US20140364044A1

US20140364044A1 - Polishing pad and method of manufacturing the same

Info

Publication number: US20140364044A1
Application number: US14/464,985
Authority: US
Inventors: Bong-su Ahn; Young-jun Jang; Sang-Mok Lee; Hwi-Kuk CHUNG; Kee-Cheon Song; Seung-geun Kim; Jang-Won SEO; Jeong-Seon CHOO
Original assignee: Samsung Electronics Co Ltd; KPX CHEMICAL CO Ltd
Current assignee: Samsung Electronics Co Ltd; KPX CHEMICAL CO Ltd
Priority date: 2012-02-20
Filing date: 2014-08-21
Publication date: 2014-12-11
Also published as: CN103252729A; US20130212951A1; KR20130095430A; TW201338923A; WO2013125807A1; JP2013169645A; JP5588528B2

Abstract

Polishing pad and method of manufacturing the same, the method including: (a) mixing materials for forming a polishing layer; (b) mixing at least two from among inert gas, a capsule type foaming agent, a chemical foaming agent, and liquid microelements that are capable of controlling sizes of pores, with the mixture in (a) so as to form two or more types of pores; (c) performing gelling and hardening of the mixture generated in (b) so as to form a polishing layer including the two or more types of pores; and (d) processing the polishing layer so as to distribute micropores defined by opening the two or more types of pores on a surface of the polishing layer.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This is a divisional application of U.S. patent application Ser. No. 13/761,338, filed on Feb. 7, 2013 which claims priority from the Korean Patent Application No. 10-2012-0016845, filed on Feb. 20, 2012 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a polishing pad and a method of manufacturing the same, and more particularly, to a polishing pad that allows a polishing slurry to be effectively collected and supplied and a method of manufacturing the same.
2. Description of the Related Art
A chemical mechanical planarization/polishing (CMP) process has been used for global planarization of semiconductor devices and has become important with tendencies to an increase in the diameter of a wafer, a high integration density, a micro line width, and a multilayer wiring structure.
In a CMP process, a polishing speed and the flatness of a wafer are important, and the performance of such a CMP process depends on conditions of CMP equipment and performances of a polishing slurry and a polishing pad that are consumable members. In particular, the polishing pad allows the polishing slurry supplied in a state where the polishing pad is in contact with the surface of the wafer, to be uniformly dispersed onto the wafer so that physical abrasion is provoked by abrasive particles contained in the polishing slurry and protrusions of the polishing pad.
In this case, a polishing pad's surface directly contacting the wafer needs to be saturated with the polishing slurry so that the polishing slurry flows smoothly. To this end, techniques for forming micro holes (for example, pores) in the polishing pad's surface are disclosed in U.S. Pat. No. 5,578,362 and the like.
In this way, it is very important to maintain the polishing pad's surface to be saturated with the polishing slurry so as to increase the role and performance of the polishing pad in the CMP process. Thus, grooves in various shapes are formed in the polishing pad so as to form a large slurry flow, and micro holes are formed in the polishing pad's surface by opening a microporous material, as described above.
Among them, techniques for forming grooves in various patterns have been developed; however, techniques relating to a plurality of pores for forming micro holes are limited to restrictively using methods of forming predetermined pores.
That is, there are advantages and disadvantages depending on methods of forming a plurality of pores according to the related art. In actuality, the CMP process is used by adjustment in consideration of the advantages and disadvantages.
However, as a semiconductor process is required to be more minute and more elaborate, the CMP process also requires an improved technique for forming a plurality of pores so as to satisfy the demand.

SUMMARY OF THE INVENTION

The present invention provides a polishing pad that may maximize polishing performance and planarization performance by collecting and using a polishing slurry when a chemical mechanical planarization/polishing (CMP) process is performed and a method of manufacturing the same.
According to an aspect of the present invention, there is provided a polishing pad that performs a polishing process by moving in contact with a surface of an object to be polished, the polishing pad including a polishing layer, wherein the polishing layer comprises two or more types of pores, of which sizes are controlled by using at least two from among inert gas, a capsule type foaming agent, a chemical agent, and liquid microelements, and micropores that are defined by opening the two or more types of pores are distributed on a surface of the polishing layer.
According to another aspect of the present invention, there is provided a method of manufacturing a polishing pad, the method including: (a) mixing materials for forming a polishing layer; (b) mixing at least two from among inert gas, a capsule type foaming agent, a chemical foaming agent, and liquid microelements that are capable of controlling sizes of pores, with the mixture in (a) so as to form two or more types of pores; (c) performing gelling and hardening of the mixture generated in (b) so as to form a polishing layer comprising the two or more types of pores; and (d) processing the polishing layer so as to distribute micropores defined by opening the two or more types of pores on a surface of the polishing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of a polishing pad according to an embodiment of the present invention;

FIG. 2 is an enlarged scanning electron microscope (SEM) photograph of a cross-section of a polishing layer of the polishing pad illustrated in FIG. 1;

FIG. 3 is a schematic diagram of a polishing apparatus employing the polishing pad of FIG. 1;

FIG. 4 is a flowchart illustrating a method of manufacturing the polishing layer of the polishing pad according to an embodiment of the present invention;

FIGS. 5 and 6 are SEM photographs of pores formed in the surface of a polishing layer including pores formed by inert gas and pores formed by liquid microelements, according to an embodiment of the present invention; and

FIG. 7 illustrates comparison of the polishing efficiency of a polishing pad formed by using methods (Experimental Examples 2 and 3) according to the present invention with the polishing efficiency of a polishing pad formed according to the related art.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.
FIG. 1 is a cross-sectional view of a polishing pad 100 according to an embodiment of the present invention, FIG. 2 is an enlarged scanning electron microscope (SEM) photograph of a cross-section of a polishing layer 120 of the polishing pad 100 illustrated in FIG. 1, and FIG. 3 is a schematic diagram of a polishing apparatus 1 employing the polishing pad 100 of FIG. 1.
Referring to FIG. 1, the polishing pad 100 according to the current embodiment of the present invention includes a support layer 110 and a polishing layer 120. The support layer 110 is used to fix the polishing pad 100 to a platen 3, as shown in FIG. 3. The support layer 110 is made of a material having stability in order to correspond to a force pressing a silicon wafer 7, i.e., an object to be polished, which is loaded at a head 5 facing the platen 3 so that the support layer 110 supports the polishing layer 120 formed on the support layer 110 with uniform elasticity with respect to the silicon wafer 7. Accordingly, the support layer 110 is made of a nonporous, solid, and uniform elastic material mainly and has lower hardness than the polishing layer 120 formed on the support layer 110.
In addition, at least a part of the support layer 110 is transparent or semitransparent so that a light beam 170 used to detect the flatness of a surface of the object to be polished can be transmitted through the support layer 110. In FIG. 3, the object to be polished is the silicon wafer 7 having a metal or insulation layer as a layer to be polished. However, various types of substrates such as a substrate, on which a thin film transistor-liquid crystal display (TFT-LCD) is to be formed, a glass substrate, a ceramic substrate, and a polymer plastic substrate may be objects to be polished. In addition, the polishing pad 100 can be manufactured without including the support layer 110.
Also, although the polishing pad 100 has a circular shape so as to be suitable for the rotation type polishing apparatus 1, as shown in FIG. 3, the polishing pad 100 can be modified in various shapes, such as a rectangular shape, a square shape, and the like, according to the shape of the polishing apparatus 1.
As shown in FIG. 3, the polishing layer 120 directly contacts the silicon wafer 7 as the object to be polished. The polishing layer 120 can be formed by mixing or chemically combining predetermined materials for forming a polishing layer. That is, a polymeric matrix 130 that constitutes the polishing layer 120 is composed of various well-known components, and descriptions of well-known materials and forming materials will be omitted.
The polishing layer 120 may include two or more types of a plurality of pores. The sizes of two or more types of the plurality of pores are controlled by at least two selected from the group consisting of inert gas, a capsule type foaming agent, a chemical foaming agent, and liquid microelements.
That is, types of pores can be distinguished from each other by a method of forming the pores. At least two types of pores selected from the group consisting of pores formed by the inert gas, pores formed by the capsule type foaming agent, pores formed by the chemical foaming agent, and pores formed by the liquid microelements are included in the polishing layer 120 according to the present invention.
Here, pores according to their types may be formed so that their sizes are distinguished from one another; however, aspects of the present invention are not limited thereto.
Hereinafter, as an example of the present invention, it is assumed that two types of a plurality of pores, i.e., a plurality of first pores and a plurality of second pores are formed in the polishing layer 120 and in particular, the plurality of first pores therebetween are formed by the liquid microelements and the plurality of second pores are formed by the inert gas.
In this way, when the plurality of first pores formed by the liquid microelements are included in the polishing layer 120, a material formed by mixing the materials for forming the polishing layer as described above may correspond to a hydrophilic polymeric matrix containing polyalkylene glycol (hereinafter, referred to as a ‘polyalkylene glycol-containing hydrophilic polymeric matrix’) 130.
That is, the polishing layer 120 may include a plurality of first pores 141 formed of embedded liquid microelements and a plurality of second pores 142 that are gaseous pores including embedded inert gas, which are uniformly distributed in predetermined regions of the polyalkylene glycol-containing hydrophilic polymeric matrix 130.
An actual example of the plurality of first pores (liquid microelement pores) 141 and the plurality of second pores (gaseous pores) 142 included in the polishing layer 120 in this manner is as shown in FIG. 2.
A plurality of micropores 141′ and 142′, which have an open microstructure and are defined by the plurality of first pores 141 and the plurality of second pores 142, are uniformly arranged in a polishing layer surface 160, which directly contacts a silicon wafer 7.
Here, the plurality of micropores 141′ and 142′, which have an open microstructure and are defined by the plurality of first pores 141 and the plurality of second pores 142, means that, as the liquid microelements or inert gas embedded in the polishing layer 120 leak or leaks to the outside, regions in which the liquid microelements or inert gas are or is included, remain from the micropores 141′ and 142′ so that predetermined materials from the outside can be collected in the regions.
The plurality of first and second pores 141 and 142 that are embedded as the polishing pad 100 is abraded during a polishing process, are continuously exposed to the polishing layer surface 160 and form the micropores 141′ and 142′, and the micropores 141′ and 142′ are substituted by a polishing slurry 13. Thus, since only the polymeric matrix 130 exists in the polishing layer surface 160, non-uniform abrasion of the polishing pad 100 does not occur but the silicon wafer 7 as an object to be polished can be uniformly polished.
The polyalkylene glycol-containing hydrophilic polymeric matrix 130 may be formed of a material that is not dissolved in the polishing slurry 13 as a chemical solution used for planarization. For example, as shown in FIG. 3, the polyalkylene glycol-containing hydrophilic polymeric matrix 130 is formed of a material into which the polishing slurry 13 supplied through a nozzle 11 of the polishing apparatus 1 cannot infiltrate.
The polyalkylene glycol-containing hydrophilic polymeric matrix 130 may be formed by chemically combining or physically mixing a material for forming a polymeric matrix, a hydrophilic material, and a polyalkylene glycol compound.
Here, the polymeric matrix 130 formed by the material for forming a polymeric matrix may be formed of one material selected from the group consisting of polyurethane, polyether, polyester, polysulfone, polyacryl, polycarbonate, polyethylene, polymethylmetacrylate, polyvinylacetate, polyvinylchloride, polyethyleneimine, polyethersulfone, polyetherimide, polyketone, melamine, nylon, hydrocarbon fluoride, or a combination thereof.
The polyalkylene glycol-containing hydrophilic polymeric matrix 130 is formed by chemically combining or physically mixing the hydrophilic material and the polyalkylene glycol compound with the polymeric matrix 130.
The hydrophilic material may be one selected from the group consisting of polyethylene glycol, polyethylenepropylene glycol, polyoxyethylene alkylphenolether, polyoxyethylene alkylether, polyethylene glycol fatty acid ester, polyoxyethylene alkylamine ether, glycerine fatty acid ester, sugar fatty acid ester, sorbitol fatty acid ester, or a combination thereof.
The polyalkylene glycol compound may be one selected from the group consisting of compounds in which alkylene oxide is added to a compound including water or active hydrogen, or a combination thereof.
The above-described materials for forming the polishing layer 120 may include various materials apart from the materials described above.
The embedded liquid microelements that form the first pores 141 are formed of a liquid material that is not compatible with the polyalkylene glycol-containing hydrophilic polymeric matrix 130, i.e., a material selected from the group consisting of aliphatic mineral oil, aromatic mineral oil, a silicon oil which does not have a hydroxyl group at the end of molecules, soybean oil, coconut oil, palm oil, cotton seed oil, camellia oil, hardened oil, or a combination thereof.
The first pores 141 formed by the embedded liquid microelements may be dispersed into the polyalkylene glycol-containing hydrophilic polymeric matrix 130 in a micro spherical shape. The average diameter of spheres may be between 1 to 30 μm, for example, between 2 to 10 μm. The diameter of spheres in the above range is most optimal to the collection and supply of the polishing slurry 13. However, the diameter of spheres can be changed depending on a type of the polishing slurry 13, and the size of the embedded liquid microelements 141 can be also changed.
The shape of the first pores 141 formed by the embedded liquid microelements, i.e., the average diameter and concentration of spheres, can be easily and variously adjusted by a change of a degree of a hydrophilic property of the polyalkylene glycol-containing hydrophilic polymeric matrix 130.
In addition, the shape of the first pores 141 formed by the embedded liquid microelements can be easily and variously adjusted by parts by weight of a liquid material based on 100 parts by weight of a material for forming the polymeric matrix. For example, 20 to 50 parts by weight, more preferably, 30 to 40 parts by weight based on 100 parts by weight of the material for forming the polymeric matrix, i.e., based on 100 parts by weight of polyurethane is used in order to form the first pores 141 by a desired shape of the embedded liquid microelements.
The sizes and concentrations of the first pores 141 formed by the embedded liquid microelements and the micropores 141′ defined by the first pores 141 can be variously adjusted by the degree of the hydrophilic property of the polyalkylene glycol-containing hydrophilic polymeric matrix 130 and/or the amount of the liquid material. Thus, the polishing pad 100 having various polishing performances can be manufactured according to a type of an object to be polished and/or a type of the polishing slurry 13.
The second pores 142 are formed by injecting inert gas, a capsule type foaming agent, or a chemical foaming agent.
Here, the inert gas may be gas having a valence of 0 that is chemically stable, i.e., helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), or radon (Rn). Furthermore, the inert gas may be any gas that does not react with a polymeric matrix, i.e., that does not participate in a urethane reaction, such as N₂, apart from 8 group elements of the periodic table.
The foaming agent that is mixed with a predetermined material and generates a large amount of bubbles by evaporation or reaction by heat, can be largely classified into a chemical foaming agent and a physical foaming agent.
In the chemical foaming agent, foaming occurs in carbon dioxide that is generated by a reaction with water by using vitality of an isocyanate group, and thus water is used for a foaming agent. In the physical foaming agent, bubbles are formed by generating reaction heat by injecting gas or using a decomposable or evaporative foaming agent, and thus, the physical foaming agent does not participate in a polymer reaction. Types and features of these foaming agents are already well-known and thus, detailed descriptions thereof will be omitted.
The second pores 142 are formed on the polishing layer 120 by mixing the inert gas or various foaming agents (capsule type foaming agent or chemical foaming agent). The second pores 142 may have a larger radius than that of the first pores 141. Preferably, the second pores 142 are formed to have a volume corresponding to 10 times a volume of the first pores 141.
Hereinafter, a method of manufacturing the polishing layer 120 of the polishing pad 100 according to an embodiment of the present invention will be described with reference to FIG. 4.
First, materials for forming the polishing layer 120 are mixed (S100). In detail, the above-described material for forming the polyalkylene glycol-containing hydrophilic polymeric matrix 130 may be mixed with the materials for forming the polishing layer 120 (S100).
Here, the material for forming the polyalkylene glycol-containing hydrophilic polymeric matrix 130 is generated by mixing or reacting a hydrophilic material and a polyalkylene glycol compound with a material for forming a polymeric matrix. The mixing or reaction may be performed by stirring.
In the mixing process, a liquid material, such as mineral oil, is together mixed with the material for forming the polymeric matrix. In this case, inert gas (or a predetermined foaming agent that replaces the inert gas), such as Ar, may be injected.
Amounts of the mixed liquid material and the insert gas can be adjusted according to the sizes of pores to be formed depending on types.
Subsequently, gelling and hardening are performed (S510). That is, the mixture is injected into a cast having a predetermined shape and then solidified through gelling and hardening. Gelling is performed for 5 to 30 minutes at 80 to 90° C., and hardening is performed for 20 to 24 hours at 80 to 120° C. However, processing temperature and time can be variously changed to provide optimal conditions.
Last, the resultant structure of the hardening, having the predetermined shape, is processed (S520). The resultant structure is processed through taking off the cast, cutting, surface treatment, and cleaning. First, the hardened resultant structure is taken out of the cast and cut to have a predetermined thickness and shape. It is apparent that the polishing layer 120 can be formed in the shape of sheet using any method, such as casting or extrusion, known in the field of polymer sheet manufacturing in order to increase the productivity. Grooves in various shapes may be formed in a surface of the polishing layer 120 so that the polishing slurry 13 can be uniformly supplied across the working surface of the polishing layer 120.
After a cleaning process is performed, the polishing layer 120 is completed. During the cleaning process, embedded liquid microelements 141 exposed at the surface of the polishing layer 120 flow out, and thus open micropores 141′ are distributed on the polishing layer surface 160. Here, a liquid cleanser may be used to remove the embedded liquid microelements 141 from the polishing layer surface 160.
The polishing pad 100 can be constituted only by the polishing layer 120. However, when necessary, the support layer 110 can be made using a method widely known in the field of manufacturing the polishing pad 100 and is combined with the polishing layer 120 to complete the polishing pad 100.
More details of the present invention will be described by explaining specific experimental examples. Details not described below are omitted because they can be technically inferred by those skilled in the art. It will be apparent that the scope of the present invention is not limited to the following experimental examples.

Experimental Example 1

50 kg of polytetramethylene glycol (having a molecular weight of 1000), 50 kg of polyethylene glycol (having a molecular weight of 1000), and 52 kg of toluendiisocyanate were put into 200 kg of a reactor, were made to react with one another for 4 to 5 hours at 70 to 80° C. so that the NCO content of a final product was 11.0%. The viscosity of the manufactured isocyanate prepolymer was 6,900 cPs (25° C.)

Experimental Example 2

100 kg of the isocyanate prepolymer manufactured in Experimental Example 1, 46 kg of mineral oil (hereinafter, referred to as KF-70)(manufactured by the Seojin Chemical Co., Ltd.), and 33 kg of MOCA were ejected using a casting machine after undergoing a mixing head at 5000 rpm. In this case, inert gas, i.e., Ar gas was put in the mixing head at 10% of a volumetric ratio.
Thereafter, the mixture was immediately injected into a rectangular cast. Then, gelling was performed for 30 minutes, and thereafter, hardening was performed in an oven for 20 hours at 100° C.
The hardened mixture was taken out of the cast, and the surface of the hardened mixture was cut to form a polishing layer of a polishing pad.
A scanning electron microscope (SEM) photograph of pores formed on a surface of the polishing layer is shown in FIG. 5.
Polishing performance and planarization performance of the manufactured polishing pad are shown in FIG. 7 (the polishing pad according to the present embodiment is referred to as “hybrid pore 1”).

Experimental Example 3

100 kg of the isocyanate prepolymer manufactured in Experimental Example 1, 46 kg of mineral oil (hereinafter, referred to as KF-70)(manufactured by the Seojin Chemical Co., Ltd.), and 33 kg of MOCA were ejected using a casting machine after undergoing a mixing head at 5000 rpm. In this case, inert gas, i.e., Ar gas was put in the mixing head at 20% of a volumetric ratio.
Thereafter, the mixture was immediately injected into a rectangular cast. Then, gelling was performed for 30 minutes, and thereafter, hardening was performed in an oven for 20 hours at 100° C.
The hardened mixture was taken out of the cast, and the surface of the hardened mixture was cut to form a polishing layer of a polishing pad.
A scanning electron microscope (SEM) photograph of pores formed on a surface of the polishing layer is shown in FIG. 6.
Polishing performance and planarization performance of the manufactured polishing pad are shown in FIG. 7 (the polishing pad according to the present embodiment is referred to as “hybrid pore 2”). “Solid-state capsule pore” in FIG. 7 represents a polishing pad that does not use different types of composite pores (i.e., first pores and second pores) as in the present invention but uses only a single solid-state capsule pore (here, the solid-state capsule may represent hollow micropowder), and “liquid microelement pore” in FIG. 7 also represents a polishing pad that does not use different types of composite pores (i.e., first pores and second pores) as in the present invention but includes only a single liquid microelement.
When composite pores having different sizes are used, first pores having a relatively small size collect a small amount of polishing slurry particles so that precise polishing can be performed, and second pores having a relatively large size collect a large amount of polishing slurry particles at one time so that processing at high polishing speed can be performed.
In this way, different types of pores are simultaneously included in the polishing layer of the polishing pad so that a more elaborate polishing work can be carried out.
In the above-described embodiments, two types of pores are formed. However, aspects of the present invention are not limited thereto, as described above.
That is, a polishing pad according to the present invention may include three or more types of pores from among pores formed by liquid microelements, pores formed by a solid-state capsule, pores formed by injecting inert gas, and pores formed by a chemical foaming agent. The sizes of pores depending on types may be as described above or can be changed according to types of materials for forming pores or in order to increase polishing efficiency.
In particular, in a method of forming pores, the sizes of pores can be controlled by concentration or reaction temperature of a mixed material, and pores according to types may not necessarily have different sizes.
As described above, according to the present invention, multiple (double) pores (not a single pore) are controlled so that slurry collection and supply can be effectively performed and more improved CMP polishing performance can be achieved. This enables an elaborate CMP process required by a minute semiconductor process.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

What is claimed is:

1. A polishing pad that performs a polishing process by moving in contact with a surface of an object to be polished, the polishing pad comprising a polishing layer,

wherein the polishing layer comprises two or more types of pores, of which sizes are controlled by using at least two from among inert gas, a capsule type foaming agent, a chemical agent, and liquid microelements.

2. The polishing pad of claim 1, wherein the inert gas is selected from the group consisting of 8 group elements of a periodic table and gas that does not react with the materials for forming the polishing layer.

3. The polishing pad of claim 1, wherein a liquid material that constitutes the liquid microelements comprises at least one selected from the group consisting of aliphatic mineral oil, aromatic mineral oil, a silicon oil which does not have a hydroxyl group at the end of molecules, soybean oil, coconut oil, palm oil, cotton seed oil, camellia oil, hardened oil, or a combination thereof.

4. The polishing pad of claim 1, wherein the polishing layer comprises a plurality of first pores formed by the liquid microelements and a plurality of second pores having a relatively large size and formed by using at least one from among injecting the inert gas, injecting the capsule type foaming agent, and injecting the chemical foaming agent.

5. The polishing pad of claim 1, wherein micropores that are defined by opening the two or more types of pores are distributed on a surface of the polishing layer.