CN112207710A

CN112207710A - High strength polishing pad for polishing back side of wafer

Info

Publication number: CN112207710A
Application number: CN202010666525.4A
Authority: CN
Inventors: 金八坤; 刘永俊; 吴承泽; 李都炯
Original assignee: FNS Technology Co Ltd
Current assignee: FNS Technology Co Ltd
Priority date: 2019-07-10
Filing date: 2020-07-10
Publication date: 2021-01-12
Also published as: KR20210007124A; KR102345784B1

Abstract

The present application relates to a high strength polishing pad for polishing the back side of a wafer. The polishing pad comprises a polishing layer, wherein the polishing layer has a grid of asperity elements in a polishing surface, and the hardness of the polishing layer is 60 Shore D to 90 Shore D. The high-strength polishing pad for polishing the back surface of a wafer according to the present application has an excellent impurity removal effect and excellent durability.

Description

High strength polishing pad for polishing back side of wafer

Cross Reference to Related Applications

The present application claims the benefit of korean patent application No.10-2019-0083014, filed on 7/10 in 2019, the disclosure of which is incorporated herein by reference.

Technical Field

The present application relates to a high-strength polishing pad for polishing the back side of a wafer comprising a polishing layer.

Background

The semiconductor manufacturing process is performed in the order of initial wafer fabrication-circuit design-mask fabrication-wafer processing-chip assembly. Among them, wafer processing is a series of processes for constructing circuits on a wafer, and is composed of detailed processes such as diffusion, photolithography, etching, deposition, ion implantation, and polishing. The deposition process is a process of forming a conductive or insulating film by a chemical reaction or a physical method, and is performed not only on the front surface but also on the back surface of the wafer, and in this case, particles or other impurities may be generated on the back surface of the wafer, and the generated particles or other impurities may cause defects in the deposition process in the photolithography process and/or the chip assembly process. In particular, when there are impurities including particles present on the back surface of the wafer, when the wafer is subsequently mounted on a chuck of an exposure apparatus, a local height difference occurs, thereby causing defocusing of patterning during polishing and possibly manufacturing a defective wafer.

Therefore, a back side polishing process needs to be performed after the photolithography process, but the related art polishing pad for back side polishing is not used separately from the polishing pad for polishing the front side of the wafer, hardness is relatively small, and thus durability is poor and an impurity removal rate is reduced due to friction with impurities, and a groove pitch optimal for impurity removal is not disclosed, and thus efficiency of removing impurities is not high.

Disclosure of Invention

Technical problem

An object of the present application is to provide a high-strength polishing pad for polishing a back surface of a wafer, which is a high-strength polishing pad for polishing a back surface of a wafer including a polishing layer having a lattice of concave-convex cells in a polishing surface, the polishing layer having a hardness of 60 shore D to 90 shore D.

However, the problems to be solved by the present application are not limited to the above-described problems, and other problems not mentioned will be clearly understood from the following description by those skilled in the art.

Technical scheme

A first aspect of the present application provides a high-strength polishing pad for polishing a back surface of a wafer, which is a high-strength polishing pad for polishing a back surface of a wafer including a polishing layer having a lattice of concave and convex cells in a polishing surface, the polishing layer having a hardness of 60 shore D to 90 shore D.

A second aspect of the present application provides a method of manufacturing a high-strength polishing pad for polishing a back surface of a wafer according to the first aspect, comprising: injecting and molding a mixture comprising a urethane-based prepolymer and a curing agent into a mold, curing the molded mixture to form a mat, and forming a concavo-convex unit grid on the mat.

Advantageous effects

The high-strength polishing pad for polishing the back surface of a wafer according to an embodiment of the present disclosure includes a lattice of concave-convex cells designed to be optimized for wafer back surface polishing, thus increasing the frequency of friction of convex portions and impurities adhering to the back surface of the wafer, and not only can slurry be smoothly flowed in and removed, but also the slurry can be uniformly supplied to the concave portions and the convex portions, so that the effect of removing impurities is excellent.

Since the hardness of the polishing pad for polishing the front surface of the wafer is 40 shore D to 65 shore D, there is an unsuitable problem for polishing the back surface of the wafer, but the high hardness polishing pad for polishing the back surface of the wafer according to the embodiments of the present application has a hardness greater than that of the polishing pad for polishing the front surface of the wafer, and thus is effective for removing impurities attached on the back surface of the wafer, and has excellent durability, which is advantageous for long-term use. In addition, since the high-hardness polishing pad for polishing the back surface of a wafer of the present application has an advantage of being able to prevent damage of a polishing layer due to friction with impurities, there is a problem of the related art that improves a polishing pad for polishing the front surface of a wafer is used to polish the back surface of a wafer, resulting in a defective wafer.

The high-hardness polishing pad for polishing the back surface of a wafer according to an embodiment of the present application does not include pores at the surface and inside of the polishing layer, thus having high hardness and being advantageous for removing impurities, and does not require an additional conditioning (conditioning) process after the polishing process, which has the advantages of reducing process steps and reducing manufacturing costs. Specifically, the polishing pad for polishing the front surface of the wafer has a small hardness so as not to scratch the front surface of the wafer, but includes air holes to improve polishing efficiency. However, when the pores are included in the polishing pad, a conditioning process must be additionally performed to remove polishing residues existing between the pores after the polishing process. In addition, when the air holes are included, the hardness can be further reduced, which is inefficient for removing impurities attached to the back surface of the wafer. Accordingly, the high-hardness polishing pad for polishing the back surface of a wafer of the present application does not include pores on the surface and inside of the polishing layer, thus having high hardness and facilitating removal of impurities, and does not require an additional conditioning process to reduce process steps and manufacturing costs. In addition, the high-hardness polishing pad for polishing the back surface of a wafer of the present application can also perform an additional conditioning process, and thus has an additional advantage of freely controlling the presence or absence of the conditioning process.

Drawings

Fig. 1 is a photograph showing a concave-convex cell grid of a high-hardness polishing pad for polishing a back surface of a wafer according to an embodiment of the present application.

Fig. 2 is a schematic view illustrating a high-hardness polishing pad for polishing the back surface of a wafer (a of fig. 2) including protrusions having concentric hexagons and a high-hardness polishing pad for polishing the back surface of a wafer (b of fig. 2) including protrusions having hexagonal island shapes according to an embodiment of the present application.

Fig. 3 is a schematic view illustrating a high-hardness polishing pad for polishing the back surface of a wafer (a of fig. 3) including protrusions having concentric triangles and a high-hardness polishing pad for polishing the back surface of a wafer (b of fig. 3) including protrusions having triangular island shapes according to an embodiment of the present application.

Fig. 4 is a schematic view illustrating a high-hardness polishing pad for polishing the back surface of a wafer (a of fig. 4) including protrusions having concentric quadrangle shapes and a high-hardness polishing pad for polishing the back surface of a wafer (b of fig. 4) including protrusions having quadrangle-shaped islands according to an embodiment of the present application.

Detailed Description

Hereinafter, implementations and embodiments of the present application will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily implement the present invention. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In addition, in order to clearly describe the present invention in the drawings, portions irrelevant to the description are omitted, and like reference numerals are assigned to like portions throughout the specification.

Throughout the specification, when a certain portion is "connected to" another portion, not only the case of "directly connecting" but also the case of "electrically connecting" where other elements are provided therebetween are included.

Throughout the specification, when a certain member is "on" another member, it includes not only a case where the certain member abuts against the another member but also a case where the other member exists between the two members.

Throughout the specification, unless otherwise specified, when a portion "includes" a certain constituent element, it means that the portion may further include other constituent elements without excluding the other constituent elements.

The terms of degree "about," "substantially," and the like as used herein are used as a meaning at or near this value when presenting inherent manufacturing and material tolerances for that meaning to prevent an unscrupulous actor from unmistakably abusing the disclosure of an accurate or absolute value in order to aid understanding of this application.

The term "step of proceeding" or "step of" used throughout the specification does not mean "step for".

Throughout the specification, the term "combination thereof" included in the expression of markush form means a mixture or combination of one or more selected from the group consisting of the constituent elements described in the expression of markush form, which means that one or more selected from the group consisting of the constituent elements described above is included.

Throughout the specification, the description of "a and/or B" means "a or B, or a and B".

Hereinafter, implementations and embodiments of the present application will be described in detail with reference to the accompanying drawings. However, the present application is not limited to these embodiments, examples, and drawings.

In an embodiment of the present application, the polishing layer has a hardness of about 60 shore D to about 90 shore D, about 65 shore D to about 90 shore D, about 70 shore D to about 90 shore D, about 75 shore D to about 90 shore D, or about 80 shore D to about 90 shore D. Specifically, since the high-strength polishing pad for polishing the back surface of the wafer of the present application has a hardness (about 40 shore D to about 65 shore D) greater than that of the polishing pad for polishing the front surface of the wafer, it is effective for removing impurities adhering to the back surface of the wafer and is excellent in durability, thus having advantageous effects in long-term use. In addition, since the high hardness polishing pad for polishing the back surface of a wafer of the present application has an advantage of preventing damage of a polishing layer due to friction with impurities, there is a problem of the prior art that the polishing pad for polishing the front surface of a wafer is used to polish the back surface of the wafer, resulting in a defective wafer.

In an embodiment of the present application, the concave-convex unit grating is a plurality of unit gratings, and a width of the concave-convex unit grating may be about 2mm or less, but is not limited thereto. Specifically, the width of the concave-convex unit grid may be about 2mm or less, about 1.5mm or less, about 1.0mm or less, or about 0.5mm or less. Since the related art polishing pad has a groove interval of about 2mm to about 3mm, the effect of removing impurities when used to polish the back surface of a wafer is small. In contrast, the high-hardness polishing pad for polishing the back surface of a wafer of the present application is designed as a fine concave-convex cell lattice having a width of 2mm or less to be optimized for polishing the back surface of a wafer, so that the frequency of friction between convex portions and impurities attached to the back surface of the wafer increases, and not only can the slurry smoothly flow in and be discharged, but also the slurry can be uniformly supplied to the concave portions and the convex portions, whereby the effect of removing impurities is excellent.

Referring to fig. 1, in a polishing surface of a high-strength polishing pad for polishing a back surface of a wafer according to an embodiment of the present application, the concavo-convex cell grating is designed to include concave and convex portions, and a width of the concavo-convex cell grating including the concave and convex portions may be 2mm, but is not limited thereto. In addition, a plurality of concave-convex unit grids may be present on the polishing surface.

In an embodiment of the present application, the width of the concave portion in the concave-convex unit grid may be about 1mm or less, but is not limited thereto. Specifically, the width of the concave portion in the concave-convex cell lattice may be about 1mm or less, about 0.8mm or less, about 0.6mm or less, or about 0.4mm or less.

In an embodiment of the present application, the shape of the convex portions in the concave-convex unit cell grid may be a grid shape, a concentric circle, a spiral shape, a polygon (triangle, quadrangle, pentagon, hexagon, etc.), a stripe shape, or an oblique line shape, but is not limited thereto.

Referring to fig. 2 to 4, the shape of the convex portion in the polishing surface of the high-hardness polishing pad for polishing the back surface of the wafer according to an embodiment of the present application may be hexagonal, triangular, or quadrangular. Specifically, since the concave portion of the black line is formed on the high-hardness polishing pad for polishing the back surface of the wafer, the convex portion of the white portion can be formed. The convex portion may be a hexagon, a triangle or a quadrangle having a concentric shape on the polishing surface (a of fig. 2, a of fig. 3 and a of fig. 4); or hexagonal, triangular or quadrangular islands (fig. 2 b, fig. 3 b and fig. 4 b), but is not limited thereto.

In an embodiment of the present application, the convex portions of the concave-convex unit grating may have an island shape, and the foreign matter on the back surface of the wafer may be removed by edges of the convex portions. Specifically, when the concavo-convex unit cell is of a lattice type, the convex portions are in a quadrangular island shape, and the edges of the convex portions may be constituted by four faces in total. In addition, since the polishing layer may be composed of a plurality of concave-convex unit grids, the polishing layer may have innumerable edges. Therefore, as the edge increases, the frequency of friction with impurities adhering to the back surface of the wafer may increase, and thus, the high-hardness polishing pad for polishing the back surface of the wafer of the present application has an excellent effect of removing impurities.

In an embodiment of the present application, the depth of the concave portion of the concave-convex unit grating may be about 0.001mm to about 5mm, but is not limited thereto. In particular, the depth of the recesses of the grid of relief cells may be about 0.001mm to about 5mm, about 0.01mm to about 4mm, about 0.1mm to about 3mm or about 0.3mm to about 2 mm.

In one embodiment of the present application, the surface and interior of the polishing layer may not include air holes, but is not limited thereto. Specifically, the polishing pad for polishing the front surface of the wafer has a small hardness so as not to scratch the front surface of the wafer, but includes air holes to improve polishing efficiency. However, when the pores are included in the polishing pad, a conditioning process must be additionally performed to remove polishing residues existing between the pores after the polishing process. In addition, when the air holes are included, the hardness can be further reduced, which is inefficient for removing impurities attached to the back surface of the wafer. Therefore, the high-hardness polishing pad for polishing the back surface of a wafer of the present application does not include pores at the surface and inside of the polishing layer, and thus has high hardness and facilitates removal of impurities. And no additional conditioning process is required to reduce process steps and manufacturing costs. In addition, the high-hardness polishing pad for polishing the back surface of a wafer of the present application can also perform an additional conditioning process, and thus has an additional advantage of freely controlling the presence or absence of the conditioning process.

In an embodiment of the present application, as the number of the uneven cell grids per unit area of the polishing surface increases, the removal rate of the foreign matter on the back surface of the wafer increases. Specifically, as the number of the uneven unit grids per unit area of the polishing surface increases, the frequency of friction between the convex portions and the impurities adhering to the back surface of the wafer increases, and the slurry is uniformly supplied to the concave and convex portions so that the impurity removal effect can be improved.

In one embodiment of the present application, the polishing layer may have a thickness of about 0.1mm to about 5mm, but is not limited thereto. Specifically, the polishing layer can have a thickness of about 0.1mm to about 5mm, about 0.5mm to about 4.5mm, about 1.0mm to about 4.0mm, or about 1.5mm to about 3.5 mm.

In one embodiment of the present application, the polishing layer may have a specific gravity of about 0.5g/cm³To about 2.0g/cm³But is not limited thereto. Specifically, the polishing layer may have a specific gravity of about 0.5g/cm³To about 2.0g/cm³About 0.8g/cm³To about 1.8g/cm³Or about 1.0g/cm³To about 1.5g/cm³。

In one embodiment of the present application, the polishing layer may have an elongation of about 10% to about 450%, but is not limited thereto. Specifically, the polishing layer may have an elongation of about 10% to about 450%, about 50% to about 400%, about 100% to about 350%, or about 150% to about 300%.

In one embodiment of the present application, the polishing layer may have a compressibility of about 0.1% to about 20%, but is not limited thereto. Specifically, the polishing layer may have a compressibility of about 0.1% to about 20%, about 0.1% to about 10%, about 0.2% to about 8%, about 0.3% to about 5%, or about 0.4% to about 1%.

The high-hardness polishing pad for polishing the back surface of a wafer according to an embodiment of the present application may further include a sub-pad.

In one embodiment of the present application, the subpad may have a hardness less than the polishing layer. Specifically, the subpad may have a hardness of about 40 shore a to about 60 shore a. Specifically, the hardness of the subpad may be about 40 shore a to about 60 shore a, about 45 shore a to about 60 shore a, or about 50 shore a to about 60 shore a.

In one embodiment of the present application, the subpad has a thickness of about 0.001mm to about 3mm and a specific gravity of about 0.1g/cm³To about 1.2g/cm³And the compressibility may be about 0.1% to about 30%, but is not limited thereto.

In one embodiment of the present application, the subpad supports the polishing layer and may act as a cushion. The sub-mat may be any suitable sub-mat. Suitable subpads may include polyurethane foam subpads, impregnated felt subpads, microporous polyurethane subpads, sintered urethane subpads, or polyolefin foam subpads. The subpad may generally be more malleable and compressible than the polishing layer. The subpad may be secured to the polishing layer by any suitable means. In particular, the polishing layer and subpad may be secured by adhesive or attached by welding or similar techniques.

The high-hardness polishing pad for polishing the back surface of a wafer according to an embodiment of the present application may further include a release film layer.

In one embodiment of the present application, the release film layer may include a polyolefin selected from the group consisting of low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, and polypropylene; glycols consisting of poly (tetramethylene ether) glycol (PTMG), polypropylene glycol (PPG) and polyethylene glycol (PEG); polyurethanes composed of polymers having unreacted NCO groups; polyvinyl chloride; cellulose-based polymers consisting of cellulose acetate and cellulose butyrate; acrylic acid; polyesters and copolyesters consisting of PET and PETG; a polycarbonate; polyamides composed of nylon 6/6 and nylon 6/12; and high-performance plastics composed of polyether ether ketone, polyphenylene oxide, polysulfone, polyimide and polyetherimide.

In one embodiment of the present application, the polishing layer, subpad, and/or substrate may be secured between each by adhesive or attached by welding or similar techniques. Typically, an intermediate backing layer, such as a polyethylene terephthalate film, may be disposed between the pads. The adhesive may be a Pressure Sensitive Adhesive (PSA) or a hot melt adhesive. Pressure sensitive adhesives are adhesives in which the adhesive material functions when pressure is applied for adhesion to an adhesive surface, either for securing the pads to the platform or for adhesion between the pads. For the pressure-sensitive adhesive, an adhesive such as a polyacrylate component, an epoxy component or a rubber component, which is commonly used in the art, may be used, and a double-sided pressure-sensitive adhesive tape coated on both sides of a release film layer (PET film or felt) with an adhesive or bonding material may be used. The hot melt adhesive is a cured reactive hot melt adhesive which has not been curedExhibits a melting temperature of about 50 ℃ to about 150 ℃, specifically about 115 ℃ to about 135 ℃, in the cured state, and also exhibits a usable time of 90 minutes or less after melting. More specifically, the hot Melt adhesive may include, for example, Mor-Melt available from Rohm and Haas^TMR5003。

In the first and second aspects, even if description is omitted, contents common to each other can be applied.

In an embodiment of the present application, the pad may be a polyurethane foam (polyurethane cake), and the polyurethane foam-forming mixture may include a urethane-based prepolymer and a curing agent, but is not limited thereto. Prepolymers generally refer to polymers having a relatively low molecular weight, wherein the degree of polymerization stops in an intermediate step, thereby facilitating molding in the manufacture of the final shaped article. The prepolymer may be formed by itself or may be formed after reaction with other polymerizable compounds, and for example, the prepolymer may be prepared by reacting an isocyanate compound with a polyol. The polyurethane resin prepared from the urethane-based prepolymer may have a weight average molecular weight (Mw) of about 500 to about 3,000g/mol, but is not limited thereto. Specifically, the polyurethane resin may have a weight average molecular weight of about 600g/mol to about 2,000g/mol or about 700 to about 1,500 g/mol.

The isocyanate compound used in the preparation of the urethane prepolymer may be one or more isocyanates selected from the group consisting of Toluene Diisocyanate (TDI), naphthalene-1, 5-diisocyanate, p-phenylene diisocyanate, tolidine diisocyanate, 4' -diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

The polyol used for preparing the urethane based prepolymer is one or more polyols selected from the group consisting of polyether polyol, polyester polyol, polycarbonate polyol and acrylic polyol.

The curing agent may be at least one of an amine compound and an alcohol compound. Specifically, the curing agent may be one or more compounds selected from the group consisting of aromatic amines, aliphatic amines, aromatic alcohols, and aliphatic alcohols. For example, the curing agent may be one or more selected from the group consisting of 4, 4' -methylenebis (2-chloroaniline) (MOCA), diethyltoluenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, m-xylylenediamine, isophoronediamine, ethylenediamine, diethylenetriamine, triethylenetetramine, polypropylenediamine, polypropylenetriamine, ethyleneglycol, diethyleneglycol, dipropyleneglycol, butyleneglycol, hexylenediol, glycerin, trimethylolpropane, and bis (4-amino-3-chlorophenyl) methane.

Specifically, the urethane prepolymer and the curing agent are mixed and reacted to form a solid polyurethane, which is then formed into a sheet or the like. The isocyanate end group of the urethane prepolymer may react with an amine group, an alcohol group, etc. of the curing agent. The reaction between the urethane-based prepolymer and the curing agent is completed in the mold, so that a cake-like molded body cured in the shape of the mold can be obtained. Thereafter, the obtained molded body may be appropriately sliced or cut to be processed into a sheet for manufacturing a polishing pad.

In an embodiment of the present application, the method of forming the uneven cell grid on the pad surface is a method of machine cutting using a jig (such as a bite of a predetermined size), a method of curing by putting a resin into a mold having a predetermined surface shape, a method of forming by pressing a resin with a platen having a predetermined surface shape, a method of forming using a photolithography method, a method of forming using a printing method, a laser forming method using a carbon dioxide laser, or embossing thermoforming, but is not limited thereto.

In an embodiment of the present application, the shape of the convex portions in the concave-convex cell grating may be a polygon (triangle, quadrangle, pentagon, hexagon, etc.), a circle, a stripe, a spiral, an oblique line, a cone, or a pyramid, but is not limited thereto.

The above description of the present application is for exemplary purposes, and it will be understood by those of ordinary skill in the art to which the present application pertains that the present application may be easily modified into other specific forms without changing the technical spirit or essential features of the present application. It is therefore to be understood that the above described embodiments are illustrative in all respects, not restrictive. For example, each constituent element described as a single type may be implemented in a distributed manner, and similarly, constituent elements described as distributed may be implemented in a combined form.

The scope of the present application is indicated by the appended claims rather than the detailed description, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and equivalent concepts are included in the scope of the present application.

Claims

1. A high strength polishing pad for polishing a back side of a wafer, the polishing pad comprising a polishing layer,

the polishing layer has a grid of concave-convex elements in a polishing surface,

the polishing layer has a hardness of 60 Shore D to 90 Shore D.

2. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the concave-convex unit grids are a plurality of,

the width of the concave-convex unit grating is less than 2 mm.

3. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 2, wherein,

the width of the concave part in the concave-convex unit grid is less than or equal to 1 mm.

4. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the shape of the convex parts in the concave-convex unit grid is polygonal, circular, stripe-shaped, spiral, oblique line-shaped, conical or pyramid-shaped.

5. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the convex part of the concave-convex unit grid is in an island shape,

removing impurities on the back surface of the wafer through the edge of the convex portion.

6. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the depth of the concave part of the concave-convex unit grid is 0.001mm to 5 mm.

7. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the surface and interior of the polishing layer do not include pores.

8. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

as the number of the uneven cell grids per unit area of the polishing surface increases, the removal rate of the impurities on the back surface of the wafer increases.

9. The high strength polishing pad for polishing the back surface of a wafer as recited in claim 1, wherein,

the polishing layer has a thickness of 0.1mm to 5mm,

the specific gravity of the polishing layer is 0.3g/cm³To 1.5g/cm³，

The polishing layer has an elongation of 10% to 450%,

the polishing layer has a compressibility of 0.1% to 20%.

10. A method of manufacturing a high-strength polishing pad for polishing a back surface of a wafer according to claim 1, comprising:

injecting a mixture containing a urethane prepolymer and a curing agent into a mold and molding;

curing the shaped mixture to form a mat,

a grid of concave and convex cells is formed on the pad.

11. The method of manufacturing a high-strength polishing pad for polishing a back surface of a wafer according to claim 10, wherein,

the convex parts of the concave-convex unit grating are in the shapes of polygons, circles, stripes, spirals, diagonals, cones or pyramids.