JP2000218551A - Manufacture of polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make easy control of structure of a polishing pad by immersing a polymer compact in a solution containing a polymerization monomer, and enabling the compact to have the monomer polymerization reaction. SOLUTION: A polymer compact mainly composed of polyurethane obtained from polyisocianate polyol in a solution containing a vinyl compound such as a polymerization monomer using methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, metacryl acid, and fumaric acid. Thereafter, a monomer polymerization reaction is made to occur in the compact. Accordingly, it is possible to easily control structure of a polishing pad polishing a surface of an insulation layer or metal wire formed on a semiconductor substrate, and improve the safety.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polishing pad for a semiconductor substrate, and more particularly, to mechanically planarize the surface of an insulating layer formed on a semiconductor substrate such as silicon and the surface of metal wiring. To a method for manufacturing a polishing pad to be manufactured.

[0002]

2. Description of the Related Art Large-scale integrated circuits (LSI) typified by semiconductor memories have been increasingly integrated year by year, and accordingly, the technology for manufacturing large-scale integrated circuits has been increasing. Further, with the increase in the density, the number of stacked semiconductor device manufacturing locations has also increased. Due to the increase in the number of layers, unevenness of the main surface of the semiconductor wafer caused by stacking, which has not been a problem in the past, has become a problem. As a result, for example, Nikkei Microdevice July 1994 Issue 50
As described on page 57, chemical mechanical polishing (CMP) is performed for the purpose of compensating for a lack of depth of focus at the time of exposure due to unevenness caused by laminating, or for improving wiring density by flattening through holes. : Chemical
The planarization of a semiconductor wafer using a mechanical polishing technique has been studied.

A polishing pad used in such a CMP is required to have a physical property of 90 degrees or more in A hardness from the viewpoint of flatness. Currently used polishing pads include an isocyanate-terminated urethane prepolymer and 4,4'-methylene- as shown in JP-A-8-500622.
It is produced by reacting bis 2-chloroaniline (MOCA). However, in this manufacturing method, MOCA
Is a harmful chemical substance, so there is a problem in terms of handling, and because of its high reactivity, it is difficult to control the structure of the polishing pad.In addition, burrs are generated when grooves are formed on the pad surface. There was a problem.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polishing pad for use in a mechanical flattening process for smoothing the surface of an insulating layer or a metal wiring formed on a semiconductor substrate by polishing. Another object of the present invention is to provide a manufacturing method that is highly safe and easily controls the structure of the polishing pad.

[0005]

Means for Solving the Problems As means for solving the problems, the present invention has the following constitution. "Immerse the polymer molding in a solution containing the monomer for polymerization,
A method for producing a polishing pad, comprising: impregnating a polymer molded product with a monomer for polymerization, and then subjecting the polymer molded product to a polymerization reaction of the monomer. "The manufacturing method of the polishing pad, wherein the polymer molded product contains polyurethane as a main component.""The solution containing a monomer for polymerization contains a vinyl compound and a polymerization initiator, and has a specific gravity of The method for producing a polishing pad according to any one of the above, wherein the solvent contains a solvent that does not substantially react with the vinyl compound in a proportion of 0.8 or less in the range of 1 to 50% by weight. "

[0006]

Embodiments of the present invention will be described below.

The polymer molding of the present invention forms the basis of a polishing pad. The internal structure of the polymer molding roughly defines the structure of the polishing pad. Since the polishing pad usually has closed cells, it is preferable that the polymer molded article also has closed cells. The closed cell diameter is preferably 1000 μm or less because the flatness of the local unevenness of the semiconductor substrate is good. The more preferable diameter of the closed cell is 500 μm or less, and the more preferable diameter is 300 μm or less. The expansion ratio of the polymer molded product is preferably in the range of 1.01 to 3 times. If the expansion ratio is less than 1.01, the number of closed cells is small, so that the slurry holding property is unfavorably low. When the expansion ratio exceeds 3 times, the flatness of the local unevenness becomes poor, which is not preferable. The expansion ratio can be determined from the ratio of the specific gravity of the obtained polymer molded product to the specific gravity of the constituent materials.
For example, when the specific gravity of the obtained polymer molded product is 0.7 and the specific gravity of the constituent material is 1.0, the expansion ratio is 1.0.
/0.7=1.43. The material of this polymer molding is
The swelling ratio of the vinyl compound at 20 ° C. is 1.05 or more (the swelling ratio is defined as the weight of the polymer molded product before immersion in the vinyl compound and the weight of the polymer molded product swelled for 24 hours and the vinyl compound swelled) The material is not particularly limited as long as it is a material represented by a ratio.) However, a material containing polyurethane as a main component is preferable from the viewpoint of easy formation of closed cells. Polyurethane is a polymer synthesized based on a polyaddition reaction or polymerization reaction of polyisocyanate. The compound used as the symmetry of the polyisocyanate is an active hydrogen compound, that is, a compound containing two or more polyhydroxy or amino groups. Examples of the polyisocyanate include, but are not limited to, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. A typical polyol is polyhydroxy, but examples of the polyol include polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol. A polymer molded product containing polyurethane as a main component obtained from a polyisocyanate and a polyol can easily control the structure because the cell diameter can be relatively freely controlled, but when used as a polishing pad for flatness, the hardness is high. Is low, and cannot be used as is. According to the production method of the present invention, the polymer molded product can be raised to a hardness required for flatness, and the structure of the polymer molded product (for example, a closed cell structure)
Can be maintained.

The polymerization monomer used in the present invention is not particularly limited as long as it is a raw material for polymerization such as addition polymerization, polycondensation, and polyaddition. In particular, a vinyl compound used as a monomer for addition polymerization is easily reacted. Can be preferably used. The vinyl compound is a compound having a vinyl group having a carbon-carbon double bond. Specifically, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacrylic acid, glycidyl methacrylate, ethylene glycol dimethacrylate, fumaric acid,
Examples include dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, dimethyl maleate, diethyl maleate, dipropyl maleate, acrylonitrile, acrylamide, vinyl chloride, styrene, α-methylstyrene, and the like. The polymer polymerized from the vinyl compound in the present invention is a polymer obtained by polymerizing the above vinyl compound, and specifically, polymethyl methacrylate, polyethyl methacrylate, poly (n-butyl methacrylate), Isobutyl methacrylate, poly (2-ethylhexyl methacrylate), polyisodecyl methacrylate, poly (n-lauryl methacrylate), poly (2-hydroxyethyl methacrylate),
Poly (2-hydroxypropyl methacrylate), poly (2-hydroxyethyl acrylate), poly (2-hydroxypropyl acrylate), poly (2-hydroxybutyl methacrylate), polydimethylaminoethyl methacrylate, polydiethylaminoethyl methacrylate, polymethacrylic acid , Polyglycidyl methacrylate, polyethylene glycol dimethacrylate, polyfumaric acid, polydimethyl dimethyl fumarate, diethyl polyfumarate, polypropyl fumarate, polymaleic acid, dimethyl polymaleate, diethyl polymaleate, dipropyl polymaleate, polyacrylonitrile, polyacrylamide, polyvinyl chloride, Polystyrene, poly (α-
Methylstyrene) and the like.

In the present invention, as a method for initiating polymerization, a method such as simple heating, irradiation with radiation, irradiation with light, or the like can be used. In particular, a polymerization initiator is preferable, and as the polymerization initiator, a compound that is decomposed by applying heat to generate a radical is preferably used. Such polymerization initiators include peroxides and azo compounds. Specific examples include cumene hydroperoxide, tert-butyl hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, and acetyl peroxide. , Lauroyl peroxide, azobisisobutyronitrile and the like.
The specific gravity of the solution of the vinyl compound and the polymerization initiator of the present invention is 0.1.
It is preferable to include a solvent that does not substantially react with the vinyl compound of 8 or less in a range of 5% by weight or more and 50% by weight or less, because the uniformity of the obtained polishing pad can be obtained. Specific examples of solvents that do not substantially react with the vinyl compound having a specific gravity of 0.8 or less include pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane, decane,
Examples include undecane, dodecane, tridecane, tetradecanepentadecane, hexadecane, heptadecane, octadecane, nonadecane, and the like, but are not particularly limited. In addition, even if paraffin or the like is solid at normal temperature but becomes liquid when the temperature is increased, the specific gravity is 0.1.
If it is 8 or less, it can be used. A polymer molded product is prepared by impregnating a solution of the vinyl compound and the polymerization initiator of the present invention in a range of 1% by weight to 50% by weight of a solvent which does not react with a substantial vinyl compound having a specific gravity of 0.8 or less. Is kept at a temperature equal to or higher than the polymerization initiation temperature for a certain period of time for both the polymer molded product and the impregnating solution. During this time,
The vinyl compound swells in the molded polymer, and further the polymerization starts to be cured. As a result, the hardness of the obtained composite polymer molding is higher than the hardness of the polymer molding used. The composite polymer molded product can be formed into a polishing pad by slicing with a slicer.

The present invention provides a method for manufacturing a polishing pad for use in a mechanical flattening step for smoothing the surface of an insulating layer or a metal wiring formed on a semiconductor substrate by polishing, which has high safety. In addition, the structure of the polishing pad can be easily controlled.

[0011]

EXAMPLE 1 30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 1 part by weight of water, 0.2 parts by weight of triethylamine, 1.8 parts by weight of a silicone foam stabilizer and 0.08 parts by weight of tin octylate The mixture was mixed by a RIM molding machine and discharged into a mold to perform pressure molding. The obtained polymer molded body is a block-shaped foamed polyurethane having a thickness of 2 cm and a square of 30 cm. The hardness is 40 degrees in A hardness, the expansion ratio is 1.5 times, and the bubble diameter is 200μ at the maximum.
m, and the average bubble diameter was 39 μm. A solution prepared by mixing 70 parts by weight of methyl methacrylate, 30 parts by weight of n-decane, and 0.1 part by weight of azobisisobutyronitrile is prepared and filled in a container. The polymer molded article of the foamed polyurethane is immersed in this solution. Then, the whole container is kept at 70 ° C. for 6 hours.
The obtained composite polymer molded body was sliced to a thickness of 1.2 m.
m, and the surface was grooved to prepare a polishing pad. The hardness of the obtained polishing pad is 95 in A hardness.
Degree, the expansion ratio is 1.6 times, and the average cell diameter is 55 μm.
The sliced surface was good, and the occurrence of burrs was small during groove cutting. 0.25μm on 6 inch silicon wafer
Al wirings having a width and a height of 1.2 μm were formed at an interval of 0.5 mm, and a tetraethoxysilane was formed thereon by CVD to form an insulating film having a thickness of 3 μm. The irregularities on the surface of the insulating film were 11,000 angstroms at the center of the wafer and 11000, 1150 at four peripheral portions.
0, 11200 and 11400 angstroms. This substrate is attached to the polishing head of a polishing machine and 37 rpm
m, the polishing pad is fixed to a platen of a polishing machine, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. The polishing pressure is 0.05 MPa for 6 minutes while supplying a silica-based polishing agent at 225 ml / min. Polishing was performed. The unevenness of the surface of the insulating film after polishing is 700 angstroms at the center of the wafer and 60 at four peripheral portions.
0, 800, 700, and 700 angstroms. Thus, the uniformity of the flatness over the entire surface of the 6-inch semiconductor substrate is obtained. Example 2 30 parts by weight of polypropylene glycol, 40 parts by weight of tolylene diisocyanate, 0.5 parts by weight of water, 0.2 parts by weight of tripropylamine, 1.8 parts by weight of a silicone foam stabilizer, and 0.08 parts by weight of tin octylate Was mixed by a RIM molding machine, and discharged into a mold to perform pressure molding. The obtained polymer molded body is a block-shaped foamed polyurethane having a thickness of 3 cm and a square of 50 cm. The hardness is 45 degrees in A hardness, the expansion ratio is 1.5 times and the bubble diameter is 250μ at the maximum.
m, and the average bubble diameter was 25 μm. A solution prepared by mixing 75 parts by weight of methyl methacrylate, 25 parts by weight of n-decane, and 0.1 part by weight of azobisisobutyronitrile is prepared and filled in a container. The polymer molded article of the foamed polyurethane is immersed in this solution. Then, the whole container is kept at 70 ° C. for 6 hours.
The obtained composite polymer molded body was sliced to a thickness of 1.2 m.
m, and the surface was grooved to prepare a polishing pad. The hardness of the obtained polishing pad is 96 in A hardness.
Degree, the expansion ratio is 1.6 times, and the average cell diameter is 40 μm.
The sliced surface was good, and the occurrence of burrs was small during groove cutting. 0.25μm on 6 inch silicon wafer
Al wirings having a width and a height of 1.2 μm were formed at an interval of 0.5 mm, and a tetraethoxysilane was formed thereon by CVD to form an insulating film having a thickness of 3 μm. The irregularities on the surface of the insulating film were 11,000 angstroms at the center of the wafer and 11000, 1150 at four peripheral portions.
0, 11200 and 11400 angstroms. This substrate is attached to the polishing head of a polishing machine and 37 rpm
m, the polishing pad is fixed to a platen of a polishing machine, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. The polishing pressure is 0.05 MPa for 6 minutes while supplying a silica-based polishing agent at 225 ml / min. Polishing was performed. The unevenness of the surface of the insulating film after polishing was 700 Å at the center of the wafer and 50 at the four peripheral portions.
0, 600, 500, and 400 angstroms. Thus, the uniformity of the flatness over the entire surface of the 6-inch semiconductor substrate is obtained. Example 3 30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 0.5 part by weight of water, 0.2 part by weight of tributylamine, 1.8 parts by weight of a silicone foam stabilizer, and 0.08 parts by weight of tin octylate are RIM. The mixture was mixed by a molding machine and discharged into a mold to perform pressure molding. The obtained polymer molded body is a block-shaped foamed polyurethane having a thickness of 1 cm and a square of 50 cm. Hardness is A hardness 45
Degree, the expansion ratio is 1.3 times and the cell diameter is 150 at the maximum.
μm, and the average bubble diameter was 25 μm. A solution prepared by mixing 100 parts by weight of methyl methacrylate and 0.1 part by weight of azobisisobutyronitrile is prepared and filled in a container,
The foamed polyurethane molded article is immersed in this solution and kept at room temperature for one week. Polymerization was carried out at 70 ° C. for 10 hours with the obtained foamed polyurethane in which methyl methacrylate was swollen sandwiched between glass plates.
The obtained composite polymer molded body was sliced to a thickness of 1.2 m.
m, and the surface was grooved to prepare a polishing pad. The hardness of the obtained polishing pad is 95 in A hardness.
Degree, the expansion ratio is 1.4 times, and the average cell diameter is 35 μm.
The sliced surface was good, and the occurrence of burrs was small during groove cutting. 0.25μm on 6 inch silicon wafer
Al wirings having a width and a height of 1.2 μm were formed at an interval of 0.5 mm, and a tetraethoxysilane was formed thereon by CVD to form an insulating film having a thickness of 3 μm. The irregularities on the surface of the insulating film were 11,000 angstroms at the center of the wafer and 11000, 1150 at four peripheral portions.
0, 11200 and 11400 angstroms. This substrate is attached to the polishing head of a polishing machine and 37 rpm
m, the polishing pad is fixed to a platen of a polishing machine, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. The polishing pressure is 0.05 MPa for 6 minutes while supplying a silica-based polishing agent at 225 ml / min. Polishing was performed. The unevenness of the surface of the insulating film after polishing was 700 Å at the center of the wafer and 50 at the four peripheral portions.
0, 700, 500, and 700 angstroms. Thus, the uniformity of the flatness over the entire surface of the 6-inch semiconductor substrate is obtained. Comparative Example 1 78 parts by weight of a polyether-based urethane polymer (Adiprene L-325 manufactured by Uniroyal) and 4,4'-methylene-
20 parts by weight of bis 2-chloroaniline and 1.8 parts by weight of hollow polymer microspheres (Expancel 551 DE) were RI
The mixture was mixed by an M molding machine and discharged into a mold to form a polymer molded body. The expansion ratio of the obtained polymer molded article is 1.5 times and the average cell diameter is 29 μm. This polymer molded body was sliced to a thickness of 1.2 mm with a slicer, and the surface was grooved to prepare a polishing pad. The expansion ratio of the polishing pad is 1.
Five times, the average bubble diameter was 29 μm, the surface of the slice was slightly burred, and burrs were generated considerably at the time of grooving. For this purpose, the surface of the polishing pad was buffed and deburred. 0.2 on 6 inch silicon wafer
Al wirings having a width of 5 μm and a height of 1.2 μm are formed at an interval of 0.5 mm, and further, tetraethoxysilane is further
An insulating film was formed to have a thickness of 3 μm by VD. The unevenness of the surface of the insulating film is 1100 at the center of the wafer.
0 angstroms, 11000, 4 in the surrounding area
1500, 11200 and 11400 angstroms. This substrate was attached to the polishing head of a polishing machine and 37
The polishing pad is fixed to a platen of a polishing machine by rotating the polishing pad at 36 rpm, and the polishing pad is rotated at 36 rpm in the same direction as the rotation direction of the polishing head. Polishing was performed. The unevenness of the surface of the insulating film after polishing was 700 angstroms at the central portion of the wafer and 8 at the four peripheral portions.
00, 1100, 900, and 700 angstroms, and good flatness could not be obtained.

[0012]

According to the present invention, in polishing for use in a mechanical flattening step of polishing and smoothing the surface of an insulating layer or a metal wiring formed on a semiconductor substrate,
It is possible to provide a manufacturing method with high safety and easy control of the structure of the polishing pad.

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Claims (4)

[Claims] 1. A step of immersing a polymer molding in a solution containing a polymerization monomer, impregnating the polymer molding with the polymerization monomer, and causing a polymerization reaction of the monomer on the polymer molding. A method for manufacturing a polishing pad. 2. The method for producing a polishing pad according to claim 1, wherein the polymer molding comprises polyurethane as a main component. 3. A solution containing a monomer for polymerization containing a vinyl compound and a polymerization initiator, wherein a solvent having a specific gravity of 0.8 or less and not substantially reacting with a vinyl compound is used.
3. The method for producing a polishing pad according to claim 1, wherein said polishing pad is contained in a range of% by weight. 4. The method for manufacturing a polishing pad according to claim 1, wherein the polishing pad is for polishing a semiconductor substrate.