Polishing pad with endpoint detection window

Abstract

To provide a polishing pad with an endpoint detection window.SOLUTION: A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) comprises a polishing layer, a subpad layer, a top window portion, a bottom window portion, and a support. The support extends from the polishing layer toward a top window peripheral surface, and is adjacent to the top window peripheral surface. The bottom window portion has a larger cross-section than the top window portion. The pad includes a gap between a bottom window peripheral surface and a subpad material. The pad can be used for endpoint using optical detection, acoustic detection, or both.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The field of the invention is polishing pads used in chemical mechanical polishing. [Background technology]

[0002] Chemical Mechanical Planarization (CMP) is a variation of a polishing process widely used to flatten or planarize the constituent layers of integrated circuits or similar structures. In particular, CMP is often used to produce flat, uniform layers of defined thickness in the manufacturing build of three-dimensional circuit structures through additive stacking and planarization processes. CMP can remove excess deposited material on a substrate (e.g., wafer) surface to produce an extremely flat layer of uniform thickness, with uniformity extending across the entire substrate (e.g., wafer) area. When the uniform thickness is across the entire wafer, it is known as global uniformity.

[0003] CMP utilizes a liquid, often called a slurry, which may contain nano-sized particles. The slurry is dispensed onto the surface of a rotating multilayer polymer pad (sometimes called a polishing sheet), which is mounted on a rotating platen. The polishing pad includes a polishing layer and may include a subpad. A substrate (e.g., a wafer) is mounted on a separate fixture or carrier with a separate rotation mechanism and pressed against the surface of the pad under a controlled load. This can increase the rate of relative motion between the substrate (e.g., wafer) and the polishing pad, resulting in high rates of shear or wear on both the substrate and pad surfaces. Shear and slurry particles trapped at the pad / substrate interface abrade the substrate (e.g., wafer) surface, removing material from the substrate surface. Control of the removal rate and uniformity of removal are important. It is also useful to use metrology to determine when polishing has met its desired goals (e.g., film thickness, exposure of intended underlying structures, etc.). This is known as endpoint detection.

[0004] Various types of film thickness metrology can be used for endpoint detection, along with real-time control software. Endpoint detection processes periodic signals, such as collimated, uncollimated, or acoustic signals, to prevent wafer yield problems from both under-polishing and over-polishing. For example, one approach to endpoint detection is an optical endpoint detection system that uses the transmission of light of a desired wavelength through the polishing pad; the light is reflected from the substrate being polished, and the reflected optical signal is then returned to an interferometer. This requires that at least a portion of the polishing pad be sufficiently transparent to the light source used to obtain an acceptable signal-to-noise ratio. The metrology device can be located within the body of the polishing apparatus or the platen that holds the pad.

[0005] In certain pad structures where optical detection is used, the pad material itself can be transparent to the desired optical wavelengths and / or can have a design that allows effective transmission of the signal wave. Alternatively, the pad can include alternative structures to facilitate wave transmission. For example, a transparent polymer can be provided around which an opaque material is molded to create a transparent window. See, for example, U.S. Patent No. 5,623,999. As another example, an opening can be provided through the entire pad. See, for example, U.S. Patent No. 5,623,999 and U.S. Patent No. 5,623,999. A third approach is to form a pad with an opening into which a transparent window material is inserted and held in place by an adhesive. See, for example, U.S. Patent No. 5,623,999. Various forms of polishing pads with windows have been proposed. See, for example, (Patent Document 5), (Patent Document 6), (Patent Document 7), (Patent Document 8), (Patent Document 9), (Patent Document 10), (Patent Document 11), (Patent Document 12), (Patent Document 13), (Patent Document 14), (Patent Document 15), (Patent Document 16), (Patent Document 17), (Patent Document 18), (Patent Document 19), (Patent Document 20), (Patent Document 21), (Patent Document 22), (Patent Document 23), (Patent Document 24), (Patent Document 25), (Patent Document 26), and (Patent Document 27).

[0006] Transmission of the signal wave through the boundary between the gap (e.g., air) and the surface of the window can result in refraction or reflection of the signal wave, which can introduce noise or reduce the signal, thereby reducing the effectiveness of using the signal wave for endpoint detection. Therefore, in another approach, an optical fiber can be inserted into an opening in the subpad. See U.S. Patent No. 5,623,999.

[0007] The transmission of other vibrational waves, such as acoustic waves, can include non-porous windows. See, for example, U.S. Patent Nos. 5,929,997 and 5,929,997.

[0008] In addition, because the window is typically formed from a different material than the polishing layer, other problems can arise. In particular, the elastic modulus and stiffness of the solid polymer window material are typically higher than those of the surrounding composite pad, so differential compression during the polishing process can result in deformation near the window. Differences in the coefficient of thermal expansion (CTE) and thermal conductivity (K) between the polishing material and the window can further exacerbate the problem. As the top surfaces of the pad and window heat up due to friction during CMP, the differences in CTE and K cause additional transient stresses and deformations. This can cause the window area to protrude above the top surface of the pad polishing area during use. The protruding window can cause scratches on the substrate during polishing. Additionally, gaps in the peripheral area around the protruding area can act as traps for slurry, conditioning debris, and other foreign contaminants, potentially leading to increased scratch defects. Furthermore, as the pad conditions during use, the conditioning wear rate is significantly higher in the raised areas due to increased contact pressure. Such differential thinning of the window can disrupt the optical signal and ultimately lead to breakthrough in the window, a catastrophic failure resulting in a reduced lifespan of the pad.

[0009] CMP polishing pad windows are designed for use with specific endpoint detection systems for specific polishing equipment. For example, there is one window design used for optical endpoint detection systems and another type of window used for eddy current detection systems. This limits the usefulness of a particular pad to a specific endpoint detection system. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,605,760 [Patent Document 2] U.S. Patent No. 8,961,266 [Patent Document 3] U.S. Patent No. 7,497,763 [Patent Document 4] U.S. Patent No. 5,893,796 [Patent Document 5] U.S. Patent No. 7,621,798 [Patent Document 6] U.S. Patent No. 7,081,044 [Patent Document 7] U.S. Patent No. 7,195,539 [Patent Document 8] U.S. Patent No. 8,475,228 [Patent Document 9] U.S. Patent No. 10,569,383 [Patent Document 10] U.S. Patent Application Publication No. 2021 / 0402556 [Patent Document 11] US Patent Application Publication No. 2022 / 0226956 [Patent Document 12] US Patent Application Publication No. 2020 / 164483 [Patent Document 13] US Patent Application Publication No. 2015 / 232549 [Patent Document 14] U.S. Patent No. 9,126,304 [Patent Document 15] US Patent Application Publication No. 2008 / 0207089 [Patent Document 16] US Patent Application Publication No. 2017 / 0120417 [Patent Document 17] US Patent Application Publication No. 2016 / 263721 [Patent Document 18] U.S. Patent No. 7,398,714 [Patent Document 19] U.S. Patent No. 7,435,161 [Patent Document 20] US Patent Application Publication No. 2005 / 064802 [Patent Document 21] U.S. Patent No. 9,475,168 [Patent Document 22] U.S. Patent No. 6,045,439 [Patent Document 23] U.S. Patent No. 6,716,085 [Patent Document 24] U.S. Patent No. 8,475,228 [Patent Document 25] U.S. Patent No. 7,264,536 [Patent Document 26] Japanese Patent No. 5142866 [Patent Document 27] Chinese Patent No. 113478382 [Patent Document 28] US Patent Application Publication No. 2010 / 184357 [Patent Document 29] US Patent Application Publication No. 2023 / 0009737 [Patent Document 30] US Patent Application Publication No. 2023 / 0009519 Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, there remains a need for improved polishing pads with window areas for use in endpoint detection, particularly pads that offer one or more of the following advantages: reducing or avoiding scratching of the substrate during polishing; better managing or tolerating stress on the pad during polishing while providing uniform polishing and good pad life; and being useful for more than one type of signal wave. [Means for solving the problem]

[0012] Disclosed herein is a polishing pad for chemical mechanical polishing. The polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) comprises a polishing layer, a subpad layer, an upper window portion, a bottom window portion, and a support. The polishing layer has a polishing surface and a polishing-layer interface opposite the polishing surface. The polishing layer comprises a polishing material. The subpad layer has a subpad interface adjacent to the polishing-layer interface and a bottom surface opposite the subpad interface. The subpad layer comprises a subpad material. The upper window portion comprises the upper window material and has a polishing face surface preferably recessed from the polishing surface, an upper window interface opposite the polishing face surface, and an upper window peripheral surface extending from the polishing face surface to the upper window interface. The support extends from the polishing layer toward the upper window peripheral surface and is adjacent to the upper window peripheral surface. The support comprises an upper support surface and a support interface opposite the upper support surface. The bottom window portion has a bottom window interface, a bottom window bottom surface, and a bottom window peripheral surface extending from the bottom window interface to the bottom window bottom surface, and the area defined by the bottom window bottom surface, the bottom window peripheral surface, and the bottom window interface is filled with bottom window material. The bottom window interface is adjacent to the top window interface and adjacent to at least a portion of the support interface. The pad includes a gap between the bottom window peripheral surface and the subpad material.

[0013] Also disclosed is a method of polishing that includes providing a substrate to be polished, providing a polishing pad as disclosed herein, providing a slurry on the polishing pad, moving the substrate relative to the polishing pad, and transmitting a signal wave through a window material and detecting the signal wave reflected from the substrate through the window and the slurry to determine when polishing is complete. The signal wave can be an optical wave, an acoustic wave, or both.

[0014] Reference will now be made to the drawings, which are exemplary embodiments, in which like elements are numbered alike. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view through the thickness of a portion of an example polishing pad disclosed herein. [Figure 2] 1 is a cross-sectional view through the thickness of a portion of an example polishing pad disclosed herein. [Figure 3] 1 is a cross-sectional view through the thickness of a portion of an example polishing pad disclosed herein. [Figure 4] 1 is a cross-sectional view through the thickness of a portion of an example polishing pad disclosed herein. [Figure 5] FIG. 2 is a cross-sectional view through the thickness of a portion of FIG. 1 with an encapsulation layer added. [Figure 6] FIG. 1 is a top view of an example of a polishing pad disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention discloses a polishing pad useful in chemical mechanical polishing, which includes a polishing layer having a polishing surface, a subpad, and a window extending through the polishing layer and the subpad.

[0017] The window comprises two portions. The top portion comprises a first window material and is positioned within the opening in the polishing layer. The support extends from the polishing material to a peripheral edge of the top portion. The polishing face surface of the top portion of the window is recessed from the polishing surface of the polishing layer. The bottom portion comprises a second window material and is positioned within the opening in the subpad material. The bottom portion is adjacent to the top portion of the window on the opposite side of the polishing side of the polishing pad. The bottom portion has a peripheral edge that is larger than the peripheral edge of the top portion. In other words, the bottom portion covers the entire bottom surface of the top portion and also covers a portion of the bottom surface of the support. A gap exists between the peripheral edge of the bottom portion and the subpad material. At least a portion of the gap underlies at least a portion of the support.

[0018] The pad structure may provide one or more of the following advantages: Avoiding scratches on the substrate being polished by the top of the polishing window, facilitating alignment of the top and bottom window portions, increasing tolerance for misalignment of the top and bottom window portions, and mitigating compressive and shear stresses generated during the polishing process. For example, having a bottom window portion with larger peripheral edges than the top window portion may facilitate alignment of the window portions within the opening and increase tolerance for misalignment of these portions from the center point. As another example, the recesses, supports, and gaps (preferably when the gaps are below at least a portion of the supports) allow for greater flexibility and stress relief during polishing without affecting the pad surface. This increased flexibility may extend the pad's lifespan and reduce polishing defects. As yet another example, the flexibility and recesses in the top portion of the window may avoid protrusion of the window material above the top polishing surface, which could lead to defects or scratches. For example, a concave top window surface avoids or prevents direct pressure transmission between the window and the substrate (e.g., a silicon wafer). Furthermore, such recesses can avoid problems caused by differences in conditioning wear rates between the polishing layer material and the first window material.

[0019] Referring to Figures 1-6, pad 1 includes polishing layer 10 having polishing surface 11, subpad layer 20, top window portion 30, bottom window portion 40, and support 60. Figure 6 shows polishing surface 11 without microtexture or macrotexture; the polishing surface can include macrotexture, such as grooving or perforations, and microtexture. The groves can be, for example, concentric circular, radial, concentric circular + radial, or any other grove configuration. Figure 6 shows pad 1 including three window regions 2. Other pad configurations not shown can have one window region, two window regions, four window regions, or more than four window regions. Figure 6 shows circular windows in window region 2. However, other shapes, such as oval, rectangular (optionally with curved corners), etc., can be used. Figures 1-5 show cross sections through the thickness of the pad at window regions 2 of various exemplary configurations.

[0020] Abrasive layer 10 has an abrasive surface 11 and an abrasive layer interface 13 opposite abrasive surface 11. Abrasive layer 10 includes an abrasive material 14, such as a porous or non-porous polymer.

[0021] Subpad layer 20 has a subpad interface 23 adjacent polishing layer interface 13 and a bottom surface 21 opposite the subpad interface. Subpad layer 20 includes subpad material 24.

[0022] The upper window portion 30 is located in the opening in the polishing layer 10. The upper window portion includes an upper window material 34. The upper window portion 30 has an abrasive face surface 31 recessed from the polishing surface 11, an upper window interface 33 opposite the abrasive face surface, and an upper window peripheral surface 32 extending from the abrasive face surface 31 to the upper window interface 33.

[0023] The support 60 extends from the polishing layer 10 to the upper window peripheral surface 32. The support 60 includes an upper support surface 61 and a support interface 63 opposite the upper support surface 61. The bottom window portion 40 has a peripheral edge 42 dimension that is larger than the peripheral edge dimension of the upper portion 30, so that the support 60 and the bottom window portion 40 are partially vertically aligned. For example, a portion of the support interface 63 and the bottom window interface 43 can be in direct contact, or an adhesive or bonding layer, such as a pressure-sensitive adhesive (not shown), can physically connect a portion of the bottom window interface 43 and a portion of the support interface 63. When the support is adjacent to the upper window material, the upper support surface 61 can be substantially coplanar with the window polishing face surface 31. The support interface 63 can be substantially coplanar with the polishing layer interface. The support interface 63 can overlap at least a portion of the gap 45. This structure improves flexibility and reduces stress.

[0024] The support 60 can be integral with the abrasive material 14. The support 60 can be of the same composition as the abrasive material 14. Alternatively, the support 60 can comprise a different material than the abrasive material 14. The support 60 can be a separate element attached to the polishing layer 10. The top window portion 30, the support 60, and the polishing layer 10 can form a seal that prevents the passage of slurry or particulates from the polishing side of the pad to the other side of the pad. An adhesive can be used between the top window portion 30 and the support 60. If the support 60 is a separate element attached to the polishing layer 10, an adhesive can be used to facilitate its attachment.

[0025] 1-5 depict the sidewall surface 15 of the abrasive material 14, extending from the abrasive surface 11 to the upper support surface 61, as a vertical surface perpendicular to the upper support surface 61. In alternative forms not shown, this sidewall surface 15 can be at an angle other than a right angle, forming a slope from the abrasive surface 11 to the upper support surface 61, or the sidewall surface 15 can be curved. The upper window recess 3 is defined by the sidewall surface 15, the upper support surface 61, and the abrasive face surface 31 of the upper window portion 30. In particular, the upper window recess is defined by the volume between the sidewall surface 15 and the upper support surface 61 below the plane of the abrasive surface 11 and above the abrasive face surface 31.

[0026] 1-5 including gap 45 but without top window recess 3 would be less flexible and less able to withstand forces during polishing. Additionally, such pads would be more likely to cause scratches on the substrate being polished by the top window portion, since they are typically made of a harder material than the polishing layer.

[0027] The bottom window portion 40 is located in the opening in the subpad layer 20. The bottom window portion 40 includes a bottom window interface 43, a bottom window bottom surface 41, and a bottom window peripheral surface 42 that extends from the bottom window interface 43 to the bottom window bottom surface 41. The bottom window material 44 fills the area defined by the bottom window bottom surface 41, the bottom window peripheral surface 42, and the bottom window interface 43. The bottom window interface 43 and the top window interface 33 can be in direct contact, or an adhesive or bonding layer, such as a pressure-sensitive adhesive (not shown), may physically connect the bottom window interface 43 and the top window interface 33. A gap (or void space) 45 separates the bottom window peripheral surface 42 and the subpad material 24.

[0028] 1 and 2, gap 45 is adjacent to and below support 60 and is not adjacent to or below abrasive material 14. In Figure 3, part of gap 45 is adjacent to (e.g., below) support 60, while part of gap 45 is adjacent to (e.g., below) abrasive material 14. In Figure 4, gap 45 is adjacent to and below abrasive material 14.

[0029] 5 shows an example including an optional sealing layer 52 underlying the bottom window portion 40 and gap 45. The optional sealing layer improves transmission of acoustic signals. In other alternatives not shown, the sealing layer 52 can be underlying only the bottom window portion 40, or the sealing layer 52 can be underlying the bottom window portion 40, gap 45, and subpad layer 20. The sealing layer 52 can be used as an additional feature with any of the embodiments shown in FIGS. 1-4. The sealing layer 52 can be a non-adhesive film. The sealing layer can include a polymer film, such as a polyester film.

[0030] The sealing layer 52 can optionally have a layer of adhesive (not shown) on the bottom surface 21 to facilitate adhesion of the pad 1 to a platen (not shown). The sealing layer can provide one or more of the following advantages: facilitates insertion of the window into the pad with proper alignment; provides a uniform surface on the bottom of the pad; prevents adhesive leakage between the window and the side edges of the polishing layer 10, subpad 20, or both; helps hold the top and bottom window portions 30 and 40 in place, respectively; and prevents slurry leakage to the bottom side of the polishing pad 1. In another alternative, the sealing layer can be adhered to the bottom window surface 41, as shown in FIGS. 1 or 2. Additionally, a sealing layer can be applied to both the bottom window surface of the subpad and the bottom surface of the subpad.

[0031] 1 , support 60 allows for simplified alignment during fabrication of top and bottom window portions 30 and 40, respectively. In particular, window portions 30 and 40 may be first bonded together and then placed within and secured to support support interface 63 of support 60. Adhesives such as epoxy resins and hot melt adhesives are ideal for securing the windows in place. Top window recess 3 isolates window 30 below polishing surface 11. In particular, this reduces stress and eliminates scratches that could otherwise be caused by friction from top window portion 30 against the wafer.

[0032] Referring to Figures 1 and 2, the design of Figure 2 has two major features that distinguish it from Figure 1. First, gap 45 provides a smaller space between bottom window portion 40 and subpad 20. This reduced space improves window alignment for simplified manufacturing. Therefore, the smaller the space, the better the alignment. However, maintaining some space allows for better compression of subpad 20. Second, a portion of support 60 is fixed to subpad 20. By fixing the support to subpad 20, more stress is concentrated on support 60 during polishing. Advantageously, support 60 is constructed from the same material as polishing layer 10 to match its deformation characteristics and eliminate material mismatch stresses that may be accentuated during polishing.

[0033] 2 and 3, FIG. 3 is similar to FIG. 2, except that gap 45 extends below polishing layer 10. This design increases the flexibility of support 60 during polishing. Furthermore, it reduces the compressive force on support 60. Finally, it provides additional space for expansion of bottom window portion 40 and subpad 20 adjacent to the bottom window portion during polishing.

[0034] 1 and 4, Fig. 4 is similar to Fig. 1 except that gap 45 exists only below polishing layer 10. This design increases the stiffness of polishing layer 10 adjacent top window recess 3 and sidewall surface 15. This increased stiffness can reduce reductions in polishing rate due to excessive compression of the polishing layer.

[0035] Referring to the figure, The total thickness of the polishing pad (e.g., polishing layer + subpad) is preferably 4 mm or less. For example, the total thickness of the polishing pad can be 1 to a maximum of 4 mm, 1.5 to a maximum of 4 mm, 1.7 to a maximum of 3.5 mm, or 2 to a maximum of 3 mm. The polishing layer can have a thickness of 0.5 to a maximum of 3 mm, 0.7 to a maximum of 2.5 mm, 1.2 to a maximum of 2.2 mm, or 1 to 2 mm. The subpad can have a thickness of 0.5 to a maximum of 3 mm, 0.7 to a maximum of 2.5 mm, or 1 to 2 mm.

[0036] The depth of the recess (e.g., the vertical difference between the height of the polishing surface 11 and the height of the polishing face surface 31) can be, for example, in the range of 0.05, 0.1, 0.2, or 0.3 mm to a maximum of 1.1 mm, a maximum of 1, a maximum of 0.8 mm, a maximum of 0.6 mm, or a maximum of 0.4 mm.

[0037] The length of the support 60 (i.e., the distance from the polishing layer 10 to the upper window peripheral surface 32) can be, for example, 0.1, 0.3, 0.5, 1, 2, 3, or 4 mm to a maximum of 20, 15, 10, or 5 mm. The thickness of the support 60 can be, for example, 0.4 to 2.5 mm. The thickness of the support 60 where it abuts the upper window portion 30 can be the same as the thickness of the upper window portion 30. The thickness of the support can be the same throughout its entire length, or the thickness may increase slightly toward the polishing layer. The upper window portion 30 can have a thickness of, for example, 0.4 to 2.5 mm and a cross-sectional dimension perpendicular to the thickness of 2, 3, 4, 5, or 6 mm to a maximum of 30, 25, 20, or 15 mm. Bottom window portion 40 can have a thickness of 0.5 up to 3, 0.7 up to 2.5, or 1 to 2 mm, and preferably has a thickness within 0.1 mm of the thickness of subpad layer 20. Bottom window portion 40 can have a cross-sectional dimension perpendicular to its thickness that is larger than the cross-section of the top window portion, such that a portion of bottom window interface 43 is adjacent (i.e., in contact directly or through a bond or adhesive layer) with support interface 63. For example, the cross-sectional dimension perpendicular to the thickness of bottom window portion 40 can be 5%, 10%, 15%, 20%, 30%, 40%, or 50% up to 200%, up to 150%, or up to 100% larger than the cross-sectional dimension of top window portion 30. The gap 45 from the bottom window portion 40 to the subpad material can be from 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, or 5 mm up to 40, up to 30, up to 20, up to 10, up to 9, up to 8, up to 7, or up to 6 mm.

[0038] The upper window material can be a material conventionally used in such windows in polishing pads. This is desirable because the conditioning rate of such conventional materials will already be designed to work well with the conditioning rate of the surrounding polishing material. The upper portion can be relatively rigid (compared to the elastomeric bottom portion of the window) so that the upper portion in the plane of or parallel to the upper polishing surface does not substantially deform during polishing.

[0039] The top window material can be a polymer or polymer blend. For optical detection systems, the top window material should have sufficient transmittance at the wavelength of light used by the optical metrology. This can be useful if the window material has a hardness or thermal expansion coefficient similar to that of the material used in the polishing layer. Examples of top window materials include polyurethane, acrylic polymer, and cyclic olefin copolymer (e.g., TOPAS 8007).

[0040] The upper window portion is advantageously made from an aliphatic polyisocyanate-containing material ("prepolymer"). The prepolymer is the reaction product of an aliphatic polyisocyanate (e.g., a diisocyanate) and a hydroxyl-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include, but are not limited to, methylenebis-4,4'cyclohexylisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, tetramethylene-1,4-diisocyanate, 1,6-hexamethylene-diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-isopropyl ether, ... Examples of suitable aliphatic polyisocyanates include cyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, uretdione of hexamethylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and mixtures thereof. Preferred aliphatic polyisocyanates have less than 10% by weight of unreacted isocyanate groups.

[0041] Advantageously, the curing agent is a polydiamine. Preferred polydiamines include, but are not limited to, diethyltoluenediamine ("DETDA"), 3,5-dimethylthio-2,4-toluenediamine and its isomers, 3,5-diethyltoluene-2,4-diamine and its isomers, such as 3,5-diethyltoluene-2,6-diamine, 4,4'-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) ("MCDEA"), polytetramethyleneoxide-di-p-aminobenzoate, N,N'-dialkyldiamine ... Examples of suitable curing agents include aminodiphenylmethane, p,p'-methylenedianiline ("MDA"), m-phenylenediamine ("MPDA"), methylene-bis-2-chloroaniline ("MBOCA"), 4,4'-methylene-bis-(2-chloroaniline) ("MOCA"), 4,4'-methylene-bis-(2,6-diethylaniline) ("MDEA"), 4,4'-methylene-bis-(2,3-dichloroaniline) ("MDCA"), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 2,2',3,3'-tetrachlorodiaminodiphenylmethane, trimethylene glycol, di-p-aminobenzoate, and mixtures thereof. Preferably, the curing agent of the present invention includes 3,5-dimethylthio-2,4-toluenediamine and its isomers. Suitable polyamine curing agents include both primary and secondary amines.

[0042] Additionally, other curing agents, such as diols, triols, tetraols, or hydroxy-terminated curing agents, may be added to the polyurethane compositions. Suitable diol, triol, and tetraol groups include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, low molecular weight polytetramethylene ether glycol, 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, resorcinol-di-(beta-hydroxyethyl)ether, hydroquinone-di-(beta-hydroxyethyl)ether, and mixtures thereof. Preferred hydroxy-terminated curing agents include 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, and mixtures thereof. Both the hydroxy-terminated and amine curing agents can contain one or more saturated, unsaturated, aromatic, and cyclic groups. Additionally, the hydroxy-terminated and amine curing agents can contain one or more halogen groups. The polyurethane composition can be formed using a blend or mixture of curing agents. However, if desired, the polyurethane composition can be formed using a single curing agent.

[0043] The bottom window portion can comprise a different material than the top window portion. For example, the bottom window material can be less stiff or more compressible than the top window material. The bottom window material can comprise an elastomeric material. As used herein, "elastomeric material" means something that deforms when subjected to a force but substantially returns to its original shape when the force is removed. A gap between at least a portion of the elastomeric material and at least a portion of the subpad material allows the elastomeric material of the bottom portion of the window to deform into the gap when the pad is subjected to a downforce (but substantially returns to its original shape when the downforce is removed). In particular, the thickness of the bottom portion can decrease under a downforce, while the periphery can expand in a direction perpendicular to the downforce. This compression reduces deformation forces on the polishing layer, particularly the polishing surface. The compressibility of the bottom portion can be selected to substantially match the compressibility of the surrounding subpad material, the surrounding polishing material, or both. The window extends to the bottom edge of the pad, thereby avoiding reflection and refraction of the signal wave at the solid / gas or solid / vacuum interface.

[0044] The bottom window material can have a lower modulus of elasticity than the top window material. Desirably, the elastomeric material can have a refractive index and optical transmittance similar to that of the top window layer. A wide range of transparent elastomers can be used, such as polyurethanes, polyolefins, polyamides, polyacrylates, styrenic block copolymers, and silicone elastomers. A preferred family of materials is silicone elastomers. Desirably, the elastomeric material can be easily cast or molded into the appropriate shape.

[0045] CMP pads are manufactured with a variety of polishing layer and subpad layer thicknesses and modulus values. For example, a CMP pad may have a polishing layer with a tensile storage modulus of 300-400 MPa, while the subpad may have a tensile storage modulus of 5-30 MPa. The compressibility of the overall composite is significantly affected by the relative layer thicknesses. The pad design of the present invention allows for a simple method for selecting an appropriate lower window layer material. For example, standard compressibility test methods can be used on test samples of the pad stack and window stack, allowing for rapid compressibility matching prior to any pad fabrication.

[0046] The abrasive material of the abrasive layer 10 can include a polymer. The abrasive material 14 can be opaque throughout the thickness of the abrasive layer 10. Pores can be provided, for example, by the addition of hollow flexible polymer elements (e.g., hollow microspheres), blowing agents, foaming, or supercritical carbon dioxide. Examples of polymeric materials for the abrasive layer include polyurethane, polycarbonate, polysulfone, nylon, polyether, polyester, polystyrene, acrylic polymers, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, epoxy resin, silicone, copolymers thereof (e.g., polyether-polyester copolymers), and combinations or blends thereof. The abrasive layer can include a polymer that is a polyurethane formed by the reaction of one or more polyfunctional isocyanates with one or more polyols. For example, a polyisocyanate-terminated urethane prepolymer can be used. The polyfunctional isocyanate used to form the polishing layer of the chemical mechanical polishing pad of the present invention can be selected from the group consisting of aliphatic polyfunctional isocyanates, aromatic polyfunctional isocyanates, and mixtures thereof. For example, the polyfunctional isocyanate used to form the polishing layer of the chemical mechanical polishing pad of the present invention can be a diisocyanate selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, para-phenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and mixtures thereof. The polyfunctional isocyanate can be an isocyanate-terminated urethane prepolymer formed by reacting a diisocyanate with a prepolymer polyol.The isocyanate-terminated urethane prepolymer can have 2 to 12 weight percent, 2 to 10 weight percent, 4 to 8 weight percent, or 5 to 7 weight percent unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the polyfunctional isocyanate-terminated urethane prepolymer can be selected from the group consisting of diols, polyols, polyol diols, copolymers thereof, and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of polyether polyols (e.g., poly(oxytetramethylene) glycol, poly(oxypropylene) glycol, and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. For example, the prepolymer polyol can be selected from the group consisting of polytetramethylene ether glycol (PTMEG), ester-based polyols (ethylene adipate, butylene adipate, etc.), polypropylene ether glycol (PPG), polycaprolactone polyols, copolymers thereof, and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of PTMEG and PPG. When the prepolymer polyol is PTMEG, the isocyanate-terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 2 to 10 wt % (more preferably 4 to 8 wt %; most preferably 6 to 7 wt %).Examples of commercially available PTMEG-based isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., e.g., PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, and PET-75D); Adiprene® prepolymers (available from Chemtura, e.g., LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D, and L325); and Andur® prepolymers (available from Anderson Development Available from Polypropylene Glycol Company, for example, 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, and 75APLF. When the prepolymer polyol is PPG, the isocyanate-terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 3 to 9 wt % (more preferably 4 to 8 wt %, and most preferably 5 to 6 wt %). Examples of commercially available PPG-based isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., e.g., PPT-80A, PPT-90A, PPT-95A, PPT-65D, PPT-75D); Adiprene® prepolymers (available from Chemtura, e.g., LFG 963A, LFG 964A, LFG 740D); and Andur® prepolymers (available from Anderson Development Company, e.g., 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). The isocyanate-terminated urethane prepolymer can be a low-free isocyanate-terminated urethane prepolymer having a free toluene diisocyanate (TDI) monomer content of less than 0.1% by weight. Non-TDI-based isocyanate-terminated urethane prepolymers can also be used.For example, isocyanate-terminated urethane prepolymers, including those formed by the reaction of a polyol such as 4,4'-diphenylmethane diisocyanate (MDI) and polytetramethylene glycol (PTMEG) with an optional diol such as 1,4-butanediol (BDO), are acceptable. When such isocyanate-terminated urethane prepolymers are used, the unreacted isocyanate (NCO) concentration is preferably 4 to 10 wt%, more preferably 4 to 10 wt%, and most preferably 5 to 10 wt%. Examples of commercially available isocyanate-terminated urethane prepolymers in this category include Imuthane® prepolymers (available from COIM USA, Inc., e.g., 27-85A, 27-90A, 27-95A); Andur® prepolymers (available from Anderson Development Company, e.g., IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP); and Vibrathane® prepolymers (available from Chemtura, e.g., B625, B635, B821).

[0047] The subpad 20 can include a polymeric material. The subpad material 24 can be more compliant (more elastic) than the abrasive material. The subpad 20 can include a porous layer. Examples of polymeric materials for the subpad layer include polyurethane, polycarbonate, polysulfone, nylon, epoxy resin, polyether, polyester, polystyrene, acrylic polymer, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, silicone, copolymers thereof (e.g., polyether-polyester copolymers), and combinations or blends thereof.

[0048] Polishing pads as disclosed herein can be prepared through a variety of processes, including inserting a separate window assembly into a pad with a matching opening, adding a lower window component to a pad where the upper window component is already cast in place in the upper pad layer, or inserting the window assembly into a net-shape mold used to prepare the upper pad layer blank, followed by lamination of a subpad and optional application of a pressure-sensitive adhesive.

[0049] For example, a plug containing the material for the upper portion of the window can be placed in a mold, and the abrasive material can be formed into a block or cake around the plug. The block or cake can then be sliced ​​into layers having the desired thickness of the abrasive layer. The bottom portion of the window can be applied to the surface of the upper portion of the window. For example, a pre-formed bottom portion can be glued, or the bottom portion can be cast or molded. A subpad can be laminated or cast onto the bottom surface of the abrasive layer.

[0050] A window assembly having a top portion and a bottom portion as described herein can be placed in a mold, and an abrasive layer can be formed around the relevant portions. A subpad can then be applied by lamination.

[0051] As another example, the polishing pads disclosed herein can be manufactured by providing a window assembly in a mold having a recess in the mold to hold at least a portion of the bottom portion of the window, and molding a polishing layer around the portion of the window that protrudes into the mold cavity. This forms a polishing layer with a recessed plug, with a portion of the plug protruding beyond the polishing layer. To form the subpad portion of the pad, a subpad can be molded in a second molding step in a separate mold, provided that the subpad includes a spacer to provide clearance.

[0052] If desired, recesses for window areas 2 are cut into the top surface of the pad. The polishing layer 10 can also be cut to provide a macrotexture. Cutting to form the recesses can be done, for example, by milling using a CNC mill or other machining device configured to cut polymers.

[0053] A method of using the polishing pad disclosed herein includes providing a substrate to be polished, providing a polishing pad disclosed herein, optionally providing a slurry on the polishing pad, contacting the polishing pad with the substrate, moving the substrate and the polishing pad relative to each other (e.g., in a rotational motion), transmitting a signal wave through a window, and detecting the signal wave reflected from the substrate and returned through the window to determine when polishing is complete. When optical detection is used, the use of a translucent slurry is preferred. This method can use optical signal waves, vibration (e.g., acoustic) signal waves, or both optical and vibration signal waves.

[0054] The present disclosure further includes the following aspects.

[0055] Aspect 1: A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer), comprising a polishing layer, a subpad layer, a top window portion, a bottom window portion, and a support. The polishing layer has a polishing surface and a polishing-layer interface opposite the polishing surface. The polishing layer comprises a polishing material. The subpad layer has a subpad interface adjacent the polishing-layer interface and a bottom surface opposite the subpad interface. The subpad layer comprises a subpad material. The top window portion comprises the top window material and has a polishing face surface preferably recessed from the polishing surface, a top window interface opposite the polishing face surface, and a top window peripheral surface extending from the polishing face surface to the top window interface. The support extends from the polishing layer toward the top window peripheral surface and is adjacent to the top window peripheral surface. The support comprises an upper support surface and a support interface opposite the upper support surface. The bottom window portion has a bottom window interface, a bottom window bottom surface, and a bottom window peripheral surface extending from the bottom window interface to the bottom window bottom surface, and the area defined by the bottom window bottom surface, the bottom window peripheral surface, and the bottom window interface is filled with bottom window material. The bottom window interface is adjacent to the top window interface and adjacent to at least a portion of the support interface. The pad includes a gap between the bottom window peripheral surface and the subpad material.

[0056] Embodiment 2: The polishing pad of embodiment 1, wherein an upper portion of the gap is defined by a support interface.

[0057] Embodiment 3: The polishing pad of embodiment 1, wherein an upper portion of the gap is defined by a support interface and a polishing interface.

[0058] Embodiment 4: The polishing pad of any one of the preceding embodiments, wherein the upper support surface is coplanar with the polishing face surface of the upper window portion.

[0059] Embodiment 5: The polishing pad of any one of the preceding embodiments, wherein the bottom window material is an elastomer.

[0060] Embodiment 6: The polishing pad of any one of the preceding embodiments, wherein the support interface is coplanar with the polishing layer interface, the top window interface, or both.

[0061] Embodiment 7: The polishing pad of any one of the preceding embodiments, wherein a seal is formed between the support and the top window material.

[0062] Embodiment 8: The abrasive layer of any one of the preceding embodiments, wherein the support is integral with the abrasive layer.

[0063] Aspect 9: The polishing layer of any one of the preceding aspects, wherein the top window material and the bottom window material are transparent to radiation used for optical signals, such that the polishing pad is suitable for both optical and vibrational endpoint detection.

[0064] Aspect 10: A polishing method comprising providing a substrate to be polished, providing a polishing pad described in any one of the previous aspects, providing a slurry on the polishing pad, moving the substrate relative to the polishing pad, transmitting a signal wave through a window material, and detecting the signal wave reflected from the substrate and returned through the window and the slurry to determine when polishing is complete, wherein the signal wave is an optical wave, an acoustic wave, or both.

[0065] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., the range "up to 25% by weight, and more specifically, 5% to 20% by weight" includes the endpoints and all intermediate values ​​in the range "5% to 25% by weight," etc.).

[0066] Furthermore, the listed upper and lower limits can be combined to form ranges (e.g., "at least 1 wt. % or at least 2 wt. %" and "up to 10 wt. % or 5 wt. %" can be combined to form the ranges "1-10 wt. %" or "1-5 wt. %" or "2-10 wt. %" or "2-5 wt. %").

[0067] As used herein when describing surfaces or portions, "adjacent" means in direct contact or next to each other but separated only by a bonding or adhesive layer.

[0068] The present disclosure can either comprise, consist of, or consist essentially of any suitable components disclosed herein. The present disclosure can additionally or alternatively be formulated to be free or substantially free of any components, materials, ingredients, adjuvants, or species used in prior art compositions or that are not necessary to achieve the function and purpose of the present disclosure.

[0069] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety, except that if a term in an incorporated reference conflicts or conflicts with a term in the present application, the term in the present application takes precedence over the conflicting term in the incorporated reference.

[0070] Unless otherwise specified herein, all test standards are the latest standards in effect as of the filing date of this application or, if priority is claimed, as of the filing date of the earliest priority application in which the test standard appears. [Explanation of symbols]

[0071] 1 pad 2 Window Area 3 Upper window recess 10 Polishing layer 11 Polished surface 13 Polishing layer interface 14 Abrasive materials 15 Side wall 20 Subpad Layer 21 Bottom 23 Subpad interface 24 Subpad material 30 Upper window part 31 Polished face 32 Upper window periphery 33 Upper window interface 34 Upper window material 40 Bottom window part 41 Bottom window bottom 42 Bottom window periphery 43 Bottom window interface 44 Bottom Window Material 45 Gap 52 Sealing layer 60 Support 61 Upper support surface 63 Support interface

Claims

1. A polishing pad 1 for chemical mechanical polishing, a polishing layer 10 having an abrasive surface 11 and an abrasive-layer interface 13 opposite said abrasive surface 11, said abrasive layer 10 comprising an abrasive material 14; a subpad layer (20) having a subpad interface (23) adjacent said polishing layer interface (13) and a bottom surface (21) opposite said subpad interface, said subpad layer (20) comprising a subpad material (24); an upper window portion 30 including an upper window material 34 having a polishing face surface 31 recessed from said polishing surface 11, an upper window interface 33 opposite said polishing face surface, and an upper window peripheral surface 32 extending from said polishing face surface 31 to said upper window interface 33; a support 60 extending from the polishing layer 10 toward and adjacent the upper window peripheral surface 32, the support 60 including an upper support surface 61 and a support interface 63 opposite the upper support surface 61; a bottom window portion 40 having a bottom window interface 43, a bottom window bottom surface 41, and a bottom window peripheral surface 42 extending from the bottom window interface to the bottom window bottom surface, the area defined by the bottom window bottom surface 41, the bottom window peripheral surface 42, and the bottom window interface 43 being filled with a bottom window material 44, the bottom window interface 43 being adjacent to the top window interface 33 and adjacent to at least a portion of the support interface 63; and including a gap 45 between said bottom window peripheral surface 42 and said subpad material.

2. The polishing pad of claim 1 , wherein an upper portion of the gap is defined by the support interface.

3. The polishing pad of claim 1 , wherein an upper portion of the gap is defined by the support interface and the polishing interface.

4. The polishing pad of claim 1 , wherein the upper support surface is coplanar with the polishing face surface of the upper window portion.

5. The polishing pad of claim 1 , wherein the bottom window material is an elastomer.

6. 10. The polishing pad of claim 1, wherein the support interface is coplanar with the polishing layer interface, the top window interface, or both.

7. The polishing pad of claim 1 , wherein a seal is formed between the support and the top window material.

8. The polishing pad of claim 1 , wherein the support is integral with the polishing layer.

9. 10. The polishing pad of claim 1, wherein the top window material and the bottom window material are transparent to radiation used for optical signals, such that the polishing pad is suitable for both optical and vibrational endpoint detection.

10. Providing a substrate to be polished; Providing the polishing pad of claim 1; providing a slurry on the polishing pad; moving the substrate relative to the polishing pad; transmitting a signal wave through the window material; and detecting the signal wave reflected from the substrate and back through the window and slurry to determine when polishing is complete. A polishing method comprising:

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