JP7311749B2 - polishing pad - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polishing pad, and more particularly to a polishing pad comprising a polishing layer made of hard urethane, a cushion layer, and an adhesive layer for bonding the polishing layer and the cushion layer.

Conventionally, polishing pads have been used to polish objects to be polished such as optical materials, semiconductor substrates, and glass substrates for hard disks. A polishing pad including a cushion layer and an adhesive layer for bonding the polishing layer and the cushion layer is known (Patent Document 1).
When polishing an object to be polished using such a polishing pad, liquid slurry is supplied between the object to be polished and the polishing pad to perform mechanical polishing and chemical polishing with the polishing pad and the slurry. It has become.

JP 2008-226992 A

Here, when the slurry is supplied and the object to be polished is polished, the cushion layer constituting the polishing pad becomes wet by absorbing the slurry, but the central portion, which is less likely to be soaked with the slurry, may maintain a dry state.
If the physical properties of the entire polishing pad change when the cushion layer becomes wet, the physical properties of the outer peripheral portion and the central portion of the polishing pad will differ during polishing. There is a risk that the polishing rate will fluctuate between the initial stage and the final stage of polishing.
In view of such problems, the present invention provides a polishing pad that exhibits little change in physical properties between wet and dry conditions and has a stable polishing rate from the beginning to the end of polishing.

That is, the polishing pad according to the invention of claim 1 comprises a polishing layer made of hard urethane, a cushion layer having elasticity, and an adhesive layer for bonding the polishing layer and the cushion layer,
When the dynamic viscoelasticity measurement in the compression mode was performed under the conditions of a temperature range of 20 to 80° C. and a temperature increase rate of 5° C./min in a state in which the polishing layer, the cushion layer, and the adhesive layer were laminated. ,
Storage elastic modulus at 40°C in the dry state of the polishing pad (placed in a constant temperature and humidity chamber at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) and held for 40 hours), and wet The ratio of the storage elastic modulus at 40° C. in the state (immersed in static water and placed in a vacuum chamber for 1 hour vacuum degassing, then immersed in static water for 2 hours hydration treatment) is 0.7 to 1.0. It is characterized by being 0.

In the above invention, by setting the ratio of the storage modulus in the dry state to the storage modulus in the wet state within a predetermined range, changes in the physical properties of the polishing pad as a whole in the dry state and the wet state can be suppressed.
As a result, even if the outer peripheral portion of the cushion layer is wet and the central portion is dry, stable polishing can be performed with the outer peripheral portion and the central portion of the polishing pad.

FIG. 2 is a side view of a polishing device with a polishing pad; Sectional drawing of a polishing pad.

1 shows a side view of a polishing apparatus 2 equipped with a polishing pad 1 according to the present invention, which polishes an object 3 to be polished such as a semiconductor substrate.
The polishing apparatus 2 includes a polishing surface plate 4 provided below for supporting the polishing pad 1, a support surface plate 5 provided above for supporting the object to be polished 3, and slurry supply means 6 for supplying slurry. It has
The polishing pad 1 and the object to be polished 3 each have a substantially disk shape. The polishing pad 1 is fixed to the polishing surface plate 4 by double-sided tape or the like, and the object to be polished 3 is vacuum-adsorbed to the supporting surface plate 5. there is
The polishing surface plate 4 and the support surface plate 5 are relatively rotated by a driving means (not shown), and the support surface plate 5 is provided so as to reciprocate radially from the center position of the polishing surface plate 4. The polishing pad 1 and the object to be polished 3 slide while rotating relatively.
The slurry supply means 6 supplies slurry, which is a mixture of required chemicals and abrasive grains, to the polishing surface formed on the upper surface of the polishing pad 1, so that the slurry is applied to the polishing surface and the object 3 to be polished. By entering between them, the object 3 to be polished is polished.
The polishing apparatus itself having such a configuration is conventionally known, and further detailed description thereof will be omitted. In addition to the polishing apparatus 2 having the above configuration, the polishing apparatus 2 may have other configurations such as a polishing apparatus 2 in which the support surface plate 5 is not driven and the support surface plate 5 is rotated along with the rotation of the polishing surface plate 4. A polishing device 2 can also be used.

FIG. 2 shows a cross-sectional view of the polishing pad 1 according to the present embodiment. The polishing pad 1 includes a polishing layer 11 made of hard urethane, an elastic cushion layer 12, and the polishing layer 11 and the cushion layer 12. The cushion layer 12 is fixed to the polishing surface plate 4 using double-sided tape or the like.
The hard urethane that constitutes the polishing layer uses a urethane prepolymer, which is a reaction intermediate between a polyol component and an isocyanate component, and is mixed with a curing agent (chain extender) such as diamines or diols, a foaming agent, a catalyst, etc. It is produced by a prepolymer method in which the resulting polyurethane composition is cured. The polishing layer 11 is formed by molding a polyurethane-polyurea resin molded body by mixing a prepolymer, a curing agent, and a hollow body, and slicing the polyurethane-polyurea resin molded body. A foamed polyurethane sheet can be used, with a thickness of 0.5-2 mm, a Shore D hardness of 20-60, and a density of 0.60-0.95 g/cm ³ .
As the cushion layer 12, a polyurethane resin-impregnated nonwoven fabric or a foam in which the polyurethane resin enters the fibers and voids are formed can be used. 10 to 60, a density of 0.05 to 0.50 g/cm ³ , and a compressibility of 3 to 40%.

In order to manufacture the polishing layer 11, a preparatory step of preparing at least a urethane bond-containing isocyanate compound as a prepolymer, a curing agent, and a hollow body; A mixing step of obtaining a mixed liquid for molding; a molded body molding step of molding a polyurethane-polyurea resin molded body from the molded body-molding mixed liquid; and forming a polishing layer 11 having the polished surface from the polyurethane-polyurea resin molded body. and a polishing layer forming step.

In the preparation step, at least a urethane bond-containing isocyanate compound, a curing agent, and a hollow body are used as raw materials for the polyurethane-polyurea resin molding. Furthermore, a polyol compound may be used together with the above components, and components other than the above may be used in combination within a range that does not impair the effects of the present invention.
The urethane bond-containing isocyanate compound prepared in this preparation step is a compound obtained by reacting the following polyisocyanate compound and polyol compound under conditions normally used, and contains a urethane bond and an isocyanate group in the molecule. It is a thing. Further, other components may be contained in the urethane bond-containing isocyanate compound within a range that does not impair the effects of the present invention.
As the urethane bond-containing isocyanate compound, a commercially available one may be used, or a compound synthesized by reacting a polyisocyanate compound and a polyol compound may be used. The above reaction is not particularly limited, and an addition polymerization reaction may be carried out using a method and conditions known in the production of polyurethane resins.
For example, to a polyol compound heated to 40° C., a polyisocyanate compound heated to 50° C. is added while stirring in a nitrogen atmosphere, and after 30 minutes the temperature is raised to 80° C. and further reacted at 80° C. for 60 minutes. It can be manufactured by such a method.

First, the polyisocyanate compound means a compound having two or more isocyanate groups in the molecule. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in its molecule.
For example, diisocyanate compounds having two isocyanate groups in the molecule include 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, Ethyridine diisothiocyanate and the like can be mentioned.
Furthermore, as the polyisocyanate compound, a diisocyanate compound is preferred, among which 2,4-TDI, 2,6-TDI and MDI are more preferred, and 2,4-TDI and 2,6-TDI are particularly preferred.
These polyisocyanate compounds may be used alone or in combination of multiple polyisocyanate compounds.

Next, the polyol compound means a compound having two or more alcoholic hydroxyl groups (OH) in the molecule.
Examples of the polyol compound used for synthesizing the urethane bond-containing isocyanate compound include diol compounds such as ethylene glycol, diethylene glycol (DEG) and butylene glycol, triol compounds, and the like; poly(oxytetramethylene) glycol (or polytetramethylene ether glycol). polyether polyol compounds such as (PTMG); polyester polyol compounds such as a reaction product of ethylene glycol and adipic acid or a reaction product of butylene glycol and adipic acid; polycarbonate polyol compounds, polycaprolactone polyol compounds, and the like.
Also, trifunctional propylene glycol to which ethylene oxide is added can be used. Among these, PTMG or a combination of PTMG and DEG is preferred.
The above polyol compound may be used alone, or a plurality of polyol compounds may be used in combination.

Here, the NCO equivalent of the prepolymer, which indicates the molecular weight of PP (prepolymer) per NCO group, is preferably 200 to 800, more preferably 300 to 700, and 400 to 600. is even more preferred.
Specifically, the NCO equivalent of the prepolymer can be determined as follows.
NCO equivalent of prepolymer = (parts by mass of polyisocyanate compound + parts by mass of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound x parts by mass of polyisocyanate compound / molecular weight of polyisocyanate compound) - (polyol compound Number of functional groups per molecule x parts by mass of polyol compound/molecular weight of polyol compound)]

As the curing agent (also referred to as chain extender), for example, a polyamine compound and/or a polyol compound can be used.
A polyamine compound means a compound having two or more amino groups in the molecule, and aliphatic or aromatic polyamine compounds, particularly diamine compounds can be used.
For example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter referred to as MOCA) ), polyamine compounds having the same structure as MOCA, and the like.
In addition, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxy Ethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine and the like can be mentioned.
As the polyamine compound, a diamine compound is preferable, MOCA, diaminodiphenylmethane, and diaminodiphenylsulfone are more preferable, and MOCA is particularly preferable.
The polyamine compound may be used alone or in combination of multiple polyamine compounds.
In order to facilitate mixing with other components and/or to improve the uniformity of cell diameter in the subsequent step of forming a molded body, the polyamine compound is preferably heated and degassed under reduced pressure, if necessary. As the defoaming method under reduced pressure, a method known in the production of polyurethane may be used. For example, defoaming can be performed at a degree of vacuum of 0.1 MPa or less using a vacuum pump.
When a solid compound is used as the curing agent (chain extender), it can be defoamed under reduced pressure while being melted by heating.

Moreover, as a polyol compound as a curing agent, any compounds such as diol compounds and triol compounds can be used without particular limitation. It may also be the same as or different from the polyol compound used to form the prepolymer.
Specific examples include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3 low molecular weight diols such as -methyl-1,5-pentanediol and 1,6-hexanediol; and high molecular weight polyol compounds such as poly(oxytetramethylene)glycol, polyethylene glycol and polypropylene glycol.
The above polyol compound may be used alone, or a plurality of polyol compounds may be used in combination.

Here, the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent to the isocyanate groups present at the ends of the urethane bond-containing isocyanate compound, is 0.60 to 1.40. Mix each component so that The R value is preferably 0.65 to 1.30, more preferably 0.70 to 1.20.

The hollow bodies mean microspheres having voids. Microspheres include spherical, ellipsoidal, and near-spherical shapes. Examples of hollow bodies include unfoamed heat-expandable microspheres and unfoamed heat-expandable microspheres, which are composed of an outer shell (polymer shell) made of a thermoplastic resin and a low-boiling-point hydrocarbon contained in the outer shell. Examples include those obtained by heating and expanding a spherical body.
Examples of the polymer shell include acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, vinyl chloride-ethylene copolymer, etc., as disclosed in JP-A-57-137323. A thermoplastic resin 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.

Next, the mixing step will be described. In the mixing step, the urethane bond-containing isocyanate compound as a prepolymer, the curing agent and the hollow bodies prepared in the preparation step are fed into the mixer and stirred and mixed. The mixing step is carried out in a state where the components are heated to a temperature that ensures the fluidity of the components.
There are no particular restrictions on the mixing order, but a mixed liquid in which the urethane bond-containing isocyanate compound and the hollow body are mixed and a mixed liquid in which the curing agent and, if necessary, other components are mixed are prepared, and the two mixed liquids are mixed. It is preferable to supply them into a vessel and mix and stir them. In this manner, a mixed solution for forming a molded body is prepared.

Next, in the molding molding step, the mixture for molding molding prepared in the mixing step is poured into a mold at 50 to 100° C. and cured to mold a polyurethane polyurea resin molding.
At this time, the mixture is cured by reacting the prepolymer and the curing agent to form a polyurethane polyurea resin.
Then, in the polishing layer forming step, the polyurethane-polyurea resin molded body obtained in the molded body molding step is sliced into sheets, the sliced resin sheets are cut into circular shapes, and if necessary, a grating is applied to a surface corresponding to the polishing surface. grooves, etc., are formed.

For the cushion layer 12, a foam such as polyethylene foam or polyurethane foam or an impregnated nonwoven fabric impregnated with resin can be used.
When the impregnated non-woven fabric is used as the cushion layer 12, in order to manufacture the cushion layer 12, at least a step of wet-coagulating the thermoplastic polyurethane resin impregnated into the non-woven fabric substrate, and buffing both sides of the wet-coagulated fiber assembly. and a step of performing. The nonwoven fabric substrate of this embodiment is not particularly limited, and various known substrates can be employed.
Examples of nonwoven fabric substrates include polyolefin-based, polyamide-based, and polyester-based nonwoven fabrics. Moreover, the method for entangling the fibers when obtaining the nonwoven fabric substrate is not particularly limited, and for example, needle punching or hydroentangling may be used.
The nonwoven fabric base can be used singly or in combination of two or more types selected from the above-mentioned nonwoven fabric substrates. The non-woven fabric substrate has many gaps between fibers and is highly absorbent, but impregnating it with a resin fills the gaps with the resin, resulting in a decrease in water absorption.

The resin with which the non-woven fabric base is impregnated includes polyurethanes such as polyurethane and polyurethane polyurea, acrylics such as polyacrylate and polyacrylonitrile, vinyls such as polyvinyl chloride, polyvinyl acetate, and polyvinylidene fluoride, polysulfone, and polyethersulfone. polysulfones such as cellulose, acylated celluloses such as acetylated cellulose and butyrylated cellulose, polyamides and polystyrenes.

The density of the nonwoven fabric is preferably 0.3 g/cm ³ or less, more preferably 0.1 to 0.2 g/cm ³ in the state (web state) before resin impregnation. Further, the density of the nonwoven fabric after resin impregnation is preferably 0.5 g/cm ³ or less, more preferably 0.3 to 0.4 g/cm ³ . If the density of the nonwoven fabric is too high, the processing accuracy tends to deteriorate, and if it is too low, it tends to absorb water relatively easily.
The adhesion rate of the resin to the nonwoven fabric is expressed by the weight of the resin adhered to the weight of the nonwoven fabric, and is preferably 50% or more, more preferably 75 to 200%. If the adhesion rate of the resin is too high, the cushion layer 12 tends not to exhibit the desired cushioning properties.

As for the impregnated nonwoven fabric, a water repellent agent may be added to the resin to be impregnated to enhance the water repellency of these resins. The water repellent agent is one that has the effect of improving the water repellency of the surface of the impregnated nonwoven fabric impregnated with the resin by being contained in the resin. water repellent agents, metallic compound water repellent agents, and the like.
Among these, metal compound-based water repellents are preferable from the viewpoint of chemical resistance and stirring uniformity with resin, and zirconium compounds such as zirconium chloride, zirconium nitrate, zirconium sulfate, and zirconium acetate are more preferable, and zirconium acetate is further preferable. preferable. The water repellent may be used alone or in combination of two or more.
It is desirable that the water repellent agent is uniformly present in the cushion layer 12. The amount of the water repellent agent to be added is preferably 0.5% by weight or more, more preferably 0%, based on 100% by weight of the resin impregnated into the nonwoven fabric substrate. .7 to 1.5% by weight. If the amount of the water repellent agent is too large relative to the amount of resin, the peel strength with the adhesive layer 13 tends to decrease, and if it is too small, the desired water repellent performance tends to be unobtainable.

The adhesive layer 13 has a core material made of polyethylene terephthalate (PET), and a pressure-sensitive adhesive such as an acrylic adhesive is formed on the front and back surfaces of the core material. The adhesive layer 13 is not particularly limited, and can be arbitrarily selected from double-sided tapes known in the art.
A double-sided tape is attached to the surface of the abrasive layer 11 opposite to the abrasive surface, and a cushion layer 12 is attached to the surface of the double-sided tape opposite to the abrasive layer 11 side. In the polishing pad 1 of this embodiment, a polishing layer 11 and a cushion layer 12 are laminated with an adhesive layer 13 interposed therebetween.

The polishing pad 1 of the present embodiment having the above configuration has a ratio of the storage modulus of the polishing pad 1 in a dry state to a storage modulus in a wet state (storage modulus in a wet state/storage modulus in a dry state ) is between 0.7 and 1.0.
Here, the term "dry state" refers to a state in which liquid is not adhered to the polishing pad 1. Specifically, the state in which the polishing pad 1 has been shipped or the state immediately after being installed in the polishing apparatus can be considered.
On the other hand, the wet state refers to a state in which the polishing pad 1 is soaked with a liquid. It is conceivable that it has soaked.
The storage elastic modulus E' is a measure of the energy stored and completely recovered per cycle when a sinusoidally varying stress is applied to the foam. By setting the ratio to the storage elastic modulus E′ in the wet state within the above range, the polishing pad 1 of this embodiment has a stable polishing rate.
Table 1 below shows the test results of the polishing pad 1 of Example 1 according to the present invention and the polishing pad of Comparative Example 1 in a dry state and a wet state, respectively.

Example 1
As the polishing pad 1 of Example 1, a 1.3 mm thick polyurethane sheet is used for the polishing layer 11, a 1.25 mm thick impregnated nonwoven fabric impregnated with polyurethane resin is used for the cushion layer 12, and an adhesive layer 13 used a double-sided tape having a PET core material with a thickness of 0.16 mm. A double-faced tape having a core made of PET and having a thickness of 0.27 mm was adhered to the surface of the cushion layer 12 opposite to the polishing layer 11 .

The polishing layer 11 of the polishing pad 1 of Example 1 was obtained as follows.
100 parts of a urethane prepolymer having an NCO equivalent of 460 obtained by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG) and diethylene glycol (DEG), and the outer shell portion is acrylonitrile-vinylidene chloride. 3.1 parts of unexpanded microspheres having a particle size of 5 to 15 μm and having isobutane gas encapsulated in the shell, made of a copolymer, and 4,4′-methylene-bis(cyclohexyl isocyanate) (water 2 parts of added MDI) were added and mixed to obtain a urethane prepolymer mixture.
The obtained urethane prepolymer mixed liquid was charged into the first liquid tank and kept at 80°C. Separately from the first liquid tank, 28 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (MOCA) as a curing agent was placed in the second liquid tank and heated to 120°C. The components were heated and melted and mixed to obtain a curing agent melt.
Next, the liquids in the first liquid tank and the liquid in the second liquid tank were injected from respective inlets of a mixer provided with two inlets, and stirred and mixed to obtain a mixed liquid. At this time, the mixing ratio was adjusted so that the R value representing the equivalent ratio of the amino groups and hydroxyl groups present in the curing agent to the isocyanate groups present at the ends of the urethane prepolymer was 0.90.
The obtained mixed liquid was cast into a mold preheated to 100° C., and was primarily cured at 110° C. for 30 minutes. The formed block-shaped molded product was extracted from the mold and subjected to secondary curing in an oven at 130° C. for 2 hours to obtain a polyurethane polyurea resin molded product. The resulting polyurethane-polyurea resin molding was allowed to cool to 25° C., heated again in an oven at 120° C. for 5 hours, and sliced to a thickness of 1.3 mm to obtain polishing layer 11 .

Moreover, the cushion layer 12 was obtained as follows.
A nonwoven fabric made of polyethylene fibers having a density of 0.150 g/cm ³ was immersed in an impregnating resin solution in which 0.3 part of carbon black was added as a pigment to 100 parts of a polyurethane resin (“C1367” manufactured by DIC).
After the immersion, the impregnating resin solution was squeezed out using a mangle roller capable of applying pressure between a pair of rollers, and the nonwoven fabric was substantially uniformly impregnated with the impregnating resin solution. Then, the impregnated resin was coagulated by immersion in a coagulating liquid consisting of water at room temperature to obtain a resin-impregnated nonwoven fabric.
After that, the resin-impregnated nonwoven fabric was taken out from the coagulating liquid, further immersed in a washing liquid consisting of water to remove N,N-dimethylformamide (DMF) in the resin, and then dried. After drying, a cushion layer was obtained from which the surface skin layer was removed by buffing. The resulting impregnated nonwoven fabric serving as a cushion layer had a thickness of 1.25 mm and a density of 0.31 g/cm ³ . Also, the adhesion rate of the resin was 100%.

The abrasive layer 11 and the cushion layer 12 obtained in this manner were bonded together via a double-faced tape (adhesive layer 13) having a PET core material. A double-faced tape having a PET core material was adhered to the surface opposite to the surface where the cushion layer 12 was adhered to the polishing layer 11 .

Comparative example 1
As the polishing pad 1 of Comparative Example 1, IC1000 with a thickness of 1.3 mm manufactured by Nitta Haas was used as the polishing layer 11, and SUBA400 with a thickness of 1.2 mm manufactured by Nitta Haas was used as the cushion layer 12. , a double-sided tape having a PET core material was used as the adhesive layer 13 . A double-faced tape having a core made of PET was attached to the surface of the cushion layer 12 opposite to the polishing layer 11 .

The polishing pads 1 of Example 1 and Comparative Example 1 thus obtained were subjected to the following operations to prepare the dry polishing pad 1 and wet polishing pad 1 .
First, the polishing pads 1 of Example 1 and Comparative Example 1 were cut into 9 mm squares and used as test pieces. (±5%) in a constant temperature and humidity chamber and held for 40 hours. On the other hand, the wet polishing pad 1 was put into a vacuum chamber with the test piece immersed in still water, subjected to vacuum degassing for 1 hour, and then immersed the test piece in still water for 2 hours of hydrous treatment. obtained by doing

The dry and wet specimens obtained in this manner were put into the following experimental apparatus, and experiments were conducted under the following experimental conditions. , tan δ (=E″/E′) were obtained.
Test equipment: RSA3 manufactured by TA Test mode: Compression Frequency: 1.6 Hz (10 rad/sec)
Temperature range: 20-80°C
Heating rate: 5°C/min
Strain range: 0.10%
Initial load: 1000g
Measurement interval: 1 point/°C

As a result of the experiment, the polishing pad 1 of Example 1 had a ratio of the storage elastic modulus E' in the dry state to the storage elastic modulus E' in the wet state of 0.93. On the other hand, the ratio in the polishing pad 1 of Comparative Example 1 was 1.26.
In the above experimental results, the value (change rate) of the ratio of the storage elastic modulus E′ in the dry state to the storage elastic modulus E′ in the wet state is the value of the storage elastic modulus E′ of the polishing pad 1 in the dry state and the wet state. Showing the degree of difference, the value of the above ratio close to 1 means that the storage modulus E′ changes little in dry and wet conditions.
Further, when the value of the ratio is less than 1, it means that the polishing pad 1 becomes soft when wet. Furthermore, a value of the above ratio greater than 1 means that the polishing pad 1 becomes hard when wet.

Here, when the polishing pad 1 is attached to the polishing apparatus 1 to polish the object 3 to be polished, slurry is supplied between the polishing pad 1 and the object 3 to be polished. It adheres to the polishing pad 1 and penetrates into the cushion layer 12 in particular.
At this time, the slurry permeates into the cushion layer 12 from the side portion of the polishing pad 1, that is, from the outer peripheral portion of the circular polishing pad 1, but does not reach the central portion of the polishing pad 1 with difficulty. On the other hand, the slurry hardly penetrates into the polishing layer 11 and is blocked by the adhesive layer 13 formed between the polishing pad 1 and the cushion layer 12, so that the slurry hardly penetrates into the central portion of the cushion layer 12.例文帳に追加
As a result, immediately after the polishing pad 1 is used to polish the object 3 to be polished, although the outer peripheral portion of the cushion layer 12 is in a wet state with the slurry, the central portion is maintained in a dry state. The central portion of the cushion layer 12 becomes wet.
That is, the fact that the ratio of the storage elastic modulus of the entire polishing pad 1 to the storage elastic modulus in the wet state is small as in Example 1 means that the change in the physical properties of the entire polishing pad 1 between the initial stage and the final stage of polishing is indicates that it is small.
On the other hand, when the ratio of the storage elastic modulus of the entire polishing pad 1 to the storage elastic modulus in the wet state is large as in Comparative Example 1, the physical properties of the entire polishing pad 1 change between the initial stage and the final stage of polishing. It shows big.

Table 2 above shows experimental results of evaluating variations in the polishing rate from the initial stage to the final stage of polishing from the thickness of the polishing layer 11 and the polishing rate for the polishing pads 1 of Example 1 and Comparative Example 1. Here, the thicker the polishing layer 11 corresponds to the initial stage of polishing, and the thinner the polishing layer 11, the closer to the final stage of polishing.
In this experiment, the polishing pads 1 of Example 1 and Comparative Example 1 were first installed in a polishing apparatus and subjected to dressing treatment. Polished with. After that, when the predetermined polishing is completed, the polishing layer is subjected to the dressing process again to have the thickness shown in Table 2, and the polishing process is repeated, and the polishing rate is observed for each thickness of the polishing layer. Thus, the stability of the polishing rate was evaluated.
Polishing machine: F-REX300X (manufactured by Ebara Corporation)
Disk: A188 (manufactured by 3M)
Rotation speed: (Surface plate) 70 rpm, (Top ring) 71 rpm
Polishing pressure: 3.5 psi
Abrasive temperature: 20°C
Abrasive discharge rate: 200ml/min
Abrasive: PLANERLITE7000 (manufactured by Fujimi Corporation)
Object to be polished: Cu film substrate Polishing time: 60 seconds Pad break: 35N 10 minutes Conditioning: Ex-situ, 35N, 4 scans

The stability of the polishing rate was determined as follows.
Regarding the Cu film on the substrate before and after polishing by the polishing apparatus, 121 points were randomly selected over the entire substrate, and the thickness of those points before and after the polishing test was measured.
Based on the measured thickness, calculate the average value of the thickness before the polishing test and the average value of the thickness after the polishing test, and calculate the average value of the polished thickness by taking the difference between these average values. bottom.
Then, the polishing rate (Å/min) was obtained by dividing the obtained average value of the polished thickness by the polishing time. The thickness was measured in the DBS mode of an optical film thickness and film quality measuring device (KLA-Tencor, Model No. "ASET-F5x").

As a result of the experiment, when the value of the ratio of the storage elastic modulus E′ of the polishing pad 1 in the dry state and the wet state is within a predetermined range like the polishing pad 1 of Example 1, the outer peripheral portion and the central portion of the polishing pad 1 A stable polishing rate can be maintained from the initial stage to the final stage of polishing because the physical properties of the polishing pad 1 do not change much from one part to another, and in-plane uniformity can be obtained between the outer peripheral part and the central part of the polishing pad 1 .
On the other hand, when the ratio of the storage elastic modulus E' of the polishing pad 1 in the dry state and the wet state is large as in Comparative Example 1, the change in physical properties is large between the outer peripheral portion and the central portion of the polishing pad 1. Therefore, the polishing rate was not stable, and the difference in polishing rate between the initial stage and the final stage of polishing increased.

REFERENCE SIGNS LIST 1 polishing pad 2 polishing device 3 object to be polished 4 polishing surface plate 5 support surface plate 6 slurry supply means 11 polishing layer 12 cushion layer 13 adhesive layer

Claims (4)

A polishing pad comprising a polishing layer made of hard urethane, an elastic cushion layer, and an adhesive layer bonding the polishing layer and the cushion layer,
When the dynamic viscoelasticity measurement in the compression mode was performed under the conditions of a temperature range of 20 to 80° C. and a temperature increase rate of 5° C./min in a state in which the polishing layer, the cushion layer, and the adhesive layer were laminated. ,
Storage elastic modulus at 40°C in the dry state of the polishing pad (placed in a constant temperature and humidity chamber at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) and held for 40 hours), and wet The ratio of the storage elastic modulus at 40° C. in the state (immersed in static water and placed in a vacuum chamber for 1 hour vacuum degassing, then immersed in static water for 2 hours hydration treatment) is 0.7 to 1.0. 0. 2. The polishing pad according to claim 1, wherein said cushion layer is an impregnated nonwoven fabric impregnated with polyurethane resin. 2. The polishing pad according to claim 1, wherein said cushion layer contains a water-repellent agent. 2. The polishing pad according to claim 1, wherein the polishing layer has a D hardness of 20-60.

Images