Preparation method of polishing layer of chemical mechanical polishing pad and chemical mechanical polishing pad

Abstract

The present invention relates to the technical field of chemical mechanical polishing pads, and provides a method for preparing a polishing layer of a chemical mechanical polishing pad and a chemical mechanical polishing pad. The polishing layer prepared by the present invention is used in the polishing pad, which can effectively improve the problem of inconsistent polishing rate when the polishing pad polishes a wafer. The preparation steps of the polishing layer include: (1) pouring a mixture including a polyurethane prepolymer, a curing agent and partially expanded polymer expanded microspheres into a casting cavity of a mold, wherein the partially expanded polymer expanded microspheres can expand secondary upon heating; the mold has a temperature regulating function, and has multiple temperature regulating areas along the cross section of the casting cavity of the mold; (2) regulating the temperature of each temperature regulating area so that the temperature of at least two of the temperature regulating areas is different; and (3) performing a post-treatment including vulcanization on the mixture to obtain a polishing layer, wherein the density difference between each polishing layer area of ​​the polishing layer is 0.05-0.3 g / cm 3 , the hardness range is 5-10D.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing pads, and in particular to a method for preparing a polishing layer of a chemical mechanical polishing pad and the chemical mechanical polishing pad. Background Art

[0002] In the manufacture of integrated circuits and other electronic devices, multiple layers of conductive, semiconducting, and dielectric materials are deposited on the surface of a wafer and partially or selectively removed from the surface of the semiconductor wafer. Thin layers of conductive, semiconducting, and dielectric materials can be deposited using a variety of deposition techniques. Common deposition techniques used in modern wafer processing include physical vapor deposition (PVD, also known as sputtering), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical deposition (ECD). Common removal techniques include wet and dry etching.

[0003] As the wafer stack material layers are sequentially deposited and removed, the top surface of the wafer becomes less flat. Since subsequent semiconductor processing (e.g., photolithography, metallization, etc.) requires the wafer to have a flat surface, the wafer needs to be planarized.

[0004] Planarization can be used to remove unwanted surface topography and surface defects, such as rough surfaces, agglomerated materials, lattice damage, scratches, and contaminated layers or materials. Furthermore, in the damascene process, material is deposited to fill recessed areas created by patterned etching. However, the filling step cannot be completely precise, and overfilling can occur. Therefore, it is necessary to remove material outside the recessed areas.

[0005] Chemical mechanical polishing (CMP) is commonly used in the manufacture of high-density integrated circuits to smooth material layers deposited on substrates and remove excess material during the damascene process. In a traditional CMP process, the substrate remains on a polishing head. The polishing head presses the backside of the substrate against a rotating polishing pad in the presence of a polishing slurry. Material from the substrate surface in contact with the polishing pad is removed through a combination of chemical and mechanical forces provided by the polishing slurry and the relative motion of the substrate and polishing pad. Typically, after a thin film deposition cycle, the polished substrate undergoes one or more CMP processes. Once the CMP operation is complete, the substrate can be transferred from the CMP processing area to the next device manufacturing step, such as photolithography, etching, or deposition.

[0006] The interaction between the polishing layer, polishing medium and wafer surface during CMP has been the subject of increasing research and analysis, with the development of polishing pads being a key focus.

[0007] As early as 1993, H.F. Reinhardt et al. proposed in patent CN 1059219C a method for casting a polyurethane mixture containing microspheres into a block and then cutting this block into thin polishing pads. This method has been proven to be a viable method for producing porous polishing pads. Since the advent of CMP as a key process in semiconductor manufacturing, most polishing pad development has followed a similar path, involving testing numerous porous and non-porous polymer materials and their mechanical properties. Patents such as CN101239457B, CN104551977A, and CN101642897B have continuously varied their composition to alter their mechanical properties. Patents such as CN1082567A, CN105382680B, and CN102950550B focus on casting methods. However, regardless of the changes in raw materials or manufacturing process, the requirement for uniform polishing pads remains constant.

[0008] However, in actual use, it has been found that when polishing wafers with a uniform polishing pad, the polishing head and the polishing disc rotate in the same direction but at different speeds, resulting in a certain degree of uneven distribution of slurry on the polishing pad. This can cause the edge of the wafer profile (the polishing rate at each point in the radial direction) to appear too fast. This phenomenon can affect the subsequent processing of the wafer, thereby affecting the wafer yield and production volume. Summary of the Invention

[0009] In response to at least one of the shortcomings of the prior art, the present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad and a chemical mechanical polishing pad. The polishing layer prepared in the present invention can effectively improve problems such as inconsistent polishing rates when the polishing pad is polishing a wafer.

[0010] To achieve its purpose, the present invention provides the following technical solutions:

[0011] In one aspect, the present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad, wherein the method is used to prepare a polishing layer including a plurality of polishing layer regions with different densities and hardnesses along a cross section of the polishing layer;

[0012] The preparation steps of the polishing layer include:

[0013] (1) pouring a mixture comprising a polyurethane prepolymer, a curing agent and partially expanded polymer expandable microspheres into a pouring cavity of a mold, wherein the partially expanded polymer expandable microspheres can be heated to expand a second time; the mold has a temperature regulating function and has a plurality of temperature regulating areas along a cross section of the pouring cavity of the mold;

[0014] (2) adjusting the temperature of each of the temperature adjustment zones so that the temperature of at least two of the temperature adjustment zones is different, and causing the partially expanded polymer expandable microspheres in the casting cavity corresponding to the positions of the temperature adjustment zones with different temperatures to undergo secondary expansion to different degrees;

[0015] (3) The mixture treated in step (2) is subjected to post-treatment including vulcanization to obtain the polishing layer, wherein the density difference between each polishing layer region of the polishing layer is 0.05-0.3 g / cm 3 , the hardness range is 5-10D.

[0016] A second aspect of the present invention provides a chemical mechanical polishing pad suitable for semiconductors, wherein the polishing pad is provided with a polishing layer prepared by the preparation method described above.

[0017] A third aspect of the present invention provides use of the chemical mechanical polishing pad described above in chemical mechanical polishing.

[0018] The technical solution provided by the present invention has the following beneficial effects:

[0019] The method of the present invention is used to prepare a polishing layer comprising a plurality of polishing layer regions with different densities and hardnesses, and the density difference between the different polishing layer regions is set to 0.05-0.3 g / cm 3 The hardness range is 5-10D. Compared with the polishing layer that does not meet this requirement, it can significantly reduce the polishing inconsistency when the polishing pad is used in chemical mechanical polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the secondary expansion curve of polymer expanded microspheres I.

[0021] Figure 2 This is the secondary expansion curve of polymer expanded microspheres II (461DE20d70).

[0022] Figure 3 This is a schematic diagram of the temperature adjustment area distribution of the casting cavity of a mold in an example.

[0023] Figure 4 Schematic diagram of the temperature adjustment area distribution of the casting cavity of the mold in another example.

[0024] Figure 5 Schematic diagram of the temperature adjustment area distribution of the casting cavity of the mold in another example.

[0025] Figure 6 Schematic diagram of the temperature adjustment area distribution of the casting cavity of the mold in another example.

[0026] Figure 7Schematic diagram of the temperature adjustment area distribution of the casting cavity of the mold in another example.

[0027] Figure 8 Schematic diagram of the temperature adjustment area distribution of the casting cavity of the mold in another example.

[0028] Figure 9 This is the wafer removal rate after polishing with the polishing pad in Comparative Example 1.

[0029] Figure 10 This is the wafer removal rate after polishing with the polishing pad in Comparative Example 2.

[0030] Figure 11 is the wafer removal rate after polishing with the polishing pad in Example 1.

[0031] Figure 12 This is the wafer removal rate after polishing with the polishing pad in Example 2.

[0032] Figure 13 This is the wafer removal rate after polishing with the polishing pad of Example 3.

[0033] Figure 14 This is the wafer removal rate after polishing with the polishing pad of Example 4.

[0034] Figure 15 This is the secondary expansion curve of polymer expanded microspheres III.

[0035] Figure 16 This is the secondary expansion curve of polymer expanded microspheres IV.

[0036] Figure 17 This is a schematic diagram of the mold, in which the temperature control module of the base is not shown.

[0037] Figure 18 for peace Figure 3 Schematic top view of a mold base that matches the temperature adjustment area distribution. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0040] The present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad, wherein the method is used to prepare a polishing layer including a plurality of polishing layer regions with different densities and hardnesses along a cross section of the polishing layer;

[0041] The preparation steps of the polishing layer include:

[0042] (1) pouring a mixture comprising a polyurethane prepolymer, a curing agent and partially expanded polymer expandable microspheres into a pouring cavity of a mold, wherein the partially expanded polymer expandable microspheres are capable of secondary expansion upon heating; wherein the mold has a temperature regulating function and has a plurality of temperature regulating zones along a cross section of the pouring cavity of the mold;

[0043] (2) adjusting the temperature of each of the temperature adjustment zones so that the temperature of at least two of the temperature adjustment zones is different, and causing the partially expanded polymer expandable microspheres in the casting cavity corresponding to the positions of the temperature adjustment zones with different temperatures to undergo secondary expansion to different degrees;

[0044] (3) The mixture treated in step (2) is subjected to post-treatment including vulcanization to obtain the polishing layer, wherein the density difference between each polishing layer region of the polishing layer is 0.05-0.3 g / cm 3 , the hardness range is 5-10D.

[0045] In the process of preparing the polishing layer of the present invention, partially expanded polymer expandable microspheres are used. A mixture containing such partially expanded polymer expandable microspheres is poured into a mold. By adjusting the temperature of each temperature adjustment zone in the mold and making the temperatures of at least two temperature adjustment zones different, the partially expanded polymer expandable microspheres in the casting cavity corresponding to the positions of the temperature adjustment zones with different temperatures undergo different degrees of secondary expansion according to product requirements. For example, the polymer expandable microspheres in some zones do not undergo secondary expansion, while the polymer expandable microspheres in some zones do undergo secondary expansion, or the polymer expandable microspheres in all zones undergo secondary expansion, but to different degrees, etc. By adjusting the mold temperature to make the partially expanded polymer expandable microspheres have different expansion behaviors, a polishing pad with the desired density and hardness extremes can be obtained. The inventors have found that the polishing layer finally obtained by the above temperature adjustment comprises multiple polishing layer zones with different densities and hardnesses, and the density extreme difference between the different polishing layer zones is 0.05-0.3 g / cm 3 , and a hardness range of 5-10D. Compared to polishing layers that do not meet this requirement, this method can significantly reduce polishing inconsistencies when used in chemical mechanical polishing. The method of the present invention can be used to prepare a polishing layer, allowing for flexible temperature adjustment to achieve the desired density and hardness ranges.

[0046] Preferably, the density and hardness differ between adjacent polishing layer regions.

[0047] Herein, "extreme density difference" refers to the density difference between the highest and lowest density polishing layer regions within each polishing layer region. "Extreme hardness difference" refers to the hardness difference between the highest and lowest hardness polishing layer regions within each polishing layer region.

[0048] Specifically, the polishing layer includes two or more polishing layer regions, for example, 2, 3, 4, 5, 6, 7, 8 or more polishing layer regions, preferably 4 or more, and more preferably 5 or more. In some preferred embodiments, the polishing layer includes a central polishing layer region and a peripheral polishing layer region surrounding the central polishing layer region. In some preferred embodiments, the polishing layer includes a central polishing layer region and multiple peripheral polishing layer regions disposed around the central polishing layer region, and the multiple peripheral polishing layer regions are sequentially arranged from the inside out, for example, there are more than 2 or more than 3 peripheral polishing layer regions. In some preferred embodiments, the polishing layer includes multiple polishing layer regions with a fan-shaped outer contour. In some embodiments, the polishing layer is evenly or unevenly divided into the multiple polishing layer regions. In some embodiments, at least some of the polishing layer regions have a regular or irregular shape, preferably an irregular shape.

[0049] Furthermore, the division of the temperature regulating areas of the casting cavity of the mold matches the distribution of the polishing layer areas of the polishing layer, for example, each temperature regulating area and a polishing layer area of ​​the polishing layer have matching shapes and sizes.

[0050] Preferably, the partially expanded polymer microspheres have an initial expansion temperature of 60-70°C, reaching maximum expansion capacity and ceasing expansion at 80-100°C. It is well known in the art that when adding polymer expandable microspheres to a castable, the isocyanate prepolymer (i.e., polyurethane prepolymer) must be heated to 60-80°C to ensure uniform dispersion of the microspheres. Prior to pouring the mixture into the mold, the temperature of the mixture is approximately 35-55°C. In the present invention, polymer expandable microspheres with these expansion characteristics are preferred, as they are more conducive to achieving a polishing layer with desired density and hardness differences in different regions.

[0051] Preferably, in step (1), the partially expanded polymer expanded microspheres are first dispersed in the polyurethane prepolymer, and the dispersion is performed at 60-80°C; then, before the pouring, the curing agent is added and mixed evenly; in some embodiments, in step (1), before the pouring, the temperature of the mixture is 35-55°C.

[0052] Further preferably, the partially expanded polymer microspheres are unexpanded polymer microspheres that are partially expanded by heating and have a volume V0, and the volume of the partially expanded polymer microspheres when reaching maximum expansion capacity is 1.2-2 times the volume V0 (determined by TMA test).

[0053] Preferably, in step (2), the temperature of each of the temperature adjustment regions does not exceed 100° C., and the temperature of at least part of the temperature adjustment regions is greater than or equal to the initial expansion temperature of the partially expanded polymer expanded microspheres.

[0054] Preferably, after the partially expanded polymer expandable microspheres reach their maximum expansion capacity during the heating and expansion process, the temperature at which they rupture and leak when heated further is not less than about 120°C.

[0055] Preferably, the particle size D50 of the partially expanded polymer expanded microspheres is 5-100 μm, and the true density is 0.02-0.2 g / cm 3 .

[0056] Preferably, the unexpanded polymer expanded microspheres have a volume expansion capacity of not less than 30 times, as determined by TMA test.

[0057] Preferably, the partially expanded polymer expandable microspheres undergo secondary expansion in a linear or substantially linear expansion manner when heated to the initial expansion temperature until the maximum expansion capacity is reached.

[0058] Furthermore, a single-piece polishing layer for preparing a polishing pad is obtained through steps (1) to (3), i.e., the polishing layer is prepared using a single-piece method. Single-piece means that the polishing layer prepared through the above steps does not need to be cut into multiple pieces for preparing the polishing layer of the polishing pad, but a slicing operation to remove the smooth polyurethane skin on the surface after vulcanization may be included.

[0059] In some embodiments, the mixture is poured into the mold to a thickness of 0.2-1 cm. Specifically, when pouring the mixture, the mold can be moved by a conveyor belt to achieve continuous pouring. For example, a movable slide rail and a fixed slot can be provided on the conveyor belt.

[0060] Post-treatments such as vulcanization and curing performed when preparing the polishing layer are well known in the art and are not particularly limited thereto. In some examples, in step (3), the curable liquid obtained by pouring into the mold in step (2) is pushed into an oven for vulcanization and curing to obtain a polyurethane "cake". The cake is then cooled and sliced ​​to remove the smooth polyurethane skin on the surface. The cake is then sanded, patterned, and laminated, and then punched to the desired size to obtain a complete polishing pad. In order to facilitate the delivery of the polishing medium or slurry to the polishing pad-wafer interface for effective polishing, macro grooves can be machined or molded on the polishing surface of the polishing pad (i.e., patterned). Finally, the buffer layer and the backing adhesive are laminated, and the cake is punched to a specific size to obtain a complete polishing pad.

[0061] About polymer expanded microspheres:

[0062] As is well known in the art, polymer expandable microspheres are heat-expandable microspheres obtained by polymerization of a mixture of monomeric materials capable of forming a thermoplastic polymer shell and at least one blowing agent under the action of a polymerization catalyst. The microspheres expand when heated; the blowing agent is a low-boiling-point organic compound. The monomers are polymerized to form a polymer shell layer, and the low-boiling-point organic compound is coated inside the microspheres to form a core layer.

[0063] A typical preparation method for polymer expandable microspheres that expand in volume upon heating includes the following steps: A) adding monomers, low-boiling-point organic matter, and a polymerization catalyst into a reactor and mixing to prepare an oil phase; B) mixing water and a dispersant to prepare an aqueous phase; C) mixing the aqueous phase and the oil phase to obtain an emulsion, which is then heated to react to obtain a microsphere slurry; and D) separating and drying the slurry to obtain the polymer expandable microspheres (i.e., unexpanded polymer expandable microspheres).

[0064] One of the improvements of the present invention is that the polymer expanded microspheres used in preparing the polishing layer are unexpanded polymer expanded microspheres that are heated at a certain temperature for a certain period of time to obtain partially expanded polymer expanded microspheres (i.e., polymer expanded microspheres that have not reached their maximum expansion capacity), and the partially expanded polymer expanded microspheres have the ability to expand a second time by heating in the mold.

[0065] In step A) above, the monomer is selected from one or more organic compounds having double and / or triple bonds that can undergo free radical polymerization. Specifically, for example, the monomer can be selected from one or more of acrylonitrile, methacrylonitrile, styrene, (o-, m-, p-)methylstyrene, ethylstyrene, halostyrene, methyl acrylate, methyl methacrylate, methacrylic acid, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, vinyl acetate, vinyl laurate, vinyl stearate, vinyl halide, vinylidene halide, vinylidene halide, acrylamide, N-isopropylacrylamide, methacrylamide, and hydroxyethyl methacrylate. Preferred monomers are one or more of acrylonitrile, methacrylic acid, methacrylonitrile, vinylidene chloride, methyl acrylate, methyl methacrylate, and acrylamide.

[0066] In the above step B), the polymerization catalyst is, for example, selected from one or more azo and peroxide compounds, such as: one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, dilauroyl peroxide, dibenzoyl peroxide, tert-butyl perisobutyrate, bis(4-tert-butylcyclohexyl)peroxydicarbonate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, and di-tert-butyl peroxide, preferably one or more of azobisisobutyronitrile, dilauroyl peroxide, and dibenzoyl peroxide. The amount of the polymerization catalyst used is, for example, 0.1-5 wt% of the monomer material.

[0067] In step A), the low-boiling-point organic compound may be a single compound or a combination of multiple compounds. The low-boiling-point organic compound is, for example, one or more selected from butane, isobutane, pentane, isopentane, hexane, cyclohexane, octane, isooctane, hexafluoropropane, perfluorohexanone, ethyl acetate, petroleum ether, diethyl ether, benzene, toluene, and methyl chloride. Preferably, the low-boiling-point organic compound is used in an amount of 5-40 wt% of the total weight of the oil phase.

[0068] In step B) above, the dispersant can be a nanoparticle powder or suspension, for example, one or more selected from silicon dioxide, silica sol, magnesium hydroxide, and calcium carbonate. It should be noted that the dispersant can also be prepared in situ from several substances through a reaction. For example, when magnesium hydroxide is used as the dispersant, it can be produced by reacting sodium hydroxide and magnesium chloride in the system, without the need for direct addition of magnesium hydroxide. The amount of the dispersant used is 2-20% by weight of the oil phase, preferably 4-12%.

[0069] In the above step C), the oil phase accounts for 10%-50% of the total mass of the water phase and the oil phase.

[0070] For example, in step C) above, the emulsion is heated to 40-95°C and reacted for approximately 20 hours to obtain a microsphere slurry. This slurry is filtered to obtain a microsphere filter cake, which is then washed with water to obtain a clean microsphere filter cake. The filter cake is crushed and dried in an oven at 50-60°C to obtain a heat-expandable microsphere powder (i.e., unexpanded polymer expanded microspheres). In some examples, the heat-expandable microsphere powder can be heated in an oven at a temperature of 10-50°C, depending on the initial expansion temperature of the microspheres, for a period of time to prevent full expansion, thereby obtaining a partially expanded polymer expanded microsphere powder. This powder can continue to expand when heated again to its initial expansion temperature. Preferably, the partially expanded polymer expanded microspheres are sieved and cleaned before use. This sieve removal removes oversized microspheres or microsphere agglomerates, as well as metal impurities and cracked microsphere crusts.

[0071] The polymer expanded microspheres have a polymer shell layer and a core material wrapped by the shell layer. Preferably, the glass transition temperature T gs Higher than the boiling point T of the core material c , and T gs -T c The value is at least greater than 10℃.

[0072] About mold:

[0073] The mold used in preparing the polishing layer can be a mold with corresponding temperature regulation function already available in the art. Figure 17 As shown, the mold includes a base 100 and a mold ring 200 disposed on the base 100, and a pouring space (i.e., a pouring cavity 300) is defined by the base 100 and the mold ring 200. Specifically, in the method of the present invention, a mold having multiple temperature adjustment zones along the cross section of the pouring cavity 300 of the mold is selected; Figure 18 As shown, it is a schematic top view of the base 100 of the mold in an example; the temperature control modules are configured in the base 100 of the mold corresponding to different temperature adjustment areas, so that the temperature of different casting cavity areas can be adjusted; specifically, as Figure 18 As shown, along the cross-section of the casting cavity, the inner cavity of the mold base 100 corresponding to different casting cavity areas is provided with corresponding heat medium flow channels 1a', 2a', 3a', 4a'. Specifically, each heat medium flow channel can be divided by a partition 101. The corresponding mold casting cavity temperature control area distribution diagram is shown in FIG. Figure 3, including temperature adjustment areas 1-4, that is, the flow areas of each heat medium flow channel in the mold base 100 corresponding to the temperature adjustment area are delineated according to the corresponding temperature adjustment area design. Heat medium (such as thermal oil) flows in the heat medium flow channel, and a temperature adjustment device (such as a heating device that can adjust the temperature of the heat medium) is configured to adjust the temperature of the heat medium. The temperature of the heat medium flowing into each heat medium flow channel is adjusted by heating or cooling the heat medium by the temperature adjustment device, thereby adjusting the temperature of the corresponding casting cavity area (or temperature adjustment area); Figure 18 As shown, each heat medium flow channel on the base 100 is equipped with a temperature probe 104 to monitor the temperature; each heat medium flow channel of the mold is connected to a temperature regulating device for regulating the temperature of the thermal oil to achieve precise temperature control, for example, the temperature regulating device is a multi-circuit mold temperature controller; each heat medium flow channel is provided with a thermal oil inlet 102 and a thermal oil outlet 103, preferably the thermal oil inlet 102 and the thermal oil outlet 103 are both threaded holes, which are connected to the mold temperature controller through the threaded holes, and preferably each heat medium flow channel is set as a labyrinth cavity to improve the accuracy of temperature control. Figure 4-8 The temperature adjustment area distribution diagram of the casting cavity of several other molds is shown. The base 100 of these molds can refer to Figure 18 The main difference in configuring the temperature control module in the manner shown is that the flow area of ​​the heat medium flow channel is adjusted accordingly according to the arrangement of the temperature control area of ​​the corresponding casting cavity, which will not be described in detail. Figure 4 The casting cavity of the mold is provided with temperature regulating zones 1-8, Figure 5 The casting cavity of the mold of FIG6 is provided with temperature regulating areas 1-3, and the casting cavity of the mold of FIG6 is provided with temperature regulating areas 1-4. Figure 7 、 8 The casting cavity of the mold is respectively provided with temperature regulating areas 1-3.

[0074] Each heat medium flow channel of the mold base corresponds to a temperature adjustment area of ​​the casting cavity, and further corresponds to a polishing layer area of ​​the polishing layer. Figure 3-8 The schematic diagram of the arrangement of each polishing layer area of ​​the polishing layer prepared by the mold with the temperature adjustment area distribution can also be referred to Figure 3-8 The polishing layer obtained has a center O or a circle center O. Figure 3 For example, based on Figure 3 The polishing layer prepared by the mold of the temperature adjustment area 1-4 shown includes four evenly divided fan-shaped polishing layer areas. Figure 4 For example, based on Figure 4 The polishing layer prepared by the mold of the temperature adjustment zones 1-8 shown includes eight evenly divided sector-shaped polishing layer regions. Figure 5 、 7 , 8 respectively have temperature adjustment areas 1-3, Figure 6There are temperature adjustment areas 1-4, where Figure 6 、 7 , 8 is the uneven division of each temperature adjustment area, Figure 7 、 8 Some of the temperature regulation areas are irregular in shape; Figure 5 、 6 The polishing layer prepared by the mold divided by the temperature adjustment areas of 7, 8 includes a central polishing layer area and two or three peripheral polishing layer areas arranged on the periphery of the central polishing layer area, and each peripheral polishing layer area is sequentially arranged from the inside to the outside.

[0075] In some embodiments of the present invention, the base of the mold used is a rectangular metal plate with a thickness of 2-5 cm and a side length of 105-120 cm, and the mold ring is a circular metal ring with a diameter of 90-100 cm, a height of 2-5 cm, and a thickness of 2-4 cm, and is made of metal such as aluminum and iron.

[0076] About polyurethane prepolymer and curing agent in the mixture:

[0077] The polyurethane prepolymer commonly used in the preparation of polishing layers in the art can be used, and there is no particular limitation on this. Specifically, the polyurethane prepolymer is mainly prepared with aromatic isocyanate and aliphatic isocyanate, and is prepared together with polymer polyol and small molecule chain extender. Aromatic isocyanates include, for example, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, xylene diisocyanate, 3,3'-dimethylbenzene-4,4'-biphenyl diisocyanate, triphenylmethane triisocyanate, 4,4',4" triphenylthiophosphate triisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, etc., and a mixture of one or more of the following. Aliphatic isocyanates are, for example, a mixture of one or more of 4,4'-dicyclohexylmethane diisocyanate, cyclohexane dimethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc. Preferably, the mass fraction of the aliphatic isocyanate in the prepolymer is 10%-15%, and the mass fraction of the aromatic isocyanate component in the prepolymer is 25%-40%. The aliphatic isocyanate can significantly reduce the rate of reaction heat release and the maximum temperature of the reaction heat release, and can also prolong the gel time of the reaction between the polyurethane prepolymer and the curing agent.

[0078] Polymer polyols used for chain extension in polyurethane prepolymers are primarily classified into polyether polyols, polyester polyols, and other oligomer and polymer polyols. Polyester polyols include, for example, mixtures of one or more of alkyd polyester polyols, polycaprolactone polyols (PCL), polycarbonate polyols (PCDL), and the like. Polyether polyols include, for example, mixtures of one or more of polyoxypropylene polyols, polytetramethylene glycol (PTMG), and copolyether polyols. Small molecule chain extenders can be selected from diamines or small molecule polyols and alcoholamines, including 1,4-butanediol, ethylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, methylpropylene glycol, diethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, butylethylpropylene glycol, diethylpentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, glycerol, ethanolamine, and a mixture thereof. Considering various factors such as the polishing pad's strength, dynamic mechanical properties, low-temperature resistance, and hydrolysis resistance, PTMG and diethylene glycol, or a blend thereof, are optimal. Preferably, when PTMG and diethylene glycol are selected as the polyol, the isocyanate prepolymer has an unreacted NCO content of 8.0-9.5% by weight.

[0079] In some preferred embodiments, the polyurethane prepolymer is prepared by reacting raw material components including TDI-80, 4,4'-dicyclohexylmethane diisocyanate (HMDI), polytetramethylene glycol (PTMG), and diethylene glycol (DEG); preferably, TDI-80 accounts for 25-40% of the total mass of the raw material components, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc.; HMDI accounts for 10-15% of the total mass of the raw material components, for example, 10%, 11%, 12%, 13%, 14%, 15%, etc.; PTMG accounts for 40-50% of the total mass of the raw material components, for example, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, etc.; DEG accounts for 5-10% of the total mass of the raw material components, for example, 5%, 6%, 7%, 8%, 9%, 10%, etc. When the synthesis of the prepolymer reaches the reaction endpoint, the unreacted isocyanate groups (NCO) account for 8.0-9.5% of the total prepolymer mass, for example, 8%, 8.5%, 9%, 9.5%, etc. The endpoint determination method can refer to the existing technology and is not limited in any way by the present invention.

[0080] In some embodiments, the curing agent is a two-component curing agent, specifically a two-component curing agent comprising a diamine curing agent and a multifunctional polyether polyol. This two-component curing agent exhibits more controllable exothermicity, longer working time, and improved flexibility and elongation at break compared to a diamine curing agent and a polyether polyamine.

[0081] Among them, diamine curing agents include 3,3'-dichloro-4,4'-methylenediphenylmethane (MOCA), 3,5-dimethylthiotoluenediamine, 3,5-diethyltoluenediamine, 4,4'-methylenebis(2-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenedianiline (MDEA), 4,4'-methylenebis(2-isopropyl-6-methyl)aniline, 4,4'-methylenebis(2-methyl-6-diethylaniline), 4,4'-methylenebis(2-ethylaniline), propylenediamine bis(4-aminobenzoate), 4,4'-di-secondary One or more of butylaminodiphenylmethane, 1,4-bis-sec-butylaminobenzene, 3,5-diamino-4-chlorobenzoic acid isobutyl ester, 2,4-diamino-3,5-dimethylthiochlorobenzene, toluenediamine, 2,4-diamino-3-methylthio-5-propyltoluene, 4,4'-diaminodicyclohexylmethane, trimethylethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and quinoline diamine, and more preferably one or more of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis-sec-butylaminodiphenylmethane and isomers thereof.

[0082] Preferably, the multifunctional polyether polyol used to form the curing agent contains 2 to 6 hydroxyl groups per molecule and has a hydroxyl value of 400-1000 mg KOH / g, including polyoxypropylene triol with one or more of glycerol, trimethylolpropane, ethanolamine, diethanolamine, triethanolamine, etc. as initiators; polyether tetraol with one or more of ethylenediamine, pentaerythritol, toluenediamine, methylenedianiline, etc. as initiators; polyether pentol obtained by ring-opening polymerization of propylene oxide with diethylenetriamine or xylitol as initiators; hexahydroxy polyether obtained by initiating one or more of sorbitol, mannitol, sucrose, diethylenetriamine, triethylenetetramine, etc., etc. Examples of commercially available polyhydroxy polyol curing agents include Voranol from Dow Chemical Company. ® Polyols, Poly-G polyethers from Arch Chemicals in the United States, Actcol series polyethers from Mitsui Chemicals in Japan, and multifunctional polyethers produced by many companies in China including Shandong Bluestar Dongda Chemical Co., Ltd., Shanghai Gaoqiao Petrochemical Company Polyurethane Division, Nanjing Hongbaoli, Hebei Yadong, etc.

[0083] Taking Hebei Yadong as an example, the following table lists a variety of preferred high molecular weight polyol curing agents.

[0084] Table 1

[0085]

[0086] In some preferred embodiments, the curing agent comprises: 50-90 wt% of a diamine curing agent, preferably selected from 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,5-dimethylthiotoluenediamine, 3,5-diethyltoluenediamine, 4,4'-methylenebis(2-chloro-2,6-diethylaniline) (MCDEA) and 4,4'-methylenedianiline (MDEA), 4,4'-methylenebis(2-isopropyl-6-methyl)aniline, 4,4'-methylenebis(2-methyl-6-diethylaniline), 4,4'-methylenebis(2-ethylaniline), propylenediamine bis(4-aminobenzoate), 4,4'-bis-sec-butylaminodiphenylmethane, 1,4-bis-sec-butylaminobenzene, 3,5-diamino-4-chlorobenzoic acid isobutyl ester, 2,4-diamino-3,5-dimethylthiochlorobenzene, methyl At least one of phenylenediamine, 2,4-diamino-3-methylthio-5-propyltoluene, 4,4'-diaminodicyclohexylmethane, trimethylethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and quinoline diamine, more preferably at least one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis-sec-butylaminodiphenylmethane and isomers thereof; and 10-50% of a multifunctional polyether polyol, such as 10%, 20%, 40%, and 50% of a multifunctional polyether polyol, wherein the multifunctional polyether polyol is prepared by ring-opening homopolymerization or copolymerization using polyhydroxyl groups, primary amino compounds, or alcoholamines as initiators and epoxy compounds such as ethylene oxide and propylene oxide as polymerization monomers; preferably having a functionality of 2-6, such as 2, 3, 4, 5, and 6, and a hydroxyl value of 400-1000. Examples of polyether polyols having a hydroxyl value of 400 mg KOH / g, 500 mg KOH / g, 600 mg KOH / g, 700 mg KOH / g, 800 mg KOH / g, 900 mg KOH / g, and 1000 mg KOH / g are examples.

[0087] In some examples, in the mixture for casting, the amount of partially expanded polymer expanded microspheres added is 0.1-10wt%, for example, 1-5wt%, based on the mass of the polyurethane prepolymer; and the stoichiometric ratio (molar ratio) of the active hydrogen-containing groups in the curing agent to the unreacted isocyanate groups in the polyurethane prepolymer is 0.85-0.95.

[0088] The hardness and density of each polishing layer region are not particularly limited. For example, the density of each polishing layer region can be 0.6-1.05 g / cm3 The hardness can be, for example, 30-70D or 50-90A, but the key is that the density difference between the polishing layer regions required by the present invention must be 0.05-0.3 g / cm 3 , the hardness range is 5D-10D.

[0089] The present invention also provides a chemical mechanical polishing pad suitable for semiconductors, wherein the polishing pad is provided with a polishing layer prepared by the preparation method described above.

[0090] The present invention also provides use of the chemical mechanical polishing pad described above in chemical mechanical polishing.

[0091] The present invention will be further described below by way of examples, but it should not be understood that the present invention is limited thereto.

[0092] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0093] Description of the detection method:

[0094] Thermal expansion curve of polymer expanded microspheres: measured using a Mettler TMA / SDTA2+ TMA tester with a heating rate of 15°C / min, a load of 0.06N, and a ceramic crucible with a cover. This test method is referred to herein as the "TMA test."

[0095] D50 and particle size distribution: measured by laser particle size analyzer, model Bettersize 2600, using dry method and shading rate of 5%-20%.

[0096] True density of microspheres: measured by a true density meter, including high-purity nitrogen and a five-position analytical balance. The density meter model is ACCUPYCTMII 1340. The atmosphere used is nitrogen, the gas supply pressure is 0.4 psi, the sample cup is 100 ml, the inflation pressure is 0.2 psi, the air intake speed is 0.05 psi / min, the number of inflations is 3, and the number of cycles is 1.

[0097] Density of polishing layer: measured according to GB / T 4472-2011.

[0098] Hardness of polishing layer: measured according to ISO 7619 D.

[0099] Some of the raw materials used in the Examples and Comparative Examples are described as follows:

[0100] Polymer expanded microspheres I:

[0101] Weigh 30 g of acrylonitrile monomer, 8 g of vinylidene chloride monomer, 4 g of methacrylic acid, 8 g of methyl methacrylate monomer, 0.3 g of ethylene glycol dimethacrylate, 10 g of cyclohexane, and 0.3 g of polymerization initiator azobisisobutyronitrile, and mix them to prepare an oil phase;

[0102] Weigh 200g of water and 12g of silica sol and mix them to form the aqueous phase;

[0103] The aqueous phase and the oil phase were mixed and emulsified to obtain an emulsion, which was polymerized at 65°C and 400 rpm for 20 hours. The resulting slurry was filtered to obtain a microsphere filter cake, which was then dried in an oven at 60°C to obtain expandable microsphere powder. The expandable microsphere powder was sampled and subjected to TMA testing, which showed that the microspheres had a volume expansion capacity of 65 times.

[0104] The obtained microsphere powder was spread flat in a metal container and heated at 95°C for 100 seconds to obtain low-density microsphere powder (i.e., partially expanded polymer microspheres). The microspheres had a D50 particle size of 17.83 μm, a particle size distribution width of 1.125, and a true density of 0.0706 g / cm 3 The volume when the maximum expansion capacity is reached is about 1.6 times the current volume. The secondary expansion curve obtained by TMA test is as follows Figure 1 As shown, through Figure 1 It can be seen that the initial expansion temperature of the partially expanded polymer microspheres during secondary expansion by heating is 75°C, and the maximum expansion capacity is reached at 96°C.

[0105] The partially expanded polymer microspheres are polymer microspheres containing impurities. The partially expanded polymer microspheres are subjected to the following screening operation:

[0106] The microspheres are added to the silo of the air flow screen through a peristaltic pump and the equipment is started. After passing through the spiral conveying system, the microspheres are mixed with the air flow, atomized, and then enter the mesh drum. Under the dual action of the mesh drum rotation and wind, the microspheres penetrate the 200-mesh 316L stainless steel filter and enter the discharge port. Metal impurities, broken crusts in the microspheres, large-sized microspheres or microsphere agglomerates that cannot pass through the mesh are discharged from the impurity discharge port along the mesh drum wall.

[0107] The density of the sieved microspheres was measured using an automatic gas displacement true density analyzer ACCUPYC II 1345, and the particle size change of the microspheres was measured using a laser particle size distribution analyzer Bettersize 2600, as shown in Table 2 below.

[0108] Table 2

[0109]

[0110] Polymer expanded microspheres II: commercially available 461DE20d70 microspheres from Nouryon, with a particle size of 5-100 μm and a true density of 0.02-0.2 g / cm 3 , is a partially expanded microsphere. The secondary expansion curve obtained by TMA test of the microsphere is as follows Figure 2 As shown, the initial expansion temperature is 110°C and the maximum expansion capacity is reached at 125°C.

[0111] The Nouryon 461DE20d70 microspheres were sieved using the same sieving procedure as the polymer expanded microspheres I. The true density of the sieved microspheres was measured using an ACCUPYC II 1345 automatic gas displacement density analyzer. The particle size change of the microspheres was measured using a Bettersize 2600 laser particle size analyzer, as shown in Table 3 below.

[0112] Table 3

[0113]

[0114] Polymer expanded microspheres III:

[0115] Weigh 28 g of methyl acrylate monomer, 4 g of vinylidene chloride monomer, 10 g of butyl acrylate, 8 g of methacrylic acid monomer, 0.3 g of ethylene glycol dimethacrylate, 10 g of n-butane, and 0.3 g of polymerization initiator tert-butyl cyclohexyl peroxydicarbonate, and mix them to prepare an oil phase;

[0116] Weigh 200g of water and 15g of silica sol and mix them to form the aqueous phase;

[0117] The aqueous phase and the oil phase were mixed and emulsified to obtain an emulsion, which was polymerized at 55°C and 400 rpm for 20 hours. The resulting slurry was filtered to obtain a microsphere filter cake, which was then air-dried at room temperature to obtain expandable microsphere dry powder. The expandable microsphere dry powder was sampled and subjected to TMA testing, which showed that the microspheres had a volume expansion capacity of 58 times.

[0118] The obtained microsphere powder was spread flat in a metal container and heated at 50°C for 90 seconds to obtain low-density microsphere powder (i.e., partially expanded polymer microspheres). The microspheres had a D50 particle size of 20.36 μm, a particle size distribution width of 1.137, and a true density of 0.0696 g / cm 3 The volume when the maximum expansion capacity is reached is about 1.3 times the current volume. The secondary expansion curve obtained by TMA test is as follows Figure 15 As shown, through Figure 15 It can be seen that the initial expansion temperature of the partially expanded polymer microspheres during secondary expansion by heating is 40°C, and the maximum expansion capacity is reached at 65°C.

[0119] The partially expanded polymer microspheres are polymer microspheres containing impurities. The partially expanded polymer microspheres are subjected to the following screening operation:

[0120] The microspheres are added to the silo of the air flow screen through a peristaltic pump and the equipment is started. After passing through the spiral conveying system, the microspheres are mixed with the air flow, atomized, and then enter the mesh drum. Under the dual action of the mesh drum rotation and wind, the microspheres penetrate the 200-mesh 316L stainless steel filter and enter the discharge port. Metal impurities, broken crusts in the microspheres, large-sized microspheres or microsphere agglomerates that cannot pass through the mesh are discharged from the impurity discharge port along the mesh drum wall.

[0121] The density of the sieved microspheres was measured using an automatic gas displacement true density analyzer ACCUPYC II 1345, and the particle size change of the microspheres was measured using a laser particle size distribution analyzer Bettersize 2600, as shown in Table 4 below.

[0122] Table 4

[0123]

[0124] Polymer expanded microspheres IV:

[0125] Weigh 5 g of acrylonitrile monomer, 30 g of vinylidene chloride monomer, 6 g of methacrylic acid, 4 g of methyl methacrylate monomer, 0.3 g of ethylene glycol dimethacrylate, 9 g of isobutane, and 0.3 g of polymerization initiator tert-butyl cyclohexyl peroxydicarbonate, and mix them to prepare an oil phase;

[0126] Weigh 200g of water and 12g of silica sol and mix them to form the aqueous phase;

[0127] The aqueous phase and the oil phase were mixed and emulsified to obtain an emulsion, which was polymerized at 55°C and 400 rpm for 20 hours. The resulting slurry was filtered to obtain a microsphere filter cake, which was then dried in an oven at 65°C to obtain expandable microsphere powder. The expandable microsphere powder was sampled and subjected to TMA testing, which showed that the microspheres had a volume expansion capacity of 70 times.

[0128] The obtained microsphere powder was spread flat in a metal container and heated at 100°C for 80 seconds to obtain low-density microsphere powder (i.e., partially expanded polymer microspheres). The microspheres had a D50 particle size of 18.78 μm, a particle size distribution width of 1.102, and a true density of 0.0681 g / cm 3 The volume when the maximum expansion capacity is reached is about 1.7 times the current volume. The secondary expansion curve obtained by TMA test is as follows Figure 16 As shown, through Figure 16 It can be seen that the initial expansion temperature of the partially expanded polymer microspheres during secondary expansion by heating is 90°C, and the maximum expansion capacity is reached at 115°C.

[0129] The partially expanded polymer microspheres are polymer microspheres containing impurities. The partially expanded polymer microspheres are subjected to the following screening operation:

[0130] The microspheres are added to the silo of the air flow screen through a peristaltic pump and the equipment is started. After passing through the spiral conveying system, the microspheres are mixed with the air flow, atomized, and then enter the mesh drum. Under the dual action of the mesh drum rotation and wind, the microspheres penetrate the 200-mesh 316L stainless steel filter and enter the discharge port. Metal impurities, broken crusts in the microspheres, large-sized microspheres or microsphere agglomerates that cannot pass through the mesh are discharged from the impurity discharge port along the mesh drum wall.

[0131] The density of the sieved microspheres was measured using an automatic gas displacement true density analyzer ACCUPYC II 1345, and the particle size change of the microspheres was measured using a laser particle size distribution analyzer Bettersize 2600, as shown in Table 5 below.

[0132] Table 5

[0133]

[0134] Comparative Example 1

[0135] Comparative Example 1 used the partially expanded polymer expanded microspheres I after screening in Table 2 above;

[0136] The isocyanate prepolymer used has an unreacted isocyanate NCO content of 8.95-9.35 wt%, and is obtained by reacting 36 wt% TDI-80, 14 wt% HMDI, 7 wt% DEG, and 43 wt% PTMG-1000.

[0137] Curing agent: 85% by weight of 3,3'-dichloro-4,4'-methylenediamine (MOCA) and 15% by weight of YD-303 (Yadong Company);

[0138] Polymer expandable microspheres I and isocyanate prepolymer were mixed and dispersed at a dispersion temperature of 60°C and then transferred to a casting machine. The partially expanded polymer expandable microspheres I were added at a concentration of 3.18 wt% of the isocyanate prepolymer. During casting, the dispersion of microspheres and isocyanate prepolymer was mixed with a curing agent at the casting machine head to form a mixture (temperature between 35-55°C). The molar ratio of active hydrogen groups in the curing agent to unreacted NCO groups in the isocyanate prepolymer was measured to be 0.87. The mixture was poured through the casting head at 1000 rpm into a room-temperature mold with a diameter of 910 mm, forming a polyurethane cake approximately 1 cm high.

[0139] After pouring, wait until the surface of the mixture in the mold is solidified and has no fluidity. Transfer the polyurethane cake to an oven and maintain it at 106°C for 16 hours. After curing, cool it to room temperature, remove the polyurethane cake from the oven mold, and slice it into 80-mil thick slices at room temperature. During the slicing process, discard the incomplete slices when slicing the surface. Density data is measured according to GB / T 4472-2011. Density and hardness are sampled and tested three times, and the average value is obtained.

[0140] Comparative Example 2

[0141] Comparative Example 2 was carried out with reference to Comparative Example 1, except that the partially expanded polymer expanded microspheres I were replaced with the sieved commercially available Nouryon microspheres 461DE20d70 shown in Table 3.

[0142] The density and hardness of the polishing layer prepared in Comparative Example 1-2 are shown in Table 6.

[0143] Table 6

[0144]

[0145] Example 1

[0146] In this embodiment, the partially expanded polymer microspheres I after screening in Table 2 above were used;

[0147] The same isocyanate prepolymer as in Comparative Example 1 was used;

[0148] Curing agent: 85% by weight of 3,3'-dichloro-4,4'-methylenediamine (MOCA) and 15% by weight of Yadong Company's YD-303;

[0149] Polymer expandable microspheres I and isocyanate prepolymer were mixed and dispersed at a dispersion temperature of 60°C and then transferred to a casting machine. The amount of polymer expandable microspheres I added to the partially expanded isocyanate prepolymer was 3.18 wt %. During casting, the dispersion of microspheres and isocyanate prepolymer was mixed with a curing agent at the casting machine head to form a mixture (temperature between 35-55°C). The molar ratio of active hydrogen groups in the curing agent to unreacted NCO in the isocyanate prepolymer was measured to be 0.87. The mixture was poured through the casting head at 1000 rpm into a room temperature mold with a diameter of 910 mm (see the schematic diagram of the temperature control zone division of the mold for details). Figure 3 ), forming a polyurethane cake with a height of about 1 cm; the specific temperature parameters of each temperature adjustment area of ​​the mold are shown in Table 7;

[0150] After pouring, wait until the surface of the mixture in the mold is solidified and has no fluidity, transfer the polyurethane cake to an oven and keep it at 106℃ for 16 hours. After the curing is completed, cool it to room temperature, take the polyurethane cake out of the oven mold, and cut it into slices with a thickness of 80 mil at room temperature. During the slicing process, discard the incomplete slices when slicing the surface layer to obtain the formal slices. Figure 3 Samples were taken from the center of the four polishing layer areas corresponding to the temperature adjustment areas 1-4 of the mold shown. Three samples were taken from each area. The density of each area was measured by the water displacement method according to GB / T 4472-2011. The hardness was also measured. Each sample was tested three times. The average of the test results of the samples taken from each area was used as the test result. The results are shown in Table 7.

[0151] Example 2

[0152] The method is carried out in accordance with Example 1, except that: the temperature adjustment area division diagram of the mold used is shown in FIG. Figure 4 , the specific temperature parameters of each temperature adjustment area 1-8 of the mold are shown in Table 7.

[0153] The thin slice prepared in Example 2 was sampled from the center of the eight polishing layer areas corresponding to the temperature adjustment areas of the mold, and the density and hardness of each area were tested with reference to Example 1. The test results are shown in Table 7.

[0154] Table 7

[0155]

[0156] Note: The area numbers in Table 7 correspond to the numbers of the temperature control areas of the corresponding molds. For example, area 1 in Example 1 corresponds to Figure 3 The test results of the polishing layer area obtained in the temperature adjustment area 1 of the mold shown are the same as those in Tables 8-12, which will not be repeated here.

[0157] Example 3

[0158] The method is carried out in accordance with Example 1, except that: the temperature adjustment area division diagram of the mold used is shown in FIG. Figure 5 , the specific temperature parameters of each temperature adjustment area 1-3 of the mold are shown in Table 8.

[0159] The thin slice prepared in Example 3 was sampled along its cross section according to the three polishing layer areas corresponding to the temperature adjustment areas of the mold. The measured density and hardness of each area are shown in Table 8.

[0160] Example 4

[0161] The method is carried out in accordance with Example 1, except that: the temperature adjustment area division diagram of the mold used is shown in FIG. Figure 6 , the specific temperature parameters of each temperature adjustment area 1-4 of the mold are shown in Table 8.

[0162] The thin slice prepared in Example 4 was sampled from the four polishing layer areas corresponding to the temperature adjustment areas of the mold. The density and hardness of each area were measured and can be found in Table 8.

[0163] Table 8

[0164]

[0165] Example 5

[0166] The same procedure was followed as in Example 1, except that the specific temperature parameters of the temperature adjustment zones 1-4 of the mold were as shown in Table 9.

[0167] The thin slices prepared in this example were sampled from four polishing layer regions corresponding to the temperature adjustment regions of the mold. The measured density and hardness of each region are shown in Table 9.

[0168] Table 9

[0169]

[0170] Example 6

[0171] The method is carried out in accordance with Example 1, except that: the temperature adjustment zones 1-3 of the mold are divided into a schematic diagram as shown in FIG. Figure 7 , the specific temperature parameters of each temperature adjustment area 1-3 of the mold are shown in Table 10.

[0172] The thin slices prepared in this example were sampled from three polishing layer regions corresponding to the temperature adjustment regions of the mold. The measured density and hardness of each region are shown in Table 10.

[0173] Table 10

[0174]

[0175] Example 7

[0176] The method is carried out in accordance with Example 1, except that: the temperature adjustment zones 1-3 of the mold are divided into a schematic diagram as shown in FIG. Figure 8 , the specific temperature parameters of each temperature adjustment area 1-3 of the mold are shown in Table 11.

[0177] The thin slices prepared in this example were sampled from three polishing layer regions corresponding to the temperature adjustment regions of the mold. The measured density and hardness of each region are shown in Table 11.

[0178] Table 11

[0179]

[0180] Comparative Examples 3-4

[0181] Comparative Examples 3-4 were carried out with reference to Example 1, except that:

[0182] In Comparative Examples 3-4, the specific temperature parameters of the temperature adjustment zones 1-4 of the mold are respectively shown in Table 12.

[0183] Table 12

[0184]

[0185] Comparative Examples 5-6

[0186] Comparative Examples 5 and 6 were carried out with reference to Example 1, except that different partially expanded polymer expanded microspheres were used;

[0187] Among them, Comparative Example 5 uses the partially expanded polymer expanded microspheres III after screening, which have Figure 15 The secondary expansion curve shown (obtained by TMA test) shows that the initial expansion temperature of the partially expanded polymer expanded microspheres III is 40°C.

[0188] Comparative Example 6 used partially expanded polymer microspheres IV after sieving, which had Figure 16 The secondary expansion curve shown (obtained by TMA test) shows that the initial expansion temperature of the partially expanded polymer expanded microspheres III is 90°C.

[0189] In Comparative Examples 5 and 6, the amount of partially expanded polymer expanded microspheres added to the mixture used for casting was both 3.07 wt %.

[0190] During the implementation of Comparative Example 5, it was found that when dispersing the polymer expanded microspheres III in the isocyanate prepolymer, if the temperature was lower than 60°C, uniform dispersion could not be achieved; however, when the isocyanate prepolymer was heated to 60°C for dispersion, secondary expansion occurred during the dispersion stage of the microspheres into the isocyanate prepolymer, and the degree of expansion was difficult to control. As a result, after the mixture was poured into the mold, it was difficult to obtain a polishing layer with extremely poor density and hardness that met the requirements of the present invention by temperature adjustment in different temperature adjustment areas of the mold.

[0191] In Comparative Example 6, microspheres IV ( Figure 16During implementation, it was discovered that if the mixture was not heated to above 70°C before pouring, it would be difficult to heat it to the required expansion temperature (above 90°C) before the mixture gelled and solidified when subsequently poured into the mold. As a result, the mixture gelled and solidified before reaching the required temperature, failing to achieve the desired expansion level. Consequently, it was difficult to obtain a polishing layer with the desired density and hardness, which was extremely poor. Furthermore, it was discovered that if the mixture was heated to above 70°C before pouring and then poured into the mold, while a product with the desired density and hardness could be achieved through temperature regulation in each temperature control zone, the resulting product would have numerous flow mark defects, leading to casting failures, likely due to the intense exotherm.

[0192] The polishing layers obtained in Examples 1-7 of the present application have no flow mark defects on their surfaces.

[0193] The polishing layer sheets prepared in the above-mentioned comparative examples and embodiments were sanded and then grooved, and the surface was patterned in the form of concentric circles to form grooves with a common geometric center on the polishing layer. The spacing between the grooves of the polishing layer was uniform, and the polishing layer contained a complete and continuous outermost groove with a groove width of 0.5 mm and a depth of 0.7 mm. The polishing layer was bonded to SUBAIV (DOW) and then punched into a polishing pad with a diameter of 300 mm.

[0194] Polishing performance test conditions: The polisher was an F-REX300X 300mm chemical mechanical planarization system. The polishing slurry was CeO2 (diluted with DI water at a volume ratio of 1:3). The pad dresser was a diamond dresser. During polishing, the polishing pressures were 210 / 215 / 219 / 226 / 229 / 226 / 259 / 281 hPa (A1-A8), the polishing time was 60 seconds, the polishing pad and polishing head speeds were 87 / 93 rpm, the polishing material was silicon oxide (the polishing material), the polishing slurry flow rate was 300 ml / min, and the drop point was set at 36 mm. Ex-situ polishing (offline dressing) was selected, the polishing pad and polishing head speed ratio was 70 / 80 rpm, and the polishing time was 50 seconds.

[0195] Performance testing process: The polishing pad is flatly attached to the polishing plate, and the dresser begins initial dressing. After dressing is completed, the first round of polishing is performed (polishing 1 pc of wafer). The thickness of the wafer surface is measured before and after polishing, and the polishing rate is calculated. The test collects the polishing rate of two rounds (1 pc and 500 pcs).

[0196] The wafer polishing test results of Examples 1-7 and Comparative Examples 1-4 are shown in Table 11. The wafer removal rate results after polishing with the polishing pads of Comparative Examples 1-2 and Examples 1-4 are shown in Table 11. Figure 9-14 shown.

[0197] Table 13

[0198]

[0199] in, ; is the polishing rate at each point on the polished wafer, is the average polishing rate of each point on the polished wafer, and n is the number of position points recorded on the polished wafer.

[0200] Range is the difference between the average polishing rate of the first 100 wafers and the average polishing rate of the last 500 wafers.

[0201] The polishing pad based on the polishing layer provided in the embodiment of the present invention can meet the requirements of the efficient and high-speed development of integrated circuits and the subsequent deposition process of chemical mechanical polishing in the IC process. The requirements for the oxide wafer surface after the oxide CMP process are a polishing rate RR ≥ 1000 Å / min and a polished wafer surface inconsistency Nu ≤ 5%, Range ≤ 100 Å / min.

[0202] Polishing experiments have shown that the chemical mechanical polishing pad embodiments provided by the present invention, manufactured with surface macrotextures, fully meet or exceed the requirements for oxide wafer surfaces after CMP processes. The polishing experiment results show that the chemical mechanical polishing pad embodiments provided by the present invention meet or exceed polishing requirements.

[0203] Comparing the polishing results of Examples 1-7 with those of Comparative Examples 1 and 2, it can be seen that the polished surfaces prepared in the Examples have a variety of regions with different densities and hardnesses and the density difference of different regions is controlled to be 0.05-0.3 g / cm 3 The hardness gradient ranges from 5-10D, demonstrating superior polishing rate stability compared to polishing pads with a single density and hardness. This further demonstrates that single-density polishing pads are insufficient to address issues such as excessive polishing rates at the wafer edge due to speed differences between the polishing head and disc, and uneven distribution of slurry on the polishing pad. The polishing pad with the density gradient of the present invention can mitigate wafer edge defects and effectively improve wafer surface flatness after polishing.

[0204] The difference between Comparative Examples 3 and 4 and Example 1 is that the requirement that "the density difference between the polishing layer regions is 0.05-0.3 g / cm 3 , the hardness range is 5-10D", and the polishing results do not meet the expected results in both Nu and Range.

[0205] Compared with Example 1, Example 2 has a similar density range. The main difference is that the polishing pad of the latter has more density division areas. Comparing the polishing results, it is found that the polishing pad of Example 2 has better inconsistency performance on the 1st and 500th wafers than the polishing pad of Example 1. This shows that the polishing pad with more different density areas is more effective in improving the stability of the polishing rate (Nu and Range are reduced).

[0206] In Examples 3 and 4, the polishing rates showed a common convergence in polishing inconsistency (Nu decreased). The difference was that the Range difference of Example 4 was narrower than that of Example 3. The polishing pad of Example 4 contained a lower density and softer polishing area. The expansion of the density span effectively reduced the polishing rate and improved the fluctuation of the polishing removal rate during the life of the polishing pad.

[0207] Comparing Example 5 with Example 1, it can be seen that the polishing rates are basically the same under the conditions of maintaining a certain density span and hardness extremes; secondly, comparing Examples 6 and 7 with Example 3, it can be seen that the polishing results of irregular areas are slightly better than those of regular areas.

[0208] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a polishing layer of a chemical mechanical polishing pad, characterized in that: The preparation method is used to prepare a polishing layer including a plurality of polishing layer regions with different densities and hardnesses along a cross section of the polishing layer; The preparation steps of the polishing layer include: (1) pouring a mixture comprising a polyurethane prepolymer, a curing agent and partially expanded polymer expandable microspheres into a pouring cavity of a mold, wherein the pouring thickness of the mixture is 0.2-1 cm, and the partially expanded polymer expandable microspheres can be expanded secondary by heating; the mold has a temperature regulating function, and a plurality of temperature regulating areas are provided along the cross section of the pouring cavity of the mold; The initial expansion temperature of the partially expanded polymer microspheres is 60-70°C, and the expansion capacity reaches the maximum at 80-100°C and stops expanding. In step (1), the partially expanded polymer expanded microspheres are first dispersed in the polyurethane prepolymer, and the dispersion is performed at 60-80° C., and then before the pouring, the curing agent is added and mixed uniformly to obtain the mixture; and before the pouring, the temperature of the mixture is 35-55° C.; (2) adjusting the temperature of each of the temperature adjustment zones so that the temperature of at least two of the temperature adjustment zones is different, and causing the partially expanded polymer expandable microspheres in the casting cavity corresponding to the positions of the temperature adjustment zones with different temperatures to undergo secondary expansion to different degrees; (3) The mixture treated in step (2) is subjected to post-treatment including vulcanization to obtain a single-piece polishing layer, wherein the density difference between each polishing layer region of the polishing layer is 0.05-0.3 g / cm 3 , the hardness range is 5-10D.

2. The preparation method according to claim 1, characterized in that The density and hardness of adjacent polishing layer regions are different.

3. The preparation method according to claim 1, characterized in that The polishing layer includes two or more polishing layer regions; And / or, the polishing layer includes a central polishing layer region and a peripheral polishing layer region surrounding the central polishing layer region; or, the polishing layer includes a central polishing layer region and a plurality of peripheral polishing layer regions disposed around the central polishing layer region, and the plurality of peripheral polishing layer regions are sequentially arranged from the inside out; or, the polishing layer includes a plurality of polishing layer regions having a sector-shaped outer contour; and / or, the polishing layer is evenly or unevenly divided into a plurality of polishing layer regions; And / or, at least a portion of the polishing layer region has a regular or irregular shape.

4. The preparation method according to any one of claims 1 to 3, characterized in that The division of the temperature adjustment areas of the casting cavity of the mold matches the distribution of the polishing layer areas of the polishing layer.

5. The preparation method according to any one of claims 1 to 3, characterized in that The partially expanded polymer microspheres are unexpanded polymer microspheres that are partially expanded by heating and have a volume V0, and the volume of the partially expanded polymer microspheres when they reach maximum expansion capacity is 1.2-2 times the volume V0.

6. The preparation method according to claim 5, characterized in that In step (2), the temperature of each of the temperature adjustment areas does not exceed 100° C., and the temperature of at least part of the temperature adjustment areas is greater than or equal to the initial expansion temperature of the partially expanded polymer expanded microspheres.

7. The preparation method according to any one of claims 1 to 3, characterized in that After the partially expanded polymer expandable microspheres reach their maximum expansion capacity during the heating and expansion process, the temperature at which they rupture and leak gas is not less than 120° C. when further heated; And / or, the particle size D50 of the partially expanded polymer expanded microspheres is 5-100 μm, and the true density is 0.02-0.2 g / cm 3 ; And / or, the unexpanded polymer expanded microspheres have a volume expansion capacity of not less than 30 times.

8. The preparation method according to any one of claims 1 to 3, characterized in that The partially expanded polymer expandable microspheres expand secondarily in a linear or substantially linear expansion manner when heated to the initial expansion temperature until the maximum expansion capacity is reached.

9. A chemical mechanical polishing pad suitable for semiconductors, characterized in that: The polishing pad is provided with a polishing layer prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the chemical mechanical polishing pad according to claim 9 in chemical mechanical polishing.

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