Multifunctional endpoint detection window

Abstract

To provide a multifunctional endpoint detection window.SOLUTION: A polishing pad for chemical mechanical polishing includes: a top window material, which is transparent to light, and which forms a seal with a polishing material, with a subpad material, or both; a bottom window material, having a void space inward from a peripheral surface if the bottom window material exists. The void space is aligned to allow light passing through a top window portion with respect to the void space enabling optical end-point detection. Vibrational signals can be transmitted through the top window material or the polishing material and through the bottom window material enabling acoustic end-point detection.SELECTED DRAWING: Figure 2A

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 type of polishing process widely used to flatten or planarize the building layers of integrated circuits or similar structures. Specifically, CMP is frequently used to produce flat, uniform layers of a specified thickness in the fabrication of three-dimensional circuit structures through additive deposition and planarization. CMP can remove excess material deposited on the substrate (e.g., wafer) surface to produce extremely flat layers of uniform thickness, with uniformity prevailing across the entire substrate (e.g., wafer) area. When uniform thickness prevails across the entire wafer, this is known as global uniformity.

[0003] CMP uses 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 pad surface under a controlled load. This can result in high relative motion between the substrate (e.g., wafer) and the polishing pad, resulting in high shear or wear rates on both the substrate and the pad surface. Slurry particles trapped at the shear and pad / substrate interface abrade the substrate (e.g., wafer) surface, removing material from the substrate surface. Removal rate control and uniformity are important. Additionally, it is 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 called endpoint detection.

[0004] Various types of film thickness metrology, along with real-time control software, can be used for endpoint detection. Endpoint detection processes periodic signals, such as collimated, non-collimated, or acoustic signals, to avoid wafer yield problems resulting 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 a polishing pad. The light reflects off the polished substrate, and the reflected light 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 equipment can be located inside the body of the polishing machine or the platen that holds the pad.

[0005] For certain pad structures where optical detection is used, the pad material itself may be transparent to the desired optical wavelength and / or have a design that allows effective transmission of the signal wave. Alternatively, the pad may include alternative structures that promote wave transmission. For example, a transparent polymer may be provided, and an opaque material may be formed around such a polymer to create a transparent window. See, for example, U.S. Patent No. 5,629,994. As another example, an opening may be provided through the entire pad. See, for example, U.S. Patent No. 5,629,994 and U.S. Patent No. 5,629,994. A third approach is to form a pad with an opening into which a transparent window material is inserted and held in place with an adhesive. See, for example, U.S. Patent No. 5,629,994. Various versions of polishing pads with windows have been proposed. See, for example, Patent Documents 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, and 27.

[0006] Transmission of the signal wave through the boundary between the void (e.g., air) and the window surface can cause refraction or reflection of the signal wave, which can create 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, for example, U.S. Patent No. 5,929,994.

[0007] For transmission of other vibration waves, such as acoustic waves, non-porous windows are used, see, for example, U.S. Patent Nos. 5,629,997 and 5,629,997.

[0008] Additionally, because the window is typically formed from a material separate from the polishing layer, other problems can arise. Specifically, the modulus and resistance of the solid polymer window material are typically higher than those of the surrounding composite pad, resulting in differential compression during the polishing process, resulting in deformation near the window. The problem can be further exacerbated by differences in the coefficient of thermal expansion (CTE) and thermal conductivity (K) between the polishing material and the window. As the top surface of the pad and the window heat up due to friction during CMP, the differences in CTE and K cause additional overstress and overdeformation. This can cause the window region to protrude above the top surface of the pad's polishing area during use. The protruding window can scratch the polished substrate. Additionally, the voids in the surrounding area around the protruding area act as traps for slurry, conditioning debris, and other foreign contaminants, which can also increase the scratch defect rate. Furthermore, the pad is conditioned during use, and the conditioning wear rate is significantly higher in the raised areas due to increased contact pressure. Such differential window thinning can interfere with the optical signal and ultimately cause the window to break, a catastrophic failure that shortens the life 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 Application Publication 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 an improved polishing pad having a window area for use in endpoint detection that is useful for multiple endpoint detection systems. [Means for solving the problem]

[0012] Disclosed herein is a polishing pad for chemical mechanical polishing, comprising a polishing layer, a subpad, and a window region extending through the pad. The polishing layer has a polishing surface, a polishing-layer interface opposite the polishing surface, and the polishing layer comprises an abrasive. The subpad layer has a subpad interface adjacent to the polishing-layer interface and a bottom surface opposite the subpad interface, and the subpad layer comprises a subpad material. The window region includes: (a) an optically transparent top window material, the top window material having a polishing surface, a top window peripheral surface, and a top window interface, the top window peripheral surface forming a seal with the abrasive, with the subpad interface, or with both, and (b) a bottom window portion, the bottom window portion comprising a bottom window material having a bottom window interface adjacent to the top window interface or the polishing-layer interface, a bottom window peripheral surface, a bottom window bottom surface, and a void space inward from the bottom window peripheral surface. The void space is aligned so that light passing through the top window portion can pass through the void space and into the polishing pad, allowing for optical endpoint detection. A vibration signal can be transmitted through the top window material or the abrasive material and through the bottom window material, allowing for acoustic endpoint detection.

[0013] Also disclosed herein is a method including providing a substrate to be polished, providing a polishing pad described herein, providing a slurry on the polishing pad, polishing the substrate by moving it relative to the polishing pad, and monitoring the polishing by (a) transmitting light waves through the top window material and the void and detecting light waves reflected from the substrate, (b) transmitting a vibration signal through the top window material, the polishing layer material, or both, through the bottom window material, or both (a) and (b).

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

[0015] [Figure 1] FIG. 2 is a top view of an example chemical mechanical polishing pad including a window. [Figure 2A] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 2B] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 2C] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 2D] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 3A] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 3B] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 3C] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 3D] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 4A] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 4B] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 4C] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 4D] 1 is a cross-sectional view through the thickness of a portion of a chemical mechanical polishing pad around a window region showing an example of a pad structure including a two-component window as disclosed herein. [Figure 5] 3C is a cross-sectional view parallel to the bottom plane through the subpad and bottom window portion of the polishing pad showing an example of the placement of the bottom window material as in FIG. 3B. [Figure 6] 3C is a cross-sectional view parallel to the bottom plane through the subpad and bottom window portion of the polishing pad showing an example of the placement of the bottom window material as in FIG. 3B. [Figure 7] 2D is a cross-sectional view taken parallel to the bottom plane through the subpad and bottom window portion of the polishing pad, showing an example of a bottom window material placement such as in FIG. 2D. DETAILED DESCRIPTION OF THE INVENTION

[0016] Disclosed herein is a polishing pad useful for chemical mechanical polishing. The polishing pad can be used for endpoint detection using various types of signal waves. Specifically, the polishing pad can be used for optical detection using cylindrical or non-cylindrical light, and the polishing pad can be used for vibration detection using, for example, acoustic waves. This is achieved by a window region that includes a path for transmitting light through the pad and a material for transmitting a vibration signal (e.g., acoustic wave) through the pad.

[0017] 1, for example, polishing pad 1 includes polishing surface 11 and may include grooves 12. A window area 100 is seen in pad 1. As shown in FIG. 1, the window area has a circular perimeter; however, other perimeter shapes, such as an oval, a rectangle (including a rectangle with curved corners), etc., can be used.

[0018] For example, as shown in Figures 2A-2D, 3A-3D, and 4A-4D, which show cross sections through the thickness of pad 1 in the area around window area 100, pad 1 includes polishing layer 10 with polishing surface 11, abrasive material 14 having polishing-layer interface 13. Pad 1 also includes subpad layer 20 with subpad material 24, having subpad bottom surface 21 and subpad interface 23. Subpad interface 23 can be in direct contact with polishing-layer interface 13, or an adhesive or bonding layer (not shown) can be used to connect polishing layer 10 to subpad layer 20.

[0019] The window region 100 includes an upper portion that includes an upper window material 30. The upper window has a polishing surface 31 and an upper window interface 33 opposite the polishing surface 31, and an upper window peripheral surface 32 extending from the polishing surface 31 to the upper window interface 33. The upper window material 30 forms a seal with the polishing layer material 14, the subpad interface 23 (e.g., as in FIG. 2A ), or both. The seal is formed to prevent particles or liquids used in chemical mechanical polishing from passing from above the polishing layer to below the subpad layer or below the window. Slurry below the subpad negatively impacts polishing uniformity. Slurry below the window interferes with and reduces the strength of the endpoint signal intensity. Preferably, the window material 30 forms a seal with the polishing layer material 14. For example, the upper window peripheral surface 32 can be in direct contact with the polishing layer material 14, or an adhesive (not shown) can be used to hold the upper window material 30 in place. The upper window material 30 can be in direct contact with a portion of the subpad material 24, or an adhesive (not shown) can bond the subpad material 24 to the upper window material 30 (see, e.g., FIG. 2A, where the upper window interface 33 can form a seal with the subpad interface). Alternatively, the upper window material 30 can have no contact with the subpad material 24 (see, e.g., FIG. 2C). The polishing surface 31 can be flush with the polishing surface 11, but is preferably recessed from the polishing surface, as shown in FIGS. 2A-2D, 3A-3D, and 4A-4D, where a recess 15 is preferably present.

[0020] The window further includes a bottom portion comprising a bottom window material 40. The bottom window material 40 has a bottom window interface 43, a bottom window bottom surface 41, and a bottom window peripheral surface 42 extending from the bottom window interface 43 to the bottom window bottom surface 41.

[0021] The bottom window material 40 has a void region 44 inside the bottom window material 40 extending from the bottom window interface 43 to the bottom window interface 41. This void facilitates the transmission of light through the window region. The bottom window material 40 facilitates the transmission of vibration signals through the pad. For example, as shown in FIGS. 2D and 7, the bottom window peripheral surface 42 can contact the subpad material 24. However, it is preferred that there be a void 45 between at least a portion of the bottom window peripheral surface 42 and the subpad material 24. Furthermore, channels connecting the peripheral voids 45 to the central void region 44 exist between the four bottom window material regions 40. More preferably, there is a void 45 between the bottom window peripheral surface 42 and the subpad material 24 such that there is no contact between the bottom window peripheral surface 42 and the subpad material 24, as shown, for example, in FIGS. 2A-2C, 3A-3D, 4A-4D, 5, and 6.

[0022] The top window material 30 may have larger dimensions (e.g., diameter or width and length) than the bottom window material 40 and the bottom window portion comprising the void 44 (see, e.g., FIGS. 2A and 4C). Alternatively, the top window material 30 may have the same dimensions (e.g., diameter or width and length) as the bottom window material, the void 44, and the optional void 45 (see, e.g., FIG. 2B). In yet another alternative, the top window material 30 may have smaller dimensions (e.g., diameter or width and length) than the bottom window material 40 and the bottom window portion comprising the void 44 (see, e.g., FIGS. 2C, 3B-3D, 4A-4B, and 4D).

[0023] The bottom window material 40 is positioned only below and adjacent to the top window material 30, for example, as shown in Figures 2A-2D and 3A, and such that the top window interface 33 contacts the bottom window interface 43, or these surfaces are joined together with an adhesive (not shown). Alternatively, the bottom window material 40 is positioned only below and adjacent to the abrasive 14, for example, as shown in Figures 3B and 3C, and such that the abrasive layer interface 13 contacts the bottom window interface 43, or these surfaces are joined together with an adhesive (not shown). As another alternative, a portion of the bottom window material 40 is positioned below and adjacent to the abrasive 14, and another portion of the bottom window material 40 is positioned below and adjacent to the top window material 30. For example, in Figures 3D, 4A, 4B, and 4D, a portion of bottom window interface 43 contacts polishing layer interface 13, or these surfaces are bonded together with an adhesive (not shown), and a portion of bottom window interface 43 contacts top window interface 33, or these surfaces are bonded together with an adhesive (not shown).

[0024] The bottom window material 40 can be a monolithic window material having a void (or through-hole) 44 extending from the bottom window interface 43 to the bottom window surface 41. For example, as shown in Figure 5, the bottom window material 40 can have an annular shape. However, other shapes such as ovals, rectangles, hexagons, etc. with through-holes can be used. In alternative configurations, the bottom window material 40 can include rectangular shapes as shown in Figure 6, or individual cylindrical structures such as arcs, wedges, cylinders, etc.

[0025] As shown in FIGS. 2A-2D, 3A-3D, and 4B-4D, optional encapsulation layer 50 may be present below bottom window surface 41. Alternatively, no encapsulation layer 50 is required (see, e.g., FIG. 4A). Optional encapsulation layer 50 may be disposed only adjacent to (only below) bottom window material 40 (see, e.g., FIGS. 2A-2D, 3A-3D). Alternatively, optional encapsulation layer 50 may extend from void 44 to subpad material 24, as shown in FIG. 4B, for example. Alternatively, optional encapsulation layer 50 may extend continuously from subpad material 24 across optional void 45, bottom window surface 41, and void 44, as shown in FIG. 4C. Alternatively, optional encapsulation layer 50 may extend across the entire bottom of the pad forming the bottom pad surface, as shown in FIG. 4D. The encapsulation layer is optional in all configurations, and configurations disclosed herein include those that do, such as those in Figures 2A-2D and 3A-3D, but those that do not, such as those in Figure 4A, have a bottom window bottom surface 41 that is flush with the subpad bottom surface 21. Also disclosed herein are configurations like those in Figures 2A-2D and 3A-3D, but in which the encapsulation layer 50 extends from the void 44 to the subpad material 24, as in Figure 4B (not shown). Also disclosed herein are configurations like those in Figures 2A-2D and 3A-3D, but in which the encapsulation layer 50 extends from the subpad material 24 to the subpad material across the entire window area, including the void 44, as in Figure 4C (not shown). 2A-2D and 3A-3D, but in which the encapsulation layer 50 extends across the entire bottom of the pad forming the bottom pad surface, as in FIG. 4D (not shown). For structures in which the encapsulation layer 50 extends across the air gap 44, the encapsulation layer is transparent to light intended to be used for optical signal transmission.

[0026] The overall thickness of the polishing pad (e.g., the polishing layer plus the subpad) is preferably 4 mm or less. For example, the overall 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. The thickness of the top window material can be, for example, 0.3 to a maximum of 3.2 mm, 0.4 to a maximum of 2.7 mm, 0.8 to a maximum of 2.2 mm, or 1 to 1 mm, while the thickness of the bottom window material can be 0.3 to a maximum of 3.2 mm, 0.4 to a maximum of 2.7 mm, 0.8 to a maximum of 2.2 mm, or 1 to 1 mm, as long as the overall thickness of the window does not exceed the overall thickness of the pad. The top window material may have a diameter (or length and width) of from 2 mm, 3 mm, or 4 mm up to 30 mm, up to 25 mm, up to 20 mm, up to 15 mm, or up to 10 mm. The distance from the bottom window peripheral surface 42 to the opposing bottom window peripheral surface 42 may be from 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm up to 75 mm, up to 70 mm, up to 60 mm, up to 50 mm, up to 40 mm, up to 30 mm, or up to 20 mm. The gap 44 inward from the bottom window peripheral surface 42 necessarily has a dimension smaller than the distance from the bottom window peripheral surface 42 to the opposing bottom window peripheral surface 42, but may have a dimension greater than 1 mm, greater than 2 mm, greater than 3 mm, greater than 4 mm, greater than 5 mm, greater than 6 mm, greater than 7 mm, greater than 8 mm, greater than 9 mm, or greater than 10 mm, up to 40 mm, up to 38 mm, up to 35 mm, up to 30 mm, up to 25 mm, or up to 20 mm, in a direction parallel to the polishing surface 11. The gap 45 from the bottom window peripheral surface 42 to the subpad material may be 0 mm, or may be from 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm to 40 mm, up to 35 mm, up to 30 mm, up to 25 mm, up to 20 mm, up to 15 mm, up to 10 mm, or up to 5 mm.

[0027] The depth of recess 15 can be, for example, greater than 0.1 millimeters (mm), greater than 0.2 mm, or at least 0.3 mm and up to 1.1 mm, 1 mm, 0.8 mm, 0.6 mm, or 0.4 mm. Having a thinner abrasive material in the peripheral portion of the polishing layer adjacent to upper window material 30 than in other areas of pad 100, as shown in FIGS. 2A-2D, 3A-3D, and 4A-4D, can facilitate flexibility during use. Similarly, the width of the peripheral portion can be tailored to provide the desired mechanical response for the pad material and design. The width of the peripheral region can be, for example, at least 0.05 millimeters (mm), at least 0.1 mm, at least 0.2 mm, or at least 0.3 mm and up to 1.1 mm, 1 mm, 0.8 mm, 0.6 mm, or 0.4 mm.

[0028] The top window material 30 can include a polymer or a blend of polymers. For optical detection systems, the top material 30 must have sufficient transmittance at the wavelength of light used for optical metrology. It can be useful if the top window material 30 has a hardness or thermal expansion coefficient similar to that of the material used in the polishing layer. Examples of window materials include polyurethane, acrylic polymers, and cyclic olefin copolymers (e.g., TOPAS 8007).

[0029] The upper window material 30 can be made from an aliphatic polyisocyanate-containing material ("prepolymer"). The prepolymer is the reaction product of an aliphatic polyisocyanate (e.g., diisocyanate) and a hydroxy-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include methylene bis-4,4'cyclohexyl isothiocyanate, 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-isocyanate-3,3, Preferred aliphatic polyisocyanates include, but are not limited to, 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.

[0030] The curing agent may be a polydiamine. Preferred polydiamines include diethyltoluenediamine (DETDA), 3,5-dimethylthio-2,4-toluenediamine and their isomers, 3,5-diethyltoluene-2,4-diamine and their 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'-dialkyldiaminodiphenylmethane, p,p'-methylene Examples of suitable curing agents include, but are not limited to, toluene-dianiline ("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 isomers thereof. Suitable polyamine curing agents include both primary and secondary amines.

[0031] In addition, other curing agents, such as diols, triols, tetraols, or hydroxy-terminated curing agents, may be added to the polyurethane compositions described above. 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-(β-hydroxyethyl)ether, hydroquinoline-di-(β-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 curing agent and the amine curing agent may contain one or more saturated, unsaturated, aromatic, and cyclic groups. Furthermore, the hydroxy-terminated curing agent and the amine curing agent may contain one or more halogen groups. The polyurethane composition may be formed using a blend or mixture of curing agents. However, if desired, the polyurethane composition may be formed using a single curing agent.

[0032] The bottom window material 40 may be a polymer material. Preferably, the bottom window material 40 comprises an elastomeric material. As used herein, "elastomeric material" means one that deforms when subjected to a force but substantially returns to its original shape when the force is removed. The voids 44 and, preferably, 45 allow the elastomeric material at the bottom portion of the window to deform into the void when the pad is under downforce (but substantially return to its original shape when the downforce is removed). In particular, the thickness of the bottom portion may decrease under downforce, while the periphery may 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 may be selected to substantially match the compressibility of the surrounding subpad material, the surrounding abrasive material, or both. Because the window extends to the bottom edge of the pad, reflection and refraction of signal waves at solid / gas or solid / vacuum interfaces are avoided.

[0033] The elastomeric material of the bottom window material 40 preferably has a lower modulus of elasticity than the first window material 30. Desirably, the elastomeric material may have a refractive index and optical transmittance similar to that of the top window layer. A wide variety of transparent elastomers may be used, such as polyurethanes, polyolefins, polyamides, polyacrylates, styrenic block copolymers, and silicone elastomers. A preferred family of materials is silicone elastomers. Elastomeric materials that can be easily cast or molded into the appropriate shape are desirable.

[0034] The polishing layer 10 may have a tensile storage modulus of, for example, 300-400 MPa, while the subpad layer 20 may have a tensile storage modulus of, for example, 5-30 MPa. The overall composite compressibility 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 manufacturing.

[0035] The abrasive layer material 14 may include a polymer. The abrasive may be opaque through the thickness of the abrasive layer 101. Pores may be provided, for example, by the addition of hollow flexible polymer elements (e.g., hollow microspheres), blowing agents, frothing, 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 may 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 may 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 isocyanate, 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 may 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 may 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 may be selected from the group consisting of PTMEG and PPG. When the prepolymer polyol is PTMEG, the isocyanate-terminated urethane prepolymer may 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., LF800A, LF900A, LF910A, LF930A, LF931A, LF939A, LF950A, LF952A, LF600D, LF601D, LF650D, LF667, LF700D, 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 may 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 PPT-80A, PPT-90A, PPT-95A, PPT-65D, and PPT-75D available from COIM USA, Inc.; Adiprene® prepolymers (LFG963A, LFG964A, and LFG740D available from Chemtura); and Andur® prepolymers (8000APLF, 9500APLF, 6500DPLF, and 7501DPLF available from Anderson Development Company). The isocyanate-terminated urethane prepolymer may 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 such as those formed by reacting 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%, most preferably 5 to 10 wt%). Examples of commercially available isocyanate-terminated urethane prepolymers in this category include Imuthane® prepolymers (e.g., 27-85A, 27-90A, 27-95A, etc., available from COIM USA, Inc.); Andur® prepolymers (e.g., IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP, etc., available from Anderson Development Company); and Vibrathane® prepolymers (e.g., B625, B635, B821, etc., available from Chemtura).

[0036] The subpad material 24 may include a polymeric material. The subpad material may be more compliant (or more elastic) than the abrasive material. The subpad 102 may 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.

[0037] The optional encapsulation layer 50 can provide one or more of the following benefits: facilitating insertion of the window 103 into the pad with proper alignment; providing a uniform surface to the bottom of the pad; preventing any adhesive from leaking between the side edges of the window 103 and the polishing layer 101, the subpad 102, or both; helping to hold the window 103 in place; and preventing any slurry from leaking to the bottom side of the polishing pad 1. The encapsulation layer can be, for example, a polymer such as polyester. The encapsulation layer can be a non-adhesive layer. The encapsulation layer can have a thickness of, for example, from 0.025 mm, from 0.05 mm, from 0.1 mm, to a maximum of 1 mm.

[0038] Polishing pads as disclosed herein can be made by 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 that already has a cast in the upper window component in place in the upper pad layer, or inserting the window assembly into a net-shaped mold that is used to make the upper pad layer blank followed by lamination of the subpad.

[0039] For example, a plug with a top window material 30 can be placed in a mold and the abrasive layer material 14 can be molded 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. If desired, a recess 15 can be machined after slicing the block. Alternatively, if individual layers are molded around the window with the top window material 30, the mold can include a shape to provide the recess 15. The layer with the subpad material 24 can have a window opening punched therethrough. The subpad material can be laminated to the abrasive layer material. The bottom window material 40 and optional encapsulation layer 50 can be inserted before or after lamination. Adhesives can be used to promote bonding during lamination. An optional pressure-sensitive adhesive can be applied to the bottom of the pad to promote adhesion of the pad to the platen during polishing.

[0040] Alternatively, a window assembly having a top and bottom portion as described herein can be placed in a mold, and the polishing layer can be formed around the relevant portion. A subpad can then be applied by lamination.

[0041] As another example, a polishing pad as disclosed herein can be made by applying a window assembly into a mold having a recess therein to hold at least a portion of the bottom 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 an embedded plug, with a portion of the plug protruding beyond the polishing layer. To form the subpad portion of the pad, the subpad can be molded in a separate mold in a second molding step if the mold includes a spacer to provide a gap.

[0042] A method for using a polishing pad as disclosed herein includes providing a substrate to be polished, providing a polishing pad as disclosed herein, and 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 through the window to determine when polishing is complete. When optical detection is used, the use of a translucent slurry is preferred. According to a preferred method, during polishing, both optical detection (e.g., cylindrical or non-cylindrical light waves) and vibration detection (e.g., acoustic waves) are used during the polishing of a single substrate.

[0043] The present disclosure further includes the following aspects.

[0044] Aspect 1: A polishing pad for chemical mechanical polishing, comprising: a polishing layer having a polishing surface and a polishing-layer interface facing the polishing surface, the polishing layer comprising an abrasive; a subpad layer having a subpad interface adjacent to the polishing-layer interface and a bottom surface facing the subpad interface, the subpad layer comprising a subpad material; and an upper window material that is transparent to light, the upper window material having a polishing surface, an upper window peripheral surface, and an upper window interface, the upper window peripheral surface being in contact with the abrasive, with the subpad interface, or a polishing pad comprising: an upper window material forming a seal with both the upper window material and the lower window material; and a bottom window material having a bottom window interface adjacent to the upper window interface or the polishing layer interface, a bottom window peripheral surface, a bottom window bottom surface, and a void space inward from the bottom window peripheral surface, wherein the void space is aligned so that light passing through the upper window material can pass through the void space to the polishing pad, enabling optical endpoint detection; and a vibration signal can be transmitted through the upper window material or the polishing material and through the bottom window material, enabling acoustic endpoint detection.

[0045] Aspect 2: The polishing pad of aspect 1, wherein the upper window polishing surface is recessed below the polishing surface.

[0046] Aspect 3: The polishing pad of aspect 1 or 2, wherein the pad includes an encapsulation layer adjacent the bottom surface of the bottom window.

[0047] Embodiment 4: The polishing pad of embodiment 3, wherein the encapsulation layer extends across the bottom surface of the subpad.

[0048] Aspect 5: The polishing pad of aspect 3, wherein the encapsulation layer defines a bottom surface that is coplanar with the bottom surface of the subpad.

[0049] Embodiment 6: The polishing pad of any one of embodiments 3-5, wherein the voids extend through the encapsulation layer.

[0050] Embodiment 7: The polishing pad of any one of embodiments 3-5, wherein the encapsulation layer is transparent to light and surrounds the voids.

[0051] Embodiment 8: The polishing pad of any one of embodiments 1-7, wherein there is an air gap between the bottom window peripheral surface and the subpad material.

[0052] Embodiment 9: The polishing pad of any one of embodiments 1-8, wherein an adhesive is present between the polishing layer interface and the subpad interface.

[0053] Aspect 10: The polishing pad of any one of Aspects 1 to 9, wherein the polishing layer interface is in direct contact with the subpad interface.

[0054] Embodiment 11: The polishing pad of any one of embodiments 1-10, wherein an adhesive is present between the top window interface and the bottom window interface.

[0055] Embodiment 12: The polishing pad of any one of embodiments 1-10, wherein the top window interface is in direct contact with the bottom window interface.

[0056] Embodiment 13: The polishing pad of any one of embodiments 1 to 12, wherein the bottom window material is elastic.

[0057] Embodiment 14: The polishing pad of any one of embodiments 1-13, wherein the subpad material is different from the bottom window material.

[0058] Aspect 15. A polishing method comprising: providing a substrate to be polished; providing a polishing pad according to any one of the preceding aspects; providing a slurry on the polishing pad; polishing by moving the substrate relative to the polishing pad; and monitoring the polishing by (a) transmitting light waves through the top window material and the void and detecting light waves reflected from the substrate; (b) transmitting a vibration signal through the top window material, the polishing layer material, or both, through the bottom window material, or both (a) and (b).

[0059] 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, more specifically 5% to 20% by weight" includes the endpoints and all intermediate values ​​in the range "5% to 25% by weight," etc.). Additionally, listed upper and lower limits can be combined to form ranges (e.g., "at least 1% by weight or at least 2% by weight" and "up to 10% or 5% by weight" can be combined to form the ranges "1 to 10% by weight," "1 to 5% by weight," "2 to 10% by weight," or "2 to 5% by weight").

[0060] 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.

[0061] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety, except that in the event of a contradictory or conflicting term in an incorporated reference and a term in the present application, the term in the present application shall take precedence over the conflicting term in the incorporated reference.

[0062] 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]

[0063] 1 pad 10 Polishing layer 11 Polished surface 12 grooves 13 Polishing layer interface 14 Abrasive layer material 15 recess 20 Subpad Layer 21 Bottom of subpad 23 Subpad interface 24 Sub-pad material 30 Upper window material 31 Polished surface 32 Upper window periphery 33 Upper window interface 40 Bottom window material 41 Bottom window bottom 42 Bottom window periphery 43 Bottom window interface 44 void 45 void 50 Encapsulation Layer 100 Window Area 101 Polishing layer 102 Subpad 103 Window

Claims

1. 1. A polishing pad for chemical mechanical polishing, comprising: a polishing layer having a polishing surface and a polishing-layer interface facing the polishing surface, the polishing layer comprising an abrasive; a subpad layer having a subpad interface adjacent the polishing layer interface and a bottom surface opposite the subpad interface, the subpad layer comprising a subpad material; an upper window material that is transparent to light, the upper window material having an abrasive surface, an upper window peripheral surface, and an upper window interface, the upper window peripheral surface forming a seal with the abrasive material, with the subpad interface, or both; a bottom window portion comprising a bottom window material having a bottom window interface adjacent the top window interface or the polishing layer interface, a bottom window peripheral surface, a bottom window bottom surface, and a void space inward from the bottom window peripheral surface; Equipped with the void space is aligned such that light passing through the top window portion can pass through the void space to the polishing pad, enabling optical endpoint detection; and a vibration signal can be transmitted through the top window material or the polishing material and through the bottom window material, enabling acoustic endpoint detection. Polishing pad.

2. The polishing pad of claim 1 , wherein the upper window polishing surface is recessed below the polishing surface.

3. The polishing pad of claim 1 , wherein the pad includes an encapsulation layer adjacent a bottom surface of the bottom window.

4. 10. The polishing pad of claim 1, wherein there is an air gap between the bottom window peripheral surface and the subpad material.

5. The polishing pad of claim 3 , wherein the encapsulation layer extends across the bottom surface of the subpad.

6. The polishing pad of claim 3 , wherein the encapsulation layer defines a bottom surface that is coplanar with the bottom surface of the subpad.

7. The polishing pad of claim 3 , wherein the encapsulation layer is transparent to light and surrounds the voids.

8. The polishing pad of claim 1 , wherein the bottom window material is resilient.

9. The polishing pad of claim 1 , wherein the subpad material is different from the bottom window material.

10. Providing a substrate to be polished; Providing the polishing pad of claim 1; providing a slurry on the polishing pad; polishing the substrate by moving it relative to the polishing pad; (a) transmitting light waves through the top window material and the gap and detecting the light waves reflected from the substrate; (b) transmitting a vibration signal through the top window material, the polishing layer material, or both, through the bottom window material, or both (a) and (b), thereby monitoring polishing. A polishing method comprising:

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