Polishing pad with endpoint detection window

Abstract

A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) includes a polishing layer, a sub-pad layer, a top window portion, a bottom window portion, and a support. The support extends from the polishing layer toward and adjacent to the top window peripheral surface. A cross-section of the bottom window portion is larger than a cross-section of the top window portion. The pad includes a gap between the bottom window peripheral surface and the sub-pad material. The pad may be used for endpoint detection using optical detection, acoustic detection, or both.

Description

Technical Field

[0001] The field of the invention is polishing pads for chemical mechanical polishing. Background Art

[0002] Chemical mechanical planarization (CMP) is a variant of the polishing process that is widely used to planarize or flatten the structural layers of integrated circuits, or similar structures. In particular, CMP is often used to produce flat, uniform layers of defined thickness in the manufacture of three-dimensional circuit structures built by additive stacking and planarization processes. CMP can remove excess deposited material on the surface of a substrate (e.g., a wafer) to produce an extremely flat layer of uniform thickness, where the uniformity extends across the entire substrate (e.g., wafer) area. When the uniform thickness is across the entire wafer, it is referred to as global uniformity.

[0003] CMP uses a liquid (commonly referred to as a slurry) that may contain nano-sized particles. The slurry is fed onto the surface of a rotating multilayer polymer pad (sometimes referred to as a polishing sheet), which is mounted on a rotating platen. The polishing pad includes a polishing layer and may include a sub-pad. The substrate (e.g., a wafer) is mounted in a separate fixture or bracket with a separate rotating device and pressed against the surface of the pad under a controlled load. This may cause a high relative motion rate between the substrate (e.g., wafer) and the polishing pad, and cause high shear rates or wear at both the substrate and pad surfaces. This shear and the slurry particles trapped at the pad / substrate interface wear the substrate (e.g., wafer) surface, thereby removing material from the substrate surface. It is important to control the removal rate and the uniformity of the removal. In addition, it is useful to use metrology to determine when the polishing reaches its desired target (e.g., film thickness, expected exposure of the underlying structure, etc.). This is called endpoint detection.

[0004] Various types of film thickness metrology can be used for endpoint detection in conjunction with real-time control software. Endpoint detection processes periodic signals, such as collimated light waves, non-collimated light waves, or acoustic signal waves, to avoid wafer yield issues caused by both under-polishing and over-polishing. For example, one method for endpoint detection is an optical endpoint detection system that uses light of a desired wavelength to be transmitted through a polishing pad, which is reflected from the substrate being polished, and the reflected light signal is then returned to an interferometer. This requires that at least a portion of the polishing pad is sufficiently transparent to the light source used to produce an acceptable signal-to-noise ratio. The metrology equipment can be located within the polishing equipment or within the body of the platen that holds the pad.

[0005] For certain pad structures in which optical detection is used, the pad material itself can be transparent to the desired optical wavelength and, alternatively, have a design that allows efficient transmission of the signal wave. Alternatively, the pad can include alternating structures to facilitate transmission of the wave. For example, a transparent polymer can be provided and an opaque material molded around it to create a transparent window. See, for example, US5,605,760. As another example, an opening can be provided through the entire pad. See, for example, US8,961,266 and US7,497,763. A third approach is to form a pad with an orifice into which a transparent window material is inserted and secured in place with an adhesive. See, for example, US5,893,796. Various versions of polishing pads with windows have been proposed. See, e.g., US7,621,798, US7,081,044, US7,195,539, US8,475,228, US10,569,383, US2021 / 0402556, US2022 / 0226956, US2020 / 164483, US2015 / 232549, US9,126,304, US2008 / 0207089, US2017 / 0120417, US2016 / 263721, US7,398,714, US7,435,161, US2005 / 064802, US9,475,168, US 6,045,439, US 6,716,085, US8,475,228, US7,264,536, JP 5142866, and CN 113478382.

[0006] Transmission of the signal wave through the boundary between the gap (e.g., air) and the window surface may result in refraction or reflection of the signal wave, which may generate noise or degrade the signal, thereby reducing the effectiveness of endpoint detection using the signal wave. Therefore, in another approach, an optical fiber can be inserted into an opening in the subpad. See, for example, US 2010 / 184357.

[0007] Transmission of other vibration waves (such as sound waves) may include non-porous windows. See, for example, US2023 / 0009737 and US2023 / 0009519.

[0008] Furthermore, because the window is typically formed from a different material than the polishing layer, other problems can arise. Specifically, because the modulus and stiffness of the solid polymer window material are typically higher than those of the surrounding composite pad, differential compression during the polishing process causes deformation near the window. This problem is further exacerbated by differences in the coefficient of thermal expansion (CTE) and thermal conductivity (K) between the polishing material and the window. Because the upper surfaces of the pad and window are frictionally heated during CMP, the differences in CTE and K generate additional transient stresses and deformation. This can cause the window area to protrude above the upper surface of the pad's polishing area during use. This protrusion of the window can cause scratches on the polished substrate. Furthermore, the gap in the peripheral area surrounding the protrusion can become a trap for slurry, conditioning debris, and other foreign contaminants, which can also lead to increased scratch defect rates. Furthermore, because the pad is conditioned during use, the conditioning wear rate is significantly higher in the protruding area due to the increased contact pressure. This differential thinning of the window can interfere with the optical signal and ultimately lead to window breakdown, a catastrophic failure that shortens the pad's life.

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

[0010] Therefore, there remains a need for an improved polishing pad having a window area for endpoint detection, particularly a pad that provides one or more of the following advantages: reduces or avoids scratching of the substrate being polished, manages or tolerates stress on the pad during polishing while providing uniform polishing and good pad life, and is suitable for more than one type of signal wave. Summary of the Invention

[0011] 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) includes a polishing layer, a subpad layer, a top window portion, a bottom window portion, and a support portion. The polishing layer has a polishing surface and a polishing layer interface surface opposite the polishing surface. The polishing layer includes a polishing material. The subpad layer has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface. The subpad layer includes a subpad material. The top window portion includes a top window material and has a polishing surface surface that is preferably recessed from the polishing surface, a top window interface surface opposite the polishing surface surface, and a top window peripheral surface extending from the polishing surface surface to the top window interface surface. The support portion extends from the polishing layer toward the top window peripheral surface and is adjacent to the top window peripheral surface. The support portion includes a support portion top surface and a support portion interface surface opposite the support portion top surface. The bottom window portion includes a bottom window interface surface, a bottom window bottom surface, and a bottom window perimeter surface extending from the bottom window interface surface to the bottom window bottom surface, wherein an area defined by the bottom window bottom surface, the bottom window perimeter surface, and the bottom window interface surface is filled with a bottom window material. The bottom window interface surface is adjacent to the top window interface surface and adjacent to at least a portion of the support interface surface. The pad includes a gap between the bottom window perimeter surface and the subpad material.

[0012] Also disclosed is a polishing method, comprising: 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, 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, wherein the signal wave is a light wave, an acoustic wave, or both. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Reference is now made to the drawings showing exemplary embodiments, and wherein like elements are numbered alike.

[0014] Figure 1 is a cross-sectional view through the thickness of a portion of one example of a polishing pad as disclosed herein.

[0015] Figure 2 is a cross-sectional view through the thickness of a portion of one example of a polishing pad as disclosed herein.

[0016] Figure 3 is a cross-sectional view through the thickness of a portion of one example of a polishing pad as disclosed herein.

[0017] Figure 4 is a cross-section through the thickness of a portion of one example of a polishing pad as disclosed herein.

[0018] Figure 5It passes through Figure 1 A cross section of the thickness of a portion where the encapsulation layer is added.

[0019] Figure 6 is a top view of one example of a polishing pad as disclosed herein. DETAILED DESCRIPTION

[0020] A polishing pad for chemical mechanical polishing is disclosed. The polishing pad includes a polishing layer having a polishing surface, a subpad, and a window extending through the polishing layer and the subpad.

[0021] 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 portion extends from the polishing material to a peripheral edge of the top portion. The polishing 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 and opposite the polishing side of the polishing pad. The peripheral edge of the bottom portion 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 portion. A gap exists between the peripheral edge of the bottom portion and the subpad material. At least a portion of the gap is positioned below at least a portion of the support portion.

[0022] The pad structure can provide one or more of the following advantages: preventing the top portion of the polishing window from scratching the substrate being polished, facilitating alignment of the top and bottom window portions, tolerating misalignment of the top and bottom window portions, and mitigating compressive and shear stresses generated during the polishing process. For example, making the peripheral edge of the bottom window portion larger than the peripheral edge of the top window portion can facilitate alignment of the window portions within the opening and provide greater tolerance for misalignment of these portions from the center point. As another example, the recess, support, and gap (preferably, the gap is located below at least a portion of the support) allow for greater flexibility and stress relief without impacting the pad surface during polishing. This increased flexibility can also extend the life of the pad and reduce polishing defects. As yet another example, the flexibility and recess of the top portion of the window can prevent protrusion of the window material above the top polishing surface, which could otherwise cause defects or scratches. For example, the recessed top window surface avoids or prevents direct pressure transfer between the window and the substrate (e.g., a silicon wafer). Furthermore, the recess can avoid problems arising from differences in the regulated wear rates between the polishing layer material and the first window material.

[0023] refer to Figures 1 to 6 , the pad 1 includes a polishing layer 10 having a polishing surface 11, a subpad layer 20, a top window portion 30, a bottom window portion 40, and a support portion 60. Figure 6The polishing surface 11 is shown without microtexture or macrotexture, but the polishing surface may include macrotexture (such as grooves or perforations) and microtexture.The grooves may be, for example, concentric, radial, concentric and radial, or any other groove configuration. Figure 6 A mat 1 is shown that includes three window areas 2. Other mat configurations not shown may have one window area, two window areas, four window areas, or more than four window areas. Figure 6 A circular window is shown in the window area 2. However, other shapes may be used, such as elliptical, rectangular (optionally with rounded corners) etc. Figures 1 to 5 Cross sections through the thickness of the pad in the window region 2 are shown for various exemplary configurations.

[0024] Polishing layer 20 has a polishing surface 11 and a polishing layer interface surface 13 opposite polishing surface 11. Polishing layer 10 includes a polishing material 14, such as a porous or non-porous polymer.

[0025] The subpad layer 20 has a subpad interface surface 23 adjacent to the polishing layer interface surface 13 and a bottom surface 21 opposite the subpad interface surface. The subpad layer 20 includes a subpad material 24.

[0026] A top window portion 30 is located in the opening of the polishing layer 10. The top window portion includes a top window material 34. The top window portion 30 has a polishing surface 31 recessed from the polishing surface 11, a top window interface surface 33 opposite the polishing surface, and a top window peripheral surface 32 extending from the polishing surface 31 to the top window interface surface 33.

[0027] A support portion 60 extends from the polishing layer 10 to the top window peripheral surface 32. The support portion 60 includes a support portion top surface 61 and a support portion interface surface 63 opposite the support portion top surface 61. Because the peripheral edge 42 of the bottom window portion 40 is larger than the peripheral edge of the top portion 30, the support portion 60 and the bottom window portion 40 are partially vertically aligned. For example, a portion of the support portion interface surface 63 and the bottom window interface surface 43 may be in direct contact, or an adhesive or bonding layer, such as a pressure-sensitive adhesive (not shown), may physically connect a portion of the bottom window interface surface 43 and a portion of the support portion interface surface 63. Where the support portion abuts the top window material, the support portion top surface 61 may be substantially coplanar with the polishing surface 31 of the window. The support portion interface surface 63 may be substantially coplanar with the polishing layer interface surface. The support portion interface surface 63 may be located above at least a portion of the gap 45. This configuration provides enhanced flexibility and stress relief.

[0028] The support portion 60 can be integral with the polishing material 14. The support portion 60 can be composed of the same material as the polishing material 14. Alternatively, the support portion 60 can comprise a different material than the polishing material 14. The support portion 60 can be a separate element attached to the polishing layer 10. The top window portion 30, the support portion 60, and the polishing layer 10 can form a seal, thereby preventing slurry or particles from flowing 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 portion 60. If the support portion 60 is a separate element attached to the polishing layer 10, an adhesive can be used to facilitate this attachment.

[0029] Figures 1 to 5 The sidewall surface 15 of the polishing material 14 is shown extending from the polishing surface 11 to the support top surface 61 as a vertical surface that forms a right angle with the support top surface 61. In an alternative embodiment not shown in the figure, the sidewall surface 15 can be at an angle other than a right angle, thereby forming a slope from the polishing surface 11 to the support top surface 61, or the sidewall surface 15 can be a curved surface. The top window recess 3 is defined by the sidewall surface 15, the support top surface 61, and the polishing surface 31 of the top window portion 30. In particular, the top window recess is defined by the volume between the sidewall surface 15, below the plane of the polishing surface 11, and above the polishing surface 31 and the support top surface 61.

[0030] and Figures 1 to 5 A pad similar to the one shown including the gap 45 but without the top window recess 3 would have reduced flexibility and ability to withstand forces during polishing. Additionally, such a pad would be more likely to cause the top window portion to scratch the substrate being polished because the top window portion is typically comprised of a harder material than the polishing layer.

[0031] 2. A bottom window portion 40 is positioned in the opening of the subpad layer 20. The bottom window portion 40 includes a bottom window interface surface 43, a bottom window bottom surface 41, and a bottom window perimeter surface 42 extending from the bottom window interface surface 43 to the bottom window bottom surface 41. A bottom window material 44 fills the area defined by the bottom window bottom surface 41, the bottom window perimeter surface 42, and the bottom window interface surface 43. The bottom window interface surface 43 and the top window interface surface 33 can be in direct contact, or an adhesive or bonding layer, such as a pressure sensitive adhesive (not shown), can physically connect the bottom window interface surface 43 and the top window interface surface 33. A gap (or void space) 45 separates the bottom window perimeter surface 42 and the subpad material 24.

[0032] exist Figure 1 and Figure 2 In FIG, gap 45 is adjacent to and below support 60 and is not adjacent to or below polishing material 14. Figure 3 In FIG, a portion of gap 45 is adjacent to support 60 (eg, below the support), and a portion of gap 45 is adjacent to polishing material 14 (eg, below the polishing material). Figure 4 In FIG. 4 , gap 45 is adjacent to and below polishing material 14 .

[0033] Figure 5 An example is shown that includes an optional encapsulation layer 52 located below the bottom window portion 40 and the gap 45. The optional encapsulation layer improves the transmission of acoustic signals. In other alternatives not shown, the encapsulation layer 52 can be located only below the bottom window portion 40, or the encapsulation layer 52 can be located below the bottom window portion 40, the gap 45, and the subpad layer 20. The encapsulation layer 52 can be used as Figures 1 to 4 Additional features of any of the embodiments shown: The encapsulation layer 52 may be a non-adhesive film. The encapsulation layer may comprise a polymer film, such as, for example, a polyester film.

[0034] The encapsulation layer 52 may optionally have an adhesive layer (not shown) on the bottom surface 21 to facilitate adhesion of the pad 1 to the platen (not shown). The encapsulation layer may provide one or more of the following benefits: facilitate insertion of the window into the pad with proper alignment; provide a uniform surface on the bottom of the pad; prevent any adhesive leakage between the side edges of the window and the polishing layer 1, the subpad 20, or both; help secure the top window portion 30 and the bottom window portion 40, respectively, in place; and prevent any leakage of slurry to the underside of the polishing pad 1. In another alternative, an encapsulation layer may also be added to the polishing pad 1. Figure 1 or Figure 2 As shown on the bottom window surface 41. Additionally, an encapsulation layer may be added to both the bottom window surface and the bottom surface of the subpad.

[0035] refer to Figure 1 , the support portion 60 allows for simplified alignment when the top window portion 30 and the bottom window portion 40 are manufactured separately. In particular, the window portions 30 and 40 can be joined together first and then placed within and secured to the support portion interface surface 63 of the support portion 60. Adhesives such as epoxies and hot melt adhesives are ideal for securing the windows in place. The top window recess 3 isolates the window 30 below the polishing surface 11. In particular, this reduces stress and eliminates scratches that may occur due to the top window portion 30 rubbing against the wafer.

[0036] refer to Figure 1 and Figure 2 , Figure 2 The design has Figure 1Two main features are different. First, gap 45 provides less spacing between bottom window portion 40 and subpad 20. This reduced spacing improves window alignment to simplify manufacturing. Therefore, the smaller the spacing, the better the alignment. However, maintaining some spacing allows for better compression of subpad 20. Second, a portion of support portion 60 is fastened to subpad 20. Fastening the support portion to subpad 20 concentrates more stress on support portion 60 during polishing. Advantageously, support portion 60 is constructed of the same material as polishing layer 10 to match deformation characteristics and eliminate material mismatch stresses that may be exacerbated during polishing.

[0037] refer to Figure 2 and Figure 3 , Figure 3 Similar to Figure 2 , but gap 45 extends below polishing layer 10. This design increases the flexibility of support portion 60 during polishing. In addition, this design reduces the compressive force on support portion 60. Finally, this design provides additional space for expansion of bottom window portion 40 and the subpad 20 adjacent to the bottom window portion during polishing.

[0038] refer to Figure 1 and Figure 4 , Figure 4 Similar to Figure 1 , except that the gap 45 is only below the polishing layer 10. This design increases the rigidity of the polishing layer 10 adjacent to the top window recess 3 and the sidewall surface 15. This increased rigidity can reduce the reduction in polishing rate due to excessive compression of the polishing layer.

[0039] Refer to the attached drawings.

[0040] The total thickness of the polishing pad (e.g., polishing layer plus subpad) is preferably no greater than 4 mm. For example, the total thickness of the polishing pad can be from 1 mm to 4 mm, from 1.5 mm to 4 mm, from 1.7 mm to 3.5 mm, or from 2 mm to 3 mm. The thickness of the polishing layer can be from 0.5 mm to 3 mm, from 0.7 mm to 2.5 mm, from 1.2 mm to 2.2 mm, or from 1 mm to 2 mm. The thickness of the subpad can be from 0.5 mm to 3 mm, from 0.7 mm to 2.5 mm, or from 1 mm to 2 mm.

[0041] The depth of the recess (e.g., the vertical difference between the heights of polishing surface 11 and polishing face surface 31) can be, for example, from 0.05 mm, from 0.1 mm, from 0.2 mm, or from 0.3 mm to 1.1 mm, to 1 mm, to 0.8 mm, to 0.6 mm, or to 0.4 mm.

[0042] The length of the support portion 60 (i.e., the distance from the polishing layer 10 to the top window peripheral surface 32) can be, for example, from 0.1 mm, from 0.3 mm, from 0.5 mm, from 1 mm, from 2 mm, from 3 mm, or from 4 mm, up to 20 mm, up to 15 mm, up to 10 mm, or up to 5 mm. The thickness of the support portion 60 can be, for example, from 0.4 mm to 2.5 mm. The thickness of the support portion 60 where it abuts the top window portion 30 can be the same as the thickness of the top window portion 30. The thickness of the support portion can be the same along its entire length, or the thickness can be slightly greater toward the polishing layer. The thickness of the top window portion 30 can be, for example, from 0.4 mm to 2.5 mm, and the cross-sectional dimension perpendicular to this thickness can be from 2 mm, from 3 mm, from 4 mm, from 5 mm, or from 6 mm up to 30 mm, up to 25 mm, up to 20 mm, or up to 15 mm. The thickness of the bottom window portion 40 can be from 0.5 mm to 3 mm, from 0.7 mm to 2.5 mm, from 1 mm to 2 mm, and is preferably within 0.1 mm of the thickness of the subpad layer 20. The bottom window portion 40 can have a cross-sectional dimension perpendicular to its thickness that is larger than the cross-sectional dimension of the top window portion so that it is adjacent to the support interface surface 63 at a portion of the bottom window interface surface 43 (i.e., directly in contact or in contact via a bonding layer or adhesive layer). For example, the cross-sectional dimension of the bottom window portion 40 perpendicular to its thickness can be larger than the cross-sectional dimension of the top window portion 30 by 5%, 10%, 15%, 20%, 30%, 40%, or 50% to 200%, to 150%, or to 100%. The gap 45 from the bottom window portion 40 to the sub-pad material can be from 0.1 mm, from 0.2 mm, from 0.3 mm, from 0.4 mm, from 0.5 mm, from 1 mm, from 2 mm, from 3 mm, from 4 mm, or from 5 mm up to 40 mm, up to 30 mm, up to 20 mm, up to 10 mm, up to 9 mm, up to 8 mm, up to 7 mm or up to 6 mm.

[0043] The top window material can be a material conventionally used for such windows in polishing pads. This is desirable because the adjustment rate of such conventionally used materials may have been designed to work well with the adjustment rate of the surrounding polishing material. The top portion can be relatively rigid (compared to the elastomeric bottom portion of the window) such that the top portion in the plane of or parallel to the top polishing surface does not substantially deform during polishing.

[0044] 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 in optical metrology. It may be helpful if the hardness or thermal expansion coefficient of the window material is similar to the hardness and thermal expansion coefficient of the material used in the polishing layer. Examples of top window materials include polyurethane, acrylic polymer, cyclic olefin copolymer (e.g., TOPAS 8007, etc.).

[0045] The top window portion is advantageously made of a material containing an aliphatic polyisocyanate ("prepolymer"). The prepolymer is a 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'cyclohexyl isocyanate, 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. Cyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, isocyanate dimer 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 wt.% of unreacted isocyanate groups.

[0046] 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-(tert-butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) ("MCDEA"), polytetramethylene oxide-di-p-aminobenzoate, N,N'-dialkyldiaminodiamine. Phenylmethane, 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 diparaaminobenzoate, 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.

[0047] In addition, other curing agents such as diols, triols, tetraols, or hydroxyl terminated curing agents can be added to the polyurethane compositions. Suitable diol, triol, and tetraol groups include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, relatively 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-bis-(β-hydroxyethyl)ether, hydroquinone-bis-(β-hydroxyethyl)ether, and mixtures thereof. Preferred hydroxyl-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 hydroxyl-terminated curing agents and amine curing agents may contain one or more saturated, unsaturated, aromatic, and cyclic groups. Additionally, hydroxyl-terminated curing agents and amine curing agents may contain one or more halogen groups. The polyurethane composition may be formed with a blend or mixture of curing agents. However, if desired, the polyurethane composition may be formed with a single curing agent.

[0048] The bottom window portion can comprise a different material than the top window portion. For example, the bottom window material can be less rigid or more compressible than the top window material. The bottom window material can comprise an elastomeric material. As used herein, "elastomeric material" means a material that deforms when subjected to a force but substantially returns to its original form when the force is removed. When the pad is under downward pressure, 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 (but substantially return to its original shape when the downward force is removed). In particular, the thickness of the bottom portion can decrease under downward pressure, but the circumference can expand in a direction perpendicular to the downward force. This compression reduces deformation forces in the polishing layer, particularly at 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. 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.

[0049] The elastic modulus of the bottom window material can be lower than the elastic modulus of the top window material. Desirably, the elastomeric material can have a refractive index and optical transmittance similar to the upper window layer. Various transparent elastomers can be used, for example, as polyurethane, polyolefin, polyamide, polyacrylate, styrene block copolymer and silicone elastomer. Preferred material family is silicone elastomer. Elastomer materials that can be easily cast or molded into suitable shapes are desired.

[0050] CMP pads are produced 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 to 400 MPa, while the subpad tensile storage modulus may be 5 to 30 MPa. The overall compressibility of the composite material is largely affected by the relative layer thicknesses. The design of the pad of the present invention allows for a simple method for selecting the appropriate lower window layer material. For example, standard compressibility test methods can be used on test samples of pad stacks and window stacks to allow for rapid compressibility matching before any pad is manufactured.

[0051] The polishing material of polishing layer 10 may comprise a polymer. Polishing material 14 may be opaque within the thickness of polishing layer 10. Porosity may be provided, for example, by the addition of hollow flexible polymeric elements (e.g., hollow microspheres), a foaming agent, a blowing agent, or supercritical carbon dioxide. Examples of polymeric materials for the polishing 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 polishing layer may comprise a polymer formed by the reaction of one or more polyfunctional isocyanates and 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; 1,5-naphthalene diisocyanate; tolidine diisocyanate; p-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 may have 2 to 12 wt.%, 2 to 10 wt.%, 4 to 8 wt.%, or 5 to 7 wt.% unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the multifunctional isocyanate-terminated urethane prepolymer may 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 (such as ethylene adipate, butylene adipate); polypropylene ether glycol (PPG); polycaprolactone polyol; 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 unreacted isocyanate (NCO) concentration of the isocyanate-terminated urethane prepolymer can be 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. Prepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); prepolymers (available from Chemtura, such as LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D, and L325); Prepolymers (available from Anderson Development Company, such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). When the prepolymer polyol is PPG, the unreacted isocyanate (NCO) concentration of the isocyanate-terminated urethane prepolymer can be 3 to 9 wt.% (more preferably 4 to 8 wt.%; most preferably 5 to 6 wt.%). Examples of commercially available PPG-based isocyanate-terminated urethane prepolymers include Prepolymers (available from Co-Eye, Inc., USA, such as PPT-80A, PPT-90A, PPT-95A, PPT-65D, and PPT-75D); Prepolymers (available from Chemtura, such as LFG963A, LFG 964A, LFG 740D); and Prepolymers (available from Anderson Development Corporation, such as 8000APLF, 9500APLF, 6500DPLF, and 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 wt.%. Non-TDI-based isocyanate-terminated urethane prepolymers can also be used. For example, isocyanate-terminated urethane prepolymers include those formed by reacting 4,4'-diphenylmethane diisocyanate (MDI) with a polyol such as polytetramethylene glycol (PTMEG) and optionally a diol such as 1,4-butanediol (BDO). When such isocyanate-terminated urethane prepolymers are used, the concentration of unreacted isocyanate (NCO) 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 Prepolymer (available from American company Keyi, such as 27-85A, 27-90A, 27-95A); Prepolymers (available from Anderson Development, such as IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP); and Prepolymers (available from Chemtura, such as B625, B635, B821).

[0052] The subpad 20 may comprise a polymeric material. The subpad material 24 may be more compliant (or more resilient) than the polishing material. The subpad 20 may comprise a porous layer. Examples of polymeric materials for the subpad layer include polyurethane, polycarbonate, polysulfone, nylon, epoxy resin, polyether, polyester, polystyrene, acrylic polymers, 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.

[0053] Polishing pads as disclosed herein can be prepared via a variety of processes, including inserting a discrete window assembly into a pad having matching openings, adding a lower window component to a pad that already has an upper window component cast in place in an upper pad layer, or inserting the window assembly into a mesh mold used to prepare a top pad layer blank followed by lamination of a subpad and application of an optional pressure sensitive adhesive.

[0054] For example, a plug comprising the material of the top portion of the window can be placed in a mold, and the polishing material can be molded into a block or cake around the plug. The block or cake can then be cut into layers having the desired polishing layer thickness. The bottom portion of the window can be applied to the surface of the top portion of the window. For example, a preformed bottom portion can be adhered, or the bottom portion can be cast or molded. A subpad can be laminated or cast onto the bottom surface of the polishing layer.

[0055] A window assembly having a top portion and a bottom portion as described herein can be placed in a mold and a polishing layer formed around the relevant portion.The subpad can then be applied by lamination.

[0056] As another example, a polishing pad as disclosed herein can be made by providing a window assembly in a mold having a recess therein to retain 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 an embedded plug, wherein a portion of the plug protrudes beyond the polishing layer. To form the subpad portion of the pad, the subpad can be molded in a second molding step in a separate mold, provided that the mold includes spacers to provide clearance.

[0057] If desired, recesses are cut into the top surface of the pad to create window areas 113. The polishing layer 10 may also be cut to provide macrotexture. For example, the cutting to form the recesses may be accomplished by milling with a CNC milling machine or other machining equipment configured to cut polymers.

[0058] A method of using a polishing pad as disclosed herein comprises providing a substrate to be polished, providing a polishing pad as disclosed herein, optionally providing a slurry on the polishing pad, contacting the polishing pad with the substrate and moving the substrate and the polishing pad relative to each other (e.g., in a rotational motion), and 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, a translucent slurry is preferably used. The method can use an optical signal wave, a vibration (e.g., acoustic) signal wave, or both an optical and vibration signal wave.

[0059] The present disclosure further encompasses the following aspects.

[0060] Aspect 1: A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer), the polishing pad comprising a polishing layer, a subpad layer, a top window portion, a bottom window portion, and a support portion. The polishing layer has a polishing surface and a polishing layer interface surface opposite the polishing surface. The polishing layer comprises a polishing material. The subpad layer has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite to the subpad interface surface. The subpad layer comprises a subpad material. The top window portion comprises a top window material and has a polishing surface surface that is preferably recessed from the polishing surface, a top window interface surface opposite to the polishing surface surface, and a top window peripheral surface extending from the polishing surface surface to the top window interface surface. The support portion extends from the polishing layer toward the top window peripheral surface and is adjacent to the top window peripheral surface. The support portion comprises a support portion top surface and a support portion interface surface opposite to the support portion top surface. The bottom window portion has a bottom window interface surface, a bottom window bottom surface, and a bottom window perimeter surface extending from the bottom window interface surface to the bottom window bottom surface, wherein an area defined by the bottom window bottom surface, the bottom window perimeter surface, and the bottom window interface surface is filled with a bottom window material. The bottom window interface surface is adjacent to the top window interface surface and adjacent to at least a portion of the support portion interface surface. The pad includes a gap between the bottom window perimeter surface and the subpad material.

[0061] Aspect 2: The polishing pad of aspect 1, wherein a top portion of the gap is defined by the support interface surface.

[0062] Aspect 3: The polishing pad of aspect 1, wherein a top portion of the gap is defined by the support interface surface and the polishing interface surface.

[0063] Aspect 4: The polishing pad according to any one of the preceding aspects, wherein the top surface of the support portion is coplanar with the polishing surface of the top window portion.

[0064] Aspect 5: The polishing pad of any of the preceding aspects, wherein the bottom window material is an elastomer.

[0065] Aspect 6: The polishing pad of any of the preceding aspects, wherein the support interface surface is coplanar with the polishing layer interface surface, with the top window interface surface, or with both the polishing layer interface surface and the top window interface surface.

[0066] Aspect 7: The polishing pad of any of the preceding aspects, wherein a seal is formed between the support portion and the top window material.

[0067] Aspect 8: The polishing layer according to any one of the preceding aspects, wherein the support portion is integral with the polishing layer.

[0068] Aspect 9. The polishing layer of any of the preceding aspects, wherein the top window material and the bottom window material are transmissive to radiation for an optical signal, such that the polishing pad is suitable for both optical endpoint detection and vibrational endpoint detection.

[0069] Aspect 10. A polishing method, comprising: providing a substrate to be polished, providing a polishing pad as described in any of the preceding aspects, 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 back from the substrate through the window and the slurry to determine when polishing is completed, wherein the signal wave is a light wave, an acoustic wave, or both.

[0070] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., a range of "up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%" includes the endpoint and all intermediate values ​​within the range of "5 wt.% to 25 wt.%," etc.).

[0071] In addition, the upper and lower limits can be combined to form ranges (for example, "at least 1 or at least 2 wt.%" and "up to 10 or 5 wt.%" can be combined to form the ranges "1 to 10 wt.%", or "1 to 5 wt.%", or "2 to 10 wt.%", or "2 to 5 wt.%").

[0072] As used herein when describing surfaces or portions, "adjacent" means in direct contact or close proximity and separated only by a tie or adhesive layer.

[0073] The present disclosure may alternatively comprise, consist of, or consist essentially of any suitable component disclosed herein. The present disclosure may additionally or alternatively be formulated so as to be free of, or substantially free of, any component, material, ingredient, adjuvant, or substance that is used in prior art compositions or that is otherwise not necessary to achieve the function or objectives of the present disclosure.

[0074] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in this application contradicts or conflicts with a term in the incorporated reference, the term from this application takes precedence over the conflicting term from the incorporated reference.

[0075] Unless stated to the contrary herein, all test standards are the most current 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 standards appear.

Claims

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

2. The polishing pad according to claim 1, wherein The top of the gap 45 is defined by the bearing interface surface 63 .

3. The polishing pad according to claim 1, wherein The top of the gap 45 is defined by the support interface surface 63 and the polishing interface surface 13 .

4. The polishing pad according to claim 1, wherein The support portion top surface is coplanar with the polished surface of the top window portion.

5. The polishing pad according to claim 1, wherein The bottom window material is an elastomer.

6. The polishing pad according to claim 1, wherein The support interface surface is coplanar with the polishing layer interface surface, with the top window interface surface, or with both the polishing layer interface surface and the top window interface surface.

7. The polishing pad according to claim 1, wherein A seal is formed between the support portion and the top window material.

8. The polishing layer according to claim 1, wherein The support portion is integral with the polishing layer.

9. The polishing layer according to claim 1, wherein The top window material and the bottom window material are transmissive to radiation for an optical signal, making the polishing pad suitable for both optical endpoint detection and vibrational endpoint detection.

10. A polishing method, comprising: providing a substrate to be polished, Providing the polishing pad according to claim 1, providing a slurry on the polishing pad, moving the substrate relative to the polishing pad, A signal wave is transmitted through the window material and the signal wave is detected after being reflected from the substrate through the window and slurry to determine when polishing is complete.

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