JP6382659B2 - Polishing pad - Google Patents

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 order to solve the problem of local rigidity change of the surface of the polishing pad, Patent Document 1 discloses a semiconductor device having a storage elastic modulus E ′ ratio of 1 to 3.5 at 30 ° C. and 90 ° C. or a precursor thereof. A polishing pad for flattening the surface of the substrate is disclosed. Here, E ′ is an index representing the rigidity of the resin, and it can be said that the polishing pad according to Patent Document 1 has a small change in rigidity at a normal polishing temperature ranging from 30 ° C. to 90 ° C. from the value of the ratio of E ′. . Therefore, the flatness is excellent.

  As a method for increasing the amount of polishing in one polishing operation, for example, a method of preventing scratches (scratches) on the material surface due to polishing debris accumulated at the end of one polishing operation can be considered. Although the material of Patent Document 1 does not cause a change in local rigidity of the surface of the polishing pad in response to a temperature change, polishing debris accumulates and closes the opening to further increase the temperature and maintain the rigidity. In particular, when foreign matters (such as polishing scraps and aggregates of abrasive grains) are locally generated at the end of the polishing operation, scratches are easily generated on the object to be polished.

JP 2009-33193 A

  The probability of occurrence of defects such as scratches increases as the rigidity of the polishing pad increases. The present inventors provide a polishing pad whose rigidity decreases due to an increase in polishing temperature due to accumulation of polishing debris, i.e., a polishing pad whose rigidity decreases at the end of the polishing operation in which polishing debris accumulates. The present invention was completed because it was thought that the occurrence of defects could be reduced.

That is, the present invention provides the following.
[1] A polishing pad having a polishing layer made of a polyurethane resin, wherein the polishing layer is inert to isocyanate groups, hydroxyl groups and amino groups, and has a melting point or softening point of 50 to 80 ° C. A polishing pad comprising a substance.
[2] The polishing pad according to [1], wherein the polyurethane resin is a foamed polyurethane resin.
[3] The polishing pad according to [1] or [2], wherein the non-reactive substance is selected from higher fatty acid esters, alkanes having more than 20 carbon atoms, alkylated naphthalene, and combinations thereof.
[4] The polishing pad according to [3], wherein the higher fatty acid ester is selected from glycol distearate, tristearin, and combinations thereof.
[5] The polishing pad according to [4], wherein the glycol distearate is selected from ethylene glycol distearate, propylene glycol distearate, and combinations thereof.
[6] The polishing pad according to [3], wherein the alkylated naphthalene is 2,6-diisopropylnaphthalene.
[7] The polishing pad according to [3], wherein the alkane having 20 or more carbon atoms is an alkane having 24 to 40 carbon atoms.
[8] The polishing pad according to any one of [1] to [7], wherein the polishing layer contains the non-reactive substance in an amount of 1 to 20% by weight.
[9] A method for producing a polishing pad according to [1],
Preparing a polyurethane resin curable composition comprising a polyisocyanate compound, a polyol compound, and a non-reactive substance that is inert to isocyanate groups, hydroxyl groups, and amino groups and has a melting point or softening point of 50 to 80 ° C .; Curing the polyurethane resin curable composition to form a polishing layer.
[10] A method for producing a polishing pad according to [2],
Polyurethane resin foam curable composition comprising a polyisocyanate compound, a polyol compound, a foaming agent, and a non-reactive substance which is inert to isocyanate groups, hydroxyl groups and amino groups and has a melting point or softening point of 50 to 80 ° C. And foaming and curing the polyurethane resin foam curable composition to form a polishing layer.
[11] The method according to [9] or [10], wherein the polyisocyanate compound comprises a prepolymer prepared by reacting a polyisocyanate compound and a polyol compound.
[12] 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 [8] is used.
[13] 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 [8].

  According to the present invention, defects such as scratches (scratches) of a material to be polished that are likely to occur at the end of one polishing operation are effectively reduced.

It is a figure which shows the temperature change of E 'of the polishing pad of Example 1. FIG. It is a figure which shows the temperature change of E 'of the polishing pad of Example 2. FIG. It is a figure which shows the temperature change of E 'of the polishing pad of the comparative example 1. FIG. It is a figure which shows the temperature change of E 'of the polishing pad of the reference example 1. FIG.

(Polishing pad)
The polishing pad of the present invention has a polishing layer made of polyurethane resin, in particular, foamed polyurethane 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.

(Non-reactive substance)
The polishing pad of the present invention is characterized in that the polishing layer contains a non-reactive substance that is inert to isocyanate groups, hydroxyl groups, and amino groups and that has a melting point or softening point of 50 to 80 ° C.

  When frictional heat is generated due to accumulation of polishing debris at the end of one polishing operation, in the polishing pad of the present invention, a non-reactive substance is melted or softened at a specific temperature, and E ′ of the polishing layer rapidly decreases. (Attached FIGS. 1 and 2). In a temperature range of less than 50 ° C. where accumulation of polishing debris is small, the polishing pad of the present invention maintains a high value of E ′, and the flatness of the polishing surface can be accurately achieved. On the other hand, in the temperature range exceeding 50 ° C., the polishing pad of the present invention rapidly decreases E ′ at a specific temperature. As a result, even if polishing scraps accumulate, the rigidity of the polishing pad at that portion is reduced by frictional heat, so that the occurrence of defects such as scratches is prevented. Such a rapid decrease in E 'due to the temperature rise is a novel behavior not found in the polishing pads used so far. For example, although Comparative Example 1 in which no non-reactive substance is added and the polishing pad IC1000 (manufactured by Rohm & Haas) widely used in this industry can observe a decrease in E ′, it may gradually decrease gradually. It is known by the applicant's examination. In such a commercial product, it is considered that high accuracy flatness is achieved by suppressing a decrease in E 'due to a temperature rise. On the other hand, as can be seen from a comparison of FIGS. 1 to 4, the gentle decrease in E ′ decreases to some extent even at a temperature around 40 ° C. at which no frictional heat is generated because there is not much accumulation of polishing waste. Therefore, it is not sufficient for performing desired polishing.

  Examples of the non-reactive substance include higher fatty acid esters, alkanes having more than 20 carbon atoms, and alkylated naphthalene. These compounds can be used alone or in combination of two or more. Examples of the higher fatty acid ester include glycol distearate and tristearin. Examples of glycol distearate include ethylene glycol distearate and propylene glycol distearate. Examples of the alkylated naphthalene include 2,6-diisopropylnaphthalene. Examples of the alkane having 20 or more carbon atoms include alkanes having 24 to 40 carbon atoms.

  The polishing layer comprises a non-reactive substance in an amount of 1% by weight or more, in particular 2% by weight or more, and an amount of 20% by weight or less, in particular 15% by weight or less, in particular 10% by weight or less. It is preferably included in an amount of 5% by weight or less. If the amount of the non-reactive substance is too small, it is difficult to obtain the effect of the present invention due to the addition. If the amount is too large, the strength and uniformity of the polishing layer cannot be obtained and at the same time the non-reactive substance added during polishing is eluted from the polishing layer It becomes easy to do.

(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 comprises a polyisocyanate compound, a polyol compound, and a polyurethane resin curable composition containing a non-reactive substance that is inert to isocyanate groups, hydroxyl groups, and amino groups and has a melting point or softening point of 50 to 80 ° C. And is molded by curing the polyurethane resin curable composition.

  The polishing layer can be composed of a foamed polyurethane resin. In this case, the polishing layer is inactive with respect to the polyisocyanate compound, polyol compound, foaming agent, and isocyanate group, hydroxyl group and amino group, and has a melting point or a softening point. Is formed by preparing a polyurethane resin foam curable composition containing a non-reactive substance having a temperature of 50 to 80 ° C. and foam-curing the polyurethane resin foam curable composition.

  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. (Prepolymers commonly used in the art containing unreacted isocyanate groups can also 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 using a prepolymer as a polyisocyanate compound, the curing agent is a compound that reacts with an isocyanate group in the prepolymer to complete a polyurethane resin. Examples of the curing agent (active hydrogen compound) include polyols and polyamines.

  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.

(Foaming agent)
As described above, the polishing layer of the polishing pad of the present invention is made of polyurethane resin. The polyurethane resin is produced by curing a curable composition containing a polyisocyanate compound and a polyol compound. The polyurethane resin may be in a non-foamed state or in a foamed state (foam).

  As a method for foaming the polyurethane resin curable composition, any of hollow microspheres, chemical foaming, and mechanical foaming generally employed in the art can be employed.

  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.

  Examples of chemical foaming include a method of generating carbon dioxide from an isocyanate compound by adding water.

  Examples of the mechanical foaming include a method in which an inert gas such as air, nitrogen, oxygen, carbon dioxide, helium, and argon is mechanically stirred and mixed into the foam curable composition.

(Other ingredients)
In addition, foam stabilizers, catalysts, and the like commonly used in the art may be added to the foamable composition. Examples of the foam stabilizer include a surfactant, and more specifically include, for example, a polyether-modified silicone. Any catalyst commonly used in the art can be used in the present invention.

  The invention is illustrated experimentally by the following examples, which are not intended to be construed as limiting the scope of the invention to the following examples.

(About primary polishing and finish polishing)
For example, when polishing the surface of a semiconductor wafer, there are generally a plurality of polishing steps, a primary polishing (rough polishing) step for flattening the entire wafer and a final polishing step for reducing the roughness of the wafer surface. It passes. A hard (dry) pad and a non-woven pad are used for primary polishing (rough polishing), and a soft (wet) pad is used for final polishing. The example of the polishing pad specifically described below is assumed to be used for primary polishing as can be understood from the physical property values thereof.

(E '(storage modulus) evaluation)
E ′ (storage modulus) is a measure of the energy stored per cycle and fully recovered when a sinusoidally varying stress is applied to the polishing pad. A polishing pad having a high E ′ value has low elasticity, and a low value indicates high elasticity. The polishing pad of the present invention has low elasticity at room temperature, that is, at the initial polishing temperature, and high elasticity at high temperature, that is, at the late polishing temperature. The characteristic behavior of the present invention can be visually understood by measuring the temperature change of the E ′ value. The decrease in the E ′ value can be evaluated by the E ′ ratio at 30 ° C. and 90 ° C. (E ′ (30 ° C.) / E ′ (90 ° C.)), and the range of this E ′ ratio is 5 or more and 20 or less. preferable. If it is less than 5, the elasticity is still low even in a high temperature range, and scratches are generated. If it exceeds 20, the polishing pad tends to be deformed with high elasticity, and it becomes difficult to perform polishing uniformly.

(material)
The materials used in the following examples are listed.
・ PP45 ・ ・ ・ Mitsubishi Resin's urethane prepolymer product name ・ Adiprene L325 ・ ・ ・ Uniroy Chemical Co., urethane prepolymer product name ・ DC6912 ・ ・ ・ Nippon Polyurethanes urethane prepolymer product name ・ PTMG1000 ・・ Product name of polytetramethylene glycol (PTMG) with a number average molecular weight of 1000 manufactured by Mitsubishi Chemical Corporation ・ 3,3′-dichloro-4,4′-diaminodiphenylmethane (also known as methylene bis) manufactured by Pandex E, DIC -O-chloroaniline), abbreviated as E in the table below.
・ Pandex E50: Product name of a mixture of 3,3′-dichloro-4,4′-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) and polytetramethylene glycol (PTMG) manufactured by DIC, the following table Abbreviated as E50.
DMAP: N, N-dimethyl-4-aminopyridine SZ-1605: Toray Dow Corning Silicone Surfactant Product Name Emanon 3201M-V Kao Glycol Distearate Product name, melting point 65 ° C., abbreviated 3201M-V in the table below.
-TOYOCAT-ET ... a product name of a catalyst manufactured by Tosoh Corporation, abbreviated as TT in the following table.
・ SH193: trade name of silicone foam stabilizer manufactured by Toray Dow Corning ・ Expancel 461DE20d70: trade name of Microsphere (average particle size: 15 to 25 μm), abbreviated as 461DE20d70 in the table below .
-Matsumoto Microsphere F-80DE: trade name of Microsphere (average particle size 90-130 μm) manufactured by Matsumoto Yushi Seiyaku Co., Ltd., abbreviated as F-80DE in the table below.
・ IC1000 ... Rohm & Haas Co., Ltd. Hard urethane polishing pad product name (composition unknown)

(Examples 1-3 and Comparative Examples 1-2)
The materials described in Table 1 and Table 3 were mixed, and the mixture was foamed to prepare polyurethane resin foam test pieces. Details are as follows.
-Examples 1-2, comparative example 1
A prepolymer is prepared for component A, a curing agent is prepared for component B, a catalyst, a foam stabilizer, a foaming agent, and a non-reactive substance are prepared for component C.
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 3.0 mm to prepare a urethane sheet, and a polishing pad was obtained.
Example 3 and Comparative Example 2
A prepolymer and a foaming agent are prepared for the A component, and a curing agent and a non-reactive substance are prepared for the B component.
A component and B component were degassed in advance in advance, and then supplied to the mixer. The obtained mixed liquid was poured into a mold (850 mm × 850 mm square) heated to 80 ° C., heated and cured 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.
As Reference Example 1, a polishing pad IC1000 widely used in the industry was also evaluated.

The obtained test piece was evaluated by the following method. The results are shown in Tables 2 and 4 and FIGS. 1 to 4 (* 1 to * 3 indicate symbols in Tables 2 and 4).
* 1: A hardness was measured according to JIS K7311.
* 2: Storage elastic modulus E '(MPa) is TG Instrument Japan RSAIII according to JIS K7244-4, initial load 10g, strain range 0.01-4%, measurement frequency 0.2Hz. The measurement temperature was changed from 19 ° C to 100 ° C. The results are shown in FIGS. In particular, the E ′ ratio was determined using the storage elastic modulus E ′ at 30 and 90 ° C.
* 3: Defects such as scratches were evaluated by polishing 25 substrates and using the wafer surface inspection device (Surfscan SP1DLS, manufactured by KLA Tencor) for the 21st to 25th substrates after polishing. Measurement was performed in the measurement mode, and 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 were marked with ◯, and 200 or more defects were marked with ×.

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: 2.5 psi and 3.5 psi
・ Abrasive: manufactured by Cabot, product number: SS25 (SS25 undiluted solution: pure water = 1: 1 mixture)
・ Abrasive temperature: 20 ℃
・ Abrasive discharge rate: 200ml / min
・ Work used (object to be polished): A substrate in which tetraethoxysilane is formed on a 12 inch φ silicon wafer by CVD so as to have a thickness of 1 μm of insulating film. Polishing time: 60 seconds / each time

Claims (11)

A polishing pad having a polishing layer made of a polyurethane resin, comprising a non-reactive substance in which the polishing layer is inert to isocyanate groups, hydroxyl groups and amino groups and has a melting point or softening point of 50 to 80 ° C. And the non-reactive substance is selected from higher fatty acid esters, alkylated naphthalene, and combinations thereof .   The polishing pad according to claim 1, wherein the polyurethane resin is a foamed polyurethane resin. The polishing pad according to claim 1 , wherein the higher fatty acid ester is selected from glycol distearate, tristearin, and combinations thereof. The polishing pad according to claim 3 , wherein the glycol distearate is selected from ethylene glycol distearate, propylene glycol distearate, and combinations thereof. The polishing pad according to claim 1 , wherein the alkylated naphthalene is 2,6-diisopropylnaphthalene. The polishing pad according to any one of claims 1 to 5 , wherein the polishing layer contains the non-reactive substance in an amount of 1 to 20% by weight. It is a manufacturing method of the polishing pad according to claim 1,
Preparing a polyurethane resin curable composition comprising a polyisocyanate compound, a polyol compound, and a non-reactive substance that is inert to isocyanate groups, hydroxyl groups, and amino groups and has a melting point or softening point of 50 to 80 ° C .; Curing the polyurethane resin curable composition to form a polishing layer. It is a manufacturing method of the polishing pad according to claim 2,
Polyurethane resin foam curable composition comprising a polyisocyanate compound, a polyol compound, a foaming agent, and a non-reactive substance which is inert to isocyanate groups, hydroxyl groups and amino groups and has a melting point or softening point of 50 to 80 ° C. And foaming and curing the polyurethane resin foam curable composition to form a polishing layer. The method according to claim 7 or 8 , wherein the polyisocyanate compound comprises a prepolymer prepared by reaction of a polyisocyanate compound and a polyol compound. A method of polishing a surface of the optical material or a semiconductor material, wherein the use of the polishing pad according to any one of claims 1-6. Method of reducing scratches when polishing the surface of the optical material or a semiconductor material using the polishing pad according to any one of claims 1-6.