A polishing pad

Abstract

The present invention relates to a polishing pad, the polishing pad comprising a polyurethane polishing layer, the polyurethane polishing layer containing composite metal oxide micro-units, the polyurethane polishing layer being a reaction product of a raw material combination, the raw material combination comprising an isocyanate-terminated prepolymer obtained by reacting a polyfunctional isocyanate with a polyol, a hollow microsphere polymer, and a curing agent. In the present invention, by strictly controlling the size and size distribution of the hollow microsphere polymer, the prepared polishing pad exhibits good physical and chemical properties, and has appropriate roughness and an appropriate content of metal elements, showing good polishing performance.

Description

Technical Field

[0001] The present invention relates to the polishing technology field of chemical mechanical planarization, and in particular, to a polishing pad. Background Art

[0002] As the feature size of integrated circuits develops towards deep nanometer processes, the feature size becomes smaller and smaller. The defects brought by the CMP process become more and more prominent in advanced processes, even reaching the level of seriously affecting the chip performance. Therefore, as one of the four core materials of the CMP process, pursuing the ultimate performance of the polishing pad is an eternal topic in the research and development of polishing pads. For the performance indicators of the polishing pad, there is an increasing consensus in the CMP field on the ultimate stability and uniformity. The requirements for the stability and uniformity of the polishing pad have gradually increased from the macroscopic indicators such as density, hardness, compression ratio, and compression recovery rate between different batches and between different polishing pads of the same batch to between different positions of the same polishing pad, and even to the stability and uniformity of the molecular structure regularity.

[0003] Chinese patents CN107553313B, CN108047420A, CN109015342A, WO_{2019042428}A1, and CN109824854A expound from the perspective of the formula that a polishing pad with better uniformity can be obtained by controlling heat release, controlling microsphere expansion, and introducing a new low-heat-release prepolymer, effectively alleviating the differences between different batches / sheets of polishing pads. The macroscopic indicators such as hardness, density, compression ratio, and compression recovery rate between different polishing pads are more stable and uniform, and better polishing performance is obtained in the application evaluation. However, with the refinement of the polishing process, more stringent requirements are put forward for the polishing pad in some special processes. For example, in some STI process polishings, a special CeO₂ polishing liquid is used, which puts almost harsh requirements on the surface roughness of the polishing pad during the polishing process, because its polishing rate has a serious positive correlation with the surface roughness of the polishing pad, and too high or too low roughness will cause the process control to exceed the control range.

[0004] In terms of the preparation of polishing pads, the factors affecting roughness are divided into two aspects: materials and processing technology. In terms of materials, the main components are the prepolymer, curing agent, and pore-forming agent for forming the polishing pad. The processing technology mainly affects the initial roughness of the polishing pad. However, before polishing, the surface of the polishing pad will be treated to eliminate the initial roughness difference and maintain a rough surface. After the polishing process is determined, the main factor determining the surface roughness of the polishing pad is still the polishing pad material. The prepolymer and curing agent react with each other to form the polishing pad substrate, and the pore-forming agent separates the substrate to form different pores. Theoretically, the decisive factor for surface roughness is the pore-forming agent. The larger the pore size formed by the pore-forming agent, the greater the roughness; the smaller the pore size, the smaller the roughness. The traditional pore-forming method used in the preparation of polishing pads is microsphere foaming, but the microspheres D selected from suppliers 50 range is difficult to guarantee, and products from different batches of D 50 range fluctuates greatly, resulting in large performance fluctuations in the polishing pads produced by microspheres from different batches during actual use. In addition, due to the lack of special control over the metal content of the products during the preparation of microspheres, problems such as excessive metal content in the microspheres and relatively large metal oxide particles occur, causing defects such as scratches on semiconductor devices during polishing.

[0005] Therefore, how to control the metal element content and metal oxide size in microspheres, and how to maintain appropriate and stable roughness and a high removal rate during different service life periods of a polishing pad and between different polishing pads has become an urgent issue to be solved. Summary of the Invention

[0006] In the present invention, the microspheres purchased from suppliers are further processed. While controlling the microsphere particle size and distribution range within a narrow range, by controlling the metal content and the size of metal oxides in the polishing pad, they are prepared into polishing pads, and products with extremely stable polishing performance are obtained.

[0007] The present invention provides a polishing pad, including a polyurethane polishing layer. The polyurethane polishing layer contains composite metal oxide micro-units. The polyurethane polishing layer is the reaction product of a raw material combination. The raw material combination includes an isocyanate-terminated prepolymer obtained by the reaction of a polyfunctional isocyanate and a polyol, a hollow microsphere polymer, and a curing agent. The composite metal oxide micro-units contain two or more metal elements;

[0008] Further, the metal elements include alkaline earth metal elements, boron group metal elements, and transition metal elements. The alkaline earth metal elements in the composite metal oxide micro-units include at least one of magnesium and calcium elements. The boron group metal elements include aluminum element. The transition metal elements include at least one of iron and chromium elements;

[0009] Further, the contents of various metal elements in the composite metal oxide micro-units satisfy the following conditions: the content of aluminum element does not exceed 50 ppm, the content of iron element does not exceed 70 ppm, the content of chromium element does not exceed 100 ppm, the content of magnesium element does not exceed 50 ppm, and the content of calcium element does not exceed 150 ppm;

[0010] Further, the contents of various metal elements in the composite metal oxide micro-units satisfy the following conditions: the content of aluminum element is not less than 10 ppm, the content of iron element is not less than 10 ppm, the content of chromium element is not less than 15 ppm, the content of magnesium element is not less than 10 ppm, and the content of calcium element is not less than 30 ppm;

[0011] Further, the content ratio of calcium element, magnesium element, and aluminum element in the composite metal oxide micro-units is 1-20: 2-10: 1-9, and the content ratio of iron element and chromium element is 0.2-10: 0.5-20;

[0012] Further, the particle size of the composite metal oxide micro-units is 10 μm-60 μm;

[0013] Further, the hollow microsphere polymer is subjected to classification treatment by a classification device;

[0014] Further, the classification device includes a first classification area, at least one lower classification impeller (7) is included in the first classification area, a first induced draft fan (10) is arranged at the top of the lower classification impeller (7), an intermediate material storage chamber (12) is included in the first classification area, the intermediate material storage chamber (12) is connected to the first induced draft fan (10) through a pipe, a lower material storage chamber (13) is included at the bottom of the first classification area, and a magnetic component (9) is arranged at the bottom of the first classification area;

[0015] Further, it includes a second classification area, the second classification area is connected to the first classification area through a pipe, at least two upper classification impellers (2) are included in the second classification area, the upper classification impellers (2) are arranged on the side wall of the classification pipeline in the second classification area, and the rotation main shaft of the upper classification impellers (2) forms an angle of 60-90° with the side wall of the classification pipeline. A secondary air inlet (6) is arranged at the bottom of the second classification area, one or more second induced draft fans (3) are arranged in the second classification area, one or more upper material storage chambers (5) are also arranged and connected to the second induced draft fans (3) through a pipe, and magnetic materials are arranged on the surfaces of the upper classification impellers (2);

[0016] Further, the density of the polyurethane polishing layer is 0.6-1.1 g / cm 3, the Shore hardness is 15 - 80D, the compression ratio is 0.1 - 3.0%, and the surface roughness Ra is 1.5 - 30 μm.

[0017] Advantages of the present invention:

[0018] 1. By controlling the particle size and particle size distribution of the hollow microsphere polymer within a narrow range, the prepared polishing pad product has excellent repeatability and extremely excellent polishing performance.

[0019] 2. By controlling the particle size and particle size distribution of the hollow microsphere polymer within a narrow range, the composite metal oxide micro-units inside the hollow microspheres can be regulated, and the surface roughness of the polyurethane polishing pad can be modulated. When there are appropriate amounts and appropriately sized composite metal oxide micro-units on the surface of the polyurethane polishing layer, the removal rate remains good, and scratches on the polished material by the polishing pad can be effectively reduced.

[0020] 3. While controlling the particle size of the hollow microsphere polymer, the metal element content inside the hollow microsphere polymer can be regulated. Appropriate types of composite metal oxide micro-units can play a catalytic role, which can improve the polishing performance of the polishing pad and reduce defect generation. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a sectional view of the first classification area of the classification equipment involved in the present invention;

[0023] Figure 2 It is a sectional view of the combination of the second classification area and the first classification area of the classification equipment involved in the present invention;

[0024] Figure 3 It is a schematic diagram of the polishing operation process of the polishing pad provided in the embodiments involved in the present invention;

[0025] 1 - pump, 2 - upper classification impeller, 3 - second induced draft fan, 4 - upper material outlet, 5 - upper material storage chamber, 6 - secondary air inlet, 7 - lower classification impeller, 8 - gap adjustment cone, 9 - magnetic component, 10 - first induced draft fan, 11 - intermediate material outlet, 12 - intermediate material storage chamber, 13 - lower material storage chamber, 14 - material to be polished, 15 - polishing pad, 16 - polishing machine table, 17 - bracket, 18 - polishing liquid. Detailed Embodiments

[0026] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the invention. For those not specified in the examples, the operations are carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0027] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present invention pertains. In case of conflict, the present specification shall prevail.

[0028] Polyurethane polishing layer

[0029] Generally, the manufacturing process of the polyurethane polishing layer is to heat the isocyanate-terminated prepolymer to a certain temperature to make it have a certain viscosity. Generally, hollow microsphere polymers are added to adjust the product density. Then, the mixture is mixed with a curing agent and cast to form a polyurethane casting block, which is cured under certain conditions to form a polyurethane material block, and then cut into thin slices with a certain thickness as the polyurethane polishing layer.

[0030] Among them, polyurethane is a product derived from bifunctional or polyfunctional isocyanates, such as: a mixture or copolymer of two or more of polyether urea, polyisocyanurate, polyurethane, polyurea, and polyurethane urea. In addition, the polishing effect of the polyurethane polishing layer can be effectively improved through chemical composition adjustment.

[0031] In the present invention, the polyurethane polishing layer includes a reaction product formed by the reaction of multiple raw materials. The multiple raw materials include the isocyanate-terminated prepolymer, curing agent, and optionally hollow microsphere polymers, which will be described in detail below. Preferably, the hollow microsphere polymers are mixed into the isocyanate-terminated prepolymer, and after the mixture is mixed with the curing agent, a curing reaction is carried out.

[0032] In the present invention, the polyurethane polishing layer prepared from the raw materials has the following physical and chemical properties: the density of the polyurethane polishing layer is 0.6 - 1.1 g / cm 3 , preferably the density is 0.72 - 0.75 g / cm 3 , and particularly preferably the density is 0.72 - 0.73 g / cm 3 .

[0033] The obtained polyurethane polishing layer has a Shore hardness of 15 to 80D, preferably 55 to 75D, and particularly preferably 55 to 65D. When the hardness is greater than 80D, the polyurethane polishing layer has a high removal rate, but this is accompanied by excessive defects such as scratches. When the hardness is less than 15D, while the defect rate is effectively reduced, the removal rate is severely reduced. The polyurethane polishing layer of the present invention achieves a good balance between defect rate and removal rate, significantly increasing the removal rate without increasing the defect rate (or even reducing it).

[0034] The compression ratio of the polyurethane polishing layer is 0.1-3.0%, preferably 0.35-0.7%, and particularly preferably 0.4-0.6%.

[0035] The surface roughness Ra of the polyurethane polishing layer is 1.5 to 30 μm, preferably 1.5 to 14 μm, and particularly preferably 1.5 to 13.5 μm. A surface roughness lower than 1.5 μm results in low polishing efficiency and cannot meet production needs. A surface roughness Ra greater than 30 μm increases the wear of the polyurethane polishing layer, reduces its service life, and may cause scratches to the polished surface.

[0036] Hollow microsphere polymer

[0037] In the process of preparing the polyurethane polishing layer, the hollow microsphere polymer is evenly dispersed in the polishing layer, thereby adjusting the polishing effect of the polyurethane polishing layer.

[0038] The term "hollow microsphere polymer" as used herein refers to expandable hollow polymer microspheres (hereinafter referred to as "microspheres") that expand moderately during the curing process due to the temperature increase caused by the exothermic reaction. The polishing performance of the polyurethane polishing layer can be further adjusted by adjusting the distribution (e.g., density) of the hollow microsphere polymer in the polyurethane polishing layer and adjusting the particle size of the hollow microsphere polymer. Preferably, the hollow microsphere polymer is dispersed in the polishing layer so that the final porosity of the polishing layer is 10-40%, and particularly preferably, the porosity is 15-35%.

[0039] Preferably, the hollow microsphere polymer includes but is not limited to a sac-like structure having an outer wall of polyacrylonitrile and polyacrylonitrile copolymer, and can be purchased from Akzo Nobel, Matsumoto Oil and Fat Pharmaceutical Co., Ltd. or Sekisui Chemical Co., Ltd. Microspheres or microbeads, particularly preferably, Akzo Nobel hollow microspheres or Matsumoto microbeads F series.

[0040] It should be noted that the above purchased hollow microsphere polymer is only one of many preferred hollow microsphere polymers, and is not a limitation thereto. During use, all hollow microsphere polymers that can meet the manufacturing of the polyurethane polishing layer in the art can be selected.

[0041] The polyurethane polishing layer prepared by microsphere foaming can achieve the characteristics of uniform pore size and low pore size distribution coefficient. However, the polymer microspheres purchased from suppliers are significantly restricted by products. The nominal D 50 range often has large differences. For example, for the microspheres with the brand number 551DE40D42 purchased from AkzoNobel, the nominal particle size is 30 - 50 μm, but the actually measured particle size fluctuates to 20 - 55 μm. Even if the nominal value can be reached, the particle size fluctuation is relatively large. This results in the difficulty of ensuring the stability of the physical properties of the polishing pads produced by different batches of microspheres, and thus large performance fluctuations occur during actual use. In addition, since commercial microspheres are not specifically supplied for the semiconductor industry, there is no special control over the metal components and metal content in the products, and there are many foreign objects and impurities. There are many foreign object points such as black, yellow, and brown in the microspheres, and their components include large particles formed by microsphere aggregation, composite metal oxide micro-units, etc. Therefore, in the present invention, the hollow microsphere polymer is subjected to microsphere classification treatment, which can completely remove the foreign objects and impurities therein, not only control its particle size and distribution range within a narrow range, but also effectively control the metal content therein and the particle size of the composite metal oxide micro-units. The polishing pad prepared using this hollow microsphere polymer has appropriate roughness and a high removal rate.

[0042] In the embodiment of the present invention, a classification device is provided, such as Figure 1 shown. Considering the classification efficiency and the control range of the classified particle size, at least one lower classification impeller 7 is arranged in the first classification area. Among them, a first induced draft fan 10 is arranged at the top of the lower classification impeller 7, and the first induced draft fan 10 is connected to an intermediate material storage chamber 12 through an intermediate material outlet 11, and is used to attract the materials classified by the lower classification impeller 7; a lower material storage chamber 13 is arranged at the bottom of the first classification area. Preferably, the lower material storage chamber 13 includes a magnetic component 9, which is used to attract the metal components in the hollow microsphere polymer here. Optionally, the classification device further includes an 8-gap adjustment cone, which is located below the lower classification impeller 7.

[0043] In the embodiment of the present invention, the classification principle of the classification impeller is to classify the materials according to the relative gap between adjacent classification impellers, or to classify the materials according to the absolute gap of the classification impeller itself. Preferably, in the embodiment of the present invention, the absolute gap of the blades of the preferred lower classification impeller 7 is 10 - 90 μm.

[0044] The above-mentioned magnetic component 9 can be a common magnetic component in the art. The above-mentioned magnetic component 9 has a magnetic force of 5000 Gauss to 15000 Gauss. Preferably, the magnetic force of the magnetic component 9 is 8000 Gauss to 12000 Gauss. Particularly preferably, the magnetic force of the magnetic component 9 is 8000 Gauss to 9000 Gauss.

[0045] In the present invention, preferably, it further includes a second classification area. The second classification area can be an empty classification pipeline without any classification impellers and induced draft fans, or can also include a plurality of classification impellers and induced draft fans.

[0046] In the present invention, particularly preferably, considering both classification efficiency and economy, as Figure 2 shown, the second classification area contains 4 upper classification impellers 2. Among them, considering the high efficiency of classification and the ease of equipment installation, in the embodiment of the present invention, the rotating main shaft of the upper classification impeller 2 is at a 90° angle to the side wall of the classification pipeline in the second classification area. According to the size of the particle size to be classified, the absolute clearance between the blades of the upper classification impeller 2 in the second classification area is 10-90 μm. For the full classification of microspheres, in the embodiment of the present invention, the 4 upper classification impellers 2 are respectively located on both sides of the side wall of the classification pipeline in the second classification area and are arranged in a staggered manner. In the embodiment of the present invention, 4 second induced draft fans 3 are also provided and connected to the upper classification impeller 2. The second induced draft fans 3 are used to attract the classified materials to the upper material storage chamber 5 through the upper material outlet 4; among them, a secondary air inlet 6 is provided at the bottom of the second classification area for blowing the hollow microsphere polymer passing through the second classification area into the first classification area.

[0047] In the classification equipment in the embodiment of the present invention, the classification pipeline can be one or a combination of a straight line type, an "S" type, and an "N" type. Considering equipment cost and classification time, the classification pipeline in the embodiment of the present invention is of a straight line type.

[0048] The above-mentioned magnetic material can be a common magnetic material in the art, as long as it can attract transition metal oxides, and is used to initially attract the transition metal components in the hollow microsphere polymer. The above-mentioned magnetic material has a magnetic force of 500 Gauss to 10000 Gauss.

[0049] Preferably, among them, the first classification area can accurately screen the hollow microsphere polymer with a particle size range of 20 μm to 50 μm, and the second classification area can accurately screen the hollow microsphere polymer with a particle size range of 10 μm to 20 μm.

[0050] The classification of the hollow microsphere polymer uses such as Figure 1Perform the classification using the classification device shown. Turn on the classification device. First, adjust the frequency of the upper classification impeller 2 to 25 - 90 Hz, and control the frequency of the second induced draft fan 3 to 20 - 80 Hz. The second induced draft fan 3 is used to attract the hollow microsphere polymer to the upper material storage chamber 5. There are two upper material storage chambers 5 in this classification device. Then, adjust the frequency of the lower classification impeller 7 to 10 - 80 Hz, turn on the switch of the first induced draft fan 10, and control the frequency of the first induced draft fan 10 to 20 - 80 Hz, which is used to attract the hollow microsphere polymer passing through the lower classification impeller 7 to the intermediate material storage chamber 12. Adjust the gap adjusting cone 8 to an appropriate angle, open the secondary air inlet 6, and then pump the unclassified hollow microsphere polymer into the classification device through the pump 1. The feeding speed of the pump 1 is controlled at 10 - 70 rps. After microsphere classification, take the material in the intermediate material storage chamber 12, which is the classified hollow microsphere polymer. Preferably, a magnetic component 9 is further provided below the lower material storage chamber 13 at the bottom of the classification equipment, which is used to attract the metal components in the microspheres again.

[0051] Preferably, the frequency of the upper classification impeller 2 is 30 - 65 Hz. Particularly preferably, the frequency of the upper classification impeller 2 is 50 - 65 Hz; preferably, the frequency of the lower classification impeller 7 is 10 - 45 Hz. Particularly preferably, the frequency of the lower classification impeller 7 is 30 - 45 Hz.

[0052] It should be noted that the classified hollow microsphere polymer can be the material collected in the intermediate material storage chamber or the material collected in the lower material storage chamber. The frequencies of the lower classification impeller 7 and the first induced draft fan 10 can be adjusted according to the actual classification situation, so that the classified hollow microsphere polymer is collected in the intermediate material storage chamber 12 or the lower material storage chamber 13. Preferably, in the present invention, the material collected in the lower material storage chamber is selected as the classified hollow microsphere polymer.

[0053] The polyurethane polishing layer described in the present invention contains a certain amount of composite metal oxide micro-units. Generally, these composite metal oxide micro-units are introduced by hollow microsphere polymers or introduced during the preparation process. The presence of a large number of composite metal oxide micro-units and large particle metal oxide micro-units may cause damage to the object to be polished; while performing microsphere classification, it is found that after classification, the hollow microsphere polymer can not only make its particle size distribution uniform and concentrated, but also effectively control the content of the composite metal oxide micro-units in the hollow microsphere polymer. Controlling it within a certain range can obtain a polyurethane polishing layer with more excellent polishing performance.

[0054] In the present invention, the composite metal oxide micro-units contain two or more metal elements, and the metal elements include alkaline earth metal elements, boron group metal elements, and transition metal elements. The alkaline earth metal elements include: beryllium, magnesium, calcium, strontium, and barium elements; the boron group metal elements include: aluminum element; the transition metal elements include: chromium, manganese, iron, cobalt, and nickel elements; wherein, in the embodiments of the present invention, the composite metal oxide micro-units contain two or more of iron, aluminum, magnesium, calcium, and chromium elements.

[0055] In the embodiments of the present invention, the composite metal oxide micro-units include at least one of calcium-magnesium-aluminum metal oxide micro-units or iron-chromium metal oxide micro-units. A certain content and appropriate particle size of calcium-magnesium-aluminum metal oxide micro-units can make the surface of the polyurethane polishing layer have an appropriate roughness, effectively improve the grinding removal rate, and extend the service life of the polishing pad. In addition, the present invention finds that the presence of a certain amount of iron-chromium metal oxide micro-units can cooperate with the polishing liquid to achieve a certain catalytic chemical polishing effect, which can further improve the grinding removal rate.

[0056] In the embodiments of the present invention, the general formula of the calcium-magnesium-aluminum metal oxide micro-units is: Ca a Mg b Al b O x , where a is an integer from 2 to 4, b is an integer from 1 to 3, and x = (2a + 5b) / 2; the general formula of the iron-chromium metal oxide micro-units is: Fe c Cr d O y , where c is an integer from 1 to 5, d is an integer from 2 to 8, and y = (3c + 3d) / 2.

[0057] In addition, the hollow microsphere polymer also contains agglomerated large particles of calcium-magnesium metal oxide. Due to their large particle size, generally greater than 80 μm, they are removed by microsphere classification; there is also a certain amount of ferrous component in the hollow microsphere polymer, which can be removed by filtration through the magnetic material in the second classification area.

[0058] After microsphere classification, the average particle size of the above composite metal oxide micro-units is 10 μm to 60 μm. Preferably, the average particle size of the composite metal oxide micro-units is 36 μm to 47 μm. Particularly preferably, the average particle size of the composite metal oxide micro-units is 40 μm to 45 μm.

[0059] In the present invention, after microsphere classification, the content of each metal element in the composite metal oxide micro-units is that the content of aluminum element does not exceed 50 ppm, the content of iron element does not exceed 70 ppm, the content of chromium element does not exceed 100 ppm, the content of magnesium element does not exceed 50 ppm, and the content of calcium element does not exceed 150 ppm.

[0060] In the present invention, the contents of various metal elements in the composite metal oxide micro-units after microsphere classification satisfy the following conditions: the content of aluminum element is not less than 10 ppm, the content of iron element is not less than 10 ppm, the content of chromium element is not less than 15 ppm, the content of magnesium element is not less than 10 ppm, and the content of calcium element is not less than 30 ppm.

[0061] Preferably, the content of aluminum element is 10 - 30 ppm, and particularly preferably, the content of aluminum element is 20 - 30 ppm.

[0062] Preferably, the content of iron element is 10 - 60 ppm, and particularly preferably, the content of iron element is 30 - 50 ppm.

[0063] Preferably, the content of calcium element is 35 - 70 ppm, and particularly preferably, the content of calcium element is 55 - 70 ppm.

[0064] Preferably, the content of magnesium element is 10 - 30 ppm, and particularly preferably, the content of magnesium element is 20 - 30 ppm.

[0065] Preferably, the content of chromium element is 20 - 50 ppm, and particularly preferably, the content of chromium element is 35 - 50 ppm.

[0066] Furthermore, in the present invention, the content ratio of calcium element, magnesium element, and aluminum element is 1 - 20:2 - 10:1 - 9, and the content ratio of iron element and chromium element is 0.2 - 10:0.5 - 20; preferably, the content ratio of calcium element, magnesium element, and aluminum element is 6 - 8:2 - 5:1 - 3, and the content ratio of iron element and chromium element is 2 - 3:3 - 5, and particularly preferably, the content ratio of calcium element, magnesium element, and aluminum element is 6:2:2, and the content ratio of iron element and chromium element is 3:3.5.

[0067] In the examples of the present invention, the above classification device is selected to perform microsphere classification on the hollow microsphere polymer. By adjusting the process parameters, the particle size of the composite metal oxide micro-units in the microspheres and the contents of various metal elements are controlled. Furthermore, the purpose of controlling the particle size of the composite metal oxide micro-units in the microspheres and the contents of various metal elements in the polyurethane polishing layer is achieved.

[0068] Isocyanate-terminated prepolymer

[0069] In the present invention, the isocyanate-terminated prepolymer is obtained by reacting a polyfunctional isocyanate and a polyether polyol; preferably, the prepolymer is terminated with two -NCO groups; particularly preferably, the prepolymer is a polyether-based isocyanate-terminated urethane prepolymer.

[0070] Among them, the polyfunctional isocyanates in the raw materials for preparing the isocyanate-terminated prepolymer include, but are not limited to, one or a combination of aromatic isocyanates and aliphatic isocyanates. Preferably, more than 80 mol% of aromatic isocyanate is used, more preferably more than 95 mol%, and particularly preferably 100 mol%.

[0071] Aromatic isocyanates include, but are not limited to, one or a combination of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate.

[0072] Aliphatic isocyanates include, but are not limited to, one or a combination of ethylene diisocyanate, hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate.

[0073] Preferably, the aromatic isocyanate comprises one or a combination of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and the aliphatic isocyanate comprises one or a combination of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, methylcyclohexylene diisocyanate.

[0074] Particularly preferably, the aromatic isocyanate is 2,4-toluene diisocyanate and the aliphatic isocyanate is 4,4'-dicyclohexylmethane diisocyanate.

[0075] Among them, in the raw materials for preparing the isocyanate-terminated prepolymer, the polyol can be a high molecular weight polyether polyol.

[0076] Preferably, the polyether polyols include, but are not limited to, any one of polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polytetramethylene ether glycol-polypropylene glycol, or a copolymer of two or more, or a mixture of two or more.

[0077] Optionally, the isocyanate-terminated prepolymer can also be a commercially available prepolymer obtained by reacting a polyether with TDI and MDI; the isocyanate-terminated prepolymers include, but are not limited to, any one or more combinations of the series of prepolymers LF800A, LF900A, LF910A, LF930A, LF931A, LF939A, LF950A, LF952A, LF600D, LF601D, LF650D, LF667D, LF700D, LF750D, LF751D, LF752D, LF753D, L325, LFG963A, LFG964A, LFG740D produced by Chemtura Corporation.

[0078] In the present invention, the isocyanate-terminated prepolymer contains 3.5 to 9.5 wt% of unreacted isocyanate groups -NCO; preferably, the content of unreacted -NCO in the prepolymer is controlled between 6.5 and 9.3 wt%; particularly preferably, the content of unreacted -NCO is between 7.5 and 9.25 wt%.

[0079] Curing agent

[0080] In the present invention, the curing agent is selected from one or more combinations of aromatic difunctional curing agents. The present invention has no particular limitation on the aromatic difunctional curing agent, and any suitable aromatic difunctional curing agent in the art can be used. Those skilled in the art can make appropriate selections according to specific needs.

[0081] Examples of aromatic difunctional curing agents that can be used in the present invention are: diethyltoluenediamine (DETDA), N,N'-dialkyldiaminodiphenylmethane, 3,5-diethyl-2,4-toluenediamine and its isomers (for example, 3,5-diethyl-2,6-toluenediamine), 3,5-dimethylthio-2,4-toluenediamine and its isomers, 4,4'-methylene-bis-(2-chloroaniline) (MOCA), 4,4'-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA), polyoxytetramethylene-di-p-aminobenzoate; p,p'-methylenedianiline (MDA); m-phenylenediamine (MPDA); 4,4'-methylene-bis-(2,6-diethylaniline) (MDEA), 4,4'-methylene-bis-(2,3-dichloroaniline) (MDCA), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyl diphenylmethane, 2,2',3,3'-tetrachlorodiaminodiphenylmethane, propylene glycol-di-p-aminobenzoate, and various combinations thereof, but not limited thereto.

[0082] Preferably, the curing agent comprises two or more combinations of 4,4'-methylene-bis-(2-chloroaniline) (MOCA), 4,4'-bis-(sec-butylamino)-diphenylmethane, 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA), and polyoxytetramethylene-di-p-aminobenzoate. Considering the unique chemical structure of MOCA, to ensure a suitable operating time during the preparation of the polishing pad and that the resulting polishing pad has good polishing performance, particularly preferably, the curing agent comprises one or a combination of 4,4'-methylene-bis-(2-chloroaniline) (MOCA) and 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA).

[0083] Other additives

[0084] In the present invention, an appropriate modifier can also be added to the polyurethane polishing layer to obtain more excellent comprehensive performance improvement.

[0085] Preferably, these modifiers can change at least one property of the polyurethane polishing layer, and the above properties include, but are not limited to, the group consisting of the following: porosity, rigidity, surface energy, abrasion resistance, conductivity, and chemical function. The modifying materials include, but are not limited to: antioxidants, polyols, etc.

[0086] Groove

[0087] In the present invention, grooves can be conventionally provided on the polyurethane polishing layer, and the grooves are used to receive the polishing liquid during the polishing process. The grooves can be obtained by processing after the polishing pad is formed. The setting of the grooves can ensure the smooth discharge and flow of the polishing liquid used during the polishing process. Preferably, the grooves are one or more of concentric grooves (for example, annular or spiral grooves), curved grooves, grid line grooves, regular polygon grooves (for example, hexagon, triangle), and tread pattern. Particularly preferably, the grooves are one or more of annular grooves, spiral grooves, X - Y grid grooves, hexagon grooves, triangle grooves, and fractal grooves. Particularly preferably, the cross-section of the grooves is one or more of a straight sidewall rectangle, "V" shape, "U" shape, and serrated shape.

[0088] Preferably, the width of the grooves is 0.1 - 0.6 cm, and particularly preferably, the width of the grooves is 0.2 - 0.4 cm.

[0089] Buffer layer

[0090] In the present invention, a buffer layer is further provided on the back surface of the polyurethane polishing layer, and the buffer layer can reduce the impact applied to the polishing pad during the polishing process.

[0091] Preparation method of polyurethane polishing layer

[0092] Mix the isocyanate - terminated prepolymer in a liquid state with the hollow microporous polymer after microsphere classification, and obtain the first product after vacuum degassing; mix the first product with the curing agent at 50°C under high - speed shearing to obtain the second product, then cast it into a circular mold, and after curing and cooling to room temperature, cut it into thin slices with a thickness of 2 - 3 mm to obtain the polyurethane polishing layer;

[0093] Control the temperature of the second product during the preparation process so that the initial reaction temperature of the first product and the curing agent ≤ 70°C, and the reaction peak temperature ≤ 80°C.

[0094] Polishing treatment

[0095] For the schematic diagram of the polishing treatment using the chemical - mechanical polishing pad with the above - mentioned polishing layer, reference can be made to Figure 2 , in which, the polishing pad 15 is fixed on the polishing machine table 16. The material to be polished 14 is fixed on the bracket 17. During the polishing action, first, the polishing pad 15 rotates under the action of the polishing machine table. Then, the material to be polished 14 is brought close (from top to bottom) in a direction perpendicular to the polishing pad 15 through the bracket 17. While the bracket moves downward, it rotates, and the rotation direction of the bracket 17 is the same as the rotation direction of the polishing machine table 16, so that the rotation directions of the polishing pad 15 and the material to be polished 14 are the same. During polishing, polishing liquid 18 is sprayed onto the polishing pad 15.

[0096] Example

[0097] The following further illustrates the present invention with reference to the schematic examples shown in the accompanying drawings. Through the following description, the advantages of various aspects of the present invention will become more obvious. The same reference numerals in the drawings refer to the same components. The shapes and sizes of the components in the schematic drawings are only for illustration and do not generally represent the actual shapes, sizes, and absolute positions.

[0098] Example 1

[0099] This example provides a polyurethane polishing layer T1, and its manufacturing method is as follows:

[0100] Step 1: Microsphere classification treatment

[0101] For D 50=40μm hollow microsphere polymer for microsphere classification: In this embodiment, microspheres with the brand number 551DE40D42 of AkzoNobel are selected. The frequency of the upper classification impeller is adjusted to 30 Hz, and then the frequency of the lower classification impeller is adjusted to 20 Hz. The switches of the first and second induced draft fans are turned on, and the frequencies of the first and second induced draft fans are controlled to 50 Hz. The magnetic force of the magnetic component 9 is adjusted to 8000 gauss. Subsequently, D 50 =40μm hollow microsphere polymer is pumped into the classification device through a pump. The feeding speed of the pump is controlled at 70 rps. After microsphere classification, the material in the lower material storage chamber is taken, which is the classified hollow microsphere polymer.

[0102] Step 2: Treatment of isocyanate-terminated prepolymer

[0103] Heat 100 parts by mass of the isocyanate-terminated prepolymer obtained from the reaction of 2,4-toluene diisocyanate and polytetrahydrofuran (the mass percentage of unreacted -NCO groups is 9.2%) to 80 °C and degas it under vacuum (~0.095 MPa) for 2 hours to remove the gas and small molecule compounds in the prepolymer; then add 2.45 parts by mass of the standard particle size D 50 =40μm hollow microsphere polymer after microsphere classification treatment. Stir to uniformly disperse the hollow microsphere polymer in the prepolymer, degas it again under vacuum (~0.095 MPa) for 2 hours, and then cool it to 50 °C for use.

[0104] Step 3: Curing agent dissolution

[0105] Heat 25.5 parts by mass of MOCA to 115 °C to completely melt it into a clear and transparent liquid.

[0106] Step 4: Cure the prepolymer containing hollow microsphere polymer with a curing agent

[0107] Mix the prepolymer and the curing agent under high-speed shearing, then pour it into a cylindrical mold to form a casting block with a thickness of 12 cm, and let it gel at 70 °C for 15 minutes. Then, heat the casting body to 80 °C within 30 minutes and cure it for 16 hours. After curing, let it cool to room temperature automatically in the oven, and then cut it into thin slices with a thickness of 2 mm, a total of 60 slices. Take the 5th slice from top to bottom and label it as polyurethane polishing layer T1.

[0108] Apply intermediate glue to the upper surface of the buffer layer to form an adhesive layer and bond it to the lower surface of the polyurethane polishing layer T1. Then, bond the back glue layer to the lower surface of the buffer layer to form the polishing pad P1.

[0109] Examples 2 - 11

[0110] Adopt the same process as in Example 1, select D50 The hollow polymer microspheres with a diameter of 40 μm were fractionated, and reacted with different amounts of TDI, HMDI and curing agent to obtain polyurethane polishing layers T2-11 with different effects; the raw materials, dosages and processes are summarized in Table 1, where the amounts of all materials are in parts by mass;

[0111] The upper surface of the buffer layer was coated with an intermediate adhesive to form an adhesive layer, which was bonded to the lower surface of the polyurethane polishing layers T2-11. Then, the lower surface of the buffer layer was bonded to the back adhesive layer to form the polishing pads P2-11.

[0112] Comparative Examples 1-4

[0113] Comparative Example 4 used the same microsphere fractionation process as Example 1, except that the parameters of the upper fractionation impeller, lower fractionation impeller and induced draft fan were different. Comparative Examples 1-3 adopted the same preparation process as Example 1, except that unfractionated hollow microsphere polymers of AkzoNobel (grade 551DE40D42) were used and reacted with different amounts of TDI, HMDI and curing agent to obtain polyurethane polishing layers T12-15 with different effects; the raw materials and dosages are also summarized in Table 1, where the amounts of all materials are in parts by mass; the upper surface of the buffer layer was coated with an intermediate adhesive to form an adhesive layer, which was bonded to the lower surface of the polyurethane polishing layers T12-15. Then, the lower surface of the buffer layer was bonded to the back adhesive layer to form the polishing pads P12-15.

[0114] Table 1

[0115]

[0116] Among them, TDI is 2,4-toluene diisocyanate, and HMDI is 4,4'-dicyclohexylmethane diisocyanate; MOCA is 4,4'-methylene-bis-(2-chloroaniline) (MOCA), and MCDEA is 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline).

[0117] Metal element content of polyurethane polishing layer

[0118] Element content: Contents of metal elements calcium, magnesium, aluminum, iron and chromium: Measured by ICP-AES. After a certain amount of polyurethane polishing layer was calcined at high temperature, its ash was acid-digested and then tested.

[0119] Average particle size of composite metal oxide micro-units: Calculated after measurement using a SEM scanning electron microscope.

[0120] Table 2

[0121]

[0122] Physical and chemical properties of polyurethane polishing layer

[0123] The Shore hardness, density, compression ratio, and roughness of the obtained polyurethane polishing layers T1 to T15 were measured respectively according to the following methods.

[0124] Shore hardness: Measured according to ASTM D 2240 method.

[0125] Density: Calculated according to the following formula: S.G = m / v = m / (π(d / 2)^2*h), where m is the weight of the polishing pad, d is the diameter of the polishing pad, and h is the thickness of the polishing pad.

[0126] Compression ratio: Calculated according to the following formula: Compression ratio = ((M1 - M2) / M1)×100%, where M1 is the thickness of the polyurethane polishing layer when the polyurethane polishing layer experiences 60 s and 30 kPa pressure from the unloaded state, and M2 is the thickness of the polyurethane polishing layer when the polyurethane polishing layer experiences 60 s and 180 kPa pressure from the M1 state.

[0127] Roughness: The roughness Ra is defined by the following formula (1). A measuring instrument such as this can be used. It can measure the surface roughness of 3 different inner surface areas such as the grooves of the polishing pad before use. By measuring their average surface roughness respectively, the average value is obtained from the 3 obtained average surface roughness values, which is the surface roughness Ra.

[0128] Ra = ∑|Z - Zav| / N

[0129] In the above formula, Z is the height of the rough surface, Zav is the average height of the rough surface, and N is the number of measurement points.

[0130] There is no particular limitation on the above-mentioned measuring instrument. For example, an optical surface roughness measuring instrument such as a three-dimensional surface structure analysis microscope, a scanning laser microscope, an electron beam surface morphology analysis device, or a contact surface roughness meter such as a stylus surface roughness meter can be used.

[0131] The physical and chemical properties of each polyurethane polishing layer are shown in Table 3.

[0132] Evaluation of polishing performance of polishing pad

[0133] Take the polishing pads P1 to P15 in the above Examples 1 to 11 and Comparative Examples 1 to 4. We evaluated their polishing performance through on-machine testing. The test conditions are as follows:

[0134] The test machine is AMAT Refelxion (Modify 5Zone);

[0135] The polishing liquid is ANJI 3060 (diluted 1:9, H2O2% = 1%), and the flow rate is 250 mL / min;

[0136] The dressing disk is Saesol Disk 6045C4, P / C downforce 5lbf, Head&Platen RPM: 93 / 87;

[0137] The wafer used is Patten wafer: Semitech 754, Cu Blanket wafer PreThickness 10KA.

[0138] The wafers were polished on an AMAT Refelxion tester using polishing pads P1 - 15 prepared with the polyurethane polishing layers of Examples 1 - 11 and Comparative Examples 1 - 4, and the removal rate during their life cycle was recorded during polishing.

[0139] The polished wafers were observed to determine whether they had scratches, and the results, along with the results of the above removal rates, were recorded in Table 3;

[0140] Table 3

[0141]

[0142] Among them, × - indicates no scratches; ○ - indicates a small number of minute scratches; ○○ - indicates a large number of minute scratches; ○○○ - indicates obvious scratches.

[0143] It should be noted that, based on the explanations and elaborations in the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention should also be within the scope of protection of the claims of the present invention. In addition, although this specification uses some specific terms, these terms are only for convenience of description and do not constitute any limitation to the invention.

Claims

1. A polishing pad, characterized in that, It includes a polyurethane polishing layer, in which there are composite metal oxide micro-units. The polyurethane polishing layer is a reaction product of a raw material combination, and the raw material combination includes an isocyanate-terminated prepolymer obtained by reacting a polyfunctional isocyanate with a polyol, a hollow microsphere polymer, and a curing agent. The composite metal oxide micro-units contain two or more metal elements; The metal elements include alkaline earth metal elements, boron group metal elements, and transition metal elements. The alkaline earth metal elements in the composite metal oxide micro-units include at least one of magnesium element and calcium element. The boron group metal element includes aluminum element. The transition metal elements include at least one of iron element and chromium element; The contents of the metal elements in the composite metal oxide micro-units satisfy the following conditions: the content of aluminum element does not exceed 50 ppm, the content of iron element does not exceed 70 ppm, the content of chromium element does not exceed 100 ppm, the content of magnesium element does not exceed 50 ppm, and the content of calcium element does not exceed 150 ppm.

2. The polishing pad according to claim 1, wherein The contents of the metal elements in the composite metal oxide micro-units satisfy the following conditions: the content of aluminum element is not less than 10 ppm, the content of iron element is not less than 10 ppm, the content of chromium element is not less than 15 ppm, the content of magnesium element is not less than 10 ppm, and the content of calcium element is not less than 30 ppm.

3. The polishing pad according to claim 1, wherein The content ratio of calcium element, magnesium element, and aluminum element in the composite metal oxide micro-units is 1-20:2-10:1-9, and the content ratio of iron element and chromium element is 0.2-10:0.5-20.

4. The polishing pad according to claim 1, wherein, The particle size of the composite metal oxide micro-units is 10 μm-60 μm.

5. The polishing pad according to claim 1, wherein The hollow microsphere polymer is subjected to classification treatment by a classification device. The classification device includes a first classification area, in which there is at least one lower classification impeller (7). A first induced draft fan (10) is arranged at the top of the lower classification impeller (7). A middle-grade material storage chamber (12) is included in the first classification area. The middle-grade material storage chamber (12) is connected to the first induced draft fan (10) through a pipe. The bottom of the first classification area includes a lower-grade material storage chamber (13).

6. The polishing pad according to claim 5, characterized in that A magnetic component (9) is arranged at the bottom of the first classification area.

7. The polishing pad according to claim 1, wherein, It includes a second classification area, which is connected to the first classification area through a pipe. The second classification area includes at least two upper classification impellers (2). The upper classification impellers (2) are arranged on the side wall of the classification pipeline in the second classification area, and the rotation main shaft of the upper classification impellers (2) forms an angle of 60-90° with the side wall of the classification pipeline. A secondary air inlet (6) is arranged at the bottom of the second classification area. One or more second induced draft fans (3) are arranged in the second classification area. One or more upper-grade material storage chambers (5) are also arranged and connected to the second induced draft fans (3) through pipes. Magnetic materials are arranged on the surface of the upper classification impellers (2).

8. The polishing pad according to claim 1, characterized in that, The density of the polyurethane polishing layer is 0.6 to 1.1 g / cm 3 , the Shore hardness is 15 to 80 D, the compression ratio is 0.1 to 3.0%, and the surface roughness Ra is 1.5 to 30 μm.

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