast plate available from Alcoa). In other embodiments, the cap 240 may be made from a ceramic such as alumina or a plastic material. In other embodiments using a plastic material, polyetherimide (e.g., ULTEM Resin 1000 available from Saudi Basic Industries Corporation (SABIC)) may be used. The plastic cap 240 is substantially thicker than one made from either metal or ceramic. A cap made from ceramic has a substantially thinner floor than one made from either metal or plastic.

[0034] The metals used in the polishing head assembly 200 can be a source of metal ions through the polishing chemicals or slurry and thereby contaminate the wafer. To prevent metals from the polishing head 210 from contaminating the slurry and wafer, the polishing head 210 is coated with an epoxy resin, fluorocarbon, or other suitable non-metallic material to form a barrier that provides metal ion protection.

[0035] To prevent metals used in the polishing head assembly 200 from contaminating the slurry and wafer and / or to prevent metals from the polishing chemicals or slurry from being exposed to chemicals, a band 270 surrounds a portion of the polishing head 210 and / or cap 240. The band 270 forms a barrier between the slurry and the polishing head 210 and / or cap 240. The band 270 may be a non-metallic material. In some embodiments, the band 270 is made of a plastic such as polyetherimide (e.g., ULTEM® resin 1000 available from Saudi Basic Industries Corporation (SABIC)), polyether ether ketone, polyphenylene sulfide, polyethylene terephthalate, or the like.

[0036] In this embodiment, the band 270 may surround and be sealed to the portion of the polishing head 210 at the bottom 214, the portion of the outer surface 254 of the annular wall 250 not surrounded by the polishing head 210, and the tab 248. The annular member 220 has a side inlet 272 that extends inwardly from the outer surface 224 at the bottom 214 of the polishing head 210. A side recess 274 is formed between the tab 248 and the bottom of the annular member 220 and extends along the portion of the outer surface 254 of the annular wall 250 not surrounded by the annular member 220. The band 270 is sized and shaped to surround and form a seal between the side inlet 272, the side recess 274, and the tab 248.

[0037] In some embodiments, the band 270 is non-unitary and made of two or more segments. For example, the band 270 may be made of three, four, five, or six segments. In these embodiments, the band 270 may be sealed together at a segment joint (e.g., segment joint 275 shown in FIG. 5) or may be sealed to the polishing head 210 and / or cap 240 using an adhesive, such as an epoxy adhesive. To prevent the seal between the band 270 and the polishing head 210 and / or cap 240 from loosening due to adhesive failure, the band 270 may include a connecting member 276 for securing the band 270 to the polishing head assembly 200. For example, the band 270 may include a dovetail 276 that forms a joint with an inner inlet 278 formed in the inner surface 222 of the annular member 220 and an inner recess 280 formed in the member extending above the tab 248. The dovetail grooves 276 may be used to secure the band 270 to the polishing head 210 and / or cap 240 in addition to or instead of an adhesive.

[0038] In embodiments in which the polishing head assembly 200 includes a template with a backing film and retaining ring, such as the backing film 110 and retaining ring 120 shown in FIG. 1, the band 270 may overlap at least a portion of the template to prevent metal contamination of the slurry or wafer from the polishing head 210 and / or cap 240 and / or to prevent exposure of metals from the polishing chemicals or slurry to chemicals.

[0039] Referring to FIG. 3, another example polishing head assembly 300 for use with the polishing apparatus 100 is shown. The polishing head assembly 300 includes a polishing head 310, a cap 340, and a band 370. The polishing head assembly 300 may include a template with a backing film and a retaining ring, such as the backing film 110 and the retaining ring 120 (shown in FIG. 1). The polishing head 310 has a top 312 and a bottom 314 that are substantially parallel to one another. The polishing head 310 has a platform 316 provided on the top 312 and a hole 318 extending from the platform 316 through the bottom 314.

[0040] The polishing head 310 has an annular member 320 extending downwardly from a platform 316 to a bottom 314. The annular member 320 has an inner surface 322 and an outer surface 324. The outer surface 324 forms a periphery of the polishing head 310. The annular member 320 defines a recess along the bottom 314, the recess having a concave surface 326 extending between the annular member 320. In this embodiment, the hole 318 extends from the platform 316 through the concave surface 326. The annular member 320 has a bottom edge 372 at the bottom 314 that overlaps and may be sealed to the band 370.

[0041] Cap 340 is disposed within a recess defined by annular member 320. Cap 340 includes a floor 342 surrounded by annular wall 350 that extends upwardly from floor 342. Floor 342 has a top surface 344 and a bottom surface 346. In this embodiment, bottom surface 346 extends outwardly beyond annular wall 350 to a tab 348. In other embodiments, bottom surface 346 may not extend beyond annular wall 350 such that annular wall 350 defines the outermost edge of cap 340.

[0042] The annular wall 350 has an inner surface 352, an outer surface 354, a top portion 356, and a bottom portion 358. The top portion 356 has a top edge 360 ​​and an opening 359 formed in the top edge 360. The opening 359 extends into the top portion 356 and corresponds to the hole 318. The hole 318 and the corresponding opening 359 receive a fastener 390 (e.g., a screw) for removably securing the annular wall 350 to the concave surface 326, thereby removably securing the cap 340 to the polishing head 310. The top edge 360 ​​of the annular wall 350 contacts the concave surface 326 when the annular wall 350 is secured thereto. The top portion 356 may have an O-ring 362 at the top edge 360 ​​that forms a seal when the annular wall 350 is secured to the concave surface 326.

[0043] 3, the annular wall 350 has a greater thickness at the top 356 than at the bottom 358. The thinner wall at the bottom 358 allows the bottom 358 to function as a hinge that allows the floor 342 to temporarily flex without permanently deforming relative to the polishing head 310. For example, the floor 342 may temporarily flex upward toward the polishing head 310 in response to downward vertical movement of the polishing head assembly 300 that brings the cap 340 into contact with a wafer (such as wafer W shown in FIG. 1). The inner surface 352 of the annular wall 350 may be angled at the top 356 relative to the outer surface 354 such that the thickness of the top 356 is greatest at the top edge 360 ​​and tapers downward toward the bottom 358.

[0044] At least a portion of the outer surface 354 abuts the inner surface 322 of the annular member 320 when the cap 340 is secured to the polishing head 310. Preferably, the outer surface 354 is substantially parallel to the inner surface 322. In this embodiment, the height of the annular wall 350 is greater than the downward extension of the annular member 320, and the inner surface 322 of the annular member 320 surrounds the top 356 of the annular wall 350. In other embodiments, the annular member 320 may surround a greater or lesser portion of the annular wall 350.

[0045] The floor 342 is spaced apart from the concave surface 326 when the cap 340 is secured to the polishing head 310. Thus, the annular wall 350, the top surface 344 of the floor 342, and the concave surface 326 define the chamber 305 when the cap 340 is secured to the polishing head 310. The height of the chamber 305 is determined by the height of the annular wall 350, since the top edge 360 ​​contacts the concave surface 326 when the annular wall 350 is secured to the concave surface 326. In some embodiments, the chamber 305 is pressurized with a pressurized medium or fluid. The chamber 305 may be connected to a pressure source (not shown) for supplying a pressurized medium or fluid to the chamber 305. As discussed above, the floor 342 may be able to temporarily flex relative to the polishing head 310 without permanently deforming. For example, the pressure in the chamber 305 may be adjusted to increase or decrease the flexure of the floor 342. In embodiments in which an O-ring 362 is used, the seal formed between the top edge 360 ​​and the concave surface 326 can prevent leakage of pressurized medium or fluid from the chamber 305, thereby maintaining a predetermined pressure within the chamber 305.

[0046] The polishing head 310 and cap 340 may be made from a structural material such as steel, aluminum, ceramic, or other suitable material. In some embodiments, the polishing head 310 and cap 340 are made from cast aluminum (e.g., MIC6® aluminum cast plate available from Alcoa). In other embodiments, the cap 340 may be made from a ceramic such as alumina or a plastic material. In other embodiments using a plastic material, polyetherimide (e.g., ULTEM Resin 1000 available from Saudi Basic Industries Corporation (SABIC)) may be used. The plastic cap 340 is substantially thicker than one made from either metal or ceramic. A cap made from ceramic has a substantially thinner floor than one made from either metal or plastic.

[0047] The metals used in the polishing head assembly 300 can be a source of metal ions through the polishing chemicals or slurry and thereby contaminate the wafer. To prevent metals from the polishing head 310 from contaminating the slurry and wafer, the polishing head 310 is coated with an epoxy resin, fluorocarbon, or other suitable non-metallic material to form a barrier that provides metal ion protection.

[0048] To prevent metals used in the polishing head assembly 300 from contaminating the slurry and wafer and / or to prevent metals from the polishing chemicals or slurry from being exposed to chemicals, portions of the polishing head 310 and / or cap 340 are surrounded by a band 370 that forms a barrier between the slurry and the polishing head 310 and / or cap 340. The band 370 may be a non-metallic material. In some embodiments, the band 370 is made from a plastic such as polyetherimide (e.g., ULTEM® resin 1000 available from Saudi Basic Industries Corporation (SABIC)), polyether ether ketone, polyphenylene sulfide, polyethylene terephthalate, or the like.

[0049] In this embodiment, the band 370 may surround and be sealed to the portion of the outer surface 354 of the annular wall 350 that is not surrounded by the polishing head 310, and to the tab 348. The band 370 may be sealed to the annular member 320 at a bottom edge 372. The band 370 may be sealed to the polishing head 310 and / or the cap 340 using an adhesive, such as an epoxy adhesive. To prevent the seal between the band 370 and the polishing head 310 and / or the cap 340 from loosening due to adhesive failure, the band 370 may be a unitary, integral band. The unitary, integral band 370 may be held in place by an interference fit between the band 370 and the tab 348 and between the band 370 and the bottom edge 372 when the cap 340 is secured to the polishing head 310.

[0050] In embodiments in which the polishing head assembly 300 includes a template with a backing film and retaining ring, such as the backing film 110 and retaining ring 120 shown in FIG. 1, the band 370 may overlap at least a portion of the template to prevent metal contamination of the slurry or wafer from the polishing head 310 and / or cap 340 and / or to prevent exposure of metals from the polishing chemicals or slurry to chemicals.

[0051] Referring to FIG. 4, an example of a polishing head assembly 400 for use in the polishing apparatus 100 is shown. The polishing head assembly 400 includes a polishing head 410, a cap 440, and a band 470. The polishing head assembly 400 may include a template with a backing film and a retaining ring, such as the backing film 110 and the retaining ring 120 (shown in FIG. 1). The polishing head 410 has a top 412 and a bottom 414 that are substantially parallel to each other. The polishing head 410 has a platform 416 provided on the top 412 and a hole 418 extending from the platform 416 through the bottom 414.

[0052] The polishing head 410 has an annular member 420 extending downwardly from a platform 416 to a bottom 414. The annular member 420 has an inner surface 422 and an outer surface 424. The outer surface 424 forms a periphery of the polishing head 410. The annular member 420 defines a recess along the bottom 414, the recess having a concave surface 426 extending between the annular member 420. In this embodiment, the hole 418 extends from the platform 416 through the concave surface 426. The annular member 420 has a bottom edge 472 at the bottom 414 that overlaps and may be sealed to the band 470.

[0053] Cap 440 is disposed within a recess defined by annular member 420. Cap 440 includes a floor 442 surrounded by annular wall 450 that extends upwardly from floor 442. Floor 442 has a top surface 444 and a bottom surface 446. In this embodiment, bottom surface 446 extends outwardly beyond annular wall 450 to a tab 448. In other embodiments, bottom surface 446 may not extend beyond annular wall 450 such that annular wall 450 defines the outermost edge of cap 440.

[0054] The annular wall 450 has an inner surface 452, an outer surface 454, a top portion 456, and a bottom portion 458. The top portion 456 has a top edge 460 and an opening 459 formed in the top edge 460. The opening 459 extends into the top portion 456 at the top edge 460 and corresponds to the hole 418. The hole 418 and corresponding opening receive a fastener 490 (e.g., a screw) for removably securing the annular wall 450 to the concave surface 426, thereby removably securing the cap 440 to the polishing head 410. The top edge 460 of the annular wall 450 contacts the concave surface 426 when the annular wall 450 is secured thereto. The top portion 456 may have an O-ring 462 at the top edge 460 that forms a seal when the annular wall 450 is secured to the concave surface 426.

[0055] 4, the annular wall 450 has a greater thickness at the top 456 than at the bottom 458. The thinner wall at the bottom 458 allows the bottom 458 to function as a hinge that allows the floor 442 to temporarily flex without permanently deforming relative to the polishing head 410. For example, the floor 442 may temporarily flex upward toward the polishing head 410 in response to downward vertical movement of the polishing head assembly 400 that brings the cap 440 into contact with a wafer (such as wafer W shown in FIG. 1). The inner surface 452 of the annular wall 450 may be angled at the top 456 relative to the outer surface 454 such that the thickness of the top 456 is greatest at the top edge 460 and tapers downward toward the bottom 458.

[0056] At least a portion of the outer surface 454 abuts the inner surface 442 of the annular member 420 when the cap 440 is secured to the polishing head 410. Preferably, the outer surface 454 is substantially parallel to the inner surface 422. In this embodiment, the height of the annular wall 450 is greater than the downward extension of the annular member 420, and the inner surface 422 of the annular member 420 surrounds the top 456 of the annular wall 450. In other embodiments, the annular member 420 may surround a greater or lesser portion of the annular wall 450.

[0057] The floor 442 is spaced apart from the concave surface 426 when the cap 440 is secured to the polishing head 410. Thus, the annular wall 450, the top surface 444 of the floor 442, and the concave surface 426 define the chamber 405 when the cap 440 is secured to the polishing head 410. The height of the chamber 405 is determined by the height of the annular wall 450, since the top edge 460 contacts the concave surface 426 when the annular wall 450 is secured to the concave surface 426. In some embodiments, the chamber 405 is pressurized with a pressurized medium or fluid. The chamber 405 may be connected to a pressure source (not shown) for supplying a pressurized medium or fluid to the chamber 405. As discussed above, the floor 442 may be able to temporarily flex relative to the polishing head 410 without permanently deforming. For example, the pressure in the chamber 405 may be adjusted to increase or decrease the flexure of the floor 442. In embodiments in which an O-ring 462 is used, the seal formed between the top edge 460 and the concave surface 426 can prevent leakage of pressurized medium or fluid from the chamber 405, thereby maintaining a predetermined pressure within the chamber 405.

[0058] The polishing head 410 and cap 440 may be made from a structural material such as steel, aluminum, ceramic, or other suitable material. In some embodiments, the polishing head 410 and cap 440 are made from cast aluminum (e.g., MIC6® aluminum cast plate available from Alcoa). In other embodiments, the cap 440 may be made from a ceramic such as alumina or a plastic material. In other embodiments using a plastic material, polyetherimide (e.g., ULTEM Resin 1000 available from Saudi Basic Industries Corporation (SABIC)) may be used. The plastic cap 440 is substantially thicker than one made from either metal or ceramic. A cap made from ceramic has a substantially thinner floor than one made from either metal or plastic.

[0059] The metals used in the polishing head assembly 400 can be a source of metal ions through the polishing chemicals or slurry and thereby contaminate the wafer. To prevent metals from the polishing head 410 from contaminating the slurry and wafer, the polishing head 410 is coated with an epoxy resin, fluorocarbon, or other suitable non-metallic material to form a barrier that provides metal ion protection.

[0060] To prevent metals used in the polishing head assembly 400 from contaminating the slurry and wafer and / or to prevent metals from the polishing chemicals or slurry from being exposed to chemicals, a portion of the polishing head 410 and / or cap 440 is surrounded by a band 470 that forms a barrier between the slurry and the polishing head 410 and / or cap 440. The band 470 may be a non-metallic material. In some embodiments, the band 340 is made from a plastic such as polyetherimide (e.g., ULTEM® resin 1000 available from Saudi Basic Industries Corporation (SABIC)), polyether ether ketone, polyphenylene sulfide, polyethylene terephthalate, or the like.

[0061] In this embodiment, the band 470 may surround and be sealed to the portion of the outer surface 454 of the annular wall 450 that is not surrounded by the polishing head 410, and to the tab 448. The band 470 may be sealed to the annular member 420 at the bottom edge 472. The band 470 may be secured to the polishing head 410 and / or the cap 440 using an adhesive, such as an epoxy adhesive. To prevent the seal between the band 470 and the polishing head assembly 400 from loosening due to adhesive failure, the band 470 may be a unitary, integral band. The unitary, integral band 470 may be held in place by an interference fit between the band 470 and the tab 448 and between the band 470 and the bottom edge 472 when the cap 440 is secured to the polishing head 410. In this embodiment, the tab 448 has an O-ring 474 that forms a seal between the tab 448 and the band 470. The O-ring 474 can add an additional seal to prevent chemical exposure inside the joint between the band 470 and the polishing head assembly 400. The O-ring 474 can compensate for possible unwanted clearances due to tolerance stack-up.

[0062] In embodiments in which the polishing head assembly 400 includes a template with a backing film and retaining ring, such as the backing film 110 and retaining ring 120 shown in FIG. 1, the band 470 may overlap at least a portion of the template to prevent metal contamination of the slurry or wafer from the polishing head 410 and / or cap 440 and / or to prevent exposure of metals from the polishing chemicals or slurry to chemicals.

[0063] The features of the above-described embodiment have several advantages. For example, by attaching the polishing head assembly using fasteners instead of epoxy resin, problems associated with epoxy joint failure, which is a major cause of failure during the life of the polishing head assembly, can be reduced or eliminated. When the polishing head assembly needs repair, the fasteners allow the polishing head assembly to be disassembled without the use of heat or other destructive action, reducing maintenance time that helps salvage the parts. Reassembly of the polishing head assembly can be done without applying a new material coating to the polishing head assembly, if a coating is used. An index pin may be used to ensure that the parts are assembled in their original orientation, thereby eliminating the need for repeated lapping of the parts. The index pin can therefore prevent flatness problems associated with reassembly of conventional polishing head assemblies using fasteners (e.g., screws). Also, the top edge of the annular wall of the cap can be fixed to the concave surface of the polishing head to prevent leakage of pressurized medium or fluid from the chamber of the polishing head assembly. The use of an O-ring in this connection can further improve this seal. The non-metallic band also prevents contact between the polishing chemicals or slurry and the polishing head assembly, preserving the life of the polishing head assembly and cap.

[0064] 5 and 6, a perspective view and a partial cross-sectional view, respectively, of the polishing head assembly 200 of FIG. 2 are shown. As described above, the polishing head assembly 200 includes a polishing head 210, a cap 240, and a band 270. The cap 240 has a floor 242, which has a bottom surface 246 that extends outwardly to a tab 248. As shown in FIGS. 5 and 6, the polishing head assembly 200 includes a template 295. The template 295 includes a backing film 296 and a retaining ring 298. The retaining ring 298 extends downwardly along the periphery of the backing film 296 to form a circular opening that receives a wafer W (shown in FIG. 5). In some embodiments, the height of the retaining ring 298 is less than the height of the wafer W, which facilitates reducing or eliminating contact between a polishing pad, such as the polishing pad 150 (shown in FIG. 1), and the retaining ring 298 during operation. The wafer W in this embodiment is held against the backing film 296 by surface tension.

[0065] To prevent the metal used in the cap 240 from contaminating the slurry and the wafer W, the backing film 296 of the template 295 is sealed to the bottom surface 246 of the cap 240 using a pressure sensitive adhesive. The backing film 296 is typically a thin flexible polymer pad or other suitable material. The backing film 296 preferably includes two or more layers of material (not shown). For example, the backing film 296 may have an adhesive layer, a thin plastic film layer, and a layer of thin polyurethane foam or other non-woven material (e.g., felt). The adhesive layer seals the backing film 296 to the bottom surface 246 of the cap 240. The thin plastic film layer provides a protective barrier between the cap 240 and the slurry and / or the wafer W. The layer with the polyurethane foam or non-woven material (e.g., felt) contacts the wafer and provides a surface similar to a polishing pad (such as the polishing pad 150 shown in FIG. 1). A retaining ring 298 extends downward from the backing film 296 and is typically a plastic material. The wafer is received in a retaining ring 298 and is held against the backing film 296 by surface tension. Thus, the wafer does not directly contact the cap 240.

[0066] In this embodiment, the template 295 has a perimeter that is larger than that of the cap 240 and extends outward from the tab 248. The cap 240 is surrounded by a band 270 that overlaps an outer portion of the template 295 at an overlap surface 299. A backing film 296 of the template 295 is sealed to the bottom surface 246 and to the band 270 at the overlap surface 299 using a pressure sensitive adhesive. The band 270 and template 295 together provide a protective seal between the slurry and wafer W and the polishing head 210 and cap 240, preventing the slurry and wafer W from directly contacting the polishing head 210 and cap 240.

[0067] The embodiments described herein provide the ability to disassemble the polishing head assembly without the use of heat or other destructive effects, allowing for efficient and economical repair of the polishing head assembly. The embodiments described herein provide the ability to attach the polishing head assembly with fasteners while maintaining the desired flatness of the polished wafer and other uses.

[0068] Another advantage of using the embodiments described herein is that problems associated with epoxy joint failure during the life of the polishing head assembly can be reduced or eliminated. Also, the seal formed between the cap and the concave surface prevents air from escaping from the pressurized chamber. The band and template provide additional protection between the wafer and the metal of the polishing head assembly, reducing the amount of epoxy required to attach the polishing head assembly and / or the likelihood of epoxy joint failure due to chemical exposure.

[0069] When introducing elements of the present disclosure or embodiments of the present disclosure, the articles "a," "an," "the," and "said" are intended to mean that there is one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of specific orientation terms (e.g., "top," "bottom," "side," "down," "up," etc.) is for convenience of description and does not require a specific orientation of the described article.

[0070] Because various changes may be made in the structure and methods described above without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted in an illustrative and not a limiting sense.

Claims

1. A polishing head assembly for polishing a semiconductor wafer, wherein the polishing head assembly comprises: a polishing head having a top and a recess along the bottom, the recess having a concave surface and a hole extending from the top through the concave surface; a cap disposed within the recess, the cap having an annular wall and a floor extending across the annular wall, the floor having a bottom surface and a top surface and being spaced apart from the concave surface to form a chamber between the concave surface and the top surface, the annular wall having an opening corresponding to the hole, the cap being made of a structural material; a band surrounding a first portion of the annular wall; and; the hole and the corresponding opening receive a fastening member for removably fixing the annular wall of the cap to the concave surface of the polishing head. The polishing head assembly.

2. The polishing head assembly according to claim 1, wherein the polishing head has a downwardly extending annular member that defines the recess and surrounds a second portion of the annular wall.

3. The polishing head assembly according to claim 2, wherein the band surrounds a part of the annular member.

4. The polishing head assembly according to claim 1, wherein the band is non-uniform and has at least two segments.

5. The polishing head assembly according to claim 4, wherein the band has a connecting member for fixing the band to the annular wall.

6. The polishing head assembly according to claim 1, wherein the band is a single integral band.

7. The polishing head assembly according to claim 1, wherein the band is made of a non-metallic material selected from the group consisting of polyetherimide, polyether ether ketone, polyphenylene sulfide, and polyethylene terephthalate.

8. The polishing head assembly according to claim 1, wherein the annular wall has a top edge that contacts the concave surface when the annular wall and the concave surface are fixed.

9. The polishing head assembly according to claim 8, wherein the top edge comprises an O-ring that forms a seal when the annular wall and the concave surface are fixed.

10. The polishing head assembly according to claim 1, further comprising a template attached to the bottom surface of the floor, the template comprising a backing film.

11. The polishing head assembly according to claim 10, wherein the template is attached to the bottom surface using a pressure-sensitive adhesive.

12. The polishing head assembly according to claim 10, wherein the template extends outwardly through the outer peripheral surface of the annular wall such that the band overlaps a part of the template.

13. The polishing head assembly according to claim 12, wherein the pressure-sensitive adhesive forms a seal on a part of the template where the band overlaps.

14. The polishing head assembly according to claim 10, wherein the template further comprises a retaining ring extending downward from the backing film.

15. The polishing head assembly according to claim 14, wherein the retaining ring forms an opening for receiving a semiconductor wafer, and the height of the semiconductor wafer is higher than the height of the retaining ring.

16. The polishing head assembly according to claim 15, wherein the template is used together with a liquid to hold the semiconductor wafer on the polishing head assembly by surface tension.

17. The polishing head assembly according to claim 1, wherein the cap is made of a metallic material.

18. A polishing head assembly for polishing a semiconductor wafer, wherein the polishing head assembly has a top and a downwardly extending annular member defining a recess along the bottom, the recess having a concave surface and a hole extending from the top through the concave surface, a polishing head; a cap disposed within the recess, the cap having an annular wall and a floor extending across the annular wall, the floor being spaced from the concave surface so as to form a chamber between the concave surface and the floor, the annular wall having a first portion and a second portion, the first portion having an opening corresponding to the hole, the second portion extending downward from the first portion, the cap being made of a structural material, the cap; a single integral band surrounding the second portion of the annular wall and the hole and the corresponding opening receive a fastening member for removably fixing the first portion of the annular wall of the cap to the concave surface of the polishing head, the first portion of the annular wall has a first O-ring that forms a seal when the first portion and the concave surface are fixed, a polishing head assembly.

19. The cap is A tab extending outward from the second portion of the annular wall, and A second O-ring forming a seal between the tab and the single integral band The polishing head assembly according to claim 18, having.

20. The cap is made of a metallic material, and The single integral band is made of a non-metallic material selected from the group consisting of polyetherimide, polyether ether ketone, polyphenylene sulfide, and polyethylene terephthalate, The polishing head assembly according to claim 18.

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