JP2003286359A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polishing pad which can polish a metal film covering a semiconductor wafer at a high polishing speed and exhibits an excellent smoothing performance. <P>SOLUTION: The polishing pad is comprised of an extruded foam sheet made of a polyolefin resin, or the pad is comprised of a foam sheet made of a polypropylene-based resin comprising a polypropylene having a die swell of 1.8 or more. Preferably, the above polypropylene resin is a propylene polymer (T) obtained by the polymerization method comprising the step of manufacturing a propylene polymer portion having an intrinsic viscosity of ≥5 dl/g (A) and the step of manufacturing a propylene polymer portion having an intrinsic viscosity of <3 dl/g (B), and the content of the propylene polymer portion (A) in the propylene polymer (T) is 0.05-90 wt.%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polishing pad. More specifically, the present invention relates to a polishing pad capable of polishing a metal film coated on a semiconductor wafer at a high polishing rate and having excellent planarization performance.

[0002]

2. Description of the Related Art LSI technology has made rapid progress, and recently,
Since the integrated circuit has been multi-layered, it is necessary to make the insulating film used between the lower layer and the upper layer of the multi-layer wiring substrate flatter than ever before.

As a method of flattening the insulating film, a CMP method (Chemical Mechanical Polishing) capable of surely flattening the entire insulating film is attracting attention. This method is a method in which a sheet-shaped polishing pad is mounted on a rotating disk or the like, and polishing is performed while supplying a slurry composed of an abrasive and a chemical component between the polishing pad and the semiconductor wafer. As a polishing pad used in the above, a polishing pad made of a thermoplastic resin foam is known.

[0004] For example, Japanese Patent Laid-Open No. 9-132661 discloses a CMP pad excellent in durability as a crosslinking agent and / or
Alternatively, there is described a foam for a CMP pad obtained by forming a polyolefin resin composition containing a crosslinking aid, a thermal decomposition type foaming agent, and an abrasive into a sheet, and crosslinking and foaming the sheet-shaped molded product.

Further, in Japanese Patent Laid-Open No. 2001-239455, a thermoplastic resin and a chemical foaming agent are kneaded at a temperature not higher than the decomposition temperature of the foaming agent as a polishing pad having excellent wear resistance, chemical resistance and durability. Then, while maintaining the heating state, it is filled in a pre-heated flat plate mold, and after molding, the mold is opened and foamed, and then the thermoplastic resin foam obtained by cooling with a cooling mold is obtained. A polishing pad manufactured by processing into a predetermined shape is described. However, even in the polishing pad described in the above publication, etc., it can be polished at a high polishing rate,
Further, further improvement in flattening performance has been desired.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing pad capable of polishing a metal film coated on a semiconductor wafer at a high polishing rate and having excellent planarization performance.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of such circumstances, and as a result, have found that a polishing pad made of an extruded foam sheet made of a polyolefin resin and a polypropylene resin having a die swell ratio in a certain range are used. A polishing pad made of a polypropylene resin foam sheet containing
The inventors have found that the above problems can be solved and have completed the present invention.

That is, the present invention relates to a polishing pad composed of an extruded foam sheet made of a polyolefin resin. The present invention also provides a polishing pad made of a polypropylene resin foam sheet containing a polypropylene resin having a die swell ratio of 1.8 or more, and a polishing pad in which the polypropylene resin foam sheet is an extruded foam sheet. It is related. Hereinafter, the present invention will be described in detail.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin resin used in the polishing pad made of the extruded foam sheet made of the polyolefin resin of the present invention includes high density polyethylene,
Linear low-density polyethylene, which is a copolymer of ethylene and α-olefin, low-density polyethylene produced by a high-pressure radical polymerization method, propylene homopolymer, butene homopolymer, propylene-ethylene random copolymer, Propylene-α-olefin random copolymer, propylene-ethylene-α-olefin terpolymer, copolymer component mainly consisting of propylene in at least two or more stages and propylene, ethylene and / or C 4 Examples include polypropylene-based copolymers (sometimes referred to as propylene-ethylene block copolymers) produced by polymerizing the α-olefin copolymer component of ~ 12. As the α-olefin, an α-olefin having 4 to 12 carbon atoms is preferable, and 1-butene, 1-hexene and 1-octene are particularly preferable. These polyolefin resins may be used alone or 2
You may blend and use 1 or more types.

The polypropylene resin used in the polishing pad comprising a polypropylene resin foam sheet containing a polypropylene resin having a die swell ratio of 1.8 or more according to the present invention is a homopolymer of propylene, propylene-ethylene random. Copolymer, propylene-α-olefin random copolymer, propylene-ethylene-α
-Olefin terpolymer, polymerizing a copolymer component mainly composed of propylene and a copolymer component of propylene, ethylene and / or an α-olefin having 4 to 12 carbon atoms in at least two or more stages. The polypropylene-based copolymer (may be referred to as a propylene-ethylene block copolymer) produced by
As the α-olefin, an α-olefin having 4 to 12 carbon atoms is preferable, and 1-butene, 1-hexene and 1-octene are particularly preferable. These polypropylene resins may be used alone or in combination of two or more.

The polypropylene resin has a die swell ratio of 1.8 or more, preferably 1.8 to 10, and more preferably 2.0 to 8.

The die swell ratio in the present invention is the JIS
It is a value calculated from the following formula (1) by measuring the diameter of the cross-section of the extrudate extruded in the melt flow rate (MFR) measurement according to the method of condition 14 of K7210. Die swell ratio = diameter of cross section of extrudate / diameter of orifice (1) However, the cross section of extrudate refers to a cross section perpendicular to the extrusion direction of the extrudate. The average value of the maximum value and the minimum value of the diameter is taken as the diameter of the cross section of the extrudate.

As a polypropylene resin having a die swell ratio of 1.8 or more, preferably, a step of producing a propylene polymer portion (A) having an intrinsic viscosity of 5 dl / g or more and a propylene polymer having an intrinsic viscosity of less than 3 dl / g. Combined part (B)
And a propylene polymer portion (A) content of 0.05 to 90% by weight.
Is a propylene polymer (T).

As a method for producing the propylene polymer (T), for example, after polymerizing (A) in the first step, the same polymerization tank in which (A) was polymerized is followed by (B) in the second step. ) Is a batch-type polymerization method, or two or more polymerization tanks are arranged in series, (A) is polymerized as the first step, and then the product is transferred to the next polymerization tank and Examples of the two steps include a continuous polymerization method of polymerizing (B). In the case of the continuous polymerization method, each of the first and second stage polymerization tanks may be one tank or two or more tanks.

From the viewpoint of melt strength, the intrinsic viscosity of the propylene polymer portion (A) contained in the propylene polymer (T) is usually 5 dl / g or more, preferably 5 to 20.
dl / g, more preferably 6 to 15 dl / g, and further preferably 7 to 12 dl / g.

From the viewpoint of melt strength, the content of the propylene polymer portion (A) contained in the propylene polymer (T) is usually 0.05 to 90% by weight, more preferably 0.3 to 80%. % By weight.

From the viewpoint of fluidity and processability, the intrinsic viscosity of the propylene polymer portion (B) contained in the propylene polymer (T) is usually less than 3 dl / g, preferably 0.5 dl / g or more. It is less than 3 dl / g, more preferably 0.8 to 2 dl / g.

The intrinsic viscosity of the propylene polymer part (B) can be adjusted by appropriately setting the production conditions of the propylene polymer part (B). The propylene polymer (T) is a propylene polymer part (A) in the first stage.
Of the propylene polymer part (B) is produced by the method of producing the propylene polymer part (B) in the second step, and the intrinsic viscosity [η] B of the propylene polymer part (B) is
Is the intrinsic viscosity [η] T of the finally obtained propylene polymer (T), the intrinsic viscosity [η] A of the propylene polymer portion (A), and the propylene polymer ( Content of each of the propylene polymer portion (A) and the propylene polymer portion (B) contained in T) (WA and
It can be calculated from the following equation (2) using WB). [Η] B = ([η] T × 100− [η] A × WA) ÷ WB (2) [η] T: Intrinsic viscosity of propylene polymer (T) (dl /
g) [η] A: intrinsic viscosity (d) of the propylene polymer part (A)
1 / g) WA: Content of propylene polymer part (A) (% by weight) WB: Content of propylene polymer part (B) (% by weight)

The intrinsic viscosity of the propylene polymer (T) is preferably 1 dl / g or more 7 from the viewpoint of fluidity and processability.
less than dl / g, more preferably 1 dl / g or more 5
It is less than dl / g.

The molecular weight distribution of the propylene polymer (T) is
From the viewpoint of the surface appearance of the foamed sheet, it is usually less than 10, preferably 3 to 8, and more preferably 3 to 7.
Is. The molecular weight distribution described in the present invention is the ratio (Mw / Mn) of the polystyrene-equivalent weight average molecular weight (Mw) and the polystyrene-equivalent number average molecular weight (Mn).

The propylene polymer (A) and the propylene polymer portion (B) are preferably crystalline propylene homopolymers or copolymers of propylene and ethylene and / or α-olefins having 4 to 12 carbon atoms. Is. Examples of the α-olefin include 1-butene and 4
-Methyl-1-pentene, 1-hexene, 1-octene and the like can be mentioned. The most preferable α-olefin is 1-butene.

The content of ethylene and / or C4-12 α-olefin in the copolymer of propylene and ethylene and / or C4-12 α-olefin is such that the copolymer loses crystallinity. For example, in the case of ethylene, the content of the repeating unit derived from ethylene in the copolymer is usually 10% by weight or less, and in the case of α-olefin, the content of the repeating unit in the copolymer is The content of repeating units derived from α-olefin is usually 3
It is 0% by weight or less.

The propylene polymer (A) and the propylene polymer (B) are particularly preferably a homopolymer of propylene, or a mixture of propylene and ethylene in which the content of repeating units derived from ethylene is 10% by weight or less. Random copolymer, random copolymer of propylene having a content of repeating units derived from α-olefin having 4 to 12 carbon atoms of 30 wt% or less and α-olefin having 4 to 12 carbon, or ethylene The content of the repeating unit derived from is 10% by weight or less and α having 4 to 12 carbon atoms.
The content of repeating units derived from olefins is 3
Propylene, ethylene and carbon number 4 to 0% by weight or less
It is a ternary random copolymer with 12 α-olefins.

The propylene polymer (A) and the propylene polymer (B) may be block-bonded polymers. Further, a polymer obtained by block-bonding the propylene polymer (A) and the propylene polymer (B), and the other propylene polymer (A) and the propylene polymer (B) may coexist. .

The propylene polymer (T) is produced by using a known catalyst. As the known catalyst, for example, a multi-site catalyst obtained by using a solid catalyst component containing a titanium atom, a magnesium atom and a halogen atom,
A single site catalyst obtained by using a metallocene complex or the like can be mentioned. The method for producing the propylene polymer (T) is preferably a production method using a multi-site catalyst obtained by using a solid catalyst component containing a titanium atom, a magnesium atom and a halogen atom, and more preferably JP-A-11- This is the manufacturing method described in Japanese Patent No. 228629.

The polypropylene resin foam sheet used for the polishing pad comprising the polypropylene resin foam sheet containing the polypropylene resin having the die swell ratio of 1.8 or more according to the present invention has a die swell ratio of 1.8.
In addition to the above polypropylene-based resin, other polyolefin-based resin may be added if necessary. In that case, the content of the polypropylene resin having a die swell ratio of 1.8 or more is usually 0.01 to 99.99% by weight, preferably 0.01 to 70% by weight,
It is more preferably 0.1 to 50% by weight. (However,
The total weight of the polypropylene resin foam sheet is 100% by weight. )

Other polyolefin resins that may be added to the polypropylene resin foam sheet containing the polypropylene resin having a die swell ratio of 1.8 or more, if necessary, are the same as the above-mentioned polyolefin resins. Examples thereof include high-density polyethylene, linear low-density polyethylene which is a copolymer of ethylene and α-olefin, low-density polyethylene produced by a high-pressure radical polymerization method, propylene homopolymer, and butene. Homopolymer, propylene-ethylene random copolymer,
Propylene-α-olefin random copolymer, propylene-ethylene-α-olefin terpolymer, copolymer component mainly consisting of propylene in at least two or more stages and propylene, ethylene and / or C 4 Examples include polypropylene-based copolymers (sometimes referred to as propylene-ethylene block copolymers) produced by polymerizing the α-olefin copolymer component of ~ 12. As the α-olefin, an α-olefin having 4 to 12 carbon atoms is preferable, and 1-butene, 1-hexene and 1-octene are particularly preferable.

In order to obtain a polyolefin resin extruded foam sheet having uniform cells in a polishing pad comprising the polyolefin resin extruded foam sheet of the present invention,
From the viewpoint of productivity and economy, extrusion foaming is preferably performed near the melting point of the polyolefin resin.

In order to obtain a polypropylene resin foam sheet having uniform bubbles in the polishing pad comprising the polypropylene resin foam sheet containing the polypropylene resin having a die swell ratio of 1.8 or more according to the present invention, From the viewpoint of productivity and economy, it is preferable to perform extrusion foaming near the melting point of the polypropylene resin.

Production of a polyolefin-based resin extruded foam sheet used for a polishing pad comprising the polyolefin-based resin extruded foam sheet of the present invention, and a polypropylene-based extruded foam sheet of the present invention and a die swell ratio of the present invention of 1.8 or more. Examples of the foaming agent used in the production of the polypropylene-based resin foamed sheet used for the polishing pad made of the polypropylene-based resin foamed sheet containing a resin include known foaming agents, specifically, baking soda and azodicarbonate. Examples thereof include thermal decomposition type foaming agents such as acid amides, inert gases such as carbon dioxide gas and nitrogen gas, and low boiling point organic compounds such as butane. These foaming agents may be used alone or in combination of two or more.

In both the thermal decomposition type foaming agent and the non-decomposition type foaming agent, a foaming agent having a large solubility coefficient in the molten resin of the gas that finally contributes to foaming is preferable, and carbon dioxide gas is safe and has a high solubility coefficient. Since it is a relatively large foaming agent, it is preferably used.

A bubble nucleating agent may be used for the purpose of increasing the number of bubbles generated and reducing the bubble diameter. Specifically, inorganic fillers such as talc, silica, mica, calcium carbonate, calcium silicate, barium sulfate, aluminosilicate, aluminum hydroxide and diatomaceous earth, polymethylmethacrylate, beads made of polystyrene and having a particle size of 100 μm or less, steer Metal salts such as calcium phosphate, magnesium stearate, zinc stearate and the like,
These may be used alone or in combination of two or more.

The amount of the bubble nucleating agent added is usually 0.0
It is 1 to 10% by weight, preferably 0.1 to 5% by weight, and more preferably 0.3 to 3% by weight.

As the film to be polished which can be polished by using the polishing pad of the present invention, pure Al film, AlSiCu alloy, AlC
A film made of an alloy containing Al as a main component such as u alloy, pure C
Examples thereof include a u film, a tungsten film, a titanium film, a titanium nitride film, a tantalum film, and a tantalum nitride film. As the film to be polished, it is particularly preferable to use a pure Al film which is a wiring material in a semiconductor device, a film made of an alloy containing Al as a main component such as AlSiCu alloy and AlCu alloy, a pure Cu film, a tungsten film, and a titanium film which is a barrier material. , Titanium nitride film, and the like.

The polishing pad of the present invention may be provided with a groove in order to uniformly hold the slurry on the pad surface and to smoothly discharge polishing debris. As the shape of the groove,
The shape may be a large number of concentric circles, a lattice shape, a radial shape, a spiral shape, or the like. Examples of the method of forming the groove include a cutting method using a lathe or a milling cutter, and a method of introducing the groove into the polishing pad surface by performing thermoforming such as vacuum forming.

In the polishing pad of the present invention, if necessary,
Neutralizers, antioxidants, heat stabilizers, weathering agents, crystal nucleating agents, lubricants, UV absorbers, antistatic agents, optical brighteners and other additives, and dyes, pigments and other colorants may also be added. Good.

[0037]

EXAMPLES Examples and comparative examples will be shown below, but the present invention is not limited to these examples. In addition, the physical-property value in an Example and a comparative example was measured according to the following method. (1) MFR (melt flow rate, unit: g / 10
Min) The measurement was performed under the following conditions according to JIS K7210. Polypropylene resin: temperature 230 ° C, load 2.16k
gf polyethylene resin: temperature 190 ° C, load 2.16kg
f

(2) Intrinsic viscosity (unit: dl / g) The intrinsic viscosity was measured using an Ubbelohde viscometer. The measurement was performed at a temperature of 135 ° C. using tetralin as a solvent.

(3) Polystyrene-equivalent weight average molecular weight (Mw), polystyrene-equivalent number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) G. P. C. The measurement was performed under the following conditions by (gel permeation chromatography). Model: 150CV type (manufactured by Millipore Waters) Column: Shodex M / S 80 Measurement temperature: 145 ° C. Solvent: Orthodichlorobenzene Sample concentration: 5 mg / 8 mL The calibration curve was prepared using standard polystyrene. Standard polystyrene measured under these conditions (NBS706: Mw /
Mw / Mn of Mn = 2.0) was 1.9 to 2.0.

(4) Content of ethylene unit in propylene-ethylene random copolymer (unit:% by weight) From the 13 C-NMR spectrum measured by the following method, K
Report of Akuko et al. (Macromolecules,
1982, Vol. 15, p. 1150). About 200 mg of propylene-ethylene random copolymer was uniformly dissolved in 3 ml of ortho-dichlorobenzene in a 10 mmΦ test tube to prepare a sample.
^{The 13} C-NMR spectrum was measured under the following conditions. Measurement temperature: 135 ° C Pulse repetition time: 10 seconds Pulse width: 45 ° Number of integrations: 2500 times

(5) Foaming Ratio According to JIS K7112, the density ρf of the foamed sheet was obtained by using the measuring method by the underwater substitution method. The expansion ratio was obtained by dividing the density ρs of the unfoamed thermoplastic resin by ρf. Polypropylene resin was used in the examples,
The expansion ratio was calculated with ρs = 0.9 g / cc.

(6) Evaluation of Polishing Rate The polishing rate of a Cu film polished under the following polishing conditions
It was calculated from the amount of weight change before and after polishing the film. Object to be polished: Cu film Polishing machine: MECAPOL P200 (PRESI) Polishing slurry: Silica-based slurry (pH 4, pH adjusted with nitric acid) Slurry composition: Hydrogen peroxide water 1.5 wt% L (-)- Phenylalanine 1.0% by weight Colloidal silica 2.0% by weight Rotation speed of rotating platen: 250 rpm Rotation speed of wafer holding table: 75 rpm Polishing pressure: 128 g / cm ² Polishing slurry flow rate: 55 ml / min Polishing time: 1 minute

(7) After polishing, the presence or absence of scratches on the surface texture of the object to be polished and the remaining film were visually confirmed. The film residue means that the reaction product of the Cu film as the film to be polished and the components in the polishing slurry remains on the Cu film surface, and the existence of the film residue indicates the flatness of the Cu film after polishing. Means low.

In the examples and comparative examples, the following materials were used. (A1) Polypropylene resin Mw / Mn 8.0 propylene polymer (MFR = 12) consisting of a propylene polymer part having an intrinsic viscosity of 7.7 dl / g and a propylene polymer part having an intrinsic viscosity of 1.2 dl / g
g / 10 minutes) (A2) Polypropylene resin homopolypropylene (Nobrene Y101, manufactured by Sumitomo Chemical Co., Ltd., MFR = 12.5 g / 10 minutes) (B) Polyethylene resin high pressure radical polymerization low density polyethylene (Sumikasen)
G201, Sumitomo Chemical Co., Ltd., MFR = 2g / 10
(C) Polypropylene resin composition 95% by weight of propylene-ethylene random copolymer (MFR = 6 g / 10 minutes) containing 4% by weight of ethylene units, NA-21 (manufactured by ADEKA ARGUS CORPORATION) 5% by weight % Polypropylene resin composition (D) Foaming nucleating agent Hydrocerol (manufactured by Nippon Boehringer Ingelheim Co., Ltd.)

Example 1 100 mmΦ in a 50 mmΦ single screw extruder (L / D = 42)
An apparatus equipped with a circular die (lip opening 00.5 cm) was used. 15% by weight of the polypropylene resin of (1) above, polypropylene resin of (2) above
65% by weight, (B) polyethylene resin 20% by weight, (C) polypropylene resin composition 2p
hr, the raw resin blended with 1 phr of the foam nucleating agent of the above (D) is charged into an extruder hopper and melt-kneaded,
Carbon dioxide was liquid-injected at a high melting position (L / D = 24.7) at a high pressure so that the concentration Cg was 0.28 g (carbon dioxide) / 100 g (raw material resin). After sufficiently melting and kneading the raw material resin and carbon dioxide gas, the material was cooled and adjusted to 180 ° C., introduced into a die and extruded at a discharge rate of 13 Kg / h. The foam extruded from the die was blown up by a mandrel placed immediately after it was cooled and then slit into this cylindrical foam sheet with a cutter, the cylinder was opened into a flat sheet, and it was wound by a winder. . The obtained foam was a good foam sheet having a foaming ratio of 2.3 and a thickness of 1.2 mm. This foamed sheet was cut into 200 mmφ and surface-finished with a dresser to uniformly expose the foamed layer on the surface of the foamed sheet to form a foamed polishing pad. The polishing performance evaluation results are shown in Table 1.

Comparative Example 1 An electron beam crosslinked foamed sheet (PPSM15025 manufactured by Toray Pef Co., Ltd.) having a foaming ratio of 15 times and a thickness of 2.5 mm is 200.
It was cut out into mmφ and the surface was finished with a dresser to uniformly expose the foamed layer on the surface of the foamed sheet to prepare a foamed polishing pad. The polishing pad shows a high polishing resistance, the Cu film to be polished comes off from the polishing machine during polishing,
Polishing evaluation could not be performed.

[0047]

[Table 1]

[0048]

As described above in detail, according to the present invention, a metal film coated on a semiconductor wafer can be polished at a high polishing rate, and a polishing pad having excellent planarization performance can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 23:10 C08L 23:10 (72) Inventor Yasuo Matsumi 6 Kitahara, Tsukuba-shi, Ibaraki Sumitomo Chemical Co., Ltd. In-house F-term (reference) 3C058 AA07 AA09 CB01 CB03 DA17 4F074 AA16A AA16B AB01 AB05 BA03 BA13 BA32 BA33 BA37 BC12 BC15 CA22 DA02 DA24 DA56 4J100 AA01Q AA01R AA02Q AA03 FA43 DA06 CA43

Claims (4)

[Claims] 1. A polishing pad comprising an extruded foam sheet made of a polyolefin resin. 2. A polishing pad comprising a polypropylene resin foam sheet containing a polypropylene resin having a die swell ratio of 1.8 or more. 3. The polypropylene resin has an intrinsic viscosity of 5d.
A propylene polymer (obtained by a polymerization method, comprising a step of producing a propylene polymer portion (A) having a ratio of 1 / g or more and a step of producing a propylene polymer portion (B) having an intrinsic viscosity of less than 3 dl / g ( T), and the content of the propylene polymer portion (A) contained in the propylene polymer (T) is 0.05 to 90% by weight, and the polypropylene resin foam according to claim 2. A polishing pad consisting of a sheet. 4. A polishing pad, wherein the polypropylene resin foam sheet according to claim 2 is an extruded foam sheet.