JP2016196067A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad in which a surface of a polishing layer is softened in polishing.SOLUTION: There is provided a polishing pad having a polishing layer formed of a polyurethane resin, where the polishing layer is formed by curing a polyisocyanate compound, a polyol compound, a curing agent, and a polyurethane resin curable composition containing a fine hollow sphere, and has a surface layer portion which is softened at least in polishing while saturated.SELECTED DRAWING: None

Description

  The present invention relates to a polishing sheet or a polishing pad for polishing materials that require high surface flatness such as optical materials, semiconductor substrates, semiconductor wafers, hard disk substrates, liquid crystal glass substrates, and semiconductor devices.

  Optical materials, semiconductor substrates, semiconductor wafers, hard disk substrates, liquid crystal glass substrates, and semiconductor devices are required to have very precise flatness. In addition, various materials having different hardnesses such as metal, organic and inorganic insulating materials are exposed on the surface of the semiconductor material. In order to polish the surface of such a material flatly, it is necessary that the surface of the polishing pad always maintain flatness. If the stiffness of the surface of the polishing pad changes during the polishing operation, the desired flatness cannot be achieved. For example, due to the surface of the polishing pad having locally reduced rigidity, precise flatness cannot be achieved, and a phenomenon in which only the metal part is preferentially polished (dishing) occurs.

  On the other hand, considerable polishing scraps are generated at the end of one polishing operation from the start of polishing to the replacement of the polishing pad and the polishing liquid. Since the clogging of the opening due to accumulation of polishing debris, the retention of slurry deteriorates and frictional heat is generated, the temperature of the surface of the material to be polished is from the initial to the end during one polishing operation And changes over a wide temperature range including 30 ° C to 90 ° C. Therefore, a local change in the rigidity of the surface of the polishing pad can occur in accordance with this temperature change. In addition, since the polishing liquid used for chemical mechanical polishing has a strong chemical action (corrosion on the surface of the non-polished material) as the temperature rises, it tends to cause larger scratches.

In paragraph 0072 of Patent Document 1 (Japanese Patent Laid-Open No. 2008-207324), the D hardness [D (23 ° C., wet)] of the polishing pad at 23 ° C. and 23 ° C. when saturated and swollen with hot water of 50 ° C. The ratio ([D (23 ° C., wet)] / [D (23 ° C., dry)]) of D hardness [D (23 ° C., dry)] of the polishing pad is about 0.9 to 1.1, It is described that a polishing pad having this ratio of 0.9 or more can be obtained by a polishing pad having [E ′ (50 ° C., dry)] / [E ′ (50 ° C., wet)] of about 2.5 or less. Yes.
On the other hand, in paragraph 0068, the polyurethane elastic body has a large temperature dependence of the storage elastic modulus, and the temperature dependence changes by absorbing water. 23 ° C., wet) / E ′ (50 ° C., wet)] is large (for example, about 2.5 to 20). In the polishing pad of Patent Document 1, for example, the glass transition temperature is 50 ° C. or higher and the water absorption is [E ′ (23 ° C., wet) / E ′ (50 ° C., wet)] of the polishing pad can be lowered by highly filling ultrafine single fibers made of a thermoplastic resin having a mass of 4% by mass or less. It describes what you can do.
Patent Document 1 proposes to reduce the difference in hardness between dry and wet, but discloses that this problem is difficult only with a polyurethane elastic body.

  Patent Document 2 (Japanese Patent Laid-Open No. 2006-144156) discloses a polishing pad that can stably provide a high level of flatness by suppressing the difference in Shore A hardness between room temperature and 60 ° C. to 14 or less. Has been. However, Patent Document 2 does not describe the difference in hardness between the polishing layer surface and the inside.

JP 2008-207324 A JP 2006-144156 A

  The present invention provides a polishing pad in which the polishing layer surface is softened at least during polishing.

That is, the present invention provides the following.
[1]
A polishing pad having a polishing layer made of polyurethane resin,
The polishing layer is formed by curing a polyurethane resin curable composition containing a polyisocyanate compound, a polyol compound, a curing agent, and a fine hollow sphere,
A polishing pad having at least a surface layer portion softened during wet polishing.
[2]
The polishing pad according to [1], wherein the thickness of the surface layer portion is 50 μm or less.
[3]
The polishing pad according to [1], wherein the thickness of the surface layer portion is smaller than the diameter of the micro hollow sphere.
[4]
The polishing pad according to [1], wherein a first-stage penetration temperature is 50 to 100 ° C. and a second-stage penetration temperature is 150 ° C. or higher in a penetration test by a thermomechanical analysis method (TMA). .
[5]
The polishing pad according to any one of [1] to [4], wherein the polyisocyanate compound and the polyol compound include a prepolymer prepared by a reaction between the polyisocyanate compound and the polyol compound.
[6]
A method for polishing a surface of an optical material or a semiconductor material, wherein the polishing pad according to any one of [1] to [4] is used.
[7]
A method for reducing scratches when polishing the surface of an optical material or a semiconductor material using the polishing pad according to any one of [1] to [4].

  According to the present invention, since the surface of the polishing layer is softened at least during polishing, defects such as scratches on the object to be polished can be suppressed. In addition, a high polishing rate can be maintained by giving the polishing layer an appropriate hardness.

It is a figure which shows the outline of the penetration test by a thermomechanical analysis method (TMA). 3 is a graph showing the results of a penetration test of the polishing pad of Example 1. It is a graph which shows the result of the penetration test of the polishing pad of Example 2. It is a graph which shows the result of the penetration test of the polishing pad of the comparative example 1.

(Polishing pad)
The polishing pad of the present invention has a polishing layer made of a polyurethane foam resin. The polishing layer is disposed at a position in direct contact with the material to be polished, and the other part of the polishing pad may be made of a material for supporting the polishing pad, for example, an elastic material such as rubber. Depending on the rigidity of the polishing pad, the entire polishing pad can be a single polishing layer.

  The polishing pad of the present invention is similar in shape to a general polishing pad except that it is difficult to cause defects such as scratches on the material to be polished when polishing scraps accumulate, and is used in the same manner as a general polishing pad. For example, the polishing layer can be pressed against the material to be polished while rotating the polishing pad, or can be polished against the polishing layer while rotating the material to be polished.

The polishing pad of the present invention is characterized in that the polishing layer is formed by curing a polyurethane resin curable composition containing a polyisocyanate compound, a polyol compound, a curing agent, and micro hollow spheres, and is softened at least during wet polishing. It has a surface layer part.
Regarding the characteristic surface layer portion, the thickness of the surface layer portion is preferably 50 μm or less, and in particular, the thickness of the surface layer portion is preferably smaller than the diameter of the micro hollow sphere.
Please refer to the attached drawings of the present application and the embodiments described later. In the penetration test by thermomechanical analysis (TMA), in the examples of the present invention, the first stage penetration temperature is 50 to 100 ° C., and the second stage penetration temperature is 150 ° C. or more. The penetration was confirmed. Although the penetration depth at the first stage of needle penetration was 50 μm or less, the diameter of the micro hollow sphere used in the example was about 55 μm. It can be understood that the needle does not depend on moving or deforming the micro hollow sphere. On the other hand, the polishing pad of the comparative example did not show a two-stage penetration temperature, but only a one-stage penetration temperature exceeding 150 ° C.
That is, the polishing pad of the present invention begins to soften when the polishing temperature reaches 40 ° C., but the polishing pad as a whole is not softened and maintains flatness. For this reason, the surface is softened so as not to cause a condition such as scratches during polishing, but since this softening is limited to the surface of the polishing pad, the entire polishing pad is too soft and the desired flatness and polishing rate There is no such thing as not getting.

(Polishing pad manufacturing method)
The polishing pad of the present invention can be prepared by a generally known production method such as molding or slab molding. First, a polyurethane block is formed by these manufacturing methods, the block is formed into a sheet shape by slicing or the like, a polishing layer formed from a polyurethane resin is formed, and bonded to a support or the like. Alternatively, the polishing layer can be formed directly on the support.

  More specifically, the polishing layer has a double-sided tape attached to the surface opposite to the polishing surface of the polishing layer, cut into a predetermined shape, and becomes the polishing pad of the present invention. The double-sided tape is not particularly limited, and any double-sided tape known in the art can be selected and used. In addition, the polishing pad of the present invention may have a single layer structure consisting only of a polishing layer, and a multilayer in which another layer (lower layer, support layer) is bonded to the surface of the polishing layer opposite to the polishing surface. It may consist of

  The polishing layer is formed by preparing a polyurethane resin curable composition containing a polyisocyanate compound and a polyol compound and curing the polyurethane resin curable composition.

  The polishing layer is composed of a foamed polyurethane resin, and foaming can be performed by dispersing a foaming agent containing fine hollow spheres in the polyurethane resin. In this case, a polyurethane containing a polyisocyanate compound, a polyol compound, and a foaming agent. The resin foam curable composition is prepared, and the polyurethane resin foam curable composition is foam-cured and molded.

  The polyurethane resin curable composition may be a two-component composition prepared by mixing, for example, a liquid A containing a polyisocyanate compound and a liquid B containing other components. The B liquid containing the other components can be further divided into a plurality of liquids and mixed with three or more liquids to form a composition.

  The polyisocyanate compound may include a prepolymer prepared by the reaction of a polyisocyanate compound and a polyol compound, as commonly used in the art. As the prepolymer, those commonly used in the art containing unreacted isocyanate groups can be used in the present invention.

(Isocyanate component)
As an isocyanate component, for example,
m-phenylene diisocyanate,
p-phenylene diisocyanate,
2,6-tolylene diisocyanate (2,6-TDI),
2,4-tolylene diisocyanate (2,4-TDI),
Naphthalene-1,4-diisocyanate,
Diphenylmethane-4,4′-diisocyanate (MDI),
4,4′-methylene-bis (cyclohexyl isocyanate) (hydrogenated MDI),
3,3′-dimethoxy-4,4′-biphenyl diisocyanate,
3,3′-dimethyldiphenylmethane-4,4′-diisocyanate,
Xylylene-1,4-diisocyanate,
4,4′-diphenylpropane diisocyanate,
Trimethylene diisocyanate,
Hexamethylene diisocyanate,
Propylene-1,2-diisocyanate,
Butylene-1,2-diisocyanate,
Cyclohexylene-1,2-diisocyanate,
Cyclohexylene-1,4-diisocyanate,
p-phenylene diisothiocyanate,
Xylylene-1,4-diisothiocyanate,
Ethylidine diisothiocyanate etc. are mentioned.

(Polyol component)
As a polyol component, for example,
Ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1, Diols such as 5-pentanediol and 1,6-hexanediol;
Polyether polyols such as polytetramethylene glycol (PTMG), polyethylene glycol, polypropylene glycol;
Polyester polyols such as a reaction product of ethylene glycol and adipic acid and a reaction product of butylene glycol and adipic acid;
Polycarbonate polyols;
Polycaprolactone polyol;
Etc.

(Curing agent)
When a prepolymer is used as the polyisocyanate compound, the curing agent is a compound that reacts with an isocyanate group in the prepolymer to complete the polyurethane resin. In this invention, the hardening | curing agent demonstrated below can be illustrated, for example.

  The polyol used as the curing agent is the same as the polyol component described above. Triols such as trifunctional glycerin and polyols having 4 or more functional groups can also be used.

Examples of the polyamine include diamines, which include alkylene diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine; diamines having an aliphatic ring such as isophorone diamine and dicyclohexylmethane-4,4′-diamine; 3 Diamine having an aromatic ring such as 3,3′-dichloro-4,4′-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA);
Diamine having a hydroxyl group such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, In particular hydroxyalkylalkylenediamines;
Etc. Trifunctional triamine compounds and tetrafunctional or higher polyamine compounds can also be used.
A particularly preferred curing agent is MOCA described above, and the chemical structure of this MOCA is:
It is. MOCA contains a tetramer as a by-product, and the chemical structure of the tetramer is
It is. It is preferable that 3 to 10% by weight, preferably 4 to 8% by weight, more preferably 5 to 7% by weight of the tetramer is included with the total amount of the curing agent being 100% by weight.

(Foaming agent)
A foam can be formed by mixing micro hollow spheres with polyurethane resin. The micro hollow sphere is obtained by heating and expanding an unfoamed heat-expandable microsphere composed of an outer shell (polymer shell) made of a thermoplastic resin and a low-boiling hydrocarbon encapsulated in the outer shell. . As the polymer shell, for example, thermoplastic resins such as acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, vinyl chloride-ethylene copolymer can be used. Similarly, as the low boiling point hydrocarbon encapsulated in the polymer shell, for example, isobutane, pentane, isopentane, petroleum ether and the like can be used.

(Other ingredients)
In addition, a catalyst generally used in the art may be added to the foam curable composition.

(material)
The materials used in the following examples are listed.
・ Product name of urethane prepolymer:
ADIPREN L325 made by Uniroyal
DIC Corporation Pandex C730
Novaretan UP-127 manufactured by Mitsubishi Plastics
・ Product name of MOCA:
Pandicex E, Pandex E50 made by DIC
Product name of LM-52 amine hollow particles manufactured by Ihara Chemical Co., Ltd .:
EXPANCEL 551DE40d42 made by Nippon Philite
Matsumoto Microsphere F-80DE manufactured by Matsumoto Yushi Co., Ltd.

Example 1
100 g (parts) of urethane prepolymer (pandex C730) having an NCO equivalent of 460 mainly composed of tolylene diisocyanate as the A component, and the weight ratio of the pandex E and the pandex E50 as the curing agent as the B component are 1: 1. 30.75g (parts) of the mixture (contains 6.0% by weight of tetramer with 100% by weight of curing agent), 2.25g (parts) of hollow fine particles in component C (EXPANCEL 551DE40d42 and Matsumoto Micro Prepare sphere F-80DE 4: 1). In addition, in order to show a ratio, it describes as g display and prepares a required weight (part) according to the magnitude | size of a block. Hereinafter, it is described in g (part) notation.
The A component and the B component were degassed in advance in advance, and then the A component, the B component, and the C component were supplied to the mixer.
The obtained mixed liquid was poured into a mold (890 mm × 890 mm square) heated to 80 ° C. and cured by heating for 5 hours, and then the formed resin foam was extracted from the mold. This foam was sliced to a thickness of 1.3 mm to prepare a urethane sheet, and a polishing pad was obtained.

(Example 2)
100 g (parts) of urethane prepolymer (novaletane UP-127) having an NCO equivalent of 400 containing tolylene diisocyanate as the main component for component A, and a weight ratio of pandex E and LM-52 amine as curing agents for component B: 30.5 g (part) containing 5.0% by weight of tetramer containing 100% by weight of curing agent, and 2.0 g (part) of hollow fine particles in component C (EXPANCEL 551DE40d42 and Prepare Matsumoto Microsphere F-80DE (4: 1).
Thereafter, a urethane sheet was prepared in the same manner as in Example 1 to obtain a polishing pad.

(Comparative Example 1)
As a comparative example, IC1000, which is a polishing pad manufactured by Nitta Haas, was used.

(scratch)
Defects such as scratches are evaluated by polishing 25 substrates and using the high sensitivity measurement mode of the wafer surface inspection apparatus (Surfscan SP1DLS, manufactured by KLA Tencor) for the 21st to 25th substrates after polishing. The number of defects such as scratches on the substrate surface was evaluated. In the evaluation of defects such as scratches, less than 200 defects of 0.16 μm or more on a 12-inch (300 mmφ) wafer were marked with ◯, and more than 200 defects were marked with ×.

(Polishing rate)
The conditions of the polishing test are as follows.
・ Use polishing machine: F-REX300, manufactured by Ebara Corporation
Disk: 3M A188 (# 60)
・ Rotation speed: (Surface plate) 70 rpm, (Top ring) 71 rpm
Polishing pressure: 3.5 psi
・ Abrasive: manufactured by Cabot, product number: SS25 (SS25 stock solution: pure water = 1: 1 mixed solution is used)
・ Abrasive temperature: 20 ℃
・ Abrasive discharge rate: 200ml / min
Workpiece (object to be polished): A substrate in which tetraethoxysilane is formed by PE-CVD on a 12 inch φ silicon wafer to a thickness of 1 μm of insulating film. The temperature rises to 40-50 ° C.

(Tetramer analysis conditions)
・ Analyzer used: Gel Permeation Chromatography L-7200 (Hitachi)
-Column: Ohpak KB-802.5 (exclusion limit 10000) in series-Mobile phase: DMF
・ Flow rate: 0.4mL / min
・ Oven: 60 ℃
・ Detector: RI 60 ℃
・ Sample volume: 90μL

(Penetration test by thermomechanical analysis (TMA))
As shown in FIG. 1, the outline of the test is to press a needle with a constant load against the polishing pad and measure the temperature rise of the needle and the penetration depth of the needle. If the surface of the polishing pad softens as the needle temperature rises, the needle penetrates.
The following conditions were used.
Measuring device: TMA / Q400 (TA Instruments) Intra cooler Cooling method Measuring method: Penetration mode Probe diameter: 1mmφ
Temperature increase rate: 5 ° C / min
Measurement atmosphere: Nitrogen (Flow rate: 50mL / min)
Measuring load: 50gf
Sample piece size: about 5mm x about 5mm x about 1.5mm thickness
Measurement direction: Compressed in the thickness direction (Penetration)
Pre-measurement treatment: Drop water (10 μL) onto the sample just before measurement

The results are shown in FIGS.
In Examples 1 and 2 (FIGS. 2 and 3), the needle once entered the sample from around 50 ° C., and then the needle penetration depth took a substantially constant value for a while, and the needle entered the sample again from around 150 ° C. . This result shows that in Examples 1 and 2, there is a difference in the chemical structure between the surface layer portion and the inner portion, and there is a difference in the softening temperature reflecting this.
On the other hand, in Comparative Example 1 (FIG. 4), there was no penetration of the needle up to around 180 ° C. It is considered that there is no difference in chemical structure between the surface layer and the inner part.

The results are shown in Table 1.
The first stage penetration temperature was defined as the inflection point of the curve in the graph, and the second stage penetration temperature was defined as the point where the slope of the tangent to the curve was 1 (= 45 °).
As shown in Table 1, it was found that the polishing pad of the present invention was improved in polishing performance (reduction in scratch generation rate and improvement in polishing rate) by softening the surface during polishing.

Claims (7)

A polishing pad having a polishing layer made of polyurethane resin,
The polishing layer is formed by curing a polyurethane resin curable composition containing a polyisocyanate compound, a polyol compound, a curing agent, and a fine hollow sphere,
A polishing pad having at least a surface layer portion softened during wet polishing.   The polishing pad according to claim 1, wherein the thickness of the surface layer portion is 50 μm or less.   The polishing pad according to claim 1, wherein the thickness of the surface layer portion is smaller than the diameter of the micro hollow sphere.   2. The polishing pad according to claim 1, wherein the penetration temperature of the first stage is 50 to 100 ° C. and the penetration temperature of the second stage is 150 ° C. or more in a penetration test by a thermomechanical analysis method (TMA). .   The polishing pad in any one of Claims 1-4 in which a polyisocyanate compound and a polyol compound contain the prepolymer prepared by reaction of a polyisocyanate compound and a polyol compound.   A method for polishing a surface of an optical material or a semiconductor material, wherein the polishing pad according to claim 1 is used.   A method for reducing scratches when polishing the surface of an optical material or a semiconductor material using the polishing pad according to claim 1.