JP6842029B2 - Abrasive pad - Google Patents

Description

The present invention relates to a polishing pad, and relates to a polishing pad having a polishing layer made of a woven fabric structure.

Conventionally, in order to polish the surface of an object to be polished such as glass, metal, plastic, semiconductor substrate, SiC, sapphire, compound semiconductor, etc., in addition to a polishing pad having a resin polishing layer, cloth-like polishing composed of a plurality of fibers A polishing pad with a layer is used.
As the polishing pad, a polishing pad having a polishing layer having a woven structure in which warp threads and weft threads composed of one fiber or a plurality of bundled fibers are regularly woven is known (for example, Patent Document 1). ..

Japanese Unexamined Patent Publication No. 2002-86348

Here, in recent years, there has been a demand for further reduction of scratch scratches generated when the object to be polished is polished.
In order to reduce scratches, if the slurry used for polishing the object to be polished can be appropriately held by the polishing surface of the polishing pad, it is conceivable to reduce scratches without impairing the polishing performance. ..
Therefore, the present invention provides a polishing pad capable of appropriately holding a slurry with an object to be polished and suppressing scratches.

That is, the polishing pad according to the invention of claim 1 is a polishing pad having a polishing layer made of a woven fabric structure.
The woven structure is a satin weave consisting of 5 satin or 8 satin.
The warp and weft are composed of only acetate fibers having an official moisture content of 4 to 10% and a vinegarization degree of 45% or more and less than 60% , and the warp and weft have different fineness. It is a feature.

According to the above configuration, by forming a woven structure in which warp and weft are regularly woven with fibers having an official moisture content of 4 to 10%, good water retention can be obtained on the polished surface, and the polished surface and the cover can be obtained. Since it is possible to appropriately hold the slurry between the polished material and the polished material, it is possible to suppress the occurrence of scratches.

FIG. 5 is a side view of a polishing apparatus provided with a polishing pad according to this embodiment. An enlarged plan view showing a part of the polished surface of the polishing pad. An enlarged plan view of the polished surface of the polishing pad according to another embodiment.

Hereinafter, the illustrated embodiment will be described. FIG. 1 shows a schematic view of a polishing device 2 for polishing the object to be polished 1. The polishing device 2 is located above and holds a holding surface plate 3 for holding the object to be polished 1. A polishing surface plate 5 for fixing the polishing pad 8 located below and a slurry supply means 6 for supplying a slurry between the object to be polished 1 and the polishing pad 8 are provided.
The object to be polished 1 may be a silicon wafer, an optical lens, SiC, a sapphire, or a compound semiconductor, and may be an object 1 to be polished made of other metals, plastics, ceramics, or glass. ..

The holding surface plate 3 and the polishing surface plate 5 each have a substantially disk shape, and each of them is rotated by a driving means (not shown), and the holding surface plate 3 is provided so as to be able to move up and down.
The object to be polished 1 is held on the lower surface of the holding surface plate 3 by a holder or wax (not shown), and the polishing pad is placed on the upper surface of the polishing surface plate 5 via double-sided tape (not shown). 8 is adhesively fixed.
The polishing pad 8 is composed of a cloth-shaped polishing layer 4 described below and a cushion layer 7 bonded to the polishing layer 4 via a double-sided tape (not shown), and the cushion layer 7 is a double-sided tape. It is fixed to the polishing surface plate by adhesive.
Then, when performing the polishing process, the holding surface plate 3 rotates relatively while pressing the object 1 to be polished against the polishing pad 8 on the upper surface of the polishing surface plate 5, and the slurry supply means 6 polishes the slurry. It is supplied between the object 1 and the polishing pad 8.
As the slurry supplied by the slurry supply means 6, conventionally known ones can be used depending on the object to be polished 1 and the required processing accuracy, and for example, one containing diamond abrasive grains is used. Can be done.

The polishing layer 4 of this embodiment has a cloth shape and has a circular shape having substantially the same diameter as the polishing surface plate 5. Further, the polishing layer 4 has a woven structure in which the warp Lv shown in black and the weft Lh shown in white are regularly woven as shown in FIGS. 2 and 3.
The warp Lv and weft Lh are composed of fibers having an official moisture content of 4 to 10%. When the official moisture content is 4% or more, the slurry on the polished surface appropriately swells due to its water retention, and the slurry can be easily dispersed uniformly. Further, by setting the official water content to 10% or less, excessive swelling can be suppressed.
As the fiber material having such an official moisture content, among the cellulosic fibers, those in which the hydroxyl groups are appropriately hydrophobized by acylation or the like (for example, acetate) and those in which the official moisture content is suppressed by strong twisting (for example). , Rayon, Polynosic, Cupra).
It is also possible to mix a material having a high official moisture content and a material having a low official moisture content to set the moisture content within the above range, but this is not preferable because swelling spots are likely to occur. Nylon can be said to be within the range of the official moisture content, but thermoplastic materials having a low melting point and softening point are vulnerable to frictional heat during polishing, so a cellulosic material having high heat resistance is preferably used. Above all, the fiber made of acetate is preferable because it can suppress excessive swelling without being strongly twisted and has excellent surface quality of the polished material.

Hereinafter, an example of the method for producing the acetate fiber used in this example will be described.
First, high-purity wood pulp is reacted with acetic anhydride, which gives acetate flakes with almost all hydroxyl groups acetylated.
Subsequently, the acetyl group of the obtained acetate is partially hydrolyzed with an acid to obtain acetate flakes having a required degree of vinegarization, which is dissolved in a solvent to prepare a spinning stock solution.
Next, the solvent component is removed by discharging the spinning stock solution from a minute discharge hole into a high temperature atmosphere. As a result, the acetate component solidifies, and by winding this, the acetate fiber can be obtained.
At that time, the monofilament may be wound around the discharge holes as it is, or the filaments discharged from the plurality of discharge holes may be wound as a multifilament which is bundled while falsely twisting as necessary.
The wound acetate fiber may be further crimped or cut to about 38 mm to 51 mm and used as a spun yarn, but in the case of a spun yarn, it easily falls off due to friction during polishing. , It is preferable to use it in the state of monofilament or multifilament having a long fiber length.
In this example, it is particularly desirable to use acetate fibers having a vinegarization degree (a value measured by ASTM: D-817-91 "Test method for cellulose acetate or the like") of 45% or more and less than 60%.
Such acetate fibers have good water retention, and by using the polishing pad 8 using the fibers, the slurry can be well held between the abrasive fibers and the object to be polished 1, and scratch scratches can be reduced. Can be planned.
On the other hand, when an acetate fiber having a vinegarization degree of less than 45% is used, the water retention becomes excessive, the fiber swells, and the flatness of the polished surface is impaired, so that the polishing performance deteriorates.
On the other hand, when an acetate fiber having a vinegarization degree of more than 60% is used, the water retention property becomes low and a sufficient slurry cannot be held between the vinegared object 1 and the object to be polished, which causes scratches. It becomes.

In the diacetate fiber, the diacetate fiber is used as it is as a monofilament yarn, or the fiber is used as a bundled multifilament yarn for the warp yarn Lv and the weft yarn Lh and weaved regularly to form a woven structure. The polished layer 4 can be obtained.
In this embodiment, a 75 to 160 decitex multifilament yarn in which a plurality of diacetate fibers are bundled is used. By setting the fineness to 75 decitex or more, wear resistance can be ensured even when diamond abrasive grains are used as the slurry, and conversely, by setting the fineness to 160 decitex or less, the rigidity of the yarn is high. It does not become too much, and when this is made into the polishing layer 4, scratch scratches are less likely to occur.
It is possible to use yarns having the same fineness for the warp Lv and the weft Lh, but the fineness may be different.

FIG. 2 illustrates the woven fabric structure seen from the polished surface side of the polishing layer 4, and in this embodiment, satin weave is adopted as the woven fabric structure, and in FIG. 2, the warp Lv appearing on the polished surface is black and the weft Lh. Are shown in white.
By regularly weaving the warp Lv and the weft Lh in this way to obtain the polishing layer 4, the surface of the polishing layer 4 can be made smoother and higher than when the polishing layer 4 is made of a non-woven fabric. The effect of reducing scratch scratches can be achieved.

Explaining the woven structure made of satin weave shown in FIG. 2, the satin weave uses the same number of warp threads Lv and weft threads Lh to form a certain pattern, and the warp threads Lv appearing on the polished surface in the vertical direction. Is positioned so as to jump over the four weft Lh threads, and the weft threads Lh appearing on the polished surface are not continuous in the diagonal direction.
Further, the satin weave shown in FIG. 2 has a so-called five-sheet satin structure, and the warp Lv appearing on the polished surface in the vertical direction, which is called eight-sheet satin, is located so as to jump over the seven weft Lh threads. Weaving is also known, and such a woven structure can also be adopted.
When such a satin weave is adopted for the woven fabric structure, the weft Lh is uniformly dispersed on the polished surface in FIG. 2, and the waviness of the polished surface is reduced.

Further, as the woven fabric structure constituting the polishing layer 4, a twill weave as shown in FIG. 3A and a plain weave as shown in FIG. 3B can be adopted.
In the above twill weave, the weft Lh appearing on the polished surface is continuous in the diagonal direction, and when the warp Lv and the weft Lh have the same fineness, the inclination at which the weft Lh appears is 45 with respect to the longitudinal direction of the warp. It becomes °.
Further, in the above plain weave, the warp Lv and the weft Lh are crossed one by one so that the warp Lv and the weft Lh appear like a checkerboard pattern on the polished surface.
However, in twill weave, regular steps are likely to occur in the diagonal direction of the polished surface, and in plain weave, many irregularities are likely to exist on the polished surface. Therefore, it is preferable to use the satin weave as the performance of the polishing pad. It becomes.
In addition to the woven fabric structures such as satin weave, twill weave, and plain weave, a woven fabric structure in which the warp Lv and the weft Lh are regularly woven by a conventionally known method can also be adopted.

The warp Lv and the weft Lh intersect with each other by setting the area exposed on the polished surface of either of the warp Lv or the weft Lh to be in the range of 50 to 80% with respect to the area of the polished surface. It is presumed that the waviness of the polished surface generated by the deformation of the yarn is suppressed, the flatness of the polished surface is ensured, and the above effect can be easily obtained.
The ratio of the area can be adjusted by making the fineness of the warp Lv and the weft Lh different.

Hereinafter, the following experiments were carried out using the examples and comparative examples of the present invention. The present invention is not limited to the following examples.
First, for the polishing pads 8 according to the examples and the comparative examples, the thickness, density, compressibility, compressibility, A hardness, official moisture content, and area ratio of the warp or weft on the polished surface are determined by the following methods, respectively. Was measured using.
<Thickness>
The thickness of the polishing pad was measured according to the thickness measuring method described in Japanese Industrial Standards (JIS K6550).
That is, the thickness of the polishing pad when a load of 100 g per ^{1 cm 2} was applied to the polishing pad as an initial load in the thickness direction was measured. Specifically, the polishing pad is cut into 3 pieces of 10 cm in length and 10 cm in width, and the thickness of the four corners and the center of each piece is read and measured to the minimum scale using a dial gauge (minimum scale 0.01 mm). 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.
<Density>
The density (g / cm ³ ) was calculated by measuring the weight (g) of the polishing pad cut out to the size of a predetermined size and obtaining the volume (cm ³ ) from the size.
<Compression modulus and compressive elastic modulus>
The compressibility and compressive elastic modulus were determined using a shopper type thickness measuring instrument (pressurized surface: circular with a diameter of 1 cm) in accordance with Japanese Industrial Standards (JIS L1021). Specifically, the thickness t0 after applying the initial load for 30 seconds from the unloaded state was measured, and then the thickness t1 after applying the final pressure for 5 minutes from the state of the thickness t0 was measured.
Further, all the loads were removed from the state of the thickness t1 and left for 5 minutes (in the no-load state), and then the initial load was applied again for 30 seconds, and then the thickness t0'was measured. From these, the compressibility and compressive elastic modulus are calculated using the following formulas.
Compression rate (%) = (t0-t1) / t0 × 100
Compressive modulus (%) = (t0'-t1) / (t0-t1)
At this time, the initial load was 100 g / cm ² and the final pressure was 1120 g / cm ² .
<Shore A hardness>
To measure the shore A hardness, a sample piece (10 cm x 10 cm) is cut out from the polishing pad, and multiple sample pieces are stacked so that the thickness is 4.5 mm or more, and an A type hardness tester (Japanese Industrial Standards, JIS K7311) is used. ). For example, when the thickness of one sample piece was 1.1 mm, five pieces were stacked and measured. In order to fix the sample pieces, the release paper of the double-sided tape of each sample piece was peeled off, and the measurement was performed in a state where the sample pieces were integrated.
<Official moisture content>
The dry mass of the acetate fiber used for the polishing layer 4 dried in a nitrogen atmosphere at 50 ° C. for 24 hours, and the moisture absorption weight after 24 hours in an atmosphere of 65% relative humidity and 20 ° C. were measured. From these measured values, the official moisture content is calculated using the following formula.
Official moisture content (%) = (moisture absorption weight-dry weight) / dry weight x 100
<Area ratio of warp or weft appearing on the polished surface>
With a microscope (VH-5500, manufactured by KEYENCE), the area of about 1.3 mm square on the pad surface was magnified 100 times and observed, and the obtained image was observed by image processing software (WinRooF, manufactured by Mitani Shoji Co., Ltd.). By the binarization treatment, the threads exposed on the surface and the other parts were distinguished. Then, the area ratio of the yarn exposed to a large amount on the surface was calculated from the area ratio of each of the yarn exposed on the distinguished surface and the other portion.

Then, each of the polishing pads 8 according to the examples and the comparative examples was polished under the following conditions to evaluate scratches. Here, SiC was used as the object to be polished, and a diamond abrasive grain (abrasive particle size: 3 μm) dispersion was used as the slurry.
In the evaluation of scratches, 25 pieces of objects to be polished were polished using the following polishing device, and scratches on each object to be polished were visually confirmed. In the evaluation of scratches, if scratches could not be confirmed at all, ○, if one or more sheets were confirmed, but the quality of the product was acceptable, △, one or more sheets were confirmed, and the product could not be used. The case where the product was included was evaluated as x.
Polishing device used: Single-sided polishing device Polishing speed (surface plate rotation speed): 80 rpm
Machining stress: 330 gf / cm ²
Slurry supply: 3 mL / min Polishing time: 60 minutes

(Example 1)
As the polishing pad 8 according to the first embodiment, a polishing pad 8 made of the following acetate fibers as warp threads and weave threads in a satin weave was used. Specifically, an 83 decitex yarn made of an acetate multifilament having a vinegarization degree of 55% was used as the warp yarn, and a 133 decitex yarn made of an acetate multifilament having a vinegarization degree of 55% was used as the weft yarn.
Further, as the cushion layer 7, a polyurethane resin-impregnated non-woven fabric having a Shore A hardness of 32 and a thickness of 0.7 mm was used.
Further, the polishing layer 4 and the cushion layer 7 are bonded with a double-sided tape having a thickness of 130 μm (for intermediate bonding and the base material is a polypropylene film), and the surface opposite to the cushion layer 7 and the polishing layer 4 has a thickness of 130 μm (). The polishing pad 8 was obtained by adhering the base material with a double-sided tape of PET) for adhering to a platen.
As shown in Table 1 above, as an experimental result, no scratch scratches were observed on all the objects to be polished, and good results could be obtained. It is presumed that this is because the polishing layer 4 of the polishing pad 8 according to the embodiment has an appropriate official moisture content and good water retention, so that the slurry can be well held between the polishing surface and the polishing surface. Will be done.

(Example 2)
Next, the polishing pad 8 used in Example 2 has the same configuration as in Example except that the twill weave shown in FIG. 3A is adopted as the woven structure of the polishing layer 4.
As a result of the experiment, scratches were observed on some of the objects to be polished, but the quality of the product was acceptable.
This is because in the polishing pad 8 according to the second embodiment, as shown in FIG. 3A, a twill weave in which weft threads Lh continuously appear in the polishing surface in the diagonal direction is adopted as the knitting structure, so that the polishing surface is oblique. It is presumed that a step in the direction was generated, and the influence of the step in the diagonal direction on the flatness of the surface was the cause of scratches.

(Comparative Example 1)
The polishing pad 8 used as Comparative Example 1 uses 83 decitex yarns made of acetate multifilament having a vinegarization degree of 61% as the warp yarns as the polishing layer 4, and acetate multifilaments having a vinegarization degree of 61% as the weft yarns. It has the same configuration as that of Example 1 except that 167 decitex yarn is used.
As a result of the experiment, scratches were observed on a plurality of objects to be polished. This is because the official moisture content of the polishing pad according to Comparative Example 1 is low, so that the water retention is low, and it becomes impossible to hold a sufficient slurry between the polishing pad and the object to be polished 1, resulting in scratches. It is inferred that.

1 Object to be polished 2 Polishing device 4 Polishing pad Lv Warp Lh Weft

Claims (4)

In a polishing pad having a polishing layer made of a woven structure,
The woven structure is a satin weave consisting of 5 satin or 8 satin.
The warp and weft are composed of only acetate fibers having an official moisture content of 4 to 10% and a vinegarization degree of 45% or more and less than 60% , and the warp and weft have different fineness. Characterized polishing pad. The polishing pad according to claim 1 , wherein the area exposed on the polishing surface of either the warp or the weft is 50 to 80% of the area of the polishing surface. The polishing pad according to claim 1 or 2 , wherein the warp and weft are monofilament or multifilament. The polishing pad according to any one of claims 1 to 3 , wherein the warp and weft have a fineness of 75 to 160 decitex.

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