CN118418036A - Polishing pad with endpoint window - Google Patents

Abstract

A polishing pad for chemical mechanical polishing includes a polishing layer having a top polishing surface, a bottom surface, and a thickness. The polishing layer includes a porous polishing material and a window region. The exposed top surface of the transparent window is recessed from the top polished surface. A transparent window extends from the recessed region to the bottom surface of the polishing pad. The transparent window is imperforate and a portion of the top surface adjacent the peripheral portion of the transparent window is coplanar with the top surface of the transparent window and the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer.

Description

Polishing pad with end window

Technical Field

The field of the invention is polishing pads for chemical mechanical polishing.

Background technique

Chemical mechanical planarization (CMP) is a variation of a 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 a flat, uniform layer of defined thickness in the manufacture of three-dimensional circuit structures built by additive stacking and planarization processes. The CMP process removes 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 over the entire substrate (e.g., wafer) area. When the uniform thickness is over the entire wafer, it is referred to as global uniformity.

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 result in a high relative motion rate between the substrate (e.g., a wafer) and the polishing pad, and result in a resulting high shear rate or wear at the substrate and pad surfaces. The shear and slurry particles captured at the pad/substrate interface wear the substrate (e.g., wafer) surface, resulting in material removal from the substrate surface. Controlling the removal rate and uniformity of removal is important for achieving overall uniformity.

Various types of film thickness metrology and real-time control software can be used to achieve device design goals. One approach to endpoint detection is to use light of a desired wavelength to be transmitted through the polishing pad, the light to be reflected from the substrate being polished, and then the reflected light signal to be returned to an interferometer, which processes the reflected signal to determine whether the polishing has achieved its desired goal (e.g., film thickness, expected exposure of underlying structures). The metrology equipment can be located within the body of the platen that holds the pad. 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.

For certain pad structures, the pad material itself can be transparent to the desired wavelength of light. Alternatively, a plug of a transparent polymer and an opaque material molded around it can be provided to create a transparent window. See, for example, U.S. 5,605,760. A third approach is to form a pad with a hole into which the transparent window material is inserted and secured in place with an adhesive. See, for example, U.S. 5,893,796. Various versions of these pads with windows have been proposed. See, for example, U.S. 7,621,798, U.S. 8,475,228, U.S. 10,569,383, U.S. 2021/0402556, U.S. 9,475,168.

The use of two different materials in the pad may lead to problems in use including one or more of: scratches or defects in the substrate being polished, limited usable life of the pad due to differences in wear rates of the window compared to the polishing layer, or adhesion problems between the transparent window material and the polishing pad material. Therefore, there remains a need for an improved polishing pad having a transparent window.

Summary of the invention

Disclosed herein is a polishing pad for chemical mechanical polishing, comprising a polishing layer having a top polishing surface, a bottom surface and a thickness, the polishing layer comprising a porous polishing material and a window area, wherein the window area comprises a transparent window having an exposed top surface and an exposed bottom surface to enable light to be transmitted through the polishing pad in the window area, the exposed top surface of the transparent window being recessed from the top polishing surface, the transparent window extending from the recessed area to the bottom surface of the polishing pad, the window area further comprising a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material having a top surface recessed from the top surface of the top polishing surface, and wherein the transparent window is non-porous, and wherein a portion of the top surface of the peripheral portion adjacent to the transparent window is coplanar with the top surface of the transparent window, and wherein the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the drawings which are exemplary embodiments and in which like elements are numbered alike.

FIG. 1 is a cross-sectional view of one example of a polishing pad as disclosed herein.

2 is a cross-sectional view of one example of a polishing pad as disclosed herein.

3 is a cross-sectional view of one example of a polishing pad as disclosed herein.

4 is a top view of the upper surface of an example of a pad of the present invention in which the optical window is rectangular in shape.

5 is a top view of the upper surface of an example of a pad of the present invention in which the optical window shape is an ellipse.

Detailed ways

Disclosed herein is a polishing pad that can be used for chemical mechanical polishing, the polishing pad having a design that minimizes the risk of substrate defects caused by using different materials for the polishing material and the transparent window while also minimizing adhesion problems between the transparent window and the polishing material. In particular, the polishing pad includes a polishing layer and a window area. The polishing layer has a top polishing surface and a thickness. The polishing layer includes a polishing material. The window area is recessed from the top polishing surface. The window area includes a transparent window having an exposed top surface and an exposed bottom surface to allow light to be transmitted through the polishing pad in the window area. The window area further includes a peripheral portion of the polishing material in contact with the side edge of the transparent window, wherein the peripheral portion of the polishing material also has a top surface recessed from the top surface of the top polishing surface. The peripheral portion can be a protrusion. By having a window area that is recessed from the top polishing surface of the pad and includes a peripheral portion (or protrusion) of the transparent window and the polishing material, the usable life of the polishing pad can be increased and defects caused by different characteristics of the transparent window material and the polishing material can be reduced.

Specifically, many existing polishing pads with transparent windows require that at least a portion of the window be coplanar with the top polishing surface to ensure good transmittance of light through the window and to the surface of the polished substrate. However, because the composition of the window material is different from the polishing material, different mechanical properties during use - local differences in contact pressure and texture are observed, which may lead to uneven polishing rates and increased wafer-scale non-uniformity. In addition, since the polishing pad is usually dressed with bonded diamond abrasives during use to maintain a constant polishing rate, the difference in the dressing wear rate between the upper pad material and the window may cause protrusions in the window area during continued use. It is generally observed that the development of such protrusions leads to higher levels of scratch defects and often leads to pads being replaced, thereby increasing manufacturing costs, resulting in scratches and defects on the polished substrate. Differential thinning of the window during use may also interfere with the optical signal. Differences in the coefficient of thermal expansion between the polishing material and the window material may cause additional stress and deformation.

Having a recessed window area with a top window surface recessed below the top polishing surface together with a peripheral portion of polishing material also recessed below the top polishing surface helps relieve stress in the pad and also avoids protrusion of the window material above the top polishing surface (which could cause defects or scratches).

FIG. 1 , FIG. 2 and FIG. 3 show cross-sections of three examples of polishing pads 100 as disclosed herein. The polishing pad 100 has a polishing layer 120 with a top polishing surface 110, the polishing layer having a thickness a and a window region 103. The polishing layer 120 is porous and includes a porous polishing material 101. FIG. 1 , FIG. 2 and FIG. 3 show an optional macrotexture 102 on the top surface 100 of the polishing layer 120. The macrotexture 102 can be a groove, a protrusion or a raised feature to enhance polishing and management of slurry fluid and removed material. The macrotexture can be, for example, in the form of a groove having a depth b and a width g. The macrotexture 102 can be separated from the window region 103. Alternatively, the macrotexture can intersect with a concave peripheral portion 105 of the window region 103. The window region 103 includes a transparent window 104 having a top surface 104a and a bottom surface 104b. The transparent window 104 is non-porous to facilitate the transmission of light, thereby optically measuring the polishing endpoint. The window area also includes a peripheral portion 105 having a top surface 105a. The transparent window 104 extends from the top surface 105a of the peripheral portion to the bottom surface 105b of the polishing layer 120. Typically, there is no chemical bond between the transparent window 104 and the polishing layer 120. This lack of chemical bonds between the materials makes it critical that the transparent window extends the entire length from the top surface 105a to the bottom surface 105b. This extension from the top surface 105a to the bottom surface 105b results in increased contact, which increases the friction that holds the window in place during polishing.

The transparent window 104 preferably has the same thickness as measured from the top surface 104a to the bottom surface 104b across the transparent window 104. This reduces light distortion and makes the top surface 104a of the transparent window 104 coplanar with the top surface 105a of the peripheral region 105. In addition, it makes the bottom surface 104a of the transparent window 104 coplanar with the bottom surface 105b of the polishing layer 120. The top surface 104a of the window 104 and the top surface 105a of the peripheral portion are recessed from the top polishing surface 110 by a distance c. The peripheral portion may be formed of the polishing material 101. The top surface 105a of the peripheral portion may form a protrusion having a width dimension d. Advantageously, the dimension "d" (peripheral portion or protrusion width) is greater than or equal to the dimension "a" (polishing layer thickness) minus the dimension "c" (window recess depth) or the window thickness to reduce stress from compressing the porous polishing layer 120 adjacent to the non-porous window 104. Most advantageously, dimension "d" (peripheral portion or protrusion width) is greater than dimension "a" (polishing layer thickness) minus dimension "c" (window recess depth) or window thickness to reduce stresses from compressing the porous polishing layer 120 adjacent the non-porous window 104. Since the window 104 is non-porous, it is less compressible on a scale of at least 1 mm ² when compressed by a flat circular surface having a thickness equal to the thickness of the window 104.

Polishing pad 100 can include an optional subpad 106 beneath polishing layer 120. Subpad 106 also includes opening 107 having dimension f that exposes bottom surface 104b of window 104. In FIG. 1 , dimension f is substantially similar to the dimension of surface 104b to enable light to pass through any portion of the window material.

2, dimension f of opening 107 is greater than bottom surface 104b of the window, such that peripheral portion 105 includes exposed bottom surface 105b'. Advantageously, dimension "d" (peripheral portion or protrusion width) is greater than or equal to dimension "a" (polishing layer thickness) minus dimension "c" (window recess depth) or window thickness to reduce stresses arising from compression of porous polishing layer 120 adjacent non-porous window 104. Most advantageously, dimension "d" (peripheral portion or protrusion width) is greater than dimension "a" (polishing layer thickness) minus dimension "c" (window recess depth) or window thickness to reduce stresses arising from compression of porous polishing layer 120 adjacent non-porous window 104.

In another example, as shown in FIG. 3 , the peripheral portion 105 may include a curved top surface 109 instead of a right angle as shown in FIGS. 1 and 2 . As another alternative, the transition from the top surface 110 of the polishing layer 120 to the top peripheral surface 105a may be an angle other than 90 degrees (i.e., an angled transition instead of a completely vertical transition). A portion of the top surface 104a of the window and the top surface 105a or curved 109 may be coplanar or substantially coplanar. In particular, at least a portion of the top surface 105a or curved 109 in the area contacting the side edge of the window 104 is coplanar or substantially coplanar with the top window surface 104a. As used herein, “substantially coplanar” means that the vertical distance between the top window surface 104a and the surface of the polishing material (e.g., 105a or 109) in the peripheral area is less than 0.02, less than 0.01, or less than 0.005 mm.

FIG. 4 and FIG. 5 show top views of two examples of a polishing pad 100 as disclosed herein, where 110 is a top polishing layer, 102 is an optional groove, 104 is a window and 105 is a peripheral portion of the window area. In FIG. 4 , the window 105 and the window area 103 are substantially rectangular, while in FIG. 5 , the window 105 and the window area 103 are elliptical. Other shapes (not shown) may also be used, such as squares, circles, other polygons. In addition, the top polishing layer may optionally include multiple windows (not shown), such as three or more equally spaced windows. Multiple equally spaced windows reduce the time between signal measurements. This reduction in the time between signal measurements can improve the accuracy of polishing endpoint detection.

The thinness of the polishing layer in the peripheral portion of the polishing layer relative to the overall polishing layer thickness can enable flexibility during use without negatively affecting the optical signal (e.g., the signal-to-noise ratio remains acceptable) or the pad life. In fact, the depression of the window area can extend the pad life. The depth of the window area depression (e.g., 103) can be adjusted to accommodate the properties of the material used in the pad (e.g., polishing material, window material), thereby providing the desired flexibility during use without excessive, harmful deformation. Similarly, the width of the peripheral portion can be adjusted to provide the desired mechanical response for the pad material and design. For example, the depression depth c can be greater than 0.1, greater than 0.2, or at least 0.3 millimeters (mm), up to 1.1, up to 1, up to 0.8, or up to 0.6 mm. The width d of the peripheral area can be, for example, at least 0.05, at least 0.1, at least 0.2, or at least 0.3 millimeters (mm), up to 1.1, up to 1, up to 0.8, or up to 0.6 mm. To further adjust the effective flexibility of the pad, the width f of the opening 107 can be adjusted to controllably vary the flexibility in the window region without affecting the operation of the endpoint system. By moving the subpad 106 away from the interface of the window 104 and polishing material 101, stresses at the junction can be reduced, further improving window integrity.

The major dimension e of the window material in a direction parallel to the top polishing surface can be the size of a window typically used in a CMP pad. As another example, the dimension of the window in a direction parallel to the top polishing surface is about 8 to 18 mm. The thickness of the window can be less than the overall thickness a of the polishing layer 120 to provide a recess in the window area 103. For example, the thickness of the window can be 0.3 to 3, 0.4 to 2.5, 0.5 to 2 mm, or 0.6 to 1.5 mm, provided that it is not thicker than the total pad thickness and preferably not thicker than the polishing layer.

The thickness a of the polishing layer can be from 1 up to 4, up to 3, or up to 2.5 mm. The total thickness of the polishing pad (e.g., polishing layer plus subpad) is preferably no greater than 4 mm. As described, the polishing layer can include optional macrotextures (e.g., grooves). Since the macrotexture can affect the effective modulus, the window area recess depth c, the peripheral portion width d can be variably adjusted relative to the macrotexture or groove depth b and the overall polishing layer thickness a to provide the desired flexibility, which is a feature of the pad design disclosed herein. For example, the window recess depth c can be 20% to 50%, or 30% to 40% of the overall pad thickness, or 20% to 50%, or 30% to 40% of the polishing layer thickness a. As another example, the window recess depth c can be 50% to 90%, or 60% to 80% of the macrotexture depth b. As another example, the peripheral portion width d can be 40% to 60% of the macrotexture (e.g., groove) width g. Due to the manufacturing process of the disclosed pad as discussed below, these ratios can be easily adjusted during manufacturing.

An additional advantage of the inventive design is that it can provide a simple means for determining the end of pad life. Since the window depression depth can be proportionally lower than the groove depth, pad conditioning wear over time is expected to produce a change in the endpoint signal as the window depression depth approaches zero. Since this change may occur before the macrotexture is completely removed, the pad can be discontinued before a significant change in polishing performance occurs, thereby preventing non-uniformities and defects.

The polishing material 101 of the polishing layer 120 may include a polymer. The polishing material 101 at the thickness of the polishing layer 120 may be opaque. Porosity may be provided, for example, by adding a hollow flexible polymer element (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 polymer, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, epoxy resin, silicone, their copolymers (such as polyether-polyester copolymers), and combinations or blends thereof. The polishing layer may include a polymer that is a polyurethane formed by the reaction of one or more polyfunctional isocyanates and one or more polyols. For example, polyisocyanate-terminated urethane prepolymers 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; toluidine 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%, 4-8 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-butylene glycol; 1,3-butylene glycol; 2-methyl-1,3-propanediol; 1,4-butylene glycol; 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 glycol adipate, butylene adipate); polypropylene ether glycol (PPG); polycaprolactone polyols; copolymers thereof; and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of: PTMEG and PPG. When the prepolymer polyol is PTMEG, the 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 Prepolymer (available from American Keyi Company, such as PPT-80A, PPT-90A, PPT-95A, PPT-65D, PPT-75D); Prepolymers (available from Chemtura, such as LFG 963A, LFG 964A, LFG 740D); and Prepolymer (available from Anderson Development Company, such as 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). The isocyanate-terminated urethane prepolymer can be a low-free isocyanate-terminated urethane prepolymer having a free toluene diisocyanate (TDI) monomer content of less than 0.1 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 an optional diol such as 1,4-butanediol (BDO). When such an isocyanate-terminated urethane prepolymer is used, the concentration of unreacted isocyanate (NCO) 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 Prepolymer (available from American Ke Yi Company, 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).

Window 104 can comprise the desired polymer or polymer blend, as long as it has sufficient transmittance at the wavelength used for 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 window materials include polyurethanes, acrylic polymers, cyclic olefin copolymers (e.g., TOPAS 8007, etc.). In pads where the polishing layer and one or more sub-pad layers are also polyurethanes, it may be useful to use polyurethane materials. The window is advantageously made of a material ("prepolymer") containing an aliphatic polyisocyanate. The prepolymer is the reaction product of an aliphatic polyisocyanate (e.g., a diisocyanate) and a hydroxyl-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include, but are not limited to, methylenebis-4,4′-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.

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'-dialkyldiaminodiphenylamine, 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 di-p-aminobenzoate and mixtures thereof. Preferably, the curing agent of the present invention includes 3,5-dimethylthio-2,4-toluenediamine and its isomers. Suitable polyamine curing agents include both primary amines and secondary amines.

In addition, other curing agents such as diols, triols, tetraols, or hydroxyl-terminated curing agents can be added to the above polyurethane composition. Suitable diol, triol and tetraol groups include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, lower 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.

Subpad 106 may include a polymeric material. The subpad material may be more compliant than polishing material 101 of polishing layer 102. Subpad 106 may include a porous layer. Examples of polymeric materials for the subpad layer(s) 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.

The polishing pad 100 as disclosed herein can be manufactured by providing a plug of window material in a mold and molding a polishing layer around the plug. According to one method, a thick plate of the polishing layer with a thick plug is formed and then cut into a polishing layer 120 of a desired thickness a. Then a depression of the window area 103 is cut into the polishing layer 120 in the area around the plug of window material. The polishing layer can also be cut to provide a macro texture 102. Alternatively, a single pad can be cast around the window material 104 in a mold having a desired polishing layer of depth a. When cast around the window material, the polishing pad material penetrates the irregular or rough surface of the window to provide a firm bond, thereby allowing additional processing, such as scraping a polymer cake into a polishing pad. After removal from the mold, a depression is then cut into the polishing layer in the window area to the desired depression depth c to form the window area 103. In this latter method, the macro texture 102 can be formed by the top surface of the mold, or the flat top surface can be cut again to provide the macro texture. Cutting to form the depression can be performed, for example, by milling. A commercially available example of a milling machine that may be used may be a CNC milling machine.

A method of using a polishing pad 100 as disclosed herein, comprising providing a substrate to be polished, providing a polishing pad 100 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 light through a transparent window 104 and detecting light reflected back from the substrate through the transparent window 104 to determine when polishing is complete. Preferably, a translucent slurry is used.

The present disclosure further encompasses the following aspects.

Aspect 1: A polishing pad for chemical mechanical polishing, comprising a polishing layer having a top polishing surface, a bottom surface and a thickness, the polishing layer comprising a porous polishing material and a window area, wherein the window area comprises a transparent window, the transparent window having an exposed top surface and an exposed bottom surface to enable light to be transmitted through the polishing pad in the window area, the exposed top surface of the transparent window being recessed from the top polishing surface, the transparent window extending from the recessed area to the bottom surface of the polishing pad, the window area further comprising a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material having a top surface recessed from the top surface of the top polishing surface, and wherein the transparent window is non-porous, and wherein a portion of the top surface of the peripheral portion adjacent to the transparent window is coplanar with the top surface of the transparent window, and wherein the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer.

Aspect 2: The polishing pad according to aspect 1, wherein no chemical bond exists between the transparent window and the polishing layer.

Aspect 3: The polishing pad of aspect 1 or 2, wherein the top polishing surface comprises macrotexture.

Aspect 4: The polishing pad of aspect 3, wherein the macrotexture comprises grooves.

Aspect 5: The polishing pad of aspect 4, wherein the groove intersects the peripheral portion of the window area.

Aspect 6: The polishing pad of any of the preceding aspects, further comprising a subpad adjacent to the polishing layer and opposite the top polishing surface, wherein the subpad comprises an opening in the window region to enable light to be transmitted through the transparent window.

Aspect 7: The polishing pad of aspect 1, wherein a width of the peripheral portion is greater than or equal to a thickness of the transparent window.

Aspect 8: The polishing pad of aspect 1, wherein a width of the peripheral portion is greater than a thickness of the transparent window.

Aspect 9: The polishing pad of any of the preceding aspects, wherein the top surface of the transparent window is recessed below the polishing surface to a depth of 0.1 to 1.1, preferably 0.2 to 1, more preferably 0.2 to 0.8, and most preferably 0.3 to 0.6 mm.

Aspect 10: The polishing pad as described in any one of the preceding aspects, wherein the width of the concave peripheral portion of the polishing material is 0.05 to 1.1, preferably 0.1 to 1, more preferably 0.2 to 0.8, and most preferably 0.3 to 0.6 mm.

Aspect 11: The polishing pad of any of the preceding aspects, wherein the top surface of the transparent window is coplanar with the top surface of the recessed peripheral portion of the polishing material at the contact point between the window and the recessed peripheral portion of the polishing material.

Aspect 12: The polishing pad of any of the preceding aspects, wherein a top surface of the transparent window is coplanar with a top surface of the recessed peripheral portion of the polishing material.

Aspect 13: A method of forming a polishing pad as described in any of the preceding aspects, comprising placing a plug of transparent window material in a mold and forming the polishing layer around the plug, and cutting away a portion of the polishing layer to form a window area including the recessed window and the recessed peripheral portion of the polishing material.

Aspect 14. The method of aspect 13, wherein the forming comprises forming a thick plate cut into a plurality of polishing layers, each polishing layer having a transparent window material through the thickness, and the cutting comprises removing a top portion of the transparent window material.

Aspect 15. A polishing method, comprising providing a substrate to be polished; providing a polishing pad as described in any of the preceding aspects; providing a translucent slurry on the polishing pad; moving the substrate relative to the polishing pad; transmitting light through the transparent window material, and detecting light reflected back from the substrate through the transparent window and the translucent slurry to determine when polishing is completed.

All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., the 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.). In addition, the upper and lower limits can be combined to form ranges (e.g., "at least 1 or at least 2 weight percent" and "up to 10 or 5 weight percent" can be combined into the ranges "1 to 10 weight percent", or "1 to 5 weight percent", or "2 to 10 weight percent", or "2 to 5 weight percent").

The present disclosure may alternatively include, 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 functions or objectives of the present disclosure.

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

Unless stated to the contrary herein, all test standards are the most current standards in effect as of the filing date of the present application or, if priority is claimed, as of the filing date of the earliest priority application in which the test standards appear.

Claims (10)

1. A polishing pad for chemical mechanical polishing, comprising a polishing layer having a top polishing surface, a bottom surface and a thickness, the polishing layer comprising a porous polishing material and a window area, wherein the window area comprises a transparent window, the transparent window having an exposed top surface and an exposed bottom surface to enable light to be transmitted through the polishing pad in the window area, the exposed top surface of the transparent window being recessed from the top polishing surface, the transparent window extending from the recessed area to the bottom surface of the polishing pad, the window area further comprising a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material having a top surface recessed from a top surface of the top polishing surface, and wherein the transparent window is non-porous, and wherein a portion of the top surface adjacent to the peripheral portion of the transparent window is coplanar with the top surface of the transparent window, and wherein the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer. 2 . The polishing pad of claim 1 , wherein no chemical bond exists between the transparent window and the polishing layer. 3. The polishing pad of claim 1, wherein the top polishing surface comprises grooves. 4. The polishing pad of claim 3, wherein the groove intersects the peripheral portion of the window area. 5. The polishing pad of claim 1, further comprising a subpad adjacent to the polishing layer and opposite the top polishing surface, wherein the subpad comprises an opening in the window area to enable light to be transmitted through the transparent window. 6. The polishing pad of claim 1, wherein a width of the peripheral portion is greater than or equal to a thickness of the transparent window. 7. The polishing pad of claim 1, wherein a width of the peripheral portion is greater than a thickness of the transparent window. 8. A method of forming the polishing pad of claim 1 comprising placing a plug of transparent window material in a mold and forming the polishing layer around the plug, A portion of the polishing layer is cut away to form the window region including the recessed window and the recessed peripheral portion of the polishing material. 9. The method of claim 7, wherein said forming comprises forming a thick plate cut into a plurality of polishing layers, each polishing layer having a transparent window material through the thickness, and said cutting comprises removing a top portion of said transparent window material. 10. A polishing method comprising Providing a substrate to be polished Provide a polishing pad as claimed in claim 1 providing a translucent slurry on the polishing pad, moving the substrate relative to the polishing pad, Light is transmitted through the transparent window material and light reflected from the substrate through the transparent window and translucent slurry is detected to determine when polishing is complete.