Method for preparing 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 method of the present invention is used to prepare the polishing layer, which can improve production efficiency and yield. The method comprises the following steps: providing a mold, the mold comprising a base and a mold ring arranged on the base, the inner wall of the mold ring and the base defining a casting cavity; casting a casting material for preparing the polishing layer into the casting cavity of the mold through n casting machines at the same time, wherein n≥2; and the angle between the projection of the casting ports of two adjacent casting machines on the bottom of the casting cavity and the line connecting the center of the bottom of the casting cavity is 360 o / n; During the pouring process, the base is kept horizontal, and the mold is made to move in a circular motion at an angular speed of 60-180° / min with the center of the bottom of the pouring cavity as the center of the circle.

Description

Technical Field

[0001] The 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 dielectrics, semiconductors, and dielectric materials are deposited on the surface of a wafer and partially or selectively removed from the surface of a semiconductor wafer. Thin layers of conductive dielectrics, semiconducting, and dielectric materials can be deposited using a variety of deposition techniques. Common deposition techniques 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 deposited and removed sequentially, the top surface of the wafer becomes non-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. In addition, in the damascene process, materials are deposited to fill the recessed areas created by patterned etching, but the filling step cannot be very precise and overfilling may occur. Therefore, it is necessary to remove the material outside the recessed area.

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

[0006] The interaction between the polishing layer, polishing media 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 of casting polyurethane mixed with microspheres into a block and cutting the block into several thin polishing pads. This has been proven to be a feasible method for preparing porous polishing pads. Since CMP began as a key process in semiconductor manufacturing, most polishing pad developments have been similar, involving tests of many different porous and non-porous polymer materials and the mechanical properties of these materials. The casting process of the polishing pad is also basically the same. Among them, CN1082567A et al. disclose a conventional casting method, using a casting machine from Rodel Company to mix isocyanate prepolymer, microspheres and curing agent, and then using a low viscosity window to transport the mixed liquid to the mold for curing. Generally speaking, the traditional casting method uses central casting, that is, the pouring port is in the center of the entire mold. After the prepolymer and curing agent are mixed at the pouring head of the casting machine, they flow directly into the mold from the pouring port. The pouring port rises slowly with the liquid level during the casting process, and after curing, the polishing layer is sliced ​​and grooved to obtain. In the subsequent patents CN105382680B and CN102950550 B, the pouring stage is divided into three stages. These three stages correspond to three nested circles of different radii. During the pouring process, the pouring port moves from inside to outside in the three regions in turn, moves in a spiral manner on the xy plane, and gradually rises in the z-axis direction with the pouring process. Similarly, after pouring, the slices are solidified and grooved to form a polishing layer.

[0008] Unfortunately, the polishing layer formed by the above casting methods will have many undesirable defects, such as density defects and irregular flow marks on the surface caused by increased casting height. Defective streaks refer to the difference in the packing density of microspheres in the polymer matrix or the uneven mixing of materials. Uneven density distribution refers to the inconsistent expansion of microspheres due to the inconsistent overall heat distribution during the casting and gelation process, which causes uneven density distribution from the upper layer to the lower layer and from the middle to the periphery of the entire cast product. Density defects and irregular flow marks will seriously affect the polishing effect of the surface of the polished material. In other words, the above casting methods are not conducive to improving the production efficiency and yield of PAD (polishing pad). Summary of the invention

[0009] In view of at least one shortcoming in 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 method of the present invention is used to prepare the polishing layer, which can improve production efficiency and yield.

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

[0011] The present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad, comprising the following steps:

[0012] Providing a mold, the mold comprising a base and a mold ring disposed on the base, wherein an inner wall of the mold ring and the base define a casting cavity;

[0013] The casting material for preparing the polishing layer is simultaneously cast into the casting cavity of the mold by n casting machines, wherein n≥2; and the angle between the projection of the casting ports of two adjacent casting machines on the bottom of the casting cavity and the line connecting the center of the bottom of the casting cavity is 360 o / n;

[0014] During the pouring process, the base is kept horizontal, and the mold is made to move in a circle at an angular speed of 60-180° / min with the center of the bottom of the pouring cavity as the center of the circle.

[0015] Preferably, the projection of the pouring port of each pouring machine on the bottom of the pouring cavity is located in the area of ​​1 / 3-2 / 3 of the distance between the center of the bottom of the pouring cavity and the edge of the bottom of the pouring cavity.

[0016] In some implementations, the number of the casting machines is 2-5, preferably 3-4.

[0017] Preferably, during the pouring, each of the pouring machines pours the pouring material into the pouring cavity at a constant flow rate, and the flow rate fluctuation amplitude of the pouring material of each of the pouring machines during the pouring process is controlled within ±2g / s;

[0018] In some embodiments, during the pouring, the average flow rate of the pouring material poured by each pouring machine is 60-100 g / s;

[0019] Preferably, during the pouring process, the distance between the pouring port of the pouring machine and the top surface of the pouring material in the pouring cavity is between 0-2 cm.

[0020] Preferably, during the pouring, the flow rate difference of pouring the castable material between the pouring machines is within ±5g / s.

[0021] Furthermore, the casting material comprises polyurethane prepolymer, hollow polymer expanded microspheres and a curing agent.

[0022] Furthermore, after the pouring is completed and the casting material has no fluidity in the pouring cavity, a post-treatment including vulcanization is performed.

[0023] In some embodiments, when performing the pouring, the mold is placed on a conveying device that enables the mold to perform the circular motion.

[0024] In some embodiments, the polishing layer is sliced, and the density fluctuation of different positions of the single polishing layer is less than 0.01 g / cm 3 ;

[0025] The polishing layer is sliced, and the density fluctuation between the obtained slices is less than 0.03 g / cm 3 .

[0026] The present invention also provides a chemical mechanical polishing pad, which comprises a polishing layer prepared by the preparation method described above.

[0027] The technical solution provided by the present invention has the following beneficial effects:

[0028] The method provided by the present invention uses multiple casting machines to cast at the same time, and the casting ports of the multiple casting machines are arranged according to the above-mentioned distribution method of the present invention. At the same time, during the casting process, circular motion is performed in situ at an angular velocity of 60-180° / min. The polishing layer manufactured by the above-mentioned method has significantly reduced fluctuations in the density of the polishing layer, thereby improving the production rate and yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A perspective schematic diagram of a mold having a casting cavity.

[0030] Figure 2 A schematic front view of the mold.

[0031] Figure 3 This is a top view of the pouring gate and mold during single-machine pouring.

[0032] Figure 4 This is a top view of the pouring gate and mold during dual-machine pouring.

[0033] Figure 5 This is a top view of the pouring gate and mold during three-machine pouring.

[0034] Figure 6 This is a schematic diagram of the main view of the pouring gate and mold during three-machine pouring. DETAILED DESCRIPTION

[0035] 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.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0037] The directional terms such as upper, lower, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may change accordingly according to different positions and different usage conditions. The words "inside" and "outside" refer to the direction toward or away from the geometric center of a specific component, respectively.

[0038] The present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad, comprising the following steps:

[0039] Providing a mold, the mold comprising a base and a mold ring disposed on the base, wherein an inner wall of the mold ring and the base define a casting cavity;

[0040] The casting material for preparing the polishing layer is simultaneously cast into the casting cavity of the mold by n casting machines, wherein n≥2; and the angle between the projection of the casting ports of two adjacent casting machines on the bottom of the casting cavity and the line connecting the center of the bottom of the casting cavity is 360 o / n;

[0041] During the pouring, the base is kept horizontal, and the mold is made to perform circular motion at an angular velocity of 60-180° / min with the center of the bottom of the pouring cavity as the center of the circle, that is, the center of the trajectory of the circular motion is the center of the bottom of the pouring cavity. Specifically, the angular velocity is, for example, 60, 80, 100, 120, 140, 160, 180° / min, etc.

[0042] Compared with the traditional polishing layer preparation method, the method provided by the present invention is no longer a single pouring machine pouring, but a multiple pouring machine pouring at the same time, the number of pouring machines used is ≥2, the pouring ports of the multiple pouring machines are arranged according to the above distribution method of the present invention, and the pouring process is carried out in a circular motion in situ according to the above angular velocity. The inventors have found that the polishing layer manufactured by the above method has significantly reduced polishing layer density fluctuations, and can increase the pouring height that can be achieved in a single pouring, thereby improving the production rate and yield rate.

[0043] The mold can adopt a mold structure known in the art. For example, the schematic diagram of the mold is as follows: Figure 1-2As shown, it includes a base 100 and a mold ring 200 arranged on the base 100, and the inner wall of the mold ring 200 and the base 100 jointly define a casting cavity 300. In some embodiments, the base 100 of the mold is a rectangular metal with a thickness ≥2cm and a side length ≥105cm; the mold ring 200 is a circular metal ring with a diameter ≥90cm and a height ≥40cm, and the mold ring 200 is made of aluminum, iron and other metals. The connection between the base 100 and the mold ring 200 is filled with a curable sealant. Taking the center of the bottom of the casting cavity 300 circled by the mold ring 200 as the center O, the axis perpendicular to the base 100 and passing through the center O is defined as the center axis C. The base 100 of the mold remains horizontal during the casting process, and the entire casting space is symmetrical around the center axis C. In the present invention, a multi-machine casting method is adopted to cast the casting material into the casting cavity 300 of the mold, such as Figure 4-5 The angle between the projection 400 of the pouring ports 600 of two adjacent pouring machines at the bottom of the pouring cavity 300 and the line connecting the center O of the bottom of the pouring cavity 300 is 360 o / n, that is, when viewed from the direction perpendicular to the XY plane where the base 100 is located, the angle between the projection 400 of each pouring port at the bottom of the pouring cavity 300 and the center O is 360 o / n. For example, Figure 4 In, the angle is 180°; Figure 5 In the example, the angle is 120°.

[0044] During the pouring, the base 100 is kept horizontal, and the mold is made to perform circular motion at an angular velocity of 60-180° / min with the center O of the bottom of the pouring cavity 300 as the center, that is, the center of the trajectory of the circular motion is the center O of the bottom of the pouring cavity 300; during the pouring process, the mold performs circular motion in situ.

[0045] In some examples, when pouring, the mold is placed on a conveying device that enables the mold to perform the circular motion. The conveying device can be a conveying device with corresponding functions available in the art, and there is no special restriction on this; there are many conveying devices with the above functions on the market, and conveying devices with the above functions are also disclosed in some patents or patent applications (such as CN 210417966 U, etc.). As an example, for example, some conveying devices include multiple conveying rollers with automatic conveying functions, and a placement platform is provided between the multiple conveying rollers, which can rise from the bottom of the conveying roller to the top of the conveying roller and can rotate in the horizontal direction; when pouring, the mold is placed on the placement platform, and during the pouring process, the mold is lifted to the top of the conveying roller by the placement platform, and then the placement platform is rotated to make the mold perform circular motion in situ at the required angular velocity while the base remains horizontal, and the center of the motion trajectory is the center of the bottom of the pouring cavity; after the pouring is completed, the placement platform is lowered to the bottom of the conveying roller, and the mold contacts the conveying roller and is transported downstream. In some examples, the conveyor belt width of the conveying device is 100-120 cm, and the conveyor belt is composed of multiple conveyor rollers, for example; the conveyor belt can also be provided with a movable slide rail and a fixed card slot, and the mold is transported by the conveyor belt and continuous casting is achieved; when the casting material of a mold is cast, the mold placed on the conveyor belt is moved by the conveyor belt, and a new empty mold is moved to the casting position to start the casting of the next mold.

[0046] Preferably, if Figure 4-5 As shown, the projection 400 of each pouring machine 600 on the bottom of the pouring cavity 300 is located in the region of 1 / 3-2 / 3 of the distance between the center O of the bottom of the pouring cavity 300 and the edge of the bottom of the pouring cavity 300. Specifically, from the direction perpendicular to the XY plane where the base 100 is located (i.e., the Z-axis direction), each pouring gate is located in the region of 1 / 3-2 / 3 of the distance between the center O of the bottom of the pouring cavity and its edge (i.e., the inner wall of the bottom of the mold ring 200), or it can be said that the distance between the projection 400 of the pouring gate 600 on the bottom of the pouring cavity 300 and the center O is 1 / 3-2 / 3 of the radius r of the bottom of the pouring cavity.

[0047] Preferably, the number of the casting machines is 2-5, such as 2, 3, 4, 5, etc., more preferably 3-4.

[0048] The casting material used to prepare the polishing layer can be a casting material known in the art, and there is no particular limitation on this. Specifically, the casting material includes a polyurethane prepolymer (i.e., an isocyanate prepolymer), hollow polymer expanded microspheres, and a curing agent. After the polyurethane prepolymer, the hollow polymer expanded microspheres, and the curing agent are mixed and stirred in the stirring chamber of the casting machine, they flow out from the pouring port into the casting chamber of the mold, and the casting material is solidified into a block in the casting chamber of the mold, and then subjected to post-treatment such as vulcanization to obtain the polyurethane polishing layer.

[0049] In some specific embodiments, the polyurethane prepolymer and hollow polymer expanded microspheres are premixed in a dispersing device, and then the mixture of microspheres and prepolymer and the curing agent are transferred to a casting machine, where they are stirred in a stirring chamber. During casting, the stirring speed in the stirring chamber is 500-2500 r / min, preferably 900-1400 r / min, and each casting machine maintains consistent parameters during casting.

[0050] Preferably, when performing the pouring, each of the pouring machines pours the pouring material into the pouring cavity at a constant flow rate, and the flow fluctuation amplitude of the pouring material of each of the pouring machines during the pouring process is controlled within ±2g / s; wherein "constant flow rate" includes the meaning of constant or almost constant. Preferably, when performing the pouring, the average flow rate of the pouring material poured by each of the pouring machines is 60~100 g / s. Preferably, when performing the pouring, the flow rate difference of the pouring material between each of the pouring machines is within ±5g / s.

[0051] Preferably, if Figure 6 As shown, during the pouring process, the pouring port 600 of the pouring machine is located 0-2 cm above the pouring material level 500 in the pouring cavity, and as the pouring process proceeds, the pouring port 600 is close to the pouring material level 500 and moves upward along the Z axis as the pouring material level gradually rises. That is, during the pouring process, the distance between the pouring port 600 and the top surface of the pouring material in the pouring cavity is between 0-2 cm; during the pouring process, each pouring machine always maintains a consistent pace until the pouring is completed.

[0052] Further, after the casting material has no fluidity in the casting cavity, for example, after being placed at room temperature for a period of time until the surface liquid has no fluidity, a post-treatment including vulcanization is performed, for example, the initially cured polyurethane "cake" is transferred together with the mold to an oven for vulcanization, and after the vulcanization is completed, it is cooled to room temperature and taken out, and the mold ring is removed, so that the mold base and the cured polyurethane on the base are transferred to a slicer for processing. The post-processing operation for preparing the polishing layer is well known in the art. Specifically, the polyurethane "cake" is made of isocyanate prepolymer (i.e., polyurethane prepolymer) containing hollow polymer expanded microspheres and a curing agent as raw materials through casting and curing, and is cut into thin slices by a slicer, for example, into thin slices with a thickness of about 2.20 mm, and the thickness of the polishing layer after sanding is, for example, about 2.03 μm; the surface of the thin slice is grooved to form a groove pattern (e.g., a concentric groove pattern), and is punched into a disc of a certain size, and finally a chemical mechanical polishing pad polishing layer is obtained.

[0053] The method of the present invention is used to prepare a polishing layer, and a product with more uniform density distribution can be obtained. For example, after the obtained polishing layer is sliced, the density fluctuation at different positions of the obtained single polishing layer is less than 0.01 g / cm 3 The polishing layer is sliced, and the density fluctuation between the obtained layers (i.e., between the individual polishing layers obtained by slicing) is less than 0.03 g / cm 3 , for example, less than or equal to 0.02g / cm 3 .

[0054] The isocyanate prepolymer used in the casting material for preparing the polishing layer can be a prepolymer known in the art, and there is no particular limitation on this; for example, the isocyanate prepolymer is mainly composed of aromatic isocyanate and aliphatic isocyanate, and is prepared together with a polymer polyol and a 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"thiophosphorothioate triphenyl triisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, etc. One or more Aliphatic isocyanate is, for example, a mixture of one or more of 4,4'-dicyclohexylmethane diisocyanate, cyclohexane dimethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc. Preferably, the aliphatic isocyanate accounts for 10-15% by mass of the prepolymer, and the aromatic isocyanate component accounts for 25-40% by mass of the prepolymer, wherein the aliphatic isocyanate can significantly reduce the speed of the reaction exothermic reaction and the maximum temperature of the reaction exothermic reaction, and can prolong the gel time of the reaction between the isocyanate prepolymer and the curing agent.

[0055] For example, the polymer polyol used for chain extension in the isocyanate prepolymer is mainly divided into polyether polyol, polyester polyol and other oligomer polymer polyols. Polyester polyol is selected from, for example, a mixture of one or more of alkyd polyester polyol, polycaprolactone polyol (PCL), polycarbonate polyol, (PCDL), etc. Polyether polyol includes, for example, a mixture of one or more of polyoxypropylene polyol, polytetramethylene glycol (PTMG), copolyether polyol, etc. Small molecule chain extenders may be selected from diamines or small molecule polyols and alcohol amines, such as 1,4-butanediol, ethylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, methyl propanediol, diethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, butyl ethyl propanediol, diethyl pentanediol, 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, etc. Considering the strength, dynamic mechanical properties, low temperature resistance, hydrolysis resistance and other aspects of the polishing pad, PTMG and diethylene glycol and their blends are the best choices.

[0056] For example, isocyanate prepolymers include, but are not limited to, Adiprene L325, Adiprene LF600D, LF700D, LF750D, LF751D, LF753D, LF800A, LF900A, LF930AL, LF950A, etc. of Chemtura. Preferably, the polyols used to prepare the isocyanate prepolymer are selected from PTMG and diethylene glycol, and the isocyanate prepolymer has an unreacted NCO content of 8.0-9.5% by weight.

[0057] In some preferred embodiments, the isocyanate prepolymer is formed 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, such as 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, such as 10%, 11%, 12%, 13%, 14%, 15%, etc.; PTMG accounts for 10% to 15% of the total mass of the raw material components. It 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 synthetic prepolymer reaches the reaction endpoint, the unreacted isocyanate group (NCO) accounts for 8.0-9.5% of the mass of the entire prepolymer, for example, 8%, 8.5%, 9%, 9.5% etc.

[0058] The casting material may use a curing agent known in the art. In some embodiments, the curing agent is, for example, 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 has a more controllable exothermic reaction, a longer operable time, and better flexibility and elongation at break than a diamine curing agent and a polyether polyamine.

[0059] Among them, the diamine curing agent includes, for example, 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), 4,4'-diaminodiphenylamine, 4-(4-aminobenzoate), and 4,4'-di-sec-butylaminodiphenylamine. One or more of 1,4-diaminodicyclohexylmethane, 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, more preferably 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis-sec-butylaminodiphenylmethane and isomers thereof, which account for 10-40wt% of the total mass of the curing agent.

[0060] In some examples, the preferred multifunctional polyether polyol used to form the curing agent contains 2 to 6 hydroxyl groups in each molecule, and its hydroxyl value is 400-1000 mg KOH / g, accounting for 60-90wt% of the total curing agent mass, for example, including polyoxypropylene triol with glycerol, trimethylolpropane, ethanolamine, diethanolamine, triethanolamine, etc. as initiators; polyether tetraol with ethylenediamine, pentaerythritol, toluene diamine, methylene dianiline as initiators, diethylenetriamine or xylitol as initiators, and propylene oxide The ring-opening polymerization obtains the polyether pentol; hexahydroxy polyether obtained by using sorbitol, mannitol, sucrose, diethylenetriamine, triethylenetetramine, etc. as initiators. Examples of commercially available polyhydroxy polyol curing agents include, but are not limited to, Voranol® polyols from Dow Chemical Company, Poly-G polyethers from Arch Chemicals, Japan, Actcol series polyethers from Mitsui Chemicals, 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.

[0061] Taking Hebei Yadong as an example, the following table lists a variety of preferred high molecular weight polyol curing agents.

[0062]

[0063] In a preferred embodiment, the curing agent comprises: 10-40 wt% of a diamine curing agent, for example, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 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), propylenediaminebis(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, toluenediamine, 2,4-diamino- 3-methylthio-5-propyltoluene, at least one of 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 60-90wt% of a multifunctional polyether polyol, such as 60%, 70%, 80%, and 90% of a multifunctional polyether polyol, wherein the multifunctional polyether polyol is prepared by homopolymerization or copolymerization of polyhydroxy, primary amino compounds or alcohol amines as initiators and epoxy compounds such as ethylene oxide and propylene oxide as polymerization monomers; preferably a functionality of 2-6, such as 2, 3, 4, 5, and 6, and a hydroxyl value of 400-1000. The polyether polyol having an 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, 1000 mg KOH / g, etc. may be used.

[0064] In some examples, the components of the castable include, for example, an isocyanate prepolymer prepared from raw materials mainly composed of TDI-80 / HMDI / PTMG / DEG, a curing agent mixed with 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and a multifunctional polyether, and polymer microspheres as fillers.

[0065] The hollow polymer expanded microspheres used in the casting material can be of a type known in the art, and there is no particular restriction on this; specifically, the polymer microspheres are composed of a polymer shell and internal gas. The polymer shell constituent materials include, for example, polyacrylonitrile, polyethylene, polypropylene, polydodecanamide, polycaprolactam, polydecanediamine, polysebamide, polydodecanediamine, polyadipate, polyoctylamide, polyaluminum chloride, polyacrylamide, polyaminophenol, polyaramid, polyaryl sulfone, polybutadiene-acrylonitrile, polybutylene terephthalate, polycarbonate, polycyclohexane terephthalate, polydiallyl isophthalate, polydiallyl terephthalate, polyetherester fiber, polyethylene glycol, polyethylene oxide, polyethylene oxide, polyethylene naphthalate, polyvinylidene fluoride, polyvinylidene chloride, isobutylene nitrile, etc. At least one, the best is polyvinylidene chloride and polyacrylonitrile shell, or polyacrylonitrile / methacrylonitrile shell. The hollow part of the polymer is air, nitrogen, carbon dioxide, argon, neon, ethane, butane, etc., and isobutane gas is the most preferred. The preparation method of the microspheres can refer to the existing technology without special restrictions, and can also be directly purchased from outside, such as the expanded microspheres of Nouryon, etc. The qualified microsphere products include, but are not limited to, Expancel@ Microspheres 461DE20d70 of Nouryon, etc.

[0066] Before the hollow polymer expanded microspheres are used to prepare the casting material, they are preferably subjected to air flow screening. The density of the microspheres is, for example, in the range of 0.010-0.10 g / cm 3 , for example 0.010 g / cm 3 , 0.020 g / cm 3 , 0.030 g / cm 3 , 0.040 g / cm 3 , 0.050 g / cm 3 , 0.060 g / cm 3 , 0.070 g / cm 3 , 0.080 g / cm 3 , 0.090 g / cm 3 , 0.10 g / cm 3 After screening, the unnecessary components in the microspheres are: 1) impurities in the microsphere manufacturing process, including metal particles, etc.; 2) parts of the microspheres with low density, including microspheres with obviously larger sizes and thinner shells after transitional expansion; 3) parts of the microspheres with high density, including microsphere shells damaged during the expansion process inside the microspheres, and irregular clumps of microspheres. All or part of the above components are screened out to improve the uniformity of the polymer microspheres. Preferably, the density of the microspheres after screening is controlled at 0.060-0.080 g / cm 3The particle size D50 of the treated polymer microspheres is mainly distributed in 10-30μm, such as 15μm, 20μm, 25μm, 30μm, etc., and the particle size span Span is less than 1.2, such as 1.15, 1.1, 1.05, 1.04, etc. (D50 is the median particle size or median particle size; Span=(D90-D10) / D50, D10 and D90 refer to the particle sizes corresponding to the cumulative volume distribution reaching 10% and 90%, respectively, that is, particles with a particle size smaller than D10 and D90 account for 10% and 90% of the total volume, respectively).

[0067] As mentioned above, the method of the present invention has no particular restrictions on the castable for preparing the polishing layer. As an example, the amount of hollow polymer expanded microspheres added to the castable is 0.1-10wt% of the mass of the polyurethane prepolymer, preferably 1-5wt%; in the castable, the molar ratio of the active hydrogen-containing groups in the curing agent to the unreacted isocyanate groups in the isocyanate prepolymer is 0.85-0.95.

[0068] The present invention also provides a chemical mechanical polishing pad, which comprises a polishing layer prepared by the preparation method described above.

[0069] The present invention is further described below by way of examples. The examples described in the present invention are only used as illustrations of the present invention and do not mean that the present invention is limited thereto.

[0070] 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. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0071] In the following examples and comparative examples, the hollow polymer expanded microspheres added to the castable are sieved microspheres obtained by the following method:

[0072] Using Expancel from Nouryon @ Microspheres 461DE20d70, add the polymer expanded microspheres into the silo of the air flow screen through a peristaltic pump, start the equipment, and the microspheres pass through the screw conveying system, mix with the air flow, and enter the mesh cylinder after atomization. Under the dual effects of the rotation of the mesh cylinder and the wind, the microspheres penetrate the 200-mesh 316L stainless steel filter and enter the discharge port, while metal impurities, the crust that bursts in the microspheres, and large-sized microspheres or microsphere agglomerates and other materials that cannot pass through the screen are discharged from the impurity discharge port along the wall of the mesh cylinder.

[0073] The density of the sieved microspheres was measured by a fully automatic gas displacement true density meter ACCUPYC II 1345, and the particle size change of the microspheres was measured by a laser particle size distribution meter Bettersize 2600. The results are shown in Table 1 below.

[0074] Table 1

[0075]

[0076] Example 1

[0077] Preparation of castable:

[0078] The isocyanate prepolymer used was Adiprene L325 from Chemtura, and the curing agent was 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and YD-403 from Yadong in a mass ratio of 20:80.

[0079] The hollow polymer expanded microspheres are dispersed in the isocyanate prepolymer to obtain a pre-dispersed material, wherein the amount of the hollow polymer expanded microspheres is 2.87wt% of the mass of the isocyanate prepolymer. During casting, the pre-dispersed material is stirred and mixed with a curing agent at a casting machine head at a stirring speed of 2000r / min to form a casting material, wherein the molar ratio of the active hydrogen-containing group in the curing agent to the unreacted NCO of the isocyanate prepolymer is measured at 0.87.

[0080] Example 1 Two casting machines are used to simultaneously cast the casting material into the casting cavity of the mold. The distribution diagram of the projection position 400 of the casting port of the casting machine at the bottom of the casting cavity is shown in FIG. Figure 4 The angle between the projection position 400 of the pouring ports of two adjacent pouring machines at the bottom of the pouring cavity and the line connecting the center O of the bottom of the pouring cavity is 180 o The projection position 400 of the pouring port of each pouring machine at the bottom of the pouring cavity is located at 1 / 2 of the distance between the center O of the bottom of the pouring cavity and the edge of the bottom of the pouring cavity.

[0081] During pouring, the base of the mold is kept horizontal, and the mold performs a circular motion in situ at an angular velocity of 100° / min with the center O of the bottom of the pouring cavity as the center of the circle.

[0082] During pouring, the pouring material of each pouring machine is poured into the pouring cavity at a constant flow rate (average flow rate is 80g / s), the fluctuation range of the flow rate of each pouring machine is controlled within ±2g / s, and the flow rate difference of the pouring material between each pouring machine is controlled within ±5g / s;

[0083] During the pouring process, the pouring port 600 of each pouring machine is located directly above the pouring material level 500 in the pouring cavity, and the distance is always maintained between 0-2 cm, that is, as the pouring process proceeds, the pouring port is close to the liquid level and gradually rises with the liquid level, moving upward along the Z axis, such as Figure 6 shown.

[0084] After the height of the liquid in the casting cavity reaches the predetermined height (see "casting height" in Table 1 for details), the casting is stopped. After the liquid in the casting cavity is no longer fluid, the polyurethane cake is obtained, and the surface is observed for collapse and flow mark defects. The results are shown in Table 1. The polyurethane cake is transferred to an oven at 106°C for vulcanization for 16 hours. After the curing is completed, the temperature is lowered to room temperature, and the polyurethane cake is taken out of the mold in the oven and cut into slices with a thickness of 80 mil at room temperature. During the slicing process, the incomplete slices when the surface is sliced ​​are discarded, and the thickness of the slices is tested. A qualified non-grooved polishing layer material with no defects in appearance and a thickness of about 2.03 mm is obtained, and then the polishing layer of the polishing pad is obtained by grooving and punching.

[0085] The number of slices and the number of qualified slices in this embodiment are shown in Table 2. The test results of the density span between the slices and the density span within the slices obtained by slicing are shown in Table 2.

[0086] Example 2-3

[0087] The process was carried out with reference to Example 1, except that the stirring speed of the pre-dispersed material and the curing agent at the head of the casting machine, the pouring height, the average flow rate of the casting material during pouring, and the angular velocity of the circular motion of the mold were changed. The specific process conditions of Examples 2-3 are shown in Table 2, and the others are carried out with reference to Example 1.

[0088] Embodiment 4-6

[0089] The method is carried out in accordance with Example 1, except that: three casting machines are used to simultaneously cast the casting material into the casting cavity of the mold, and the distribution diagram of the projection position 400 of the casting port of the casting machine at the bottom of the casting cavity is shown in Figure 5 The angle between the projection position 400 of the pouring ports of two adjacent pouring machines at the bottom of the pouring cavity and the line connecting the center O of the bottom of the pouring cavity is 120 o The projection position 400 of the pouring port of each pouring machine at the bottom of the pouring cavity is located at 1 / 2 of the distance between the center O of the bottom of the pouring cavity and the edge of the bottom of the pouring cavity.

[0090] The stirring speed of the pre-dispersed material and the curing agent at the head of the casting machine, the casting height, the average flow rate of the casting material during casting, and the angular velocity of the circular motion of the mold are shown in Table 2, and the rest are carried out with reference to Example 1.

[0091] Example 7

[0092] Refer to Example 1, except that the distance between the projection position of the pouring port of each pouring machine at the bottom of the pouring cavity and the center O of the bottom of the pouring cavity is 1 / 3 of the radius of the pouring cavity; when pouring, the mold is made to move in a circle with the center of the bottom of the pouring cavity as the center at an angular velocity of 60° / min.

[0093] Example 8

[0094] The method is carried out in accordance with Example 1, except that the distance between the projection position of the pouring port of each pouring machine at the bottom of the pouring cavity and the center O of the bottom of the pouring cavity is 2 / 3 of the radius of the pouring cavity.

[0095] Comparative Examples 1-3

[0096] The method is carried out in accordance with Example 1, except that: a single pouring machine is used to pour the pouring material, and the distribution diagram of the projection position 400 of the pouring port of the pouring machine at the bottom of the pouring cavity is shown in Figure 3 The projection position 400 of the pouring port of the pouring machine at the bottom of the pouring cavity is located at the center O of the bottom of the pouring cavity 300. During the pouring process, the mold does not perform a circular motion.

[0097] The stirring speed of the pre-dispersed material and the curing agent at the pouring machine head of Comparative Examples 1-3, the pouring height, and the average flow rate of the pouring material during pouring are shown in Table 2, and the rest are carried out with reference to Example 1.

[0098] Comparative Examples 4-5

[0099] The same method is used as in Example 2, except that the angular velocity of the circular motion of the mold is different (see Table 2 for details). The other methods are the same as in Example 2.

[0100] Comparative Example 6

[0101] Refer to Example 4, except that: the angles between the projected positions of the pouring ports of two adjacent pouring machines at the bottom of the pouring cavity and the line connecting the center O of the bottom of the pouring cavity are not equal, and the three angles formed by the pouring ports in pairs along the same direction are 60°, 120°, and 180° respectively.

[0102] Comparative Example 7

[0103] The method is carried out in accordance with Example 1, except that the distance between the projection position of the pouring port of each pouring machine at the bottom of the pouring cavity and the center O of the bottom of the pouring cavity is 4 / 5 of the radius of the pouring cavity.

[0104] Table 2

[0105]

[0106] In Table 2, the “qualified” in “qualified slices” means that the slice density of the slices meets the requirements of 0.73-0.77 g / cm 3 The density range is within the range, and there are no uneven color stripes on the surface, no flow mark defects such as translucent areas, etc.

[0107] Density data between layers: Among the density data obtained from the detection of each polishing layer slice, the maximum density data minus the minimum density data is the density span between layers (the density of the polishing layer slice is obtained by weighing the polishing layer slice, measuring the size of the polishing layer slice and calculating the volume of the polishing layer slice, and the density of the polishing layer slice is obtained by dividing the mass by the volume).

[0108] Intra-sheet density span: Nine points were randomly selected from the polishing layer slice, and nine 5*5cm small blocks were punched out using a small punching machine. The density span was measured using the drainage method according to GB / T 4472-2011. The maximum value minus the minimum value was the intra-sheet density span.

[0109] The “normal” in “post-casting performance” means that no surface collapse and flow mark defects were observed.

[0110] From the comparison between the above embodiments and the comparative examples, it can be seen that the method of the present invention can increase the pouring height through multi-machine pouring, and can obtain products with better quality, which are not prone to surface collapse and flow mark defects, and the density span between the polishing layers obtained by cutting is small, and the density span within the smaller single-piece polishing layer can be taken into account, with better productivity and yield.

[0111] By comparing Examples 1-6 of the present invention with Comparative Examples 1-3, it can be seen that the pourable height of the polyurethane "cake" increases with the increase in the number of pouring machines, which also means that the number of slices and the number of qualified slices are also greatly improved. The multi-machine pouring method plays a significant role in improving the productivity and yield of the polishing layer of the polishing pad.

[0112] It can be seen from Examples 1-6 that when the polishing layer is prepared by the method of the present invention, the pouring height can be increased to a higher level, for example, it can reach 15 cm or even 20 cm, and even when pouring at a higher pouring height, the density span between layers is significantly narrowed, the density within the sheet is uniform, and surface collapse and flow mark defects are not likely to occur during pouring, thereby ensuring a high pass rate.

[0113] The difference between Examples 7 and 8 and Example 1 is that the location of the pouring point is one closer to the center and the other closer to the edge of the mold. From the performance after pouring, the qualified rates (number of qualified slices / number of slices) of Examples 7 and 8 are partially lower than those of Example 1, but are still within an acceptable range.

[0114] In comparative example 7, a pouring method close to the edge of the mold is used, so that the outflowing material quickly diffuses to the mold ring and flows back to the center, which increases the mutual disturbance of the materials, the edge flow mark defects are heavier, and there are no qualified pieces as a whole. In addition, the inventors found that if a method close to the center of the mold is used, for example, the distance between the projection of the pouring port of each pouring machine at the bottom of the pouring cavity and the center O of the pouring cavity is less than 1 / 3 of the radius of the pouring cavity, the heat of the poured piece closer to the center during the pouring process cannot be completely diffused, resulting in higher heat in the central area, and obvious yellow spots, uneven color difference and other flow mark defects are prone to occur, and the qualified rate is low or even no qualified pieces.

[0115] The difference between Example 4 and Comparative Example 6 is that the pouring gates of Example 4 are evenly spaced, while the pouring gates of Comparative Example 6 are non-uniformly arranged. It is found that in Comparative Example 6, the material is easily violently disturbed, thereby causing flow mark defects. At the same time, the proximity of adjacent pouring gates also affects the dissipation of heat, causing collapse of the pouring process.

[0116] The difference between Comparative Examples 4 and 5 and Example 2 is that the angular velocity of the circular motion of the mold during pouring is different. The angular velocity of Comparative Example 4 is too small, and the heat is more concentrated during the pouring process, resulting in microsphere bursting and surface collapse. The angular velocity of Comparative Example 5 is too large, and the disturbance between the liquid flows is large during the pouring process. There are flow mark defects on the surface after pouring, which causes pouring failure.

[0117] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing a polishing layer of a chemical mechanical polishing pad, characterized in that: The steps include: Providing a mold, the mold comprising a base and a mold ring disposed on the base, wherein an inner wall of the mold ring and the base define a casting cavity; The casting material for preparing the polishing layer is simultaneously cast into the casting cavity of the mold by n casting machines, wherein n≥2; and the angle between the projection of the casting ports of two adjacent casting machines on the bottom of the casting cavity and the line connecting the center of the bottom of the casting cavity is 360 o / n; During the pouring process, the base is kept horizontal, and the mold is made to move in a circle at an angular speed of 60-180° / min with the center of the bottom of the pouring cavity as the center of the circle.

2. The method according to claim 1, characterized in that: The projection of the pouring port of each pouring machine on the bottom of the pouring cavity is located in the area of ​​1 / 3-2 / 3 of the distance between the center of the bottom of the pouring cavity and the edge of the bottom of the pouring cavity.

3. The method according to claim 1 or 2, characterized in that: The number of the pouring machines is 2-5.

4. The method according to claim 1 or 2, characterized in that: During the pouring, each of the pouring machines pours the pouring material into the pouring cavity at a constant flow rate, and the flow rate fluctuation amplitude of the pouring material of each of the pouring machines during the pouring process is controlled within ±2g / s; And / or, during the pouring, the average flow rate of the pouring material poured by each pouring machine is 60-100 g / s; And / or, during the pouring process, the distance between the pouring port of the pouring machine and the top surface of the pouring material in the pouring cavity is between 0-2 cm.

5. The method according to claim 4, characterized in that During the pouring, the flow rate difference of the pouring material between the pouring machines is within ±5g / s.

6. The method according to claim 1 or 2, characterized in that: The casting material comprises polyurethane prepolymer, hollow polymer expansion microspheres and a curing agent.

7. The method according to claim 1 or 2, characterized in that: After the pouring is completed, after the casting material has no fluidity in the casting cavity, post-treatment including vulcanization is performed.

8. The method according to claim 1 or 2, characterized in that: When performing the pouring, the mold is placed on a conveying device that can make the mold perform the circular motion.

9. The method according to claim 1 or 2, characterized in that: The polishing layer is sliced, and the density fluctuation of different positions of the single polishing layer is less than 0.01 g / cm 3 ; The polishing layer is sliced, and the density fluctuation between the obtained slices is less than 0.03 g / cm 3 .

10. A chemical mechanical polishing pad, characterized in that: The chemical mechanical polishing pad comprises a polishing layer prepared by the preparation method according to any one of claims 1 to 9.

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