JP2010149259A - Abrasive cloth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive cloth improving polishing quality by improving haze. <P>SOLUTION: The abrasive cloth 1 is provided with: a base material layer 2; and a nap layer 3 which is a porous polishing layer formed on the base material layer 2. After wet freezing is performed by applying resin liquid to a surface of the base material layer 2, a difference between the maximum and minimum of a surface roughness Ra of the nap layer 3 as an abrasive layer formed by polishing a surface of the wet solidified resin is 1 μm or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing cloth suitable for finish polishing of a semiconductor wafer, a glass substrate, a color filter and the like.

  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 to make 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 while supplying a polishing slurry 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 obtained by dissolving a urethane resin in a water-soluble organic solvent such as dimethylformamide (DMF) in a base material obtained by impregnating a urethane resin with a resin film such as PET (polyethylene terephthalate) or a nonwoven fabric. A urethane resin solution is applied, and this is treated with a coagulation liquid to form a porous silver surface layer having a large number of bubbles. The surface of the silver surface layer is buffed to form a nap layer, and the base material layer and many A suede-like polishing cloth comprising a nap layer having a plurality of bubbles is obtained.
JP 2002-59356 A

  In recent years, the quality required for finish polishing using a suede-like polishing cloth as described above has become increasingly severe. For example, light scattering is caused under a condensing lamp and observed as a cloud on the wafer surface. Improvements are also demanded for such haze and LPD (Light Point Defect: minute defects, particles, etc. after 0.1 · country O on the wafer) which are such a minute surface roughness.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a polishing cloth capable of improving the polishing quality by improving haze and the like.

  As described above, in the suede-like polishing cloth, the surface of the porous silver surface layer formed by wet coagulation is buffed and opened, but this buffing causes the surface to become fluffy and the raised hairs to fall easily. The so-called order, which is the direction, and the so-called reverse eye, which is the direction in which napping occurs, occur.

  As a result of intensive investigation based on the knowledge that the polishing slurry is unevenly held by the directionality of the order and the reverse direction, the contact with the wafer is biased and the polishing unevenness occurs. The inventors have found that polishing quality can be improved by suppressing the difference in surface roughness due to the directivity and reverse directionality, and the present invention has been completed.

  That is, the polishing cloth of the present invention is a polishing cloth including a base material layer and a porous polishing layer formed on the base material layer, and the maximum value and the minimum value of the surface roughness Ra of the polishing layer. The difference is 1 μm or less.

  This surface roughness Ra is preferably measured by a contact-type surface roughness meter.

  In one embodiment of the present invention, the porous polishing layer is formed by applying a resin solution to the surface of the base material layer and wet coagulating, and then grinding the surface of the wet coagulated resin.

  This grinding is preferably performed in a predetermined direction by a grinding roller.

  By grinding, the surface of the polishing layer becomes fuzzy, and the order in which the napping is likely to fall and the reverse order in which the napping occurs are generated. However, the maximum value of the surface roughness Ra is And the minimum value is preferably the surface roughness Ra measured in order. That is, in the polishing cloth of the present invention, the difference between the surface roughness Ra measured with the reverse eye and the surface roughness Ra measured with the forward eye is within 1 μm.

  According to the polishing cloth of the present invention, since the difference in surface roughness between the forward and reverse eyes is within 1 μm, the difference in surface roughness due to the directionality of the forward and reverse eyes is suppressed, and polishing such as haze is performed. The quality can be improved.

  According to the present invention, since the difference in surface roughness due to the direction of the order and the reverse direction of the surface of the porous polishing layer is suppressed to within 1 μm, it becomes possible to improve the polishing quality such as haze. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of an abrasive cloth according to an embodiment of the present invention.

  The polishing cloth 1 of this embodiment includes a base material layer 2 and a nap layer 3 that is a polishing layer having a large number of bubbles formed on the base material layer 2.

  As the base material layer 2, for example, a PET film, another polyester film, or an olefin film may be used, and not only a resin film but also a polyamide resin, a polyester resin, or the like non-woven fabric (felt) is made of urethane resin. What was impregnated (urethane resin impregnation nonwoven fabric) may be sufficient.

  The resin solution for forming the nap layer 3 as the polishing layer is, for example, a urethane resin dissolved 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.

  Next, a method for manufacturing the polishing cloth having the above-described configuration will be described.

  In the manufacturing method of the polishing cloth of this embodiment, a urethane resin, a surfactant, and the like are dissolved in a solvent such as dimethylformamide (DMF) and mixed, defoamed and filtered to prepare a urethane resin solution.

  This urethane resin solution is applied to the surface of a base material, for example, a PET film, wet-coagulated, washed to remove the solvent, and then the surface is buffed to open bubbles to form a base material layer made of a PET film. A nap layer 3 is formed on the surface 2 to prepare the polishing pad 1 of FIG.

  As shown in FIG. 2, the buff grinding is performed by pressing a grinding roll 5 rotating in the arrow B direction against the polishing pad 1 a conveyed in the arrow A direction by the feed roll 4.

  As shown in the partially enlarged view of FIG. 3, the buff grinding causes the surface 3a of the nap layer 3 to fluff, and the napped layer tends to fall, that is, the order in the direction of the arrow A and the raised nap occurs. A reverse eye that is opposite to the direction, that is, the arrow A direction, is generated.

  When the difference in surface roughness between the order and the reverse order becomes large, the polishing slurry is held non-uniformly, causing unevenness in contact with the wafer, and polishing unevenness is considered to occur.

  Therefore, in this embodiment, the difference between the maximum value and the minimum value of the surface roughness Ra is suppressed to within 1 μm by controlling the grinding amount at the time of buffing, the feed rate of the polishing pad, and the like.

  The maximum value of the surface roughness Ra can be obtained as the surface roughness Ra measured by the reverse eye, and the minimum value of the surface roughness Ra can be obtained as the surface roughness Ra measured by the order.

  Therefore, in this embodiment, the amount of buff grinding, feed rate, etc. are controlled so that the difference between the surface roughness Ra measured with the reverse eye and the surface roughness Ra measured with the forward eye is within 1 μm. It is.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

  The resin materials are different. Specifically, there are two types, a suede-like polishing cloth A made of ester urethane (DIC manufactured by 7667) and a suede-like polishing cloth B made of polycarbonate urethane (MP865PS made by DIC). For the suede-like polishing cloths A and B, the buffing conditions are controlled, and the difference between the maximum value and the minimum value of the surface roughness Ra is more than 1 μm, and the difference is within 1 μm. The silicon cloth was polished using the polishing cloths A2 and B2 of Example 1 as samples, and the haze and LPD of the silicon wafer surface were evaluated.

  Table 1 shows the thickness (mm) of each sample of Comparative Examples A1 and B1 and Examples A2 and B2, the average value (μm) of the surface roughness Ra, and the difference between the maximum value and the minimum value of the surface roughness Ra (μm ) Respectively. Here, the average value of the surface roughness Ra is the surface roughness Ra measured with the reverse eye, which is the direction in which napping occurs, and the surface roughness Ra measured in order, which is the direction in which napping easily falls. It is an average value, and the difference between the maximum value and the minimum value of the surface roughness Ra is a difference between the surface roughness Ra measured with the reverse eye and the surface roughness Ra measured with the reverse eye.

  The surface roughness in Table 1 was measured as follows according to JIS B0601-1994, using a Tokyo Seimitsu Surfcom 480A, which is a contact surface roughness meter. That is, the measurement was performed with a measurement length of 12.5 mm, a cutoff value of 2.5 mm, a measurement speed of 0.3 mm / sec, a measurement force of 0.07 gf, a conical diamond terminal Rtip = 10 μm, and θ = 90 °.

  In the polishing using the polishing cloths of the samples of Comparative Examples A1, B1 and Examples A2, B2, as a polishing machine, model 6CA (1 platen-20 ″, 1 head− manufactured by Strasbaugh Co., Ltd.) was used. 8 ″), and slurry (polishing liquid) is a slurry Nanopure NP8040W (dilution ratio NP8040W: DI (pure water) = 1: 40) manufactured by Nitta Haas, and an 8-inch silicon wafer is polished. As polished.

Further, the slurry flow rate was 300 ml / min, the polishing time was fixed at 5 min, and the platen rotation number and polishing pressure were polished 6 times under the following four polishing conditions.
Polishing condition-1: surface plate rotation speed 100 rpm, polishing pressure 100 gf / cm ²
Polishing condition-2: surface plate rotation speed 70 rpm, polishing pressure 100 gf / cm ²
Polishing condition-3: surface plate rotation speed 100 rpm, polishing pressure 120 gf / cm ²
Polishing condition-4: surface plate rotation speed 100 rpm, polishing pressure 150 gf / cm ²
Haze and LPD were measured with Hitachi LS6600.

  Table 2 shows the measurement results of haze, and Table 3 shows the measurement results of LPD.

  FIGS. 4 and 5 show changes in haze and LPD with respect to the platen rotation speed, and FIGS. 6 and 7 show changes in haze and LPD with respect to polishing pressure, respectively.

  As shown in Tables 2 and 3 and FIGS. 4 to 7, the sample A2 in the example in which the difference between the maximum value and the minimum value of the surface roughness Ra is within 1 μm and the sample in the comparative example in which the difference exceeds 1 μm. Comparing A1, it can be seen that the sample A2 of the example is better in both haze and LPD than the sample A1 of the comparative example.

  Further, when comparing the sample B2 of the example and the sample B1 of the comparative example, it can be seen that the sample B2 of the example is better in both haze and LPD than the sample B1 of the comparative example.

  Thus, an embodiment in which the difference between the maximum value and the minimum value of the surface roughness Ra is within 1 μm, regardless of the type of polishing cloth such as A and B, or the polishing conditions such as the polishing pressure and the platen rotation speed, It can be seen that the polishing quality is improved.

  The present invention is useful for polishing semiconductor wafers and precision glass substrates.

It is a schematic sectional drawing of the polishing cloth which concerns on one embodiment of this invention. It is a schematic block diagram which shows a grinding process. It is a figure which shows typically the surface state of the nap layer by buff grinding. It is a figure which shows the change of the haze with respect to the surface plate rotation speed of an Example and a comparative example. It is a figure which shows the change of LPD with respect to the platen rotation speed of an Example and a comparative example. It is a figure which shows the change of the haze with respect to the polishing pressure of an Example and a comparative example. It is a figure which shows the change of LPD with respect to the polishing pressure of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing cloth 2 Base material layer 3 Nap layer 5 Grinding roll

Claims (3)

A polishing cloth comprising a base material layer and a porous polishing layer formed on the base material layer,
A polishing cloth, wherein a difference between a maximum value and a minimum value of the surface roughness Ra of the polishing layer is 1 μm or less.   2. The polishing cloth according to claim 1, wherein the porous polishing layer is formed by applying a resin solution to the surface of the base material layer and wet coagulating, and then grinding the surface of the wet coagulated resin.   The polishing cloth according to claim 1 or 2 used for finish polishing of a semiconductor wafer.

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