CN110815038B - Polishing pad and preparation method and application thereof - Google Patents
Polishing pad and preparation method and application thereof Download PDFInfo
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- CN110815038B CN110815038B CN201810896250.6A CN201810896250A CN110815038B CN 110815038 B CN110815038 B CN 110815038B CN 201810896250 A CN201810896250 A CN 201810896250A CN 110815038 B CN110815038 B CN 110815038B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
- B24B37/11—Lapping tools
- B24B37/20—Lapping pads for working plane surfaces
- B24B37/26—Lapping pads for working plane surfaces characterised by the shape of the lapping pad surface, e.g. grooved
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
- B24D11/001—Manufacture of flexible abrasive materials
- B24D11/003—Manufacture of flexible abrasive materials without embedded abrasive particles
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- Mechanical Treatment Of Semiconductor (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Abstract
The invention discloses a polishing pad and a preparation method and application thereof. The polishing pad is provided with a combined sheet and a bottom liner, wherein the combined sheet is fixed on the bottom liner, the combined sheet jointly forms a polishing layer, the polishing layer is provided with a central polishing area, one or more middle polishing areas and an outer edge polishing area, the middle polishing area and the outer edge polishing area are sequentially arranged around the central polishing area, the central polishing area is circular, the middle polishing area is annular, and the outer edge polishing area is annular; annular gaps are formed between every two adjacent polishing areas and are used for receiving polishing fluid in the polishing process; the Shore hardness of the polishing layer decreases sequentially in a direction from the central polishing zone to the outer edge polishing zone; the Shore hardness gradient of two adjacent polishing zones is 0.5-5D. The hardness of the polishing pad is gradually reduced along the diameter direction, and the abrasion rate of the polishing pad is basically kept consistent in the mechanical polishing process, so that the surface of a wafer to be polished can be flattened, and the flattening efficiency is high.
Description
Technical Field
The invention relates to a polishing pad and a preparation method and application thereof.
Background
With the development of semiconductor Memory (Memory) and Logic device (Logic device), in order to increase the density of electronic devices and reduce the production cost, there is a trend of increasing the Aspect ratio (Aspect ratio) and increasing the number of conductive lines in the device manufacturing process. In the fabrication process of semiconductor integrated circuits, the surface of the wafer is increasingly uneven as the isolation structures, transistors, metal layers and dielectric layers are stacked one on top of the other. Chemical Mechanical Polishing (CMP) is the most effective process for processing silicon wafers and planarizing multi-layer wiring layers, and is also a practical technique capable of achieving local and global planarization. The chemical mechanical polishing pad is a circular sheet-like composite material with a diameter of 50-100cm, which is an important component of the CMP system and also a major consumable of CMP. The surface structure and texture of a chemical mechanical polishing pad directly affect the performance of the polishing pad, and further affect the CMP process and processing effects, and the preparation materials include polymer-impregnated fabrics, microporous membranes, porous polymer foams, and the like.
The primary goal of chemical mechanical polishing is to uniformly planarize the entire surface of the wafer and to provide repeatability of the planarization results for the same batch of wafers. The hardness (hardness or stiffness) and porosity (porosity) of the polishing pad are related to the flatness of the wafer after polishing. In a typical CMP process, the wafer is mounted upside down on a carrier (carrier) of a CMP tool and the force pushes the carrier and wafer down toward the polishing pad. The carrier and wafer rotate over a rotating polishing pad on the CMP tool polishing table, and the wafer and polishing pad may rotate in the same direction or in opposite directions. Therefore, during the rotation, the angular velocity of any point on the surface of the polishing pad is the same, but the linear velocity is different at different diameter positions, i.e., the linear velocity is larger when the diameter is larger. The problem is that the linear velocity is higher and the polishing wear rate is higher under the same physical properties (such as hardness, density, porosity or compressibility) of the polishing pad. It can be seen that the same pad has the same physical properties, and the wear rate varies with diameter, and different wear rates tend to reduce the planarization efficiency of the polishing material, and the wafer surface becomes uneven as the material layers are stacked and etched layer by layer.
As is known, a high hardness pad can increase the flatness of the wafer while a high porosity pad with high compressibility can increase the uniformity of the wafer polishing. Therefore, in order to satisfy the above requirements of hardness and porosity, the polishing pad is usually composed of at least one hard pad and at least one soft pad stacked together, such as the polishing pads disclosed in US 5212910 and US 5257478. However, the soft and soft pads may propagate pressure differently, which may sometimes result in poor polishing uniformity. If a larger number of laminated layers are used in the polishing pad, the more the variation in the physical properties of the polishing pad, and the more difficult it is to control the planarity and uniformity of wafer polishing. Moreover, such polishing pads do not directly address the problem of different wear rates of the same polishing pad.
Disclosure of Invention
The invention aims to overcome the defect that the wear rate of the polishing pad along the diameter direction is gradually increased so that the surface of a wafer to be polished becomes uneven in the prior art, and provides a novel polishing pad, and a preparation method and application thereof. The hardness of the polishing pad is gradually reduced along the diameter direction, and the abrasion rate of the polishing pad is basically kept consistent in the mechanical polishing process, so that the surface of a wafer to be polished can be flattened, and the flattening efficiency is high.
The invention solves the technical problems through the following technical scheme:
the invention provides a polishing pad, which comprises a combined sheet and a bottom lining, wherein the combined sheet is fixed on the bottom lining, the combined sheet jointly forms a polishing layer, the polishing layer comprises a central polishing area, one or more middle polishing areas and an outer edge polishing area, the middle polishing areas and the outer edge polishing areas are sequentially arranged around the central polishing area, the central polishing area is circular, the middle polishing area is annular, and the outer edge polishing area is annular; an annular gap is formed between each two adjacent polishing areas and is used for receiving polishing fluid in the polishing process; the shore hardness of the polishing layer decreases in a direction from the central polishing zone to the outer edge polishing zone; the Shore hardness gradient of two adjacent polishing zones is 0.5-5D.
The Shore hardness of the polishing layer of the polishing pad is sequentially reduced along the direction from the central polishing area to the outer edge polishing area, and the reduction of the Shore hardness can compensate the difference of the linear speeds of the polishing pad, so that the differential polishing of a substrate is not caused.
In the present invention, the polishing pad is used for polishing a wafer.
In the present invention, the Shore hardness gradient between two adjacent polishing zones is preferably 0.9 to 3D, more preferably 1 to 3D or 0.9 to 2.1D, and may be, for example, 1D, 1.1D, 1.2D, 1.3D, 1.4D, 1.5D, 1.6D, 1.9D, 2D or 2.1D. The polishing pad with the Shore hardness gradient of the two adjacent polishing areas in the range has better mechanical performance, can better compensate the difference of the linear speeds of the polishing pad, and further obtains better polishing effect, so that the surface of a wafer is smoother and flatter.
In the present invention, the shore hardness of each polishing zone may be as conventional in the art, and preferably, the shore hardness of each polishing zone is from 40 to 70D, more preferably from 60 to 70D.
In the present invention, preferably, the shore hardness of the central polishing zone is 60 to 70D.
In the present invention, the outer edge polishing zone preferably has a Shore hardness of 40 to 62D, more preferably 60 to 62D.
In the present invention, preferably, the shore hardness of the central polishing zone is 60 to 70D, the shore hardness of the outer edge polishing zone is 60 to 62D, and the shore hardness gradient between two adjacent polishing zones is 0.9 to 2.1D.
In the present invention, the number of the intermediate polishing zones is preferably 4 to 13, more preferably 5 to 8, and further more preferably 6 to 8. The polishing pad with the middle polishing areas in the number can compensate the polishing speed difference of the polishing pads with different diameters, and can remarkably improve the polishing planarization efficiency. If the number of the polishing regions is greater than 13, although the polishing planarization efficiency can be improved, the manufacturing process of the polishing pad becomes complicated and the cost is high, which is not practical.
In the present invention, the diameter of the polishing pad may be conventional in the art, and may be, for example, 50 to 100cm, preferably 50 to 90cm, and more preferably 70 to 85 cm.
In the present invention, the central polishing zone preferably has a diameter of 2 to 15cm, more preferably 10 to 15 cm.
In the present invention, the width of each polishing zone other than the central polishing zone is preferably 2 to 15cm, more preferably 2.5 to 15cm, further more preferably 2.5 to 7.5cm, and for example, may be 3cm or 5cm, and the width is the difference between the outer radius and the inner radius for the intermediate polishing zone and the outer edge polishing zone. A polishing pad having the above-described width range facilitates the flow of polishing fluid during polishing. When the polishing pad is the embedded polishing pad prepared by the following preparation method and has the width range, the preparation process can be simple, and the degumming of the combined sheet in the polishing process can be avoided.
In the present invention, the material of the polishing layer may be a material conventionally used in the art, for example, polyurethane, which refers to a product derived from a di-or polyfunctional isocyanate, the polyurethane may be, for example, one or more of polyether urea, polyisocyanurate, polyurethane, polyurea, and polyurethane urea, and the polyurethane may be a copolymer formed by two or more of polyether urea, polyisocyanurate, polyurethane, polyurea, and polyurethane urea. Better polishing effect can be obtained by adopting the polyurethane of the kind. Preferably, the polyurethane is prepared by reacting an isocyanate-terminated prepolymer obtained by reacting an isocyanate and a polyol with a mixture of a curing agent and hollow microspheres. Generally, polishing zones of different hardness can be prepared by varying the type of isocyanate, polyol, curing agent, and hollow microsphere content; preferably, polishing zones of different hardness are prepared by varying the hollow microsphere content. The process for changing the content of the hollow microspheres is easy to control, and the hollow microspheres do not participate in chemical reaction, so that main materials in different polishing areas cannot be changed greatly, other physical parameters cannot be changed greatly, the hardness of the polishing areas can be reduced by improving the content of the microspheres, and the polishing pad integrally keeps the same materials and has the required hardness.
The isocyanate is not particularly limited, and a compound known in the field of polyurethane, for example, an aromatic isocyanate and/or an aliphatic isocyanate, may be used. The isocyanate may be, for example, one or more of an aromatic diisocyanate-based compound, an aliphatic diisocyanate-based compound, and an alicyclic diisocyanate-based compound. The aromatic diisocyanate-based compound is preferably one or more of 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 2 ' -diphenylmethane diisocyanate, 2,4 ' -diphenylmethane diisocyanate, 4 ' -diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate and m-xylylene diisocyanate. The aliphatic diisocyanate compound is preferably one or more of ethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate and 1, 6-hexamethylene diisocyanate. The alicyclic diisocyanate compound is preferably one or more of 1, 4-cyclohexane diisocyanate, 4' -dicyclohexylmethane diisocyanate, isophorone diisocyanate and norbornane diisocyanate.
The polyol is not particularly limited, and a compound known in the field of polyurethane, for example, a polyether polyol and/or a polyester polyol can be used. Preferably, the polyhydric alcohol is one or more of polytetramethylene ether glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, ethylene adipate and butylene adipate, or the polyhydric alcohol is a copolymer formed by more than two of the six substances.
Wherein the type of the prepolymer is preferably
L325、
LF750 and
one or more of LF 700D.
The curing agent is not particularly limited, and may be a compound known in the field of polyurethane, for example, one or more of polyol, polyamine and alcohol amine, wherein the polyamine is diamine and other polyfunctional amines. Preferably, the curing agent is one or more of 4,4 '-methylene-bis-o-chloroaniline, 4' -methylene-bis (3-chloro-2, 6-diethylaniline), dimethylthiotoluenediamine, 1, 3-propylene-bis-p-aminobenzoate, diethyltoluenediamine, 5-tert-amyl-2, 4-and 3-tert-amyl-2, 6-toluenediamine, and chlorotoluenediamine. More preferably, the curing agent is MOCA which is 3, 3-dichloro-4, 4-diaminodiphenylmethane and/or MCDEA which is 4, 4-methylenebis (3-chloro-2, 6-diethylaniline).
Wherein when the polishing layer contains hollow microspheres, the hollow microspheres are uniformly dispersed in the polishing layer, preferably the hollow microspheres have a diameter of less than 120 microns; more preferably, the hollow microspheres have a diameter of less than 60 microns; even more preferably, the hollow microspheres have a diameter of 10 to 50 microns.
Wherein, preferably, the hollow microsphere has a saccular structure of polyacrylonitrile or polyacrylonitrile copolymer outer wall. More preferably, the hollow microspheres are of the type Expancel series or the loose microbead F series. Even more preferably, the hollow microspheres are of the type
551DE20d 42. The hollow microspheres are controlled to be uniformly distributed in the polishing layer in the different regions in a wt% content.
In the present invention, preferably, the raw material of the polishing layer includes the following components in parts by mass: 100 parts of an isocyanate-terminated prepolymer, 20-25 parts of a curing agent, and 1.0-2.4 parts of hollow microspheres; wherein the isocyanate-terminated prepolymer is obtained by reacting toluene diisocyanate and polytetrahydrofuran; the curing agent is MOCA and/or MCDEA, the MOCA is 3, 3-dichloro-4, 4-diaminodiphenylmethane, and the MCDEA is 4, 4-methylenebis (3-chloro-2, 6-diethylaniline); the hollow microspheres are of the type
551DE20d42。
In the present invention, the width of the annular gap may be the width of a trench conventionally provided in the art, and is preferably 0.1 to 0.6cm, and more preferably 0.2 to 0.4 cm.
In the present invention, preferably, the polishing layer is further provided with a radial groove, and the radial groove is used for receiving a polishing fluid in a polishing process. Wherein, the width of the radial trench is preferably 0.1-0.6cm, more preferably 0.2-0.4 cm.
In the present invention, preferably, a buffer pad is further disposed on the back surface of the polishing layer, and the buffer pad can reduce the impact applied to the polishing pad during the polishing process.
The invention also provides a preparation method of the polishing pad, which can be a casting curing process conventionally used in the field, and the annular groove is processed on the molded cured block conventionally in the field.
In the present invention, preferably, the mold used in the preparation method has an inner cavity corresponding to each polishing region of the polishing pad, and the inner cavity corresponding to the central polishing region is a central inner cavity, the inner cavity corresponding to the intermediate polishing region is an annular middle inner cavity, and the inner cavity corresponding to the outer edge polishing region is an annular outer edge inner cavity, and the preparation method includes the following steps:
(1) respectively pouring a pouring composition capable of preparing polishing areas with corresponding hardness into the central inner cavity, each annular middle inner cavity and the annular outer edge inner cavity, and curing to obtain a cured block body;
(2) separating the solidified block from the die, cutting along the radial direction of the solidified block to obtain a thin sheet, and cutting along the boundary between polishing areas with different hardness to obtain combined sheets with different hardness;
(3) and fixing the combined sheet on the bottom lining according to the corresponding hardness to obtain the embedded polishing pad.
In the present invention, preferably, the preparation method comprises the following steps:
(1) sequentially curing the casting composition capable of preparing the polishing area with corresponding hardness in the cavity of the mold from inside to outside to obtain a cured block;
(2) separating the solidified block from the die, cutting along the radial direction of the solidified block to obtain a thin sheet, and cutting along the boundary between polishing areas with different hardness to obtain combined sheets with different hardness;
(3) and fixing the combined sheet on the bottom lining according to the corresponding hardness to obtain the embedded polishing pad.
The above preparation method (i.e., the layered curing preparation method) can solve the problems of excessively high curing temperature and non-uniform distribution of hollow microspheres in the isocyanate-terminated prepolymer, thereby producing an inlaid polishing pad having uniform hardness distribution in each polishing region.
In the invention, the die for preparing the polishing pad is provided with a base and concentric rings with different diameters, wherein the concentric rings are fixed on the base and form an inner cavity together with the base, and the inner cavity is divided into a central inner cavity, an annular middle inner cavity and an annular outer edge inner cavity; the diameter of the concentric rings is 50-90 cm; the thickness of the side wall of the concentric ring is 0.1-0.6 cm; the distance between the side walls of two adjacent concentric rings is equal and is 0.4-10 cm.
In the course of research and development, the inventors found that the thickness of the side wall of the concentric rings in the above thickness range can control the gelling temperature and curing temperature of the casting composition within appropriate ranges, and thus can produce a polishing pad with uniform hardness distribution in each region.
The fixing manner of the base and the concentric ring can be conventional in the art, for example: the lower extreme of concentric ring with the base die is inlayed fixedly, can set up the structure that prevents that the embedding part is not hard up or rotatory on the mosaic structure, like prevent changeing pin, anticreep screw etc. that hangs tightly.
Wherein, the diameter of the concentric rings is preferably 70-85 cm.
Wherein, preferably, the thickness of the side wall of the concentric circular ring is 0.2-0.4 cm.
Wherein, preferably, the distance between the side walls of two adjacent concentric rings is 1-2 cm.
When the polishing pad to be prepared is an embedded polishing pad, preferably, the mold is further provided with a plurality of groove structures leading from the center of the mold to the outermost edge of the mold, and the depth of each groove structure is smaller than the height of the concentric rings of the mold. The concentric rings are connected into a whole, so that the mold is convenient to demold.
Wherein, theThe concentric rings are made of a material with certain rigidity at the processing temperature of 100-130 ℃. Preferably, the concentric rings are made of Polycarbonate (PC), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), Polyamide (PA), polyvinyl chloride (PVC), and heat-resistant alloy material T7Or heat-resistant alloy material T8. Preferably, the two side walls of the concentric rings are coated with a lubricating material, such as a fluorine-containing material, and the die coated with the lubricating material can achieve the effects of easy demoulding and convenient cleaning. Further preferably, the two side walls of the concentric rings are plated with hard chromium, and the concentric rings plated with hard chromium can play a role in preventing the die from deforming easily, demoulding easily and cleaning conveniently.
Wherein, the base is a plane rectangle according to the conventional rule in the field, the length of the base is 100 and 150cm, and the width of the base is 100 and 150 cm. Preferably, the base has a length of 100cm and a width of 120cm, depending on the size of the console.
Wherein the thickness of the base can be, for example, 2-5cm, preferably 3-4 cm.
Before casting, a T-shaped bolt is generally inserted into a T-shaped groove on an operating platform of a punch press, a pressing plate is inserted into the T-shaped bolt and screwed by a nut, the base is fastened on the operating platform by the pressing plate, and then casting can be performed.
The inner cavity can be internally provided with an inner cavity lining according to the conventional method in the field, the size of the inner cavity lining is consistent with that of the inner cavity, the upper surface of the inner cavity lining is provided with a groove, the groove can be of a parallel structure, a grid structure or a radial structure, the depth of the groove is 0.1-1cm, and the groove distance between every two adjacent grooves is equal to the width of the groove and is 0.5-8 cm. Preferably, the depth of the groove is 0.4-0.8cm, and the distance between two adjacent grooves is 3.4-5 cm. The groove with the structure is easy to demould, and the injection molding material can not be stripped from the inner cavity lining in the cutting process.
The base can be made of, for example, latex, epoxy resin, polyester (such as polycarbonate PC, polyethylene terephthalate PET, polyurethane PU), polysulfide rubber, or silicone rubber, preferably polyurethane. The base made of polyurethane and the pouring material made of polyurethane can form strong adhesive force so as to prevent the block solidified in the slicing process from being stripped from the base. In addition, the mold made of polyurethane has the advantages of light weight, easy demolding, high strength, high wear resistance, long service life, low cost, environment friendliness and the like, and is suitable for mass production of a production line.
The invention also provides an application of the polishing pad in polishing a wafer.
In the present invention, the term "polishing zone" refers to the central polishing zone, the intermediate polishing zone, and the outer edge polishing zone.
The above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
(1) the polishing pad of the present invention has different hardness distributions with diameter variation, which are sequentially decreased in hardness from the center to the edge, and the hardness distributions can compensate for the difference in linear velocity of the polishing pad and improve the polishing planarization efficiency.
(2) According to the embedded polishing pad, the annular groove formed between the adjacent combined sheets can be prevented from being processed later; the annular groove is beneficial to the flow of polishing fluid, so that the polishing efficiency is improved; the annular groove also forms a container which can store waste slag generated during polishing and reduce polishing scratches; the annular grooves simultaneously prevent fluid from flowing away, thereby maintaining a more uniform fluid distribution across the surface of the polishing pad. By adopting the layered curing preparation method, the problems of over-high curing temperature and nonuniform distribution of the hollow microspheres in the isocyanate-terminated prepolymer can be solved, so that the mosaic polishing pad with uniform hardness distribution in each polishing area is prepared.
Drawings
FIG. 1 is a schematic structural view of a polishing pad of examples 1 to 3.
FIG. 2 is a schematic structural view of a polishing pad of examples 4 to 6.
FIG. 3 is a top view of a mold used in the damascene polishing pads of examples 1-6.
FIG. 4 is a perspective view of a mold used in the damascene polishing pads of examples 1-6.
Description of reference numerals:
Circular ring side wall 13
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
The hollow microspheres in the following examples and comparative examples were Expancel series hollow microspheres of Akzo Nobel (Akzo Nobel), and the specific type was
551DE20d42。
In the following examples and comparative examples, MOCA was 3, 3-dichloro-4, 4-diaminodiphenylmethane and MCDEA was 4, 4-methylenebis (3-chloro-2, 6-diethylaniline).
In the following examples, the hardness of each polishing zone was measured as follows:
the polyurethane materials obtained in the different polishing zones were cut into a size of 2cm by 2cm according to ASTM D2240-97 as a sample for hardness measurement. The sample was placed in an environment of 23 ℃ 2 ℃ and 50% + -5% humidity for 16 hours and then measured. In the measurement, the samples were stacked to form a test sample having a thickness of 6mm or more, and the hardness was measured by an ASKER-D type hardness tester.
Examples 1 to 6
Step (1): treatment of isocyanate-terminated polyurethane prepolymers (or prepolymers for short); the specific operation is as follows: 100 parts by mass of an isocyanate terminated prepolymer (the mass percentage of unreacted NCO groups is 8.75 to 9.05%, the above specific values of each example are shown in tables 1 and 2) obtained by reacting toluene diisocyanate and polytetrahydrofuran was heated to 80 ℃ and degassed under vacuum (-0.095MPa) for 2 hours; then, adding hollow microspheres with an average diameter of 20 microns in different mass fractions (the content of the hollow microspheres is shown in Table 4), and uniformly dispersing the hollow microspheres in the prepolymer under stirring to obtain compositions with different microsphere contents; respectively degassing the obtained compositions with different microsphere contents for 2 hours under vacuum (-0.095MPa), and then cooling to 50 ℃ to obtain prepolymers with different microsphere contents.
Step (2): curing the prepolymers with different microsphere contents by using the curing agent compositions shown in tables 1 and 2; the specific operation is as follows: the prepolymer with different microsphere contents is respectively mixed with a curing agent under high-speed shearing, then respectively poured into a mould consisting of a concentric circular side wall 13 and a base 12 with different diameters (the structure of the mould is shown in figures 3 and 4), a pouring block with the thickness of 12 cm is formed, the pouring block is gelled for 15 minutes at 70 ℃, then the temperature is raised to 100 ℃ within 30 minutes, the curing is carried out for 16 hours, and the temperature is automatically reduced to room temperature in an oven after the curing is finished, so that a cured block is obtained.
And (3): demoulding, slicing and fixing the solidified block to prepare an embedded polishing pad; the specific operation is as follows: separating the obtained solidified block from the die, cutting into slices (total 60 slices) with the thickness of 2 mm, cutting along the boundary between polishing zones with different hardness to obtain combined slice groups with different hardness, numbering each combined slice group from top to bottom in sequence as 1-60, taking out the combined slice with the number of 29 to obtain the combined slice corresponding to the embodiment, and fixing the obtained combined slice on the bottom liner according to the structure size of table 3 and the hardness of table 4 to obtain the mosaic polishing pad of each embodiment, wherein the inlaid polishing pad shown in fig. 1 and 2 is obtained by referring to fig. 1 and 2, wherein all the regions not marked in fig. 1 and 2 are sequentially outward according to the serial numbers of the regions not marked.
Wherein, in examples 1-3, the structural parameters of the annular gap between two adjacent combination pieces are shown in table 1; in examples 4 to 6, the structural parameters of the annular gap between two adjacent combination pieces are shown in table 2, and the damascene polishing pads in examples 4 to 6 are further provided with four radial trenches 11 extending from the outer edge of the central polishing region to the outer edge of the outer polishing region, and the structural parameters of the radial trenches 11 are shown in table 2.
Comparative examples 1 to 2
Step (1): treatment of isocyanate-terminated polyurethane prepolymers (or prepolymers for short); the specific operation is as follows: 100 parts by mass of an isocyanate terminated prepolymer (the mass percent of unreacted NCO groups is 8.75-9.05%, and the specific values are shown in tables 1 and 2) obtained by reacting toluene diisocyanate and polytetrahydrofuran is heated to 80 ℃, and degassed under vacuum (-0.095MPa) for 2 hours; then, adding hollow microspheres with an average diameter of 20 microns in different mass fractions (the content of the hollow microspheres is shown in Table 4), and uniformly dispersing the hollow microspheres in the prepolymer under stirring to obtain compositions with different microsphere contents; respectively degassing the obtained compositions with different microsphere contents for 2 hours under vacuum (-0.095MPa), and then cooling to 50 ℃ to obtain prepolymers with different microsphere contents.
Step (2): curing the prepolymers with different microsphere contents by using the curing agent compositions (the curing agent compositions are aromatic bifunctional compositions) with the types and the parts by mass shown in the tables 1 and 2; the specific operation is as follows: respectively mixing the prepolymers with different microsphere contents with a curing agent under high-speed shearing, then respectively casting into a mold to form a casting block with the thickness of 12 cm, gelling the casting block at 70 ℃ for 15 minutes, then heating the casting block to 100 ℃ within 30 minutes, curing for 16 hours, and automatically cooling the casting block to room temperature in an oven after curing is finished to obtain the cured block.
And (3): demoulding, slicing and fixing the solidified block to prepare a common polishing pad; the specific operation is as follows: separating the obtained solidified block from the die, cutting into slices (total 60 slices) with the thickness of 2 mm, numbering 1-60 from top to bottom in sequence, and taking out the slices with the number of 29, namely the common polishing pad of the corresponding comparative example; the structural dimensions of the general polishing pads of comparative examples 1-2 are shown in Table 3.
TABLE 1 preparation parameters for polishing layers of examples 1-3 and comparative example 1
TABLE 2 preparation parameters for polishing layers of examples 4-6 and comparative example 2
TABLE 3 structural dimensions of examples 1-6 and comparative examples 1-2
TABLE 4. examples 1-6 and comparative examples 1-2 different polishing zone microsphere content and hardness parameters
Effect example 1
This effect example was evaluated mainly on polishing uniformity and planarization efficiency of the polishing layer.
The polishing pads of examples 1 to 3 and comparative example 1 obtained by the above preparation method were subjected to comprehensive evaluation of polishing performance by the in-machine test under the following test conditions:
polishing conditions: the testing machine is AMAT Refelxion (Modify 5 Zone); the polishing solution is ANJI 3060(1:9Dilution, H)2 O 21%), flow rate 200 mL/min; the dressing Disk was Saesol Disk6045C4, P/C downform 5lbf, Head&Platen RPM 93/87; the wafers (wafers) used were pattern wafers Semitech 754, Cu Blanket wafer Pre magic 10 KA; polishing load was 350g/cm2The polishing platen rotation speed was 35rpm and the wafer rotation speed was 30 rpm.
Polishing pads were prepared from the polishing layers obtained in examples 1 to 3 and comparative example 1. In lapping, polishing uniformity and planarization efficiency were recorded for 2-10h over its life cycle, and the results are summarized in tables 5 and 6.
TABLE 5 uniformity of wafers polished with the polishing pads of examples 1-6 and comparative examples 1-2
TABLE 6 planarization times for polishing pads of examples 1-6 and comparative examples 1-2
In table 6, the planarization time refers to the time required for the wafer to complete planarization.
As can be seen from Table 4, the hardness of the polishing layers of the polishing pads of examples 1 to 6 decreased from the center to the edge.
As can be seen from table 5, under the same test conditions, the polishing pads of the examples and comparative examples had little effect on the polishing uniformity of the wafers at a polishing time of 2 hours, but the polishing pads of the examples had better polishing uniformity than those of comparative examples 1-2 at a polishing time of 4 hours or more.
It can also be seen from table 5 that the polishing uniformity of the polishing pad of the example can reach even more than 83%, which is much higher than 80% of comparative example 1 and 74% of comparative example 2, after 10 hours of use.
As can also be seen from Table 6, the polishing pads of the examples had a shorter planarization time than the polishing pads of the comparative examples; that is, the polishing pads of the examples had better planarization efficiency than the polishing pads of the comparative examples.
Based on the data in tables 4-6, it can be seen that: the polishing pad with the hardness decreasing from the center to the edge can well compensate the difference of the linear speed of the polishing pad, so that the wear rate of the polishing pad tends to be consistent, and the planarization efficiency and the uniformity of polishing are improved.
Claims (24)
1. A method for producing a polishing pad, characterized in that,
the polishing pad is provided with a combined sheet and a bottom lining, wherein the combined sheet is fixed on the bottom lining to form a polishing layer, the polishing layer is provided with a central polishing area, more than one middle polishing areas and an outer edge polishing area, the middle polishing areas are sequentially arranged around the central polishing area, the outer edge polishing areas are arranged around the middle polishing areas, the central polishing areas are circular, the middle polishing areas are annular, and the outer edge polishing areas are annular; an annular gap is formed between each two adjacent polishing areas and is used for receiving polishing fluid in the polishing process; the shore hardness of the polishing layer decreases in a direction from the central polishing zone to the outer edge polishing zone; the Shore hardness gradient of two adjacent polishing areas is 0.5-5D;
the die used in the preparation method is provided with inner cavities corresponding to each polishing area of the polishing pad, the inner cavity corresponding to the central polishing area is a central inner cavity, the inner cavity corresponding to the middle polishing area is an annular middle inner cavity, the inner cavity corresponding to the outer edge polishing area is an annular outer edge inner cavity,
the polishing layer comprises the following raw materials in parts by mass: 100 parts of an isocyanate-terminated prepolymer, 20-25 parts of a curing agent, and 1.0-2.4 parts of hollow microspheres;
the preparation method comprises the following steps:
(1) respectively pouring a pouring composition capable of preparing polishing areas with corresponding hardness into the central inner cavity, each annular middle inner cavity and the annular outer edge inner cavity, and curing to obtain a cured block body;
(2) separating the solidified block from the die, cutting along the radial direction of the solidified block to obtain a thin sheet, and cutting along the boundary between polishing areas with different hardness to obtain combined sheets with different hardness;
(3) and fixing the combined sheet on the bottom lining according to the corresponding hardness to obtain the embedded polishing pad.
2. The method of claim 1, wherein the shore hardness gradient between two adjacent polishing zones is between 0.9 and 3D.
3. The method of claim 1, wherein the shore hardness gradient between two adjacent polishing zones is 1-3D or 0.9-2.1D.
4. The method of claim 1, wherein the shore hardness gradient between two adjacent polishing zones is 1D, 1.1D, 1.2D, 1.3D, 1.4D, 1.5D, 1.6D, 1.9D, 2D, or 2.1D.
5. The method of preparing a polishing pad according to claim 1, wherein each polishing zone has a shore hardness of 40 to 70D.
6. The method of preparing a polishing pad according to claim 5, wherein the shore hardness of the central polishing region is 60 to 70D;
and/or the outer edge polishing zone has a shore hardness of 40-62D.
7. The method of preparing a polishing pad according to claim 1, wherein each polishing zone has a shore hardness of 60 to 70D.
8. The method of preparing a polishing pad according to claim 1, wherein the outer edge polishing zone has a shore hardness of 60-62D.
9. The method of claim 1, wherein the shore hardness of the central polishing zone is 60-70D, the shore hardness of the outer edge polishing zone is 60-62D, and the shore hardness gradient between two adjacent polishing zones is 0.9-2.1D.
10. The method of producing a polishing pad according to any one of claims 1 to 9, wherein the number of the intermediate polishing zones is 4 to 13.
11. The method of producing a polishing pad according to any one of claims 1 to 9, wherein the number of the intermediate polishing zones is 5 to 8.
12. The method of producing a polishing pad according to any one of claims 1 to 9, wherein the number of the intermediate polishing zones is 6 to 8.
13. The method of preparing a polishing pad according to any one of claims 1 to 9, wherein the central polishing zone has a diameter of 2 to 15 cm;
and/or each polishing zone other than the central polishing zone has a width of 2-15 cm.
14. The method of preparing a polishing pad according to claim 13, wherein the central polishing zone has a diameter of 10-15 cm.
15. The method of preparing a polishing pad according to claim 13, wherein the width of each polishing zone other than the central polishing zone is 2.5 to 15 cm.
16. The method of claim 13, wherein the width of each polishing zone other than the central polishing zone is 2.5-7.5 cm.
17. The method of claim 13, wherein the width of each polishing zone other than the central polishing zone is 3cm or 5 cm.
18. The method of producing a polishing pad according to any one of claims 1 to 9, wherein the width of the annular slit is 0.1 to 0.6 cm;
and/or the polishing layer is also provided with a radial groove, and the radial groove is used for receiving polishing fluid in the polishing process; wherein, the width of the radial groove is preferably 0.1-0.6 cm;
and/or a buffer pad is arranged on the back of the polishing layer.
19. The method of preparing a polishing pad according to claim 18, wherein the width of the annular slit is 0.2 to 0.4 cm.
20. The method of preparing a polishing pad according to claim 18, wherein the width of the radial grooves is 0.2 to 0.4 cm.
21. The method of producing a polishing pad according to any one of claims 1 to 9, wherein the polishing pad has a diameter of 50 to 100 cm.
22. The method of preparing a polishing pad according to claim 21, wherein the polishing pad has a diameter of 50 to 90 cm.
23. The method of preparing a polishing pad of claim 21, wherein the polishing pad has a diameter of 70-85 cm.
24. Use of a method of preparing a polishing pad according to any one of claims 1-23 for polishing a wafer.
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