JP2006026760A - Carrier for holding material to be polished - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for holding a material to be polished having excellent durability and wear resistance. <P>SOLUTION: This carrier for holding the material to be polished is provided with a resin-made frame mounted on the inner edge part thereof, and has one or more holes for holding the material to be polished. In the carrier for holding the material to be polished, the surface of the carrier base material in a part made of metal is coated with material which is the same as the carrier base material or has a higher hardness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is directed to rotating at least one of the upper and lower surface plates and the object to be polished while simultaneously sandwiching the object to be polished between the upper and lower surface plates to which the polishing cloth is attached, so that both surfaces of the object to be polished are mirror surfaces simultaneously. A carrier for holding an object to be used for a double-side polishing apparatus for polishing, having one or more objects to be polished having a resin frame at the inner edge of the object holding hole, and a metal A carrier for holding an object to be coated, which is coated on the surface of a carrier substrate made of the same or higher hardness as the carrier substrate, and the object to be polished of the present invention having a coating thickness reduced by repeated use The present invention relates to a carrier for holding an object to be recovered, which is a reproduction of the carrier for holding an object, and a method for polishing an object to be polished using the carrier.

  In polishing of an object to be polished made of silicon wafer, compound semiconductor wafer, aluminum magnetic disk substrate, glass magnetic disk substrate or glass for fort mask, crystal oscillator, metal, etc., the object to be polished is It is held and driven by a carrier which has a holding hole adapted to the shape and is cut and molded so as to have outer peripheral teeth meshing with the internal gear and sun gear of the double-side polishing apparatus at the outer peripheral edge thereof. This carrier is mainly used as a member of a polishing apparatus for simultaneously lapping or mirror polishing a silicon wafer, a magnetic disk substrate or the like on both sides. Therefore, the thickness of the carrier material is usually slightly smaller than the thickness of the object to be polished such as a wafer, or substantially the same thickness.

  Conventionally, these carriers are made of metal materials such as steel and stainless steel, glass cloth woven with glass fibers and organic fiber cloth impregnated with epoxy resin, phenol resin, and other thermosetting resins, and several layers are pressed to obtain a predetermined thickness. Manufactured by a method that uses so-called FRP, etc., made by compression and heat curing with a machine, cuts it to a size that can hold the workpiece according to the purpose of use, and further cuts it according to the shape of the gear. It is common to be done.

  These carriers are rotated together with the silicon wafer, magnetic disk substrate, etc. in the polishing apparatus, and are forcedly driven by the internal gear and sun gear via the inner and outer peripheral teeth, so the surface is somewhat polished. As the strength decreases or the shape accuracy deteriorates, the durability decreases over time, and the gear part wears away from the polishing apparatus or the polishing conditions become unstable. Regularly replaced with a new carrier. Therefore, development of a durable carrier that can be used for as long as possible is strongly desired. For example, an FRP carrier as shown in Patent Document 1 has also been proposed.

  Conventionally, in the case of a silicon wafer or a compound wafer, the thickness is adjusted by lapping or grinding, and after acid or alkali etching, one or both surfaces are finished to a mirror surface through a process of mirror polishing (polishing). Among these, mirror polishing was performed only on one side, such as silicon wafers, but there are also objects to be polished that have been subjected to mirror polishing on both sides for the purpose of improving surface accuracy and preventing dust contamination. There is an increasing demand for double-sided mirror polishing. When performing mirror polishing (polishing) on both sides, the use of a carrier for holding an object to be polished is an indispensable condition. In this case, the wear resistance and durability of the carrier itself are important factors. From the viewpoint of wear resistance and durability, for example, a material made of a non-metallic material such as hard resin or FRP is still not sufficient as a carrier.

  Also, in recent years, the size of silicon wafers has increased, and at the same time, in order to improve the yield of chips from a single wafer, the surface sagging of the wafer outer edge is suppressed as much as possible, and the flatness of the object to be polished is improved. There is a need to reduce the width of edge exclusion. Therefore, many attempts have been made to reduce the difference between the thickness of the object to be polished and the carrier as much as possible. For example, in Patent Document 5 and Patent Document 6, the thickness of the object to be polished and the carrier are made substantially the same. A technique for improving the flatness is disclosed. In such polishing in which the thickness of the object to be polished and the carrier is substantially the same, the thickness of the carrier is gradually reduced, and there is a problem in that the flatness decreases with time. Therefore, the development of a carrier that can solve these problems simultaneously has been awaited.

As a method for improving the wear resistance and durability of the metal material substrate, it is conceivable to coat its surface with some material. For example, a ceramic-coated metal carrier as shown in Patent Document 2 is also available. Although it has been proposed, it shows extremely high performance in terms of wear resistance, but has the problem that the ceramic particles adhering to the surface fall off and cause scratches on the workpiece, and both sides are mirror polished. Can not be used. Further, Patent Document 3 discloses a recyclable carrier in which a metal surface is plated on a carrier surface made of aluminum, but it is not a method of reusing and using the carrier. Further, Patent Document 4 discloses a carrier having a dressing function in which ceramic particles are fused to uneven surfaces formed on upper and lower surfaces and the surface of the uneven surface is coated with diamond-like carbon. Although the improvement of durability and wear resistance is described by the effect, this is to prevent the ceramic particles functioning for dressing from falling off, and is different from a normal carrier.
Further, Patent Document 7 discloses a diamond-like carbon coating carrier for holding an object to be polished used for double-side polishing of a silicon wafer, a method for producing the carrier, and a polishing method using the carrier.

The present inventor has intensively studied to solve the problems of durability and wear resistance in double-sided mirror polishing of semiconductor materials such as silicon wafers, and the carrier base material is a metal having excellent wear resistance and durability. Considering that the carrier holding object covered with the carrier base material or a material harder than the carrier base material has a high durability and a small decrease in thickness. Carried out.
However, since the carrier substrate is manufactured with high thickness accuracy and accuracy and the carrier substrate surface is also coated with a specific material, the carrier for holding an object to be polished is a conventional product. In comparison, it turned out to be very expensive. Accordingly, the surface of the carrier for holding an object to be polished, which has been worn by repeated use and has a thickness of less than a certain thickness, is again coated with the carrier base material or a material having a higher hardness than the carrier base material and can be reused. The carrier for holding the polished article was examined. Further, a method for carrying out double-side polishing of an object to be polished with high flatness using the carrier for holding an object to be polished was examined.
JP 2001-38609 A JP-A-4-26177 JP2002-18707 JP-A-11-10530 JP 11-347926 JP 2000-235941 A Japanese Patent Application No. 2004-66013

  An object of the present invention is to provide an object holding carrier for use in a double-sided mirror polishing apparatus that has excellent durability and wear resistance and minimizes the occurrence of defects such as scratches on the object to be polished. It is in. Furthermore, another object of the present invention is to re-coat the carrier substrate or a material having a higher hardness than the carrier substrate on the surface of the carrier for holding an object to be polished, which has been worn by repeated use and the thickness of the coating layer has decreased. An object of the present invention is to provide a carrier for holding an object that can be recycled. Furthermore, another object of the present invention is to provide a method for carrying out double-side mirror polishing of an object to be polished with high flatness using the carrier.

The above object is a carrier for holding an object to be polished having one or more holes for holding the object to be polished with a resin frame at the inner edge, and is made of a metal of the carrier for holding an object to be polished. This can be achieved by a carrier for holding an object to be polished, characterized in that the surface of a part of the carrier substrate is coated with the same or higher hardness material as the carrier substrate. Further, it is preferable that the standard deviation of the in-plane thickness of the carrier for holding an object to be polished is 5 μm or less, and the high hardness material covering the surface of the carrier substrate is a metal belonging to Group 4A or Group 5A of the periodic table. Or a nitride thereof, a carbide thereof, a composite thereof, or diamond-like carbon.
The polishing apparatus used in the present invention rotates the at least one of the upper and lower surface plates and the object to be polished while sandwiching and pressing the object between the upper and lower surface plates to which a polishing cloth is attached. This is a so-called double-side polishing apparatus that polishes both surfaces of an object simultaneously (polishing).

  Another object of the present invention is to provide a standard for the in-plane thickness of a carrier for holding an object to be polished, by coating the surface of the carrier base of the metal portion with a material that is the same as or higher in hardness than the carrier base. A carrier for holding an object to be polished having a deviation of 5 μm or less, and the surface of the object to be polished holding whose coating layer thickness is reduced by use, is again coated with a material having the same or higher hardness than the carrier substrate. This can be achieved by a carrier for holding a recycled object to which a thickness is imparted.

  Still another object of the present invention is to attach the object-holding carrier of the present invention between the upper and lower surface plates to which an abrasive cloth is attached, and place the object to be polished in the holding hole in the object-holding carrier. After the holding, it can be achieved by a polishing method in which at least one of the upper and lower surface plates to which a polishing cloth is attached and a polishing object are rotated while supplying a polishing slurry to a processed surface, and both surfaces of the polishing object are mirror-polished.

  According to the present invention, it has become possible to easily provide a carrier for holding an object to be polished, which has excellent durability and wear resistance, and can be recycled, thereby reducing running cost. That is, the problems of conventional carriers could be solved at once.

The present invention will be described in detail below.
The essential point of the present invention is that a resin frame is provided at the inner edge of the object holding hole of the object holding carrier in order to prevent scratches generated at the end face part of the object to be polished, A metal material having excellent wear resistance and durability is used, and the carrier base material surface is coated with the same or higher hardness material as the carrier base material.

  As described above, in the actual usage form of the carrier for holding an object to be polished according to the present invention, the thickness thereof is equal to or slightly thicker than the object to be polished, and is used in a so-called carrier sizing state. The wear of the carrier itself is also severe, so it is necessary to coat the surface of the carrier substrate with a specific material. Further, it is necessary to provide a resin frame at the inner edge of the polishing object holding hole of the polishing object holding carrier for the purpose of preventing scratches generated at the end face portion of the polishing object.

  In order to polish the object to be polished with high flatness using a double-side polishing apparatus using the carrier for holding an object to be polished according to the present invention, the thickness of the carrier for holding the object to be polished and the finish of the object to be polished It is preferable that the thicknesses should be substantially the same, and at the same time, the standard deviation of the in-plane thickness of the carrier for holding an object to be polished should be small.

  If the standard deviation of the in-plane thickness of the object-holding carrier of the present invention is large, the following problems occur. First of all, because the standard deviation of the in-plane thickness of the carrier for holding an object to be polished is large, the end point detection at the end of polishing becomes inaccurate, and the standard deviation of the thickness is directly finished. Affects the flatness of the polished article and causes deterioration of the flatness. Second, if the standard deviation of the in-plane thickness of the carrier for holding an object to be polished is large, the thick portion of the carrier is preferentially polished, the coating layer of the portion is removed, and the carrier substrate is exposed.

  In the present invention, the method for coating the carrier substrate is not particularly limited, but a CVD method, a PVD method and the like are preferable. When coating is performed by CVD or PVD, the thickness of the coating layer is controlled by time. When it is going to increase the thickness of a coating layer, since the time which covering requires increases, manufacturing cost will increase. Moreover, when the thickness of the coating layer is increased, the standard deviation of the in-plane thickness of the carrier for holding an object to be polished tends to slightly increase. The standard deviation of the thickness of the object holding carrier is preferably 5 μm or less, more preferably 2 μm or less.

  In the present invention, the thickness of the coating layer applied to the surface of the carrier substrate is usually about 0.5 to 3 μm on one side, and the total thickness of the coating layers on both sides is about 1 to 6 μm. Since the thickness of the coating layer applied to the surface of the carrier base material is extremely thin in this way, in the carrier for holding an object to be polished having a standard deviation of thickness of 5 μm or more, the thick part of the carrier is preferentially polished, and the time is extremely short. The carrier substrate is exposed. Further, since the carrier is polished before the end point as described above, the end point detection at the end of polishing becomes inaccurate, and the flatness of the finished workpiece is deteriorated.

  When the standard deviation of the thickness of the carrier for holding an object to be polished of the present invention is 5 μm or less, more preferably 2 μm or less, the finished flatness of the object to be polished gives good results. Furthermore, since the coating layer is removed almost uniformly, it can be used over a long period of time, and since the thickness is uniform, it is easy to regenerate.

  In the present invention, the thickness of the carrier for holding an object to be polished refers to the average value of 12 points selected from the entire surface of the carrier for holding an object to be polished, and the thicknesses of the points are measured. The standard deviation of the thickness of the carrier for holding an object to be polished was a standard deviation value calculated by using the numerical values of the thickness measurement results at 12 locations.

  The high-hardness material covering the surface of the carrier substrate is preferably a metal belonging to Group 4A or Group 5A of the periodic table, or a nitride or carbide or composite thereof, or diamond-like carbon. Metals belonging to groups 4A and 5A of the periodic table, nitrides thereof, carbides thereof, composites thereof, or diamond-like carbon are excellent in chemical resistance and have the above-mentioned wear resistance and durability. It is most suitable as a high hardness material for coating the surface of the carrier substrate used in the present invention. Furthermore, elements belonging to groups 4A and 5A and carbon in the periodic table are not contaminating elements for the silicon wafer, and the carrier for holding an object to be polished of the present invention is in direct or indirect contact with the silicon wafer. There is little risk of contamination of silicon wafers.

  In addition, a resin frame is formed on the inner edge of the polishing object holding hole of the polishing object holding carrier according to the present invention for the purpose of preventing the occurrence of defects such as scratches and chips generated on the end surface portion of the polishing object. Provide. The material of the resin frame is not particularly limited, but thermosetting resins such as epoxy resins and phenol resins, and high melting point thermoplastic resins such as polysulfone and polycarbonate can be used. Furthermore, FRP etc. which combined the above-mentioned thermosetting resin or high melting point thermoplastic resin and fiber can also be used. Although the fiber used for FRP is not specifically limited, Organic fiber, such as an aramid fiber and a polyester fiber, is preferable.

  The metal used as the carrier substrate is not particularly limited, but for the purpose of reducing heavy metal contamination of the object to be polished, it is a metal belonging to the 4A group, 5A group of the same periodic table as the carrier substrate, or an alloy thereof. Is preferred. The metal belonging to Group 4A of the periodic table refers to titanium, zirconium, and hafnium, and the metal belonging to Group 5A of the periodic table refers to vanadium, niobium, and tantalum.

Furthermore, other objects of the present invention will be described as follows.
Another object of the present invention is to coat the surface of a carrier substrate made of metal with a material that is the same as or higher in hardness than the carrier substrate, and the standard deviation of the in-plane thickness of the carrier for holding an object to be polished is 5 μm. A carrier for holding an object to be polished, which is the same as the carrier substrate again or having a higher hardness on the surface of the carrier for holding an object to be polished whose thickness is reduced by repeated use. It is a carrier for holding an object to be polished, which is provided with a thickness by applying a coating.

  As described above, the carrier for holding an object to be polished according to the present invention has a high wear resistance because the thickness thereof substantially matches the finished thickness of the object to be polished. The thickness is reduced. The conventional carrier for holding an object to be polished becomes unusable and discarded at this point. When the carrier for holding an object to be polished according to the present invention becomes unusable, it is the same as that used for the carrier substrate on the surface of the carrier for holding an unground object to be polished, or from the carrier substrate. By applying a material with high hardness and coating it again, it can be recycled. The timing of coating again is preferably performed when the thickness of the carrier for holding the object to be polished becomes 1 μm or more thinner than the finished thickness of the object to be polished.

  As described above, the carrier for holding an object to be polished according to the present invention is preferably manufactured with a standard deviation of thickness of 5 μm or less. Moreover, the preferable thickness of the material for covering the substrate of the carrier for holding an object to be polished of the present invention is about 0.5 to 3 μm, and the occurrence of uneven wear due to repeated use is small, and the thickness of the carrier for holding an object to be polished is small. The standard deviation of does not fluctuate greatly. Therefore, the surface of the carrier for holding the object to be polished is coated again by the reduced thickness, so that it can be reused. After use, when the standard deviation of the thickness of the carrier for holding an object to be polished exceeds 5 μm, a step of correcting the standard deviation of the thickness by lapping or grinding may be provided in the pre-process or post-process of coating. . In addition, a resin frame is provided on the inner edge of the object holding hole of the object holding carrier for the purpose of preventing scratches generated at the end face of the object to be polished.

  Still another object of the present invention is to attach the carrier for holding an object of polishing of the present invention between the upper and lower surface plates to which an abrasive cloth is stuck, and to attach the object of polishing to a holding hole in the carrier for holding an object to be polished. In the polishing method in which at least one of the upper and lower surface plates and the object to be polished is rotated while supplying polishing slurry to the processing surface, and both surfaces of the object to be polished are mirror-polished. This is achieved by a polishing method which is one selected from polyurethane or a composite of nonwoven fabrics bonded with polyurethane.

The method of the present invention will be specifically described below with reference to Examples and Comparative Examples, but is not limited thereto.
Tables 1 and 3 show the polishing apparatuses and polishing conditions used in this example and the comparative example. As a polishing apparatus, a DSM-9B double-side polishing apparatus (manufactured by Speed Fam Co., Ltd.) was used. The polishing cloth used was SUBA800 and MHS-15A (Rodel). Rodel 2371 (Rodel) as an abrasive was prepared by adding 10 parts of pure water to 1 part of the stock solution and stirring.

<Manufacture of coated carrier>
An FRP frame in which aramid fibers are bonded with an epoxy resin is inserted around the object hole of the carrier substrate made of SUS304. The carrier substrate into which the resin frame was inserted was adjusted to a thickness of 550 μm and a standard deviation of thickness of 0.72 μm by lapping. After lapping, this carrier base material was mounted on a DSM-9B double-side polishing apparatus, and polishing was performed for the purpose of removing a strain layer on the surface using MHS-15A as a polishing cloth and cerium oxide slurry as an abrasive. The polished carrier substrate had a thickness of 547 μm and a standard deviation of thickness of 0.86 μm. The surface of the carrier substrate after polishing was coated with titanium nitride (TiN) by the PVD method. The carrier for holding an object to be polished completed by coating with TiN had a thickness of 550 μm and a standard deviation of thickness of 1.22 μm.
<Abrasion test and durability test>
Polishing was performed under the conditions shown in Table 1 without holding the object to be polished on the obtained coated carrier. The diluted abrasive was recycled. The wear rate was determined from the difference between the thicknesses of the carrier before and after polishing measured with a micrometer. Durability was confirmed by visual inspection.

[Comparative Examples 1 to 4]
As the carrier, four kinds of aluminum, SUS, glass epoxy resin (EG), and FR-vinylon, which are not coated with TiN, were used.
All four types had a thickness of approximately 550 μm. As in Example 1, polishing was performed under the conditions shown in Table 1 without holding the object to be polished on the carrier. The diluted abrasive was recycled. Table 2 shows the results of the polishing test in Example 1 and Comparative Examples 1 to 4.

^＊1窒化チタンは、ＳＵＳ３０４の表面に厚さ１．５μｍで被覆した
^＊2ガラスエポキシ樹脂
^＊3歯の付け根にクラック発生

^{* 1} Titanium nitride was coated on the surface of SUS304 with a thickness of 1.5 μm.
^{* 2} Glass epoxy resin
^{* 3} Cracks at the base of teeth

  The coated carrier manufactured in the example was held on a 6-inch silicon wafer as an object to be polished, and was polished under the conditions shown in Table 3. Polishing was performed with a target thickness of a 6-inch silicon wafer set to 550 μm. After polishing, flatness (TTV) was measured. As TTV, ULTRAAGE 9700 (manufactured by ADE) was used. The results are shown in Table 4.

[Comparative Example 5]
Using a carrier made of SUS having a thickness of 450 μm, polishing was performed with the target thickness of a 6-inch silicon wafer set to 550 μm under the same conditions as in Example 2. After polishing, flatness (TTV) was measured. TTV used ULTRA GAGE 9700 (made by ADE). The results are shown in Table 4.

An attempt was made to regenerate the worn carrier of the present invention used in the abrasion test of Example 1.
The thickness of the carrier of the present invention before the abrasion test was 550 μm, and the standard deviation of the thickness was 1.22 μm. The carrier after the abrasion test had a thickness of 547 μm and a standard deviation of thickness of 1.2 μm. Although the thickness of the carrier decreased by 3 μm by the abrasion test, the standard deviation of the thickness did not change.
This carrier was coated with TiN under the same conditions as in the example.
When the thickness of the carrier was measured after coating, the standard deviation of the thickness of 550 μm was 1.5 μm. A polishing test was performed under the same conditions as in Example 2 using the regenerated carrier. After polishing, flatness (TTV) was measured. The results are shown in Table 4.

Description of Examples and Comparative Examples When comparing Example 1 and Comparative Examples 1 to 4, the wear rate is remarkably good in Example 1, and FR-vinylon in which glass fibers are bonded with vinylon (Comparative Example 4) is next. Good results were obtained. After completion of the test, the damaged state of each carrier was examined by appearance inspection, and there was no change in Example 1 tested for 10 hours. There was no change in Comparative Examples 1, 2 and 3 tested for 1 hour. However, in Comparative Example 4, cracks occurred at the base of the carrier teeth.

Evaluation of Example 2 and Comparative Example 5 A 6-inch silicon wafer was held as an object to be polished on the coated carrier having a thickness of 550 μm manufactured in the example, and polishing was performed under the conditions shown in Table 3. Polishing was performed with a target thickness of a 6-inch silicon wafer set to 550 μm. In Comparative Example 5, a 6-inch silicon wafer was held as an object to be polished on an SUS carrier having a thickness of 450 μm, and polishing was performed under the conditions shown in Table 3. When the TTV of Example 2 and Comparative Example 5 were compared, the TTV of Example 2 was less than half that of Comparative Example 5.
The carrier of the present invention shown in Example 1 obtained very good results in terms of wear resistance and durability. Further, as shown in Example 2, the carrier for holding an object of the present invention is made substantially the same as the target thickness carrier 550 μm of the object to be polished, so that the TTV can be polished better than the comparative example. I was able to achieve it.

  In Example 3, 3 μm of TiN was newly coated on the carrier whose thickness was reduced by 3 μm by the wear test. Although the standard deviation of the thickness after coating slightly increased, it was within the usable range. Using this regenerated carrier, a polishing test was performed under the same conditions as in Example 2, and the flatness (TTV) of the polished wafer was measured. The results are shown in Table 4 as Example 3. When the result of Example 3 was seen, it was a result comparable with Example 2. That is, it was confirmed that the surface of the carrier for holding an object to be polished whose thickness has been reduced by repeated use can be reused by re-coating the carrier base material or a material having higher hardness than the carrier base material.

As described above, the use of the carrier for holding an object to be polished according to the present invention improves the durability and wear resistance of the carrier, which is a consumable item, and the object to be polished whose thickness has become less than a certain level by repeated use. Since the surface of the carrier for holding objects can be reused by re-coating the carrier base material or a material having a higher hardness than the carrier base material, its effect is extremely large from the economical and quality viewpoints. is there. Further, by making the standard deviation of the in-plane thickness of the carrier for holding an object to be polished to 5 μm or less, it becomes possible to provide a polishing method for polishing an object to be polished with high flatness, thereby improving the yield of silicon wafers and the like. In actual production, it can be very helpful.

Claims (5)

A carrier for holding an object to be polished having one or more objects to be polished holding holes provided with a resin frame on the inner edge, wherein the carrier base of the part made of metal of the carrier for holding an object to be polished A carrier for holding an object to be polished, characterized in that the surface is coated with a material that is the same as or higher in hardness than the carrier substrate. 2. The carrier for holding an object to be polished according to claim 1, wherein a standard deviation of an in-plane thickness of the carrier for holding an object to be polished is 5 μm or less. The high-hardness material covering the surface of the carrier substrate is a metal belonging to Group 4A or Group 5A of the periodic table, or a nitride or carbide or composite thereof, or diamond-like carbon. Item 3. A carrier for holding an object to be polished according to any one of Items 1 to 2. The surface of the carrier substrate made of metal is coated with the same or higher hardness material as that of the carrier substrate, and the standard deviation of the in-plane thickness of the carrier for holding an object to be polished is 5 μm or less. A carrier for holding an object, and the thickness of the carrier for holding an object to be polished whose thickness of the coating layer has decreased by use is again given by coating with a material that is the same as or higher in hardness than the carrier substrate. A carrier for holding a recycled object. The carrier for holding an object to be polished according to any one of claims 1 to 4 is mounted between the upper and lower surface plates to which an abrasive cloth is attached, and the holding hole in the carrier for holding an object to be polished is mounted. A polishing method for holding a workpiece and then mirror polishing both surfaces of the workpiece by rotating at least one of the upper and lower surface plates to which a polishing cloth is attached while supplying a polishing slurry to a processed surface and the workpiece. .