JP6829037B2 - Polishing pad and its manufacturing method - Google Patents

Description

The present invention relates to a polishing pad and a method for manufacturing the polishing pad. In particular, the present invention relates to a polishing pad for polishing the back surface of a semiconductor wafer (preferably a silicon wafer) and a method for manufacturing the same.

Various machining technologies are used in the semiconductor manufacturing process, and in the wafer processing process, the chipping process of dividing individual devices from the wafer on which the circuit is formed is collectively called dicing. Recently, as the diameter of wafers has increased, in order to prevent damage to thin wafers, a pre-dicing method has been developed in which the cut surface is cut in half in advance and the back surface is ground until the grooves are exposed. There is.

Conventionally, a grinding wheel using diamond, CBN (cubic boron nitride) or the like as an abrasive material has been used for grinding the back surface of the wafer, and the wafer has been thinned to a desired thickness. However, in grinding with a grinding wheel, grinding strain is formed, the bending strength of the wafer is lowered, and the risk of breakage is increased. For this reason, the generated grinding strain has been removed by polishing with dry polishing or CMP.

However, if the grinding strain of the wafer is removed by polishing, the gettering effect (the effect of capturing impurities mainly composed of heavy metals contained in the wafer outside the device area of the wafer and protecting the device from impurity contamination) disappears. There's a problem.

To solve these problems, a polishing pad having a function of removing grinding strain remaining on the back surface of the wafer and forming a gettering layer by forming a slight scratch on the back surface of the wafer without lowering the bending strength. It is disclosed (Patent Document 1).

JP-A-2015-46550

However, since the polishing pad described in Patent Document 1 is a general non-woven fabric impregnated with a liquid binder containing solid phase reaction fine particles and polishing fine particles and dried, the back surface of the semiconductor wafer is polished with the polishing pad. When this is done, the non-woven fabric fibers are exposed due to the abrasion of the polishing pad, and the fibers that have fallen off on the surface to be polished remain between the chips, wrap around to the device surface side and remain on the device surface after chipping. There was a problem that wiring failure could occur.
The present invention has been made in view of the above problems, and is a polishing pad capable of polishing the back surface of a silicon wafer (thinning process, stress relief) and forming a gettering layer, and is derived from the polishing pad. It is an object of the present invention to provide a polishing pad capable of suppressing the falling off of the fibers and easily removing the falling fibers from the device surface even if the fibers fall off.

As a result of diligent studies on a polishing pad using fibers, the present inventors have found the fiber substrate in a polishing pad containing a resin-containing fiber substrate obtained by impregnating a fiber substrate with resin and silicon carbide. A polishing pad capable of polishing (thinning, stress relief) the back surface of a silicon wafer and forming a gettering layer by using a hot water-soluble fiber as a constituent fiber, and a fiber derived from the polishing pad. The present invention has been completed by finding that a polishing pad capable of suppressing the falling off of the fibers and easily removing the falling fibers from the device surface even when the fibers fall off can be obtained.
That is, the present invention provides the following.
<1> A polishing pad containing a resin-containing fiber substrate obtained by impregnating a fiber substrate with polyurethane resin and silicon carbide.
The resin-containing fiber substrate has a polished surface for polishing the object to be polished, and when the fibers constituting the fiber substrate are charged with 0.3 g of the fibers in 100 mL of water at 40 ° C. The polishing pad, wherein 80% by mass or more of the fibers are hot water-soluble fibers that dissolve in water within 1 hour.
<2> The hot water-soluble fiber is a fiber in which 70% by mass or more of the fiber remains when 0.3 g of the fiber is added to 100 mL of water at 20 ° C. 1 hour after the addition. <1 > The polishing pad described in.
<3> The polishing pad according to <1> or <2>, wherein the hot water-soluble fiber is a polyvinyl alcohol-based fiber.
<4> The polishing pad according to any one of <1> to <3>, wherein the silicon carbide has a particle size in the range of 0.1 to 3.0 μm.
<5> The polishing pad according to any one of <1> to <4>, wherein the fiber substrate is a non-woven fabric.
<6> The polishing pad according to any one of <1> to <5>, which is used for forming a gettering layer.
<7> Step of preparing a polyurethane resin solution containing a polyurethane resin and silicon carbide,
A step of impregnating a fiber substrate with a polyurethane resin solution, and a step of immersing a fiber substrate impregnated with a polyurethane resin solution in a coagulating solution to coagulate the polyurethane resin.
Including
The fibers constituting the fiber substrate are hot water-soluble fibers in which 80% by mass or more of the fibers are dissolved in water within 1 hour from the addition of 0.3 g of the fibers into 100 mL of water at 40 ° C. The method for manufacturing a polishing pad according to any one of <1> to <6>.

According to the present invention, it is a polishing pad capable of polishing the back surface of a silicon wafer (thinning process, stress relief) and forming a gettering layer, and suppresses the falling off of fibers derived from the polishing pad, so that the fibers can be formed. It is possible to provide a polishing pad capable of easily removing the fallen fibers from the device surface even when the fallen fibers are dropped.

FIG. 1 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a frictional wear test with water at 20 ° C. using the polishing pad of Comparative Example 1. The location of the long fibers is indicated by an arrow. FIG. 2 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a frictional wear test with water at 40 ° C. using the polishing pad of Comparative Example 1. The location of the long fibers is indicated by an arrow. FIG. 3 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a frictional wear test with water at 80 ° C. using the polishing pad of Comparative Example 1. The location of the long fibers is indicated by an arrow. FIG. 4 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a frictional wear test with water at 20 ° C. using the polishing pad of Example 1. The location of the long fibers is indicated by an arrow. FIG. 5 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a friction and wear test with warm water at 40 ° C. using the polishing pad of Example 1. FIG. 6 is a photograph of the polished surface (magnification of 100 times) of the polishing pad after a frictional wear test with warm water at 80 ° C. using the polishing pad of Example 1.

<< Polishing pad >>
The polishing pad of the present invention is a polishing pad containing a resin-containing fiber substrate (hereinafter, may be referred to as a polishing layer) formed by impregnating a fiber substrate with polyurethane resin and silicon carbide (SiC), and contains the resin. The fiber substrate has a polished surface for polishing the object to be polished, and when the fibers constituting the fiber substrate are charged with 0.3 g of the fiber in 100 mL of water at 40 ° C., within 1 hour from the charging. It is characterized in that 80% by mass or more of the fibers are hot water-soluble fibers that are soluble in water.
In the present specification and the scope of patent claims, "resin-containing fiber substrate obtained by impregnating a fiber substrate with polyurethane resin and silicon carbide (SiC)" is a fiber substrate obtained by dissolving a mixture of polyurethane resin and silicon carbide in a solvent. Means a resin-containing fiber substrate formed by removing the solvent after impregnating with.
In the present specification and claims, "polyvinyl alcohol-based fiber" (PVA-based fiber) means a fiber produced from a vinyl alcohol-based polymer. The vinyl alcohol-based polymer is polyvinyl alcohol, a substituted polyvinyl alcohol in which the hydrogen atom constituting the hydroxyl group of the polyvinyl alcohol is partially substituted, and a polyvinyl alcohol or a part of the constituent unit (monomer unit) of the substituted polyvinyl alcohol is vinyl alcohol or It is a concept that includes modified polyvinyl alcohol in which a constituent unit other than the substituted vinyl alcohol is replaced.

(Fiber substrate)
The fibers constituting the fiber substrate used in the production of the polishing pad of the present invention are 1 hour after the addition of 0.3 g of the fibers (fibers used in the production of the fiber substrate) in 100 mL of water at 40 ° C. Within 80% by mass of the fiber, it is a hot water-soluble fiber that dissolves in water. When 0.3 g of the fiber is put into 100 mL of water at 40 ° C., it is preferable that 85% by mass or more of the fiber is dissolved in water within 1 hour from the addition, and 88% by mass or more of the hot water-soluble fiber. Is more preferably dissolved in water. When the solubility in water at 40 ° C. is within the above range, when the object to be polished is polished using the polishing pad and slurry or water, the polishing pad is heated to about 40 ° C. to 60 ° C. by frictional heat. The fibers existing on the surface of the polishing pad are dissolved in the slurry or water, and the fibers can be suppressed from falling off to the object to be polished (device). Further, even when the fibers fall off on the object to be polished, the fallen fibers can be easily removed from the surface of the object to be polished by the hot water treatment.
Within the scope of the present specification and claims, the solubility in water at a specific temperature is such that when 0.3 g of the resin to be measured is added to 100 mL of water at the specific temperature and allowed to stand at the temperature for 1 hour. Solubility of the resin.

The hot water-soluble fiber is preferably a fiber in which 70% by mass or more of the fiber remains when 0.3 g of the fiber is put into 100 mL of water at 20 ° C. 1 hour after the addition, and 75% by mass. It is more preferable that the above is the remaining fiber, and even more preferably 80% by mass or more of the remaining fiber. Further, the hot water-soluble fiber is a fiber in which when 0.3 g of the fiber is put into 100 mL of water at 20 ° C., only 30% by mass or less of the fiber is dissolved in water 1 hour after the addition. It is more preferable that the fiber is dissolved in water in an amount of 25% by mass or less, and even more preferably, the fiber is dissolved in water in an amount of 20% by mass or less. When the solubility in water at 20 ° C. is within the above range, the form can be maintained as a fiber substrate in the manufacturing process of the polishing pad, which is preferable.

Examples of the fiber substrate used in the production of the polishing pad of the present invention include non-woven fabrics, woven fabrics, knitting and the like. Among these, a non-woven fabric is preferable from the viewpoint of the flowability of the polishing slurry, the elasticity of the polishing pad, and the maintenance of the polishing surface state.
Examples of the hot water-soluble fiber include polyvinyl alcohol-based fiber (hereinafter, may be referred to as PVA-based fiber).
Further, the polyvinyl alcohol-based fiber is preferably a polyvinyl alcohol-based fiber produced by solvent-wet cooling gel spinning. The solvent wet cooling gel spinning is a spinning method in which the undiluted spinning solution is extruded from a nozzle in a solvent and then rapidly cooled to gelle, and after forming a stable structure, the solvent is removed.
The average degree of polymerization of the vinyl alcohol polymer used for the polyvinyl alcohol fiber is preferably in the range of 100 to 3500, particularly preferably in the range of 300 to 3000, and preferably in the range of 700 to 2500.

The vinyl alcohol-based polymer may be polyvinyl alcohol, or may be a substituted polyvinyl alcohol in which the hydrogen atom constituting the hydroxyl group of the polyvinyl alcohol is partially substituted, and is a constituent unit (monomer unit) of the polyvinyl alcohol or the substituted polyvinyl alcohol. ) May be a modified polyvinyl alcohol in which a part of vinyl alcohol or a constituent unit other than the substituted vinyl alcohol is replaced.
Examples of the substituted vinyl alcohol-based polymer include polyvinyl alcohol in which a part of hydrogen atoms constituting a hydroxyl group is substituted with an acetyl group. The substituted vinyl alcohol-based polymer can be produced, for example, by partially saponifying polyvinyl acetate obtained by polymerizing vinyl acetate.
Polyvinyl alcohol in which a part of the hydrogen atom constituting the hydroxyl group is substituted with an acetyl group (that is, a substituted polyvinyl alcohol composed of a vinyl alcohol unit and a vinyl acetate unit) is a hydroxyl group (-OH) and an acetyl group (that is, a hydroxyl group). The ratio of hydroxyl groups to the total of −OCOCH ₃ ) is preferably 80 mol% or more and less than 96 mol%. That is, the polyvinyl alcohol preferably contains a vinyl acetate unit in an amount of more than 4 mol% and 20 mol% or less.
As an example of the modified vinyl alcohol-based polymer, a vinyl alcohol unit and / or a part of vinyl acetate unit, which is a constituent unit of polyvinyl alcohol in which a part of hydrogen atoms constituting the hydroxyl group is substituted with an acetyl group, is another. Polyvinyl alcohol that has replaced the unit can be mentioned. Other units include ethylene, allyl alcohol, itaconic acid, acrylic acid, maleic anhydride and its ring open, aryl sulfonic acid, vinyl esters of fatty acids with 4 or more carbon atoms such as vinyl pivalate, vinylpyrrolidone, and Examples thereof include compounds in which a part or all of the ionic groups are neutralized. The other units are preferably contained in the modified polyvinyl alcohol in a proportion of 0.5 to 20 mol%.
Specific examples of the polyvinyl alcohol-based fiber of the present invention include Kuraray K-II (trade name) manufactured by Kuraray Co., Ltd. and Solbron manufactured by Nichibi Co., Ltd.
The thickness of the fiber substrate is not particularly limited, but is preferably in the range of 1.5 to 5.0 mm. When the thickness of the fiber substrate is within the above range, the resin does not easily move (resin migration) in the thickness direction of the non-woven fabric substrate during drying after impregnation with the resin solution, and the coating thickness of the resin is not biased. In addition, the resin solution can be sufficiently permeated into the inside of the non-woven fabric base material. The density is preferably in the range of 0.05 to 0.3 g / cm ^3, and more preferably in the range of 0.1 to 0.2 g / cm ^3. When the density is within the above range, the resin solution is less likely to flow out through the voids between the raw material fibers when impregnated with the resin solution, and the resin solution is more likely to adhere to the raw material fibers. Further, since the voids between the fibers are not closed more than necessary, the polishing characteristics are less likely to be adversely affected.

(Polyurethane resin)
The type of polyurethane resin used as the material for the polishing pad of the present invention is not particularly limited, and can be selected from various polyurethane resins according to the purpose of use. For example, one or more polyester-based, polyether-based, or polycarbonate-based resins can be used.
Examples of the polyester-based resin include a polymer of a polyester polyol containing ethylene glycol, butylene glycol or the like and adipic acid or the like, and a diisocyanate such as diphenylmethane-4,4'-diisocyanate. Examples of the polyether resin include a polymer of a polyether polyol such as polytetramethylene ether glycol and polypropylene glycol and an isocyanate such as diphenylmethane-4,4'-diisocyanate. Examples of the polycarbonate-based resin include a polymer of a polycarbonate polyol and an isocyanate such as diphenylmethane-4,4'-diisocyanate. These resins are available on the market, such as the product name "Chrisbon" manufactured by DIC Corporation, the product name "Samplen" manufactured by Sanyo Kasei Kogyo Co., Ltd., and the product name "Resamine" manufactured by Dainichi Seika Kogyo Co., Ltd. An available resin may be used, or a resin having desired properties may be produced by itself.
Among these, a polyether polyurethane resin having high chemical stability is particularly preferable.

(Resin modulus)
The polyurethane resin preferably has a resin modulus of 20 to 60 MPa, more preferably 40 to 50 MPa. When the resin modulus is within the above range, the holding property of silicon carbide is excellent, and the polishing characteristics are stabilized by the self-disintegrating property of the resin.
Resin modulus is an index showing the hardness of resin, and is the value obtained by dividing the load applied when a non-foamed resin sheet is stretched 100% (when stretched to twice the original length) by the cross-sectional area. There is (hereinafter, sometimes referred to as 100% modulus). The higher this value is, the harder the resin is.

(Silicon Carbide (SiC))
The polishing pad of the present invention includes silicon carbide.
The silicon carbide used in the polishing pad of the present invention preferably has a particle size in the range of 0.1 to 3.0 μm. The particle size of the silicon carbide is more preferably 0.15 to 1.5 μm, and even more preferably 0.2 to 1.0 μm.
When the particle size of the silicon carbide is within the above range, damage to the wafer can be removed. In addition, defects in the silicon crystal lattice can be formed, and a gettering layer having sufficient gettering performance can be formed.
In the present specification and claims, the "particle size" of silicon carbide means the median diameter.

(Mixing ratio)
In the polishing pad of the present invention, it is preferable that silicon carbide is contained in the resin-containing fiber substrate in the range of 50 to 500 parts by mass with respect to 100 parts by mass of the fiber substrate. The silicon carbide is more preferably contained in the range of 80 to 400 parts by mass, further preferably in the range of 100 to 300 parts by mass, and 150 to 250 parts by mass with respect to 100 parts by mass of the fiber substrate. It is particularly preferable that it is contained within the range of parts.
When the mass ratio of silicon carbide is within the above range, damage to the wafer can be removed. In addition, defects in the silicon crystal lattice can be formed, and a gettering layer having sufficient gettering performance can be formed.
In the polishing pad of the present invention, the polyurethane resin is preferably contained in the resin-containing fiber substrate in the range of 10 to 500 parts by mass with respect to 100 parts by mass of the fiber substrate, and is in the range of 30 to 300 parts by mass. It is more preferable that it is contained in, and it is even more preferable that it is contained in the range of 50 to 200 parts by mass.
When the mass ratio of the polyurethane resin is within the above range, while the resin holds the silicon carbide, gaps between the fibers are formed by the random structure derived from the fibers inside the polishing pad, and the polyurethane resin from the inside of the polishing pad passes through the gaps. In addition to being expected to supply SiC abrasive grains adhering to the resin, grip force in the horizontal direction, high rate due to low compression and high elasticity in the vertical direction, and low scratch performance can be obtained.

(Other ingredients)
The resin-containing fiber substrate in the polishing pad of the present invention may contain components other than the above components as long as the effects of the present invention are not impaired. Other ingredients include higher alcohols, polyether derivatives, fatty acids, fatty acid salts, cellulose derivatives, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, paraffins, organic silicones, etc. Examples include carbon, organic pigments, inorganic pigments, antioxidants and the like. The other components are preferably contained in the fiber substrate at a ratio of 20 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the fiber substrate. The lower limit value is not particularly limited, and may be 0 parts by mass, 0.1 parts by mass, or 1 part by mass.

(Other layers)
In the polishing pad of the present invention, another layer (lower layer, support layer) may be attached to the surface of the resin-containing fiber substrate opposite to the surface (polished surface) on which the object to be polished is to be polished. The types of other layers are not particularly limited, and for example, a cushion layer can be attached.
In the present specification and claims, the cushion layer means a layer having the same or lower A hardness than the polished layer. By providing the cushion layer, the influence of the hardness and flatness of the surface plate can be alleviated, and uneven contact between the work and the polished surface can be prevented. Therefore, the service life of the polishing pad can be extended and chipping (chipping of the peripheral portion of the work) can be prevented.
As the material of the cushion layer, a resin-impregnated non-woven fabric, synthetic rubber, polyethylene foam, polyurethane foam and the like can be used.
The thickness of the cushion layer is not particularly limited, but is preferably 0.1 to 10 mm, more preferably about 0.5 to 3 mm without being subject to mechanical restrictions of the polishing mechanism, and a polishing surface plate. The effect of can be reduced sufficiently.

When the polishing pad forms a multi-layer structure, the plurality of layers may be bonded and fixed to each other by using double-sided tape or an adhesive while applying pressure as necessary. The double-sided tape and adhesive used at this time are not particularly limited, and can be arbitrarily selected and used from the double-sided tapes and adhesives known in the art.

<Physical characteristics of polishing pad>
(density)
The polishing pad of the present invention preferably has a density of resin-containing fibers impregnated with polyurethane resin and silicon carbide in the range of 0.25 to 1.00 g / cm ³ , and is preferably 0.30 to 0.65 g / cm. More preferably, it is in the range of cm ³ . When the density of the resin-containing fiber is within the above range, suitable abrasive physical properties are obtained, pad wear is suppressed in the polishing process, and good polishing characteristics are maintained.

(A hardness)
In the present specification and claims, A hardness means a value measured according to JIS K7311.
In the polishing pad of the present invention, the A hardness of the resin-containing fiber is preferably 50 to 85 degrees, more preferably 60 to 80 degrees. When the A hardness is within the above range, it is moderately hard, so that gettering sites after stress relief can be easily formed, and uneven polishing and chipping can be reduced.

(Thickness)
The thickness of the resin-containing fiber substrate in the polishing pad of the present invention is not particularly limited, and can be, for example, about 0.5 to 10.0 mm.

(Use)
The polishing pad of the present invention can be suitably used as a polishing pad for wet polishing an object (object to be polished). In the present specification and claims, wet polishing is a polishing method in which an object (object to be polished) is polished with a polishing pad via a slurry, water, or the like, and is polished without using a slurry, water, or the like. It is clearly distinguished from dry polishing, in which the pad is brought into direct contact with the object (object to be polished) for polishing.
The polishing pad of the present invention refers to a back surface of a silicon semiconductor wafer or a compound semiconductor wafer such as SiC, GaAs, GaN, or sapphire (here, the back surface is a surface opposite to the surface of the wafer on which a semiconductor element is formed). (Meaning)) can be particularly preferably used as a polishing pad for forming a gettering layer by wet polishing.

The silicon carbide used in the present invention has very poor handleability (that is, it has problems such as high mechanical polishing property, poor dispersibility, high settling speed, and difficult waste liquid treatment). Therefore, for example, when a slurry containing silicon carbide as abrasive grains is dropped on a conventional polishing pad to form gettering on the back surface of a semiconductor wafer, it is necessary to increase the mechanical load to improve the dispersibility of the silicon carbide. However, when the mechanical load is increased, silicon carbide polishes the mechanical surface of the pipe or the like before the slurry is carried to the surface of the polishing pad through the pipe or the like, resulting in contamination due to device wear. In addition, since the settling speed of silicon carbide is high, there is also a problem that handling itself is difficult.
A similar problem occurs when silicon carbide is internally added to a polyurethane foam type polishing pad. That is, in the foamed polyurethane type polishing pad, since the silicon carbide must be mixed with the high-viscosity resin, the dispersibility of the silicon carbide is further deteriorated. Therefore, the mechanical load is increased in order to improve the dispersibility, and the mechanical wear due to the silicon carbide is likely to occur. As a result, contamination occurs in the polishing pad, which adversely affects polishing and gettering formation.

On the other hand, in the polishing pad of the present invention, since the silicon carbide is contained in the fiber substrate, there is no problem when the silicon carbide is used in the slurry. That is, in the polishing pad of the present invention, since silicon carbide is dispersed in the resin solution and the fiber substrate is impregnated with the resin solution, the polishing pad can be uniformly dispersed without increasing the mechanical load. As a result, there is less contamination due to equipment wear. There is no need to consider the settling rate of silicon carbide. Furthermore, since it is self-disintegrating, the polished surface can be regenerated by conditioning with a dresser, and the effect of the present invention can be maintained for a long period of time.
Further, in the polishing pad of the present invention, when 0.3 g of the fiber constituting the fiber substrate is put into 100 mL of water at 40 ° C., 80% by mass or more of the fiber is water within 1 hour from the addition. In order to dissolve the fibers, it is possible to prevent the fibers from falling off during polishing (thinning process, stress relief) of the back surface of the silicon wafer and formation of the gettering layer, and even if the fibers fall off, the fallen fibers are dissolved by warm water treatment. As a result, the fallen fibers can be easily removed from the device surface.

The polishing pad of the present invention can preferably be produced by the following method.

<< Manufacturing method of polishing pad >>
The method for producing a polishing pad of the present invention includes a step of preparing a polyurethane resin solution containing a polyurethane resin and a silicon carbide, a step of impregnating a fiber substrate with the polyurethane resin solution, and a step of impregnating the fiber substrate with the polyurethane resin solution into a coagulating liquid. The fiber constituting the fiber substrate includes a step of immersing and solidifying the polyurethane resin, and when 0.3 g of the fiber is put into 100 mL of water at 40 ° C., 80 of the fiber is added within 1 hour from the addition. It is characterized in that it is a hot water-soluble fiber in which mass% or more is soluble in water. Hereinafter, each step will be described.

<Preparation process of resin solution>
In this preparation step, a polyurethane resin solution containing a polyurethane resin and silicon carbide is prepared. As the raw material resin, the resin described in the above << polishing pad >> can be used. Examples of the solvent for dissolving the resin include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone, acetonitrile, and N-methylpyrrolidone (DMSO). NMP) and the like and mixtures thereof. Among these, DMF is preferable.
Silicon carbide may be added to the solvent before the resin is dissolved in the solvent, or may be added after the resin is dissolved in the solvent. By doing so, the silicon carbide can be uniformly dispersed in the resin solution without agglutination.
The amount of the polyurethane resin added to the solvent is preferably 10 to 100 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the solvent.
The amount of silicon carbide added to the solvent is preferably 10 to 100 parts by mass, more preferably 20 to 70 parts by mass with respect to 100 parts by mass of the solvent.

<Preparation process of fiber substrate>
As the fiber substrate in the present invention, those described in the section of "polishing pad" can be used.
The method for producing the fiber substrate is not particularly limited, and a conventionally known method is used. Specifically, it is manufactured by the needle punch method, embossing method, foam bond method, heating method (embossing, hot air, mold molding) in which heat-sealed fibers are mixed, binder bonding method, water flow entanglement method, melt blown method and spunbond method. Examples thereof include bonding with a non-woven fabric and a combination thereof. It may be appropriately selected from these according to the desired quality of the non-woven fabric. Among these, in the present invention, it is preferable to produce a fiber substrate by using a needle punching method. When the fiber substrate is manufactured by the needle punch method, the non-woven fabric also functions as a cushion layer, so that a thick non-woven fabric can be easily obtained. 100~5000g / m ² as a weight per unit area of the nonwoven fabric is preferably 0.05~0.60g / cm ³ as the density, and more preferably 0.10~0.50g / cm ^3. Further, 0.01 to 10 dtex can be used as the fineness of the fiber used for the non-woven fabric. When the density is the same, the void unit can be adjusted by changing the number of fibers per unit volume by changing the fineness of the fibers. The voids of the non-woven fabric can be adjusted by the basis weight, density and fineness of the fibers, and the porosity is preferably about 45 to 95%.
The fiber substrate used in the present invention is preferably a non-woven fabric, woven fabric, or knitted fabric made from PVA-based fibers, and preferably a non-woven fabric made from PVA-based fibers. The PVA-based fiber is, for example, a fiber obtained by wet-spinning or dry-wet-spinning a vinyl alcohol-based polymer using a stock solution solvent and an organic solvent as a solidifying solvent, wet drawing, extraction treatment, and further drying treatment. It can be obtained by performing a dry heat shrinkage treatment under a multi-stage temperature rise condition.

<Immersion process>
Next, a fiber substrate is prepared, and the fiber substrate is immersed in a polyurethane resin solution. The temperature and time are not particularly limited as long as the polyurethane resin solution is sufficiently impregnated into the fiber substrate and the fibers constituting the fiber substrate are not eluted. For example, 1 to 30 ° C. (preferably about 5 to 25 ° C.) It may be immersed for about 30 minutes (preferably about 1 to 15 minutes, more preferably about 1 to 5 minutes).

<Coagulation process>
Next, the polyurethane resin is solidified by a wet solidification method.
The wet coagulation method is a method of coagulating and regenerating a resin by impregnating a fiber substrate such as a non-woven fabric with a resin solution and immersing the impregnated fiber substrate in an aqueous coagulation solution containing water as a main component, which is a poor solvent for the resin. It is a method to be done by letting. In the coagulation liquid, the resin is coagulated and regenerated on the surface of the fibers as the replacement of the solvent (for example, DMF) of the resin solution with the coagulation liquid progresses on the surface of the resin solution adhering to the fibers of the non-woven fabric.
As the coagulating liquid, water, a mixed solution of water and a polar solvent such as DMF, or the like is used. Examples of the polar solvent include water-miscible organic solvents such as DMF, DMAc, THF, DMSO, NMP, acetone, IPA (isopropyl alcohol), ethanol and methanol. The concentration of the polar solvent in the mixed solvent is preferably 0.5 to 60% by mass.
As long as the fibers constituting the fiber substrate are not eluted, the temperature of the coagulating liquid and the immersion time are not particularly limited, and are, for example, 10 to 30 ° C. (preferably 10 to 20 ° C.) for 30 to 1440 minutes (preferably 30 to 90 minutes). ) It may be immersed.

The polishing pad obtained by the manufacturing method of the present invention has a cushioning property because the fiber substrate is impregnated with a resin and wet-solidified, and the semiconductor wafer can be prevented from being damaged during polishing.

<Washing and drying process>
The fiber substrate obtained by coagulating by the coagulation bath treatment is washed and dried.
The cleaning treatment removes the solvent remaining in the polyurethane resin solution. Examples of the cleaning liquid used for cleaning include water.
After cleaning, the polyurethane resin is dried. The drying treatment may be carried out by a conventional method, for example, drying at 60 to 120 ° C. for about 10 to 500 minutes in a dryer. A resin-containing fiber (polishing layer) can be obtained through the above steps.
Further, after the drying, one side or both sides of the resin-containing fiber may be buffed or sliced.

<< Polishing the back surface of semiconductor wafers and forming gettering layers >>
In the polishing of the back surface of the semiconductor wafer and the formation of the gettering layer by the polishing pad of the present invention, for example, the polishing pad and the semiconductor wafer of the present invention are used in the polishing apparatus, and the surface (back surface) opposite to the device forming surface of the semiconductor wafer and the polishing pad The processing strain on the back surface of the wafer is polished by chemically polishing the semiconductor wafer while pressing the semiconductor wafer against the polishing pad while dropping an alkaline slurry that does not contain abrasive grains on the polishing pad. Then, pure water is dropped onto the polishing pad and mechanically polished to give a scratch as a gettering site. Thereby, the back surface polishing and the gettering layer formation of the semiconductor wafer can be continuously performed by using one kind of polishing pad.

<Solubility test>
The polyvinyl alcohol (PVA) -based fibers (Kuraray K-II WN4 manufactured by Kuraray Co., Ltd.) and polyester fibers used in Example 1 and Comparative Example 1 according to the following test method with respect to water at 20 ° C., 40 ° C. and 80 ° C. Solubility was measured. The results are shown in Table 1.
(Test method)
0.3 g of the PVA-based fiber of Example 1 and the polyester fiber of Comparative Example 1 were put into 100 ml of water at the following temperature, allowed to stand at the temperature for 1 hour, and then filtered paper (Advantech Co., Ltd .; qualitative filter paper No. 1). ) Was used for filtration. The residue after filtration was dried in a constant temperature bath at 80 ° C. for 2 hours, and the mass of the fibers remaining undissolved was measured to determine the proportion of the dissolved fibers.

The polishing pads of Example 1 and Comparative Example 1 were manufactured by the following steps.
(Example 1)
(1) Non-woven fabric made of polyvinyl alcohol (PVA) -based fiber (Kuraray K-II WN4 manufactured by Kuraray Co., Ltd.) obtained by spinning a partially saponified PVA having a degree of polymerization of 1700 and a degree of saponification of 95 mol% in an organic solvent-based low-temperature gel. Fineness: 2d, fiber length: 51 mm) (density: 0.125 g / cm ³ ) was prepared.
(2) An abrasive grain-containing polyurethane resin solution was prepared by adding SiC having a particle size of 0.6 μm as abrasive grains to a solution in which a thermoplastic polyether polyurethane resin (100% modulus: 47 MPa) was dissolved in DMF.
(3) The non-woven fabric of (1) was impregnated with the abrasive grain-containing polyurethane resin solution of (2) at 25 ° C. for 3 minutes. Then, using water as a coagulating liquid, wet coagulation was performed at 18 ° C. for 60 minutes, and then washing and drying were performed to obtain a polishing layer. A double-sided tape was attached to one side of the obtained polishing layer to obtain a polishing pad of Example 1. The mass ratios of DMF, polyurethane resin, and SiC in the resin solution used in Example 1 are shown in Table 2.

(Comparative Example 1)
The same as in Example 1 except that a non-woven fabric made of polyester fiber (fineness: 3d, fiber length: 51 mm) (density: 0.125 g / cm ³ ) was used as the non-woven fabric instead of the polyvinyl alcohol (PVA) -based fiber. Manufactured a polishing pad. The mass ratios of DMF, polyurethane resin, and SiC in the resin solution used in Comparative Example 1 are shown in Table 2.

<< Physical characteristics >>
The density, A hardness, and thickness of the polishing pads of Example 1 and Comparative Example 1 were measured. The measuring method is as follows.

(Density g / cm ³ )
It was calculated by measuring the weight (g) of the material cut out to the size of a predetermined size and obtaining the volume (cm ³ ) from the size. The results are shown in Table 3.

(Shore A hardness)
Shore A hardness was measured according to JIS K7311. The results are shown in Table 3.

(thickness)
The thickness of the polishing pad was measured according to the thickness measuring method described in Japanese Industrial Standards (JIS K6505). That is, the thickness of the polishing pad when a load of 480 g / cm ² was applied to the polishing pad as the initial load in the thickness direction was measured. The polishing pad was cut into 3 pieces of 10 cm in length and 10 cm in width, and the thicknesses of the four corners and the center of each piece were measured using a dial gauge, and the average value of 5 points was taken as the thickness of 1 piece. The average thickness of the polishing pad was the average value of the thickness measured for each of the three pieces. The results are shown in Table 3.

<< Evaluation 1 >>
Using the polishing pads of Example 1 and Comparative Example 1, a friction and wear test was performed by the following method to evaluate the presence or absence of long fibers present on the surface of the polishing pads. The results are shown in Table 4 and FIGS. 1 to 6. The arrows in FIGS. 1 to 4 indicate long fibers.
In the frictional wear test, a rotary wear tester is used to fix the sample to an indenter, hold it, place it on a rotating disk with abrasive paper fixed, and apply warm water while applying a constant load under wet polishing conditions. The turntable was rotated for a certain period of time. The test conditions are shown below.
(Friction and wear test conditions)
Friction wear tester: Imoto Seisakusho Co., Ltd., IMC-154D type polishing speed (rotation speed): 30 rpm
Load: 191 gf / cm ²
Abrasive paper; # 180 Sandpaper Water volume: 30 ml / min
Water temperature: 20 ° C, 40 ° C or 80 ° C
Test time: 4 minutes.

<< Evaluation 2 >>
Using the polishing pads of Example 1 and Comparative Example 1, polishing was performed by the following polishing method, and the scratch density, defect scratches, and the presence or absence of fallen fibers were evaluated.

(Polishing method)
A silicon wafer and a polishing pad were set in a polishing device (manufactured by Fujikoshi Kikai Kogyo Co., Ltd .: MCP-150X), and the silicon wafer was polished while dropping an abrasive onto the polishing pad.
As the polishing agent, an alkaline solution (pH 9) containing no abrasive grains was used, and 200 ml was added dropwise to the polishing pad per minute. The rotation speed of the surface plate was 80 rpm. The pressure at which the silicon wafer was pressed against the polishing pad by the pressure head was set to 300 g / cm ² . A silicon wafer of 6 inches (152.4 mm in diameter) was used, and the polishing time was 10 minutes.
Next, the pad surface was lightly dressed with a # 200 diamond dresser, and pure water was used to drop the pad surface onto a 200 ml polishing pad per minute. The gettering layer was formed by treating under the same conditions as above.
In this embodiment, polishing with pure water was performed in order to provide a more uniform gettering layer, but polishing with pure water may be omitted depending on the required degree of the gettering layer. ..

(Presence of scratch density, defect scratches and fallen fibers)
The surface of the polished silicon wafer was visually checked with an optical microscope (dark field microscope magnification 200 times) for the optimum scratch density and defect scratches for the gettering layer, and for the presence of fallen fibers. Visual judgment was made according to the criteria of. The results are shown in Table 6.
A wafer to which a gettering layer is provided usually looks like a mirror surface, but scratches can be confirmed by irradiating the wafer with light, but defective scratches can be confirmed without irradiating light. Therefore, a scratch in the scratch density means a scratch that can be confirmed by shining light, and a defect scratch means a scratch that can be confirmed without shining light.

As is clear from Table 6, fibers derived from the polishing pad were attached to the wafer polished by the polishing pad of Comparative Example 1. On the other hand, no fiber adhesion was confirmed on the wafer polished by the polishing pad of Example 1. In addition, a scratch density suitable for the gettering layer was observed, and no defect scratches were present.

According to the present invention, it is possible to provide a polishing pad capable of polishing the back surface of a silicon wafer and forming a gettering layer without adhering fibers derived from the polishing pad to the silicon wafer. Therefore, it is extremely useful industrially.

Claims (6)

A polishing pad containing a resin-containing fiber substrate obtained by impregnating a fiber substrate with polyurethane resin and silicon carbide.
The resin-containing fiber substrate has a polished surface for polishing an object to be polished, and when the fibers constituting the fiber substrate are charged with 0.3 g of the fibers in 100 mL of water at 40 ° C. When 80% by mass or more of the fiber is dissolved in water within 1 hour and 0.3 g of the fiber is added to 100 mL of water at 20 ° C., 70% by mass or more of the fiber is added 1 hour after the addition. Is the remaining fiber, the polishing pad. The polishing pad according to claim 1, wherein the fibers constituting the fiber substrate are polyvinyl alcohol-based fibers. The polishing pad according to claim 1 or 2, wherein the silicon carbide has a particle size in the range of 0.1 to 3.0 μm. The polishing pad according to any one of claims 1 to 3, wherein the fiber substrate is a non-woven fabric. The polishing pad according to any one of claims 1 to 4, which is used for forming a gettering layer. Step of preparing polyurethane resin solution containing polyurethane resin and silicon carbide,
A step of impregnating a fiber substrate with a polyurethane resin solution, and a step of immersing a fiber substrate impregnated with a polyurethane resin solution in a coagulating solution at 10 to 30 ° C. to coagulate the polyurethane resin.
Including
When the coagulating solution is water or a mixed solution of water and a polar solvent, and the fibers constituting the fiber substrate are charged with 0.3 g of the fibers in 100 mL of water at 40 ° C. The method for producing a polishing pad according to any one of claims 1 to 5, wherein 80% by mass or more of the fibers are hot water-soluble fibers that dissolve in water within 1 hour.