JP2006255828A - Polishing cloth and manufacturing method for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the productivity of a wafer by reducing a time required for dummy polishing. <P>SOLUTION: An urethane resin solution containing polyvinyl halogenide such as a polyvinyl chloride or a vinyl halogenide copolymer such as a vinyl chloride copolymer is coated on a base material formed by impregnating a non-woven fabric with urethan resin (S9), wet-solidified (S19), washed (S11), and then heat-treated at a temperature higher than the glass transition point of a polyvinyl halogenide or a vinyl halogenide copolymer (S12). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing cloth suitable for finish polishing of a semiconductor wafer such as a silicon wafer, a glass substrate, and a color filter, and a method for manufacturing the same.

  In general, a semiconductor wafer manufacturing process includes a slicing process for slicing a single crystal ingot to obtain a thin disk-shaped wafer, a chamfering process for chamfering the outer periphery of the wafer, a lapping process for planarizing the wafer, It includes an etching process for removing the remaining processing distortion, a mirror polishing process for polishing the wafer surface into a mirror surface, and a cleaning process for cleaning the polished wafer.

  The above mirror polishing step of the wafer basically includes rough polishing mainly for adjusting the flatness and finish polishing mainly for improving the surface roughness.

  This finish polishing is performed using a suede-like polishing cloth or the like while supplying an abrasive in which colloidal silica or the like is dispersed in an alkaline solution (see, for example, Patent Document 1).

For example, a suede-like polishing cloth is coated with a urethane resin solution in which a urethane resin is dissolved in a water-soluble organic solvent such as dimethylformamide (DMF) on a base material in which a nonwoven fabric is impregnated with a urethane resin, and this is solidified. It is obtained by treating with a liquid and wet coagulating to form a porous silver surface layer, washing and drying, and then grinding the surface of the silver surface layer to form a nap layer (surface layer) having a micropore structure. Is.
JP 2003-37089 A

  In such a suede-like polishing cloth, in order to obtain a high-precision object to be polished, for example, a silicon wafer, a dummy wafer or the like is polished in an initial stage of use in which the polishing cloth is attached to a polishing apparatus and the apparatus is started up. It is necessary to perform dummy polishing as a start-up process for making the polishing cloth itself conform to the silicon wafer, and after this dummy polishing, the process shifts to polishing of the original product silicon wafer (main polishing).

  The dummy polishing described above is completed when Haze, which is one of the qualities required in the final polishing of the wafer, is below a certain value and the entire surface of the wafer is in a “wet” state. be able to.

  Here, Haze has extremely fine irregularities with a PV (Peak to Valley) value of 10 nm or less and a period of several to several tens of nm.

  The “wet” state is a state in which the wafer surface is hydrophilic, and a hydrophilic film is formed on the wafer surface by a polishing liquid or the like.

  If a hydrophilic film is not formed on the wafer surface in this way, residual particles adhere to the highly active silicon wafer surface between the time when finish polishing is finished and the next cleaning process is started. This is because surface roughness is caused and the above-mentioned Haze and LPD (Light Point Defect: minute defects around 0.1 μm, particles, etc. on the wafer) are deteriorated.

  As described above, the time until the Haze is below a certain value and the entire surface of the wafer is in a “wet” state, that is, the time required for the dummy polishing is generally required to be several hours. There is a problem that productivity is reduced accordingly.

  Therefore, the present applicant has already disclosed, as Japanese Patent Application No. 2003-129136 “Polishing Polishing Fabric” (Japanese Patent Laid-Open No. 2004-335713), a surface layer (nap) formed on the base material portion. A polishing cloth in which a polyhalogenated vinyl chloride or a vinyl halide copolymer such as vinyl chloride is contained in the surface layer mainly composed of a urethane resin is proposed. .

  According to the polishing cloth for finish polishing that has been proposed earlier, the time required for dummy polishing can be increased by adding polyvinyl halide or vinyl halide copolymer to the resin component constituting the surface layer. It can be shortened.

  The reason can be considered as follows. That is, by containing polyvinyl halide or a vinyl halide copolymer, at least one of the coefficient of friction and water absorption of the surface layer can be adjusted, and thereby the surface layer and the object to be polished in dummy polishing can be adjusted. It is considered that the reduction of Haze and the hydrophilicity (wetting) of the wafer surface can be promoted by the contribution of at least one of dynamic friction with the wafer, which is an object, and the hydroplane phenomenon.

  An object of the present invention is to improve the polishing characteristics of the polishing cloth and further reduce the time required for break-in polishing.

  As a result of investigations by the present inventors, it has been found that, by performing heat treatment, the physical properties of the surface layer are changed so as to enhance the polishing characteristics, and the present invention has been conceived.

  That is, in the method for producing a polishing cloth of the present invention, a resin solution containing a polyvinyl halide or a vinyl halide copolymer is applied to a base material and wet-coagulated, followed by heat treatment.

  Here, the base material is preferably a non-woven fabric impregnated with a resin solution such as a urethane resin solution and wet coagulated, but may be a base material such as PET (polyethylene terephthalate).

  The halogen is preferably vinyl chloride, and the resin solution containing a polyhalogenated vinyl or vinyl halide copolymer is preferably a urethane resin solution. In particular, when the base material is impregnated with urethane resin, the base side urethane resin and the applied side urethane resin are integrated and firmly bonded.

  In order to obtain stable characteristics, the heat treatment is preferably performed at a temperature equal to or higher than the glass transition point of the polyvinyl halide, and more preferably below the temperature at which the polyvinyl halide melts.

  According to the present invention, the production of an abrasive cloth in which a polyvinyl halide or a vinyl halide copolymer is contained in a resin component constituting a nap layer (surface layer) formed by wet coagulation on a base material layer. By performing the heat treatment, the characteristics of the polishing pad can be stabilized and the time required for dummy polishing can be shortened.

  The reason why the time required for dummy polishing can be shortened by performing the heat treatment in this way can be considered as follows, for example. That is, polyvinyl halide such as polyvinyl chloride is a so-called crystalline polymer, and its properties such as elasticity can be changed by heat treatment, especially at a temperature higher than the glass transition point, which is in the middle of the property change. By performing the heat treatment, it is considered that characteristics such as elasticity are stabilized and the time required for dummy polishing can be shortened.

  Further, the polishing cloth of the present invention is a polishing cloth comprising a base material layer and a nap layer formed on the base material layer, and the nap layer includes a polyvinyl halide or a vinyl halide copolymer. The stress is generated so as to warp toward the nap layer side.

  Here, the stress is generated so as to warp toward the nap layer side. The external force for flattening the entire polishing cloth, and in the natural state where no load is applied, the polishing cloth warps toward the nap layer side. That means.

  This stress is preferably generated by heat treatment.

  By applying a load to the polishing cloth so as to cancel this stress, the warp toward the nap layer side is eliminated and the whole becomes flat.

The load ^is preferably from ^{0.02g / mm 2 ~0.08g / mm 2} , more ^preferably from ^{0.03g / mm 2 ~0.07g / mm 2} , more preferably, 0.04 g / Mm ^{2 to} 0.06 g / mm ² .

^Load, not in the range of 0.02g / mm ² ~0.08g / mm 2, the heat treatment characteristic change in nap layer is insufficient or excessive due, to sufficiently reduce the time required for the dummy polishing Can not.

  According to the present invention, since the polyvinyl halide or vinyl halide copolymer is contained in the resin component constituting the nap layer (surface layer), the time required for dummy polishing can be improved by stabilizing the characteristics of the polishing cloth. It can be shortened.

  According to the present invention, a resin solution containing a polyvinyl halide or a vinyl halide copolymer is applied to a substrate, and after heat solidification, the time required for dummy polishing is compared with the conventional method. It can be shortened, and thereby the productivity of wafers and the like can be increased.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of an abrasive cloth according to an embodiment of the present invention.

  In the polishing cloth of this embodiment, a resin solution containing polyvinyl halide or a vinyl halide copolymer is applied to the layer of the substrate 1, and this is wet-coagulated to form a nap layer having a micropore structure (surface Layer) 2, the surface of the nap layer 2 is ground and the pores are opened. By the heat treatment, the nap layer 2 contracts more than the layer of the base material 1, and the entire polishing cloth 3 is flattened. In this state, the tensile stress f is generated in the surface layer 2.

  As the base material 1, for example, a non-woven fabric such as polyamide or polyester is impregnated with a urethane resin, and an olefin film sheet or polyester film sheet can be used.

  The nap layer 2 contains a polyvinyl halide or a vinyl halide copolymer.

  The resin solution for forming the nap layer 2 is obtained by, for example, dissolving a urethane resin in a water-soluble organic solvent such as dimethylformamide (DMF). As the urethane resin, polyester resins, polyether resins, polycarbonate resins and the like can be used, and different types of urethane resins may be blended.

  As the water-soluble organic solvent for dissolving the urethane resin, for example, a solvent such as dimethyl sulfoxide, tetrahydrofuran, dimethylacetamide or the like can be used in addition to the above-mentioned dimethylformamide.

  Further, a filler such as carbon black and a dispersion stabilizer such as a surfactant may be added to the organic solvent in which the urethane resin is dissolved. The filler such as carbon black is preferably blended in an amount of 5 to 30% by weight with respect to the urethane resin (solid content) to be dissolved in the water-soluble organic solvent.

  The polyvinyl halide contained in the resin solution is preferably polyvinyl chloride, but may be polyvinyl fluoride or polyvinyl bromide. The vinyl halide copolymer is preferably a vinyl chloride copolymer, for example, a vinyl chloride vinyl acetate copolymer, but other copolymers may be used.

  The content of the polyvinyl halide or vinyl halide copolymer is not particularly specified, but is 5 to 5 with respect to the urethane resin (solid content) to be dissolved in a water-soluble organic solvent such as dimethylformamide (DMF) described above. 30% by weight, preferably 10 to 25% by weight, and more preferably 12 to 22% by weight.

  The heat treatment is preferably performed at a temperature equal to or higher than the glass transition point of the polyvinyl halide, specifically, in the case of polyvinyl chloride, a temperature equal to or higher than about 70 to 80 ° C., which is the glass transition point.

  Polyhalogenated vinyl chloride such as polyvinyl chloride is a so-called crystalline polymer, and its physical properties such as strength, brittleness, elasticity, and coefficient of thermal expansion can be changed by heat treatment. As shown by the dependency, the vicinity of the glass transition point Tg is in a state where the physical properties are changing, and therefore stable physical properties can be obtained by heat treatment at a temperature higher than the glass transition point Tg.

  Further, this heat treatment is preferably performed at a temperature Tm or lower at which the polyvinyl halide melts. In this embodiment, the heat treatment is performed at a temperature lower than the melting point (around 120 ° C.) of polyvinyl chloride.

  The heat treatment time is appropriately selected depending on the thickness of the polishing pad 3, the content of polyvinyl halide, the temperature of the heat treatment, and the like.

  Next, the manufacturing method of the polishing cloth having the above configuration will be described with reference to the manufacturing process diagram of FIG. In manufacturing the polishing cloth of the present embodiment, first, a urethane resin solution is impregnated with a non-woven fabric such as polyester (S1), the urethane resin is wet coagulated (S2), and after washing to remove the solvent (S3). Then, the substrate 1 is dried with hot air (S4), and then ground (buffed) to obtain the substrate 1 (S5).

  On the other hand, urethane resin, polyvinyl chloride as polyvinyl halide, and surfactant are dissolved in a solvent such as dimethylformamide (DMF) and mixed (S6), defoamed (S7), and filtered. Then, a urethane resin solution containing polyvinyl chloride is prepared (S8).

  This urethane resin solution is applied to the base material 1 (S9), wet coagulated (S10), washed to remove the solvent (S11), and then heat-treated by, for example, a hot air dryer (S12).

  This heat treatment is preferably performed as a drying step after washing, and the temperature is preferably not lower than the glass transition point of the polyvinyl halide and not higher than the melting point Tm of the polyvinyl halide. Heat treatment is performed at 120 ° C.

  This heat treatment time is selected in consideration of the heat treatment method, productivity, polishing characteristics, and the like. For example, the heat treatment time in the case of a continuous system in which heat treatment is performed by passing between cylindrical dryers is several minutes to several hours, Preferably, it is 5 minutes to 1 hour, and the heat treatment time in the case of a batch system using a dryer or the like is 30 minutes to 24 hours, preferably 1 hour to 6 hours.

  After this heat treatment, the surface of the nap layer 2 is ground (buffed) to open the teardrop-shaped pores to obtain the polishing pad 3 (S13).

  Next, a plurality of polishing cloths having different heat treatment temperatures were manufactured as samples, and physical properties and polishing evaluation were performed.

  Here, the polishing cloth as a sample was applied to a urethane resin solution containing polyvinyl chloride on a base material 1 having a thickness of 1.1 mm obtained by impregnating a polyester nonwoven fabric with a urethane resin, and this was wet-coagulated. The surface is buffed to form a nap layer 2 having a thickness of 550 μm, and further heat-treated. Sample A is at a temperature lower than the glass transition point of polyvinyl chloride at 60 ° C., Sample B is at a temperature of 80 ° C. which is the temperature range of the glass transition point, and Sample C is near the melting point at a temperature higher than the glass transition point. Each was heat-treated at 120 ° C. for 1 hour.

  Each sample A, B, and C contained 22% by weight of polyvinyl chloride with respect to a urethane resin (solid content) dissolved in a water-soluble organic solvent.

  Table 1 shows the compression rate, recovery rate, surface roughness, and thickness of Samples A to C.

なお、圧縮率および表面粗さの測定は、ＪＩＳ‐Ｌ１０９６、ＪＩＳ‐Ｂ０６０１に基づいて行った。

The compression rate and surface roughness were measured based on JIS-L1096 and JIS-B0601.

  As shown in Table 1, there was no significant difference in physical property values depending on the heat treatment temperature.

  Next, final polishing was performed using the samples A to C under the following polishing conditions, and the polishing cloth startup time, that is, the time required for dummy polishing was measured.

The determination of the start-up time was performed by visually observing a state where the entire surface of the wafer immediately after polishing was wet, that is, a state in which the wafer surface became hydrophilic. Moreover, in the state which became hydrophilic, the value of Haze was measured with the following inspection apparatus of the silicon wafer.
Polishing conditions ・ pH: Uncontrolled ・ Slurry: NP8020 manufactured by Nitta Haas Co., Ltd.
・ ・ Polisher: Made by Strasbourg, Model: 6CA
・ ・ Platen speed: 115rpm
・ Slurry flow rate: 300 ml / min ・ Pressurization force: 100 gf / cm ²
Wafer inspection ・ Wafer inspection equipment: LS6600 manufactured by Hitachi Electronics Engineering Co., Ltd.
The result is shown in FIG. In FIG. 4, the value of Haze is indicated by a bar graph, while the start-up time is indicated by ■.

  As shown in FIG. 4, sample C, which was heat-treated at 120 ° C. near the melting point higher than the glass transition point of polyvinyl chloride, required about 20 minutes for the silicon wafer surface to become hydrophilic. The value of Haze at that time was also better than Samples A and B.

  Sample A heat-treated at 60 ° C., which is a lower temperature region than the glass transition point, takes about 60 minutes until the silicon wafer surface becomes hydrophilic, whereas in the temperature region of the glass transition point. Sample B heat-treated at 80 ° C has a shortened time of about 30 minutes until the silicon wafer surface becomes hydrophilic, and heat treatment has begun to change the polishing characteristics around the glass transition point. As described above, heat treatment at a high temperature above the glass transition point Tg is preferable for obtaining stable polishing characteristics.

  Next, a plurality of polishing cloths with different heat treatment times were produced as samples, and physical properties and polishing were evaluated.

  A polishing cloth as a sample is manufactured in the same manner as the above-described sample and heat-treated at 120 ° C. Sample D for comparison without heat treatment was sample E for comparison, sample E with heat treatment added for 1 hour, sample F for heat treatment 2 hours, sample G for heat treatment 4 hours, sample G for heat treatment 24 hours H.

  And the stress which arises in the nap layer 2 of each sample DH as a physical property of each sample DH was measured. The stress generated on the surface of the polishing pad 3 causes the polishing pad itself to warp toward the nap layer 2 as a tensile stress. Accordingly, the stress on the surface of the polishing pad 3 can be defined by the load when correcting the warping of the polishing pad 3.

  For the measurement of the stress, an autograph (manufactured by Shimadzu Corporation, AG500) was used, and the stress was measured by the following procedure. First, a sample piece 3s of the polishing pad 3 cut out to a predetermined size (for example, 60 × 60 mm) is prepared. When the sample piece 3s is placed in a state where no load is applied from the outside, the sample piece 3s warps with the nap layer 2 side inward. As shown in FIG. 5A, the sample piece 3s is placed on a flat surface plate 4 installed in an autograph so that the warped and concave portions face upward.

  Next, as shown in FIG. 5B, a plastic plate 5 that is light and larger than the sample piece 3s (for example, 65 × 65 mm) is prepared, and this is gently placed on the sample piece 3s. In this state, after confirming that the sample piece 3s still warps, the load scale is zero-calibrated.

  Next, an autograph terminal is brought into contact with the upper surface of the plastic plate 5, the terminal is gradually lowered, and a compressive load is applied to the sample piece 3s. At that time, the state of the sample piece 3 s is confirmed by visual observation from the lateral direction, and when the warp of the sample piece 3 s cannot be confirmed, the tensile load generated on the surface side of the polishing pad 3 is generated at that time. Record as stress.

FIG. 6 is a graph showing the stress (load) of each sample D to H measured as described above. From FIG. 6, it can be seen that the nap layer 2 contracts with respect to the base material 1 by the heat treatment, and a stress of 0.03 g / mm ² or more is generated on the nap layer 2 side of the polishing pad 3. It can also be seen that the tensile stress generated increases as the heat treatment time increases.

  Next, final polishing was performed using the samples D to H under the following polishing conditions, and the polishing cloth startup processing time, that is, the time required for break-in polishing was measured.

  Polishing is performed in units of 5 minutes, and the entire wafer surface immediately after each polishing is wet, that is, the state of hydrophilicity is visually determined. In the state of hydrophilicity, the wafer inspection device (Hitachi Electronics) The value of Haze was measured by LS6600 manufactured by Engineering Co., Ltd. The total polishing time until the value of Haze becomes a predetermined value or less is the time required for break-in polishing.

Polishing conditions pH: uncontrolled slurry: NP8020 manufactured by Nita Haas Co., Ltd. (dilution ratio 1:20 with pure water)
Polishing machine: Made by Strasbourg, Model: 6CA
Platen speed: 115rpm
Slurry flow rate: 300 ml / min Applied pressure: 100 gf / cm ² .

  The result is shown in FIG. FIG. 8 shows Haze values after the start-up process for sample D that was not heat-treated and sample G that was heat-treated for 4 hours.

  As shown in FIG. 7, in the heat-treated samples E to H, the start-up time is reduced by 20 minutes or more compared to the non-heat-treated sample D, and the start-up time is increased as the heat-treatment time becomes longer. It can be seen that it is as short as 20 minutes.

In short, the surface of the polishing pad ^{3, 0.02g / mm 2 ~0.08g /} mm 2, preferably, subjected to heat treatment as 0.03 g / mm ² or more 0.06 g / mm ² or less of tensile stress is generated It can be seen that the start-up time is shortened by 20 minutes or more than the conventional method.

  The present invention is useful for finish polishing of a semiconductor wafer such as a silicon wafer.

The schematic sectional drawing of the polishing cloth which concerns on embodiment of this invention. The characteristic view which shows the temperature dependence of an elasticity modulus. Manufacturing process drawing of polishing cloth. The figure which shows the starting time and Haze of the sample which varied the heat processing temperature. Explanatory drawing showing the stress measurement method The figure which shows the stress of the sample which varied the heat processing time. The figure which shows the starting time of the sample of FIG. The figure which shows Haze of the samples D and G of FIG.

Explanation of symbols

1 base material 2 surface layer 3 polishing cloth

Claims (11)

  A method for producing a polishing cloth, comprising: applying a resin solution containing a polyvinyl halide or a vinyl halide copolymer to a substrate;   The method for producing an abrasive cloth according to claim 1, wherein the heat treatment is performed at a temperature equal to or higher than a glass transition point of the polyvinyl halide.   The method for producing an abrasive cloth according to claim 1 or 2, wherein the heat treatment is performed at a temperature equal to or lower than a temperature at which the polyvinyl halide melts.   The method for producing a polishing cloth according to claim 1, wherein the halogen is chlorine.   The method for producing an abrasive cloth according to any one of claims 1 to 4, wherein the resin solution is a urethane resin solution.   The method for producing an abrasive cloth according to any one of claims 1 to 5, wherein the base material is obtained by impregnating a nonwoven fabric with a resin solution and wet coagulating it. A polishing cloth comprising a base material layer and a nap layer formed on the base material layer,
A polishing cloth comprising a polyvinyl halide or a vinyl halide copolymer in the nap layer, wherein stress is generated so as to warp toward the nap layer.   The polishing cloth according to claim 7, wherein by applying a load to the polishing cloth, the warp toward the nap layer side is eliminated and the whole becomes flat. It said ^load, polishing cloth according to claim 8 which is ^{0.02g / mm 2 ~0.08g / mm 2} .   The polishing cloth according to any one of claims 7 to 9, wherein the halogen is chlorine.   The polishing cloth according to any one of claims 7 to 10, wherein the nap layer contains a urethane resin as a main component.

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