Abrasive cloth

Abstract

Provided is an abrasive cloth which is provided with a non-woven fabric and a resin in which the non-woven fabric is impregnated as a forming material, and which is characterized in that the proportion of the forming material present from the center in the thickness direction to one surface is 30-60%, and the difference between the maximum value and the minimum value of the proportion present in the thickness direction is 10% or less.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number "201880037093.1", the filing date of July 18, 2018, the priority date of July 25, 2017, and the title of "Abrasive cloth".

[0002] Cross Reference to Related Applications

[0003] This application claims priority from Japanese Patent Application No. 2017-143436, filed July 25, 2017, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0004] The present application relates to an abrasive cloth. BACKGROUND

[0005] In the past, when polishing a polished object such as a silicon wafer, an abrasive cloth having a nonwoven fabric and a resin impregnated in the nonwoven fabric as a forming material has been used (for example, Patent Literature 1).

[0006] Here, it is known that end collapse occurs in the abrasive cloth.

[0007] If the amount of impregnation of the resin is increased to make the abrasive cloth hard, end collapse can be prevented, but in this case, the proportion of the forming material that forms the abrasive cloth in the polishing surface becomes high.

[0008] When polishing a polished object, the portion where the forming material is not present (void) becomes a space for accommodating swarf, so if the amount of impregnation of the resin is excessively increased, clogging is likely to occur.

[0009] Prior Art Documents

[0010] Patent Literature

[0011] Patent Literature 1: Japanese Patent Application Publication No. 2006-43811 SUMMARY

[0012] Technical Problem

[0013] Therefore, in view of the above problems, an object of the present application is to provide an abrasive cloth that can suppress clogging and end collapse.

[0014] Solution to Problem

[0015] The abrasive cloth according to the present application has a nonwoven fabric and a resin impregnated in the nonwoven fabric as a forming material, the proportion of the forming material in the thickness direction from the central portion to one surface is 30 to 60%, and the difference between the maximum value and the minimum value of the proportion in the thickness direction is 10% or less. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1The cross section of the polishing cloth of the example and the comparative example is shown.

[0017] Figure 2 A schematic diagram of the device used in the measurement of the air permeability value (APR) is shown.

[0018] Figure 3 The polishing rate when a wafer is polished using the polishing cloth of the example and the comparative example is shown.

[0019] Figure 4 An SEM image of the cross section of the polishing cloth of Example 1 (50 times) is shown.

[0020] Figure 5 An SEM image of the surface of the polishing cloth of Example 1 (50 times) is shown.

[0021] Figure 6 An SEM image of the cross section of the polishing cloth of Comparative Example 1 (50 times) is shown.

[0022] Figure 7 An SEM image of the surface of the polishing cloth of Comparative Example 1 (50 times) is shown. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present application will be described with reference to the drawings.

[0024] The polishing cloth according to the present embodiment is provided with a nonwoven fabric and a resin impregnated in the nonwoven fabric as a formed material.

[0025] In addition, in the polishing cloth according to the present embodiment, it is important that the proportion of the formed material from the central portion in the thickness direction to one surface is 30 to 60%, and the difference between the maximum value and the minimum value of the proportion of the formed material in the thickness direction is 10% or less.

[0026] The proportion of the formed material from the central portion in the thickness direction to one surface is 30 to 60%.

[0027] Further, the one surface becomes a polishing surface.

[0028] The "proportion of the formed material from the central portion in the thickness direction to one surface" and "the difference between the maximum value and the minimum value of the proportion of the formed material in the thickness direction" can be obtained by the following operation.

[0029] That is, the cross section is observed every 100 μm from one surface to the central portion in the thickness direction, and the proportion of the formed material is measured in each cross section.

[0030] Moreover, the arithmetic mean of the measured proportions of the formed material is used as the "proportion of the formed material from the central portion in the thickness direction to one surface", and the value obtained by subtracting the minimum value from the maximum value in the measured proportions of the formed material is used as the "difference between the maximum value and the minimum value in the thickness direction of the proportion of the formed material".

[0031] Furthermore, the proportion of the formed material in each cross section refers to the proportion of the area of the portion in which the formed material is present, when the entire area of the observed portion in each cross section is taken as 100%.

[0032] In addition, the difference between the maximum value and the minimum value in the thickness direction of the proportion of the formed material can be 0.0%, or 0.1 to 10%.

[0033] In the above measurement, the polishing cloth is photographed by CT-scanning.

[0034] Specifically, a cross-sectional image per 100 μm is obtained from one surface of the polishing cloth to the central portion in the thickness direction. Then, in the cross-sectional image, the proportion of the formed material (area ratio) in each cross section is measured by performing a binaryzation process that separates the portion other than the void (the portion in which the formed material is present).

[0035] As the CT device, a three-dimensional measurement X-ray CT device (TDM1000H-1) manufactured by Yamato Scientific Co., Ltd. can be used.

[0036] In addition, as the CT image processing software, image processing software VGStudio Max 2.1 manufactured by Volume Graphics Co., Ltd. can be used.

[0037] Moreover, as the image analysis software that calculates the proportion of the formed material (area ratio), WinRoof manufactured by Mitsuyoshi Corporation can be used.

[0038] The area of each cross section observed can be set to 1,300 μm x 1,300 μm.

[0039] For example, the proportion of the formed material (area ratio) in each cross section is measured under the following conditions.

[0040] In the above measurement, the cross section of the polishing cloth is continuously measured in accordance with the following field size.

[0041] Size of field (length x width x height): 2,000 μm x 2,000 μm x entire region in the thickness direction

[0042] In addition, the conditions of the above measurement are as follows.

[0043] Number of fields of view per rotation: 1500;

[0044] Number of frames / field of view: 10;

[0045] X-ray tube voltage [KV]: 25.000;

[0046] Magnification axis position [mm]: 10.000;

[0047] Reconstructed pixel size X [mm]: 0.003880;

[0048] Reconstructed pixel size Y [mm]: 0.003880;

[0049] Reconstructed pixel size Z [mm]: 0.003880.

[0050] The method for determining the center of the thickness direction of the polishing cloth from the image obtained by the above-described measurement is as follows.

[0051] First, on the CT image processing software "VGStudio Max", the coordinate values of the X-axis direction, the Y-axis direction, and the Z-axis direction of the polishing cloth were expressed in mm units using the coordinate designation function (volume coordinate system mode).

[0052] Next, the slope in the above-described software was adjusted using the recording function so that the thickness direction of the polishing cloth coincided with the direction of any one of the X-, Y-, and Z-axes.

[0053] Then, the average of the coordinate values of the thickness direction was calculated from the coordinate values of the thickness direction of one surface of the polishing cloth and the coordinate values of the thickness direction of the other surface, thereby determining the position of the center of the thickness direction of the polishing cloth.

[0054] In the cross-sectional image, the binarization process into the void and the portion other than the void (the portion where the formed material exists) was as follows.

[0055] In the binarization process, in order to separate the void and the portion other than the void (the portion where the formed material exists) using the VGStudio Max, the contrast of the cross-sectional image was adjusted.

[0056] The adjustment of the contrast was performed in the Ramp mode.

[0057] In the contrast adjustment, the difference between the void and the portion other than the void (the portion where the formed material exists) was made clear.

[0058] In the VGStudio Max, the adjustment of the contrast was designated as "opacity adjustment".

[0059] Specifically, in VGStudio Max's opacity adjustment settings, the lower limit of the grayscale value is set as the peak, and then the upper limit of the grayscale value is set to the range of "the peak value + 100 ± 5". Furthermore, since light transmittance varies depending on the material, the contrast adjustment range may not be this range.

[0060] Compared to the 2D image with the contrast adjustment described above, a cross-sectional image is obtained from one surface of the abrasive cloth to the center of the thickness direction at 100 μm intervals.

[0061] Next, the material presence rate in the cross-sectional images obtained above for every 100 μm was determined using WinRoof.

[0062] The measurement range in WinRoof is set to "1,300μm × 1,300μm", and the "area ratio of the part in which the forming material exists when the area of ​​the entire observation part is taken as 100%" is used as the "presence ratio of the forming material in each cross section".

[0063] In addition, in WinRoof's binarization process, the portion with a grayscale level range of "127" to "255" is considered as the portion outside the void (the portion where material is formed).

[0064] Furthermore, regarding the proportion of existence, although one aspect has been described, it is preferable that the other aspect also achieves the same proportion of existence as the first aspect.

[0065] That is, the abrasive cloth involved in this embodiment preferably has the following characteristics: the presence ratio of the above-mentioned forming material from the central portion in the thickness direction to the other surface is 30% to 60%, and the difference between the maximum and minimum values ​​of the presence ratio in the thickness direction is 10% or less.

[0066] The Asker-C hardness of the abrasive cloth involved in this embodiment is preferably 80 or higher, and more preferably 85 to 95.

[0067] Because the abrasive cloth involved in this embodiment has an Asker-C hardness of 80 or higher, it has the advantage of suppressing end collapse of the workpiece (e.g., wafer). Furthermore, because the abrasive cloth involved in this embodiment has an Asker-C hardness of 95 or lower, it has the advantage of suppressing defects (e.g., blemishes) in the workpiece.

[0068] Furthermore, the Asker-C hardness refers to the value measured according to SRIS0101 (Japan Rubber Industry Association standard specification). Additionally, the Asker-C hardness is measured on one of the aforementioned surfaces. In other words, the Asker-C hardness is measured on a polished surface.

[0069] The thickness of the abrasive cloth involved in this embodiment is preferably 0.8 to 2.0 mm, and more preferably 1.0 to 1.5 mm.

[0070] Because the abrasive cloth involved in this embodiment has a thickness of 0.8 mm or more, it has the advantage of easily mitigating the adverse effects of the plateau state of the abrasive machine on the abrasive performance. Therefore, it also has the advantage of easily and stably flattening the workpiece being abraded.

[0071] Furthermore, since the thickness of the abrasive cloth involved in this embodiment is less than 2.0 mm, the amount of deformation of the abrasive cloth during abrasion can be reduced, resulting in the advantage of suppressing end collapse of the workpiece being abraded.

[0072] Examples of fibers that make up the aforementioned nonwoven fabrics include polyester fibers and nylon fibers.

[0073] The preferred basis weight of the above-mentioned nonwoven fabric is 200-600 g / m². 2 .

[0074] The nonwoven fabric weight of the abrasive cloth involved in this embodiment is 200 g / m². 2 Therefore, the hardness easily increases, resulting in the advantage of suppressing end collapse of the workpiece being ground. Furthermore, the nonwoven fabric basis weight of the abrasive cloth involved in this embodiment is 200–600 g / m². 2 Therefore, the abrasive surface is prone to having a suitable proportion of voids. As a result, the abrasive cloth according to this embodiment, through such a configuration, has the advantage of easily suppressing changes in abrasive performance caused by void blockage due to abrasive debris, etc.

[0075] Examples of resins mentioned above include polyurethane resins.

[0076] Examples of objects to be polished using the polishing cloth described in this embodiment include silicon wafers.

[0077] The abrasive cloth involved in this embodiment is configured as described above. Next, the manufacturing method of the abrasive cloth involved in this embodiment will be described.

[0078] The following describes the manufacturing method of the abrasive cloth according to this embodiment, using a two-stage impregnation process: wet impregnating the nonwoven fabric with polyurethane resin and then dry impregnating the nonwoven fabric with polyurethane resin as an example.

[0079] In wet impregnation, polyurethane resin is dissolved in a water-soluble organic solvent to obtain the first impregnation solution.

[0080] Examples of water-soluble organic solvents include: dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and dimethylacetamide.

[0081] Furthermore, the first impregnation solution may contain a filler. Examples of such fillers include carbon black. Additionally, the first impregnation solution may contain a dispersion stabilizer. Examples of such dispersion stabilizers include surfactants.

[0082] Next, the nonwoven fabric is immersed in the first impregnation solution, and then immersed in water. As a result, the water-soluble organic solvent in the first impregnation solution adhering to the nonwoven fabric is replaced by water, the polyurethane resin solidifies, and the polyurethane resin adheres to the surface of the nonwoven fabric.

[0083] In dry impregnation, a prepolymer having isocyanate groups as terminal groups, a curing agent having an organic compound with active hydrogen, and an organic solvent are mixed to obtain a second impregnation solution.

[0084] Examples of organic solvents mentioned above include: butanone, acetone, alcohols, ethyl acetate, etc.

[0085] Then, the wet-impregnated nonwoven fabric is immersed in a second impregnation solution, and the nonwoven fabric impregnated with the second impregnation solution is heated in a drying oven. As a result, the organic solvent evaporates, and the prepolymer and curing agent undergo a curing reaction to form polyurethane resin, which is then further adhered to the surface of the nonwoven fabric.

[0086] The abrasive cloth described in this embodiment has the following advantages because it is constructed in the manner described above.

[0087] That is, the abrasive cloth according to this embodiment comprises a nonwoven fabric and a resin impregnating the nonwoven fabric as forming materials. In addition, the abrasive cloth according to this embodiment has a content of 30% to 60% of the forming material from its center portion to its surface in the thickness direction, and the difference between the maximum and minimum content of the above-mentioned content in the thickness direction is 10% or less.

[0088] The proportion of the aforementioned forming material in such abrasive cloth from the center of the thickness direction to one surface is less than 60%, thus having many pores. Therefore, even if the chips slightly clog the pores, the decrease in grinding speed is suppressed.

[0089] Furthermore, although the manufacturing method of abrasive cloth involves forming a material content that increases from the center of the thickness direction to the surface, the abrasive cloth according to this embodiment has a maximum and minimum difference of the aforementioned content in the thickness direction of less than 10%. This results in numerous voids easily existing on the surface of the abrasive cloth. Consequently, even if chips slightly clog the voids, the decrease in grinding speed is suppressed. Moreover, with this configuration, the variation in the aforementioned content from the center of the thickness direction to the surface is minimized, and even if it is trimmed, changes in grinding speed are suppressed.

[0090] Moreover, the proportion of the forming material in such abrasive cloth from the center of the thickness direction to the surface is more than 30%, thereby increasing the number of places where the material is present and making it abrasive cloth with high hardness. As a result, end collapse can be suppressed.

[0091] As can be seen from the above, according to this embodiment, an abrasive cloth that can suppress clogging and end collapse can be provided.

[0092] Furthermore, the abrasive cloth involved in this invention is not limited to the embodiments described above. Additionally, the abrasive cloth involved in this invention is not limited to the effects described above. Various modifications can be made to the abrasive cloth involved in this invention without departing from the spirit of the invention.

[0093] For example, in this embodiment, although the abrasive cloth is obtained by performing a two-stage impregnation process, the abrasive cloth can also be obtained by wet impregnation or dry impregnation alone.

[0094] Examples

[0095] The present invention will now be further illustrated with examples and comparative examples.

[0096] Made to reach Figure 1 The abrasive cloths of Examples 1 and 2, showing the proportions of the forming materials as shown in Table 1 and the physical properties shown in Table 2, were prepared. Additionally, abrasive cloths achieving the desired physical properties were prepared. Figure 1 The abrasive cloth (commercially available product) of Comparative Example 1, which shows the proportion of forming materials shown in Table 1 and the physical properties shown in Table 2.

[0097] In addition, the proportion and hardness of the forming material were determined according to the above method.

[0098] in addition, Figure 1 The term "surface" refers to "a surface (the abrasive surface described later)". Furthermore, in determining the proportion of the abrasive cloth forming material in the examples and comparative examples, cross-sectional observations were performed every 100 μm from one surface to the center of the thickness direction, and observations were also performed from one surface to a thickness of 600 μm.

[0099] Furthermore, the "average value of the presence ratio of forming material from 100 μm to 600 μm thickness" in Table 1 refers to the "presence ratio of forming material from the center to the surface in the thickness direction", and the "difference between the maximum and minimum values ​​of the presence ratio of forming material from 100 μm to 600 μm thickness" in Table 1 refers to the "difference between the maximum and minimum values ​​of the presence ratio of forming material in the thickness direction".

[0100] In addition, the compression ratio and compressive modulus were determined according to the method described in JIS L1096:2010.

[0101] Additionally, the ventilation resistance value (APR) refers to the value of airflow resistance when using airflow resistance. Figure 2 The device shown reduces the pressure lost when air passes through the thickness of the abrasive cloth (air flow rate: 30 L / min, air pressure: 100 Pa).

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106] The polishing speed was measured when polishing wafers using the polishing cloths of the examples and comparative examples.

[0107] The grinding conditions used to determine the grinding speed are shown below. Eight 40-minute grinding cycles were performed under these conditions. The wafer weight was measured after each 40-minute cycle, and the grinding speed (removal rate (RR)) was calculated from the difference between the wafer weight before and after grinding. Results are shown below. Figure 3 And Table 3.

[0108] In addition, the “RR decrease rate” shown in Table 3 refers to the decrease rate of removal rate (RR), which is obtained by the following formula.

[0109] RR decrease rate (%) = (maximum RR value - minimum RR value) / maximum RR value × 100 (%);

[0110] In addition, there was no process to remove blockages (such as processing with a brush) between each round.

[0111] Furthermore, in the measurement of grinding speed, one of the aforementioned surfaces is used as the grinding surface.

[0112] Grinding machine: Strasbaugh 6CA;

[0113] Chip: 8 (P-);

[0114] Polishing slurry: A 20-fold dilution of NP6502 (manufactured by Nitta Haas Co., Ltd.);

[0115] Grinding fluid flow rate: 100 mL / min;

[0116] Grinding time: 40 minutes per wheel.

[0117] Additionally, SEM images of the surface and cross-section of the abrasive cloth in Example 1 and Comparative Example 1 are shown below. Figures 4-7 .

[0118] Table 3

[0119]

[0120] like Figure 3 As shown in Table 3, compared with the comparative example, the decrease in abrasive speed (RR) was suppressed when using the abrasive cloth of the embodiment.

[0121] In addition, as shown in Table 3, when using the abrasive cloth of Comparative Example 1, the "maximum RR - minimum RR" is 0.53 μm / min, which is much smaller than the "maximum RR - minimum RR" of 0.06 μm / min and 0.09 μm / min when using the abrasive cloths of Examples 1 and 2.

[0122] Furthermore, as shown in Table 3, the “RR reduction rate” was 59% when using the abrasive cloth of Comparative Example 1, compared to 8% and 11% when using the abrasive cloths of Examples 1 and 2, which are relatively small values.

Claims

1. An abrasive cloth, wherein, It comprises a nonwoven fabric and a resin impregnated with the nonwoven fabric as forming materials. The proportion of the forming material from the center portion to the surface in the thickness direction is 30% to 60%, and the difference between the maximum and minimum proportions in the thickness direction is less than 10%.

2. The abrasive cloth according to claim 1, wherein, The thickness of the abrasive cloth is 0.8 to 2.0 mm.

3. The abrasive cloth according to claim 1 or 2, wherein, The abrasive cloth has an Asker-C hardness of 80 or higher.

Images