JP2010030015A - Carrier for holding polishing material and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve polishing efficiency by solving a problem caused by enlargement of a carrier body for polishing a silicon wafer, and preventing local crack or earlier exfoliation of a DLC thin film formed on a carrier surface. <P>SOLUTION: The surface of a metallic carrier body is processed by shot-peening, and a concave and convex layer with a circular recess is formed and a concave and convex layer, on which a compression residual stress and surface hardening are generated, is formed simultaneously, to give rigidity to a base material. In this method for manufacturing a carrier for holding a material to be polished, a DLC thin film having hydrogen content of 13-30 atom% and remainder of carbon is coated and formed on the surface of the base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, an object to be polished such as a silicon wafer serving as a substrate of a semiconductor element is sandwiched between a pair of upper and lower surface plates to which an abrasive cloth is attached, and either or both of the abrasive cloth and the object to be polished are pressed. The present invention relates to a carrier for holding an object to be polished used for polishing the surface of the silicon wafer by sliding the substrate while sliding and a manufacturing method thereof.

  In recent years, in the field of the semiconductor industry and the like, there are processing steps for precisely polishing the surface of these members in the manufacturing process of silicon wafers, compound semiconductor wafers, aluminum magnetic disk substrates, glass magnetic disks and the like. In this process, when polishing an object to be polished such as a silicon wafer, an outer peripheral tooth having a holding hole for holding the object to be polished and engaging with an internal gear or a sun gear of a double-side polishing machine at the outer peripheral edge. It is common to use a carrier with

  For example, FIG. 1 shows the appearance of a disk-shaped carrier (also called a holder) used when polishing a silicon wafer. Here, 1 is a holding hole for a silicon wafer, and a plurality of holes are provided in accordance with the shape of the silicon wafer. Reference numeral 2 denotes an abrasive supply hole made of a water slurry in which fine abrasive particles are suspended, and a plurality of abrasive supply holes are also provided. 3 is an outer periphery tooth | gear provided in the outer peripheral part of the carrier. Reference numeral 4 denotes variously shaped holes for reducing the weight of the carrier itself. Reference numeral 5 denotes a surface of the carrier body for forming the DLC thin film.

In the first place, since this silicon wafer itself is very thin (less than 0.5 to 1 mm), the carrier body is also made of a thin material and is polished together with the silicon wafer. Therefore, it is necessary to have excellent wear resistance. In addition, recent silicon wafers having a large diameter of 12 inches (about 30 cm) have appeared, and a plurality of silicon wafers are attached to 15 carriers, and the size of the carriers exceeds 1 m. Some are large. Such a large carrier has a problem that a large deformation stress is applied during the handling thereof, so that the silicon wafer is often damaged or dropped off. In addition, when the silicon wafer is polished, the carrier body is also polished, and the fine metal-based particles generated at this time cause a decrease in the purity of the silicon wafer.
In particular, there is a need for high-quality silicon wafers today, and even the presence of trace amounts of metal ions eluted from the carrier body during polishing is avoided, so it is important to study the material of the carrier body and develop a surface treatment film. This is a serious study issue.

  In order to solve the above-mentioned problems of the carrier, conventionally, the following proposal has been made for the configuration of the carrier. For example, Patent Documents 1 and 2 disclose a polymer material reinforced with nonmetallic glass fibers, and Patent Document 3 discloses metals such as stainless steel, SKH steel, SKD steel, and SUJ steel. The use of materials is disclosed.

Patent Document 4 discloses a metal carrier having a carrier coated with a ceramic coating, and Patent Document 5 discloses a SK steel carrier having a surface coated with metal plating. Further, Patent Document 6 discloses a technique in which ceramic particles are deposited on the surface of a metal carrier, and then a DLC thin film (diamond-like carbon thin film) is coated thereon. A technique for forming the DLC thin film directly on the surface of a metal carrier is proposed.
JP 2001-038609 A JP-A-11-010530 Japanese Patent No. 3974632 JP-A-4-26177 JP 2002-018707 A JP-A-11-010530 JP 2005-254351 A

  Among the above-described prior arts, the so-called method for coating a DLC thin film on the surface of a metal carrier body disclosed in Patent Documents 3 and 7 involves polishing the surface of the carrier body, that is, a mirror surface. Finished product is used. This is because the DLC thin film formed on the surface of the carrier bodies disclosed in Patent Documents 3 and 7 has a very thin thickness of 0.1 μm to 20 μm. It means that there was. That is, in these techniques, a DLC thin film having a thickness of about 0.1 μm cannot be evenly formed unless mirror finishing called polishing is performed.

However, according to research by the inventors, it has been found that in the case of a mirror-finished carrier body, there is the following problem when a DLC thin film is formed on the mirror surface.
(1) Mirror finish on the surface of the carrier body requires a lot of work time and increases costs. In particular, when forming a DLC thin film having a thickness of 0.1 μm, even if a slight polishing mark is present, that portion often causes a defect in the DLC thin film.
(2) Since the DLC thin film is an amorphous solid mainly composed of carbon and hydrogen generated from a hydrocarbon-based gas, it has a problem that it has a large residual stress during film formation and is easily peeled off. is there. In particular, in the case of a large carrier body having a small plate thickness, it tends to be subjected to a large deformation stress. Therefore, if the DLC thin film coated on the surface of the body is a mirror surface, the carrier body is easily peeled off. In this regard, Patent Document 3 proposes to limit the residual stress of the DLC thin film to 0.5 MPa or less, but there are many difficulties in developing a plasma CVD method therefor.
(3) When regenerating only the DLC thin film, it is difficult to remove the remaining DLC thin film, and it takes a long time to finish the mirror finish, resulting in a reduction in work efficiency, resulting in the cost of the product. Invite up.
(4) As described above, in recent years, the carrier has been made larger and made of a thin metal, and furthermore, since a large number of holes of various sizes are provided, it is possible to avoid large deformation during handling. However, there was a problem that cracks and local peeling were likely to occur in the DLC thin film.

  Accordingly, an object of the present invention is to propose a carrier configuration that can overcome the above-described problems of the prior art and an advantageous manufacturing method thereof.

  In particular, in the present invention, a carrier having a high DLC thin film adhesion to the carrier body, a high rigidity of the body, excellent handling properties, and excellent polishing efficiency, and establishment of a technology capable of efficiently manufacturing the carrier are established. The purpose is to plan.

As a result of diligent research to solve the above-mentioned problems of the prior art and realize the above object, the inventors have obtained the following knowledge.
(1) The surface of the carrier main body is not mirror-finished, and on the contrary, a surface modification treatment (so-called ““ By applying peening processing "), the processed surface is formed into a concavo-convex layer formed by fine spherical depressions, and at the same time, the processing influence layer in which any one or more of compressive residual stress and work hardening is expressed on the surface When a DLC thin film is formed on the surface of the DLC thin film, the adhesion of the DLC thin film can be remarkably improved.
(2) Since the processing influence layer is generated on the surface of the main body by the peening processing, the carrier can increase the rigidity of the carrier main body and can prevent the carrier main body from being deformed.
(3) Since the DLC thin film formed on the peened layer is affected by the peened layer and has microscopic unevenness, the abrasive particles stay in the recess during the silicon wafer polishing. As a result, the polishing efficiency is improved.
(4) When the DLC thin film made of an amorphous solid film is controlled to have a hydrogen content of 12 to 30 at% (atomic%), the DLC thin film itself is given flexibility as well as wear resistance.

  The present invention developed under such knowledge is characterized in that a metal carrier body having a shot peened layer on the surface is coated with a DLC thin film via the shot peened layer. It is a carrier for holding an abrasive.

In the carrier for holding an object to be polished according to the present invention,
(1) The shot peening layer is a concavo-convex layer formed by a spherical depression obtained by spraying a spherical shot, and at the same time, is a processing-affected layer in which at least one of compressive residual stress or work hardening is expressed. Being a layer,
(2) The shot peening layer is a layer whose surface roughness is adjusted in the range of 0.15 to 1.50 μm in Ra value and 1.55 to 6.0 μm in Rz value,
(3) The shot peening layer is a layer formed by superimposing a fine roughened layer formed by spraying square grinding particles finer than a shot on the concavo-convex layer on the surface thereof. ,
(4) The shot peening layer has a surface roughness Rsk value in a range less than ± 1, and (5) the DLC thin film has a film thickness exceeding 20 μm and exceeding the roughness Rz of the shot peening layer. Having
(6) The DLC thin film is a film having a hydrogen content of 13 to 30 atomic% and the balance being carbon.
(7) The metal carrier body is made of at least one metal / alloy selected from special steels such as aluminum alloy, titanium alloy, stainless steel, SK steel, and SKH steel,
Is a preferred solution.

  In the present invention, a shot peening layer composed of a concavo-convex layer formed by a spherical depression is formed by spraying a shot made of spherical particles on the surface of a metal carrier body, and the surface of the shot peening layer In addition, a method of manufacturing a carrier for holding an object to be polished, characterized by coating a DLC thin film.

In the manufacturing method of the object holding carrier of the present invention,
(1) A shot peening layer is formed by spraying a shot made of spherical particles on the surface of a metal carrier body, and thereafter, square grinding particles smaller than the shot grains are formed on the surface of the shot peening layer. Spraying and forming a fine roughening layer superimposed thereon, and further coating a DLC film on the surface of the shot peening layer including the roughening treatment layer,
(2) Shot or grinding particles are sprayed using 0.21 to 0.5 MPa of compressed air, and the shots and grinding particles are from a direction of 60 to 90 ° with respect to the surface of the metal carrier body. Spraying,
(3) The surface of the carrier body obtained by spraying a shot made of any one or more spherical particles selected from castings, stainless steel, high speed steel, cemented carbide, glass and ceramics. Is a fine irregular layer formed by a spherical depression, and at the same time, a layer that has become a processing-affected layer that expresses at least one of the addition of compressive residual stress or work hardening,
(4) The DLC thin film has a hydrogen content of 13 to 30 atomic% and the balance is made of carbon.
(5) The DLC thin film is coated on the surface of the carrier body by any one of a plasma CVD method, a sputtering method, and an ion plating method,
Is a preferred embodiment.

In the present invention, the following effects can be obtained by adopting the above solution.
(1) The shot peening process employed in the present invention is easier than the conventional mirror finishing process, and the processing time is shortened, so that productivity is improved.
(2) In the present invention, since the DLC thin film is formed on the shot peened layer and the adhesion area is widened, the adhesion of the thin film is greater than that of a conventional DLC thin film that is mirror-finished.
(3) Since the shot peening layer is formed by spraying a spherical shot on the surface of the carrier body, at least the surface of the layer has a work-affected layer such as work hardening, and also generates compressive residual stress. Therefore, the rigidity of the carrier body is increased. As a result, the carrier body is not deformed during handling, handling becomes easy, and fatigue strength is improved.
(4) Since the carrier according to the present invention undergoes little deformation during handling, it does not peel off even when a large residual stress is generated in the DLC thin film formed on the surface thereof. As a result, as a method for forming the DLC thin film, not only the plasma CVD method but also many methods such as an ionized vapor deposition method, an arc ion plating method, and a plasma booster method can be adopted.
(5) According to the present invention, since a carrier with less deformation at the time of handling can be obtained, the silicon wafer attached thereto is less likely to be subjected to stress accompanying deformation. Therefore, unlike the conventional case, the silicon wafer is not detached from the carrier during handling.
(6) In the present invention, the DLC thin film formed on the shot peened layer has a flatness necessary for polishing a silicon wafer while maintaining microscopic unevenness due to the influence of the carrier body surface. Therefore, when the silicon wafer is polished, ultrafine particles (0.01 to 0.1 μm) such as colloidal silica contained in the water slurry abrasive easily remain in the recesses. Moreover, since such recesses are evenly present on the surface of the DLC thin film, not only the polishing efficiency of the silicon wafer is improved, but also the polishing itself is performed uniformly and the quality is improved.
(7) The above shot peening process is very effective not only when forming a DLC thin film on a new carrier body, but also as a method for removing the DLC thin film, so that it can be used as it is as a pretreatment for regenerating the DLC thin film. This is advantageous in terms of cost.

Hereinafter, the configuration of the carrier for holding an object to be polished according to the present invention will be described together with the description of the manufacturing method.
(1) Treatment for forming a shot peening layer on the surface of a metal carrier body In the present invention, a spherical shot of a metal or non-metal having a particle size of several μm to several mm with respect to the surface of the metal carrier body. The shot peening layer is obtained by performing cold working (shot peening) to generate countless dents (scratches) while spraying the surface using compressed air and hitting the work surface (carrier body surface). Is a carrier having a DLC film formed thereon. In the present invention, if necessary, with respect to the surface of the shot peening layer, a polygonal shape such as SiC or Al ₂ O ₃ having a particle size of about several μm to 20 μm, which is smaller than a shot, preferably an acute angle. A finer surface roughening treatment may be performed by spraying square abrasive particles having corners.

For shots for shot peening, spherical particles such as cast steel, stainless steel, high speed steel, cemented carbide, glass, ceramics can be used, while for roughening treatment (blasting treatment) As the grinding particles, hard ceramic square particles such as Al ₂ O ₃ , SiO ₂ , SiC, and AlN are suitable, and particles smaller than the spherical particles used in the shot peening process are used. The reason for this is that when square grinding particles larger than the spherical particles for shot peening are used, the roughness of the treatment surface increases and the uneven surface becomes coarse, making it an inappropriate surface as a treatment surface for the DLC film. Because. In addition, with rough surface roughening, effects such as the generation of compressive stress and work hardening on the substrate surface due to shot peening processing disappear, and large concave portions generated by abrasive particles are notched when handling a thin carrier body. This is because the effect may be exerted to induce permanent deformation at the time of bending deformation of the carrier body.

  2 shows the shot peening process layer (a) (b) according to the present invention and the shot peening process surface, and further subjected to blasting process for spraying fine square grinding particles. It is the figure which observed the surface (c) (d) of the carrier main body with the electron microscope. In the shot peened layers (a) and (b) suitable for the present invention, small depressions are uniformly generated over the entire surface. The generation of this small depression surface generates a compressive stress on the surface of the carrier body, and the work hardening phenomenon becomes obvious, which increases the rigidity of the carrier body and occurs when handling a thin carrier body made of SUS304 steel. It is possible to reduce deformation such as “bending” and “deflection”.

In the present invention, if necessary, a fine concavo-convex layer such as a blasted layer (c) or (d) obtained by spraying square grinding particles such as fine SiC onto the shot peened layer is superimposed. It is more effective to use a rough surface formed by the above process. Since the roughened surface formed by superimposing such irregularities exhibits strong adhesion strength with the DLC film formed on this surface, even if a load such as some deformation, tension, compression is added to the carrier body, The effect that the DLC film is difficult to peel off is exhibited.
As can be seen from the above, in the present invention, the outline of the large spherical depression that appeared during the previous shot peening process remains as it is even after the blasting process to be performed later, and the two uneven layers are overlapped. Thus, the two processing effects act in a superimposed manner.

  Hereinafter, an example in which stainless steel (SUS304) is used as the metal carrier will be described. A metal carrier is generally finished to a thickness of about 0.5 to 1.0 mm, and its external appearance is provided with a number of large or small circular or irregular holes as shown in FIG. It is. As described above, since the metal carrier is thin, it has a characteristic of being greatly bent (deformed) when it is carried.

Therefore, in the present invention, the surface of the carrier main body shown in FIG. 1 is first subjected to the shot peening processing for spraying the above-described shot made of spherical particles, thereby generating a peening processing layer on the surface of the carrier main body. . As the spherical shot used in this shot peening processing, in addition to the metals described in JIS B2711, various spherical particles described above, for example, hard particles such as glass and ceramics, carbides and oxides. A cermet with Ni or Co (average particle size of 5 to 80 μm) or the like is used, and these shots are blown onto the surface to be processed using compressed air with a pressure of 0.2 to 0.5 MPa. This is a method of forming a shot peening layer having roughness.
(A) Arithmetic mean roughness Ra: 0.15 to 1.50 μm,
(B) Ten-point average roughness Rz: 1.55 to 6.00 μm,

  In addition, when the pressure of compressed air is lower than 0.2 MPa, the time for the shot peening process is increased and it is difficult to obtain a uniform roughened surface. On the other hand, using compressed air with a pressure higher than 0.5 MPa is not preferable because the metal carrier body is deformed.

  The preferable shot peening processing conditions applied in the present invention include the glass, ceramic particles, cermet particles, and other hard particles (Hv: 200-1500), flight speed V: (30-100). ) To spray onto the surface (working surface) of the carrier body from a direction of 60 to 90 ° at a speed of m / sec or more.

  Under such spraying conditions, a concavo-convex layer formed by a spherical depression is formed on the surface of the carrier body, and at the same time, a layer that has become a work-affected layer in which either compressive residual stress or work hardening is expressed Is obtained. In this process, if the hardness of the sprayed particles is less than Hv: 200 or the flight speed thereof is 30 m / sec or less, it may not be possible to form a shot peening layer desired in the present invention. The above hardness varies depending on the material of the carrier body, and thus cannot be specified unconditionally. However, it is desirable that Hv ≧ 900 and the flight speed V is V: 80 m / sec or more, more preferably 100 m / sec or more. It is good to do.

  The reason why attention is given to these roughness values in the present invention will be described. When the surface of the shot peening layer formed by shot peening processing, that is, the surface of the shot peening spray particles (shot), is measured with a stylus roughness tester, Ra and Rz should be recorded in the same way. Can do. According to the results of measurements performed by the inventors, even if Ra is small, Rz is always large, and within the surface roughness range recommended by the present invention, Rz often reaches 7 times or more of Ra.

  FIG. 3 shows a schematic cross-sectional view when a DLC film is formed on the treated surface after performing the above-described shot peening processing according to the present invention. Here, FIG. 3 (a) shows a DLC film formed on the surface after shot peening processing, and the surface of the base material is formed with unevenness formed by a bottom-shaped depression traced from a spherical shot. At the same time, a processing-affected layer serving as a residual stress generation source and a work hardening source is simultaneously formed on the substrate side. In addition, the projection part displayed by Rz also exists in the to-be-processed surface of a shot peening process.

  On the other hand, FIG. 3B shows shot peening in which large and small concavo-convex layers are superposed by performing a blasting process for spraying square grinding particles having a particle diameter smaller than that of the shot after the shot peening process. The cross-sectional schematic diagram when a DLC film is formed on the processed layer is shown. As shown in this figure, due to the effect of the subsequent blasting treatment, a rough surface appears in which a large rugged layer and a small rugged layer are superimposed by a broad spherical depression, and the junction area with the DLC film is dramatically increased. To improve. However, in the present invention, even if a subsequent blasting process is performed, the processing-affected layer at the time of the preceding shot peening process remains as it is, so that the rigidity of the base material can be maintained.

  In FIG. 3, 21 is a base material that is a carrier, 22 is a concavo-convex layer generated by shot peening processing, 23 is a protrusion corresponding to the Rz value measured during surface roughness, and 24 is during shot peening processing. A processing-affected layer is expressed, 25 is a DLC film, and 26 is a roughened layer generated by blast processing.

  In the present invention, after the shot peening process, if necessary, the Rz roughness value is adjusted by removing lightly using a buff or # 1000 or more polishing paper to remove mainly the convex portions. May be.

  The reason why the surface roughness Ra of the shot peening layer is restricted to the range of 0.15 to 1.50 μm is that the effect of the shot peening processing is thin if it is less than 0.15 μm, whereas if it is greater than 1.50 μm, This is because the DLC thin film formed thereon lacks uniformity, or the convex portions 25 are easily exposed depending on the film forming conditions, and the effect of covering the DLC thin film becomes poor.

  Next, in the present invention, as the roughness characteristics of the shot peening layer, it is preferable that the Rsk value is also within a predetermined management value range. That is, the roughness of this shot peening layer is managed using the skewness value (Rsk) of the roughness curve indicating the distortion in the height direction.

This Rsk value is defined by dividing the cube average of the height (Z ^(X) ) at the reference length (Ir) by the cube of the root mean square (Rq ³ ) as shown in the following equation. Is.

  As shown in FIG. 4, in the roughness curve in which the concave portion is wider than the convex portion, the Rsk value has a distribution in which the probability density function is biased toward the concave portion. Although the reverse is defined as a liability, in the present invention, the “distortion” is regulated to ± 1 or less regardless of whether the Rsk value is positive or negative.

  In the present invention, the reason why the Rsk value is regarded as important among the roughness of the peened layer is that the Rsk value is considered to be a numerical value indicating the surface property of the DLC thin film regardless of the surface roughness of the peened layer. It is.

  For example, when the surface roughness of these surfaces of a stainless steel substrate surface finished by electropolishing and subjected to peening treatment by spraying abrasive particles was measured, the results shown in Table 1 were obtained. was gotten.

  The measured values of the surface roughness such as Ra and Rz shown in Table 1 represent the roughness itself, but the Rsk value represents “distortion” of the measurement surface rather than the roughness. It is a parameter. Therefore, the inventors decided not only to regulate the surface roughness Ra and Rz but also to regulate the Rsk value as required.

Further, according to the study by the present inventors, it was found that the DLC thin film formed on the shot peened layer according to the present invention has a great influence on the performance of the silicon wafer polishing carrier. In other words, a DLC thin film coated on a stainless steel carrier having a shot peened layer having an Rsk value of less than ± 1 has a microscopic “distortion” under the influence of the Rsk value. It is considered that a fine silicon wafer abrasive such as colloidal silica stays in a portion corresponding to the “distortion” recess, and the abrasive particles improve the polishing efficiency of the silicon wafer.
In particular, since the retained portions of the abrasive particles are evenly distributed over the entire DLC thin film, the polishing of the silicon wafer is not only improved in efficiency, but the entire polished surface is polished evenly.

(2) Effect of shot peening process The metal carrier body subjected to the peening process has the following characteristics.
(A) By the shot peening processing, the processed surface of the carrier body becomes an uneven layer formed by a spherical depression obtained by spraying a spherical shot, and at least one of compression residual stress or work hardening is Since the developed processing influence layer also appears, the rigidity of the carrier body is increased. As a result, deformation such as “deflection” or “twist” that occurs when the carrier is transported or handled can be suppressed. Therefore, the damage rate due to cracking or peeling phenomenon occurring in the DLC thin film formed on the surface of the carrier main body can be reduced as compared with a mirror-finished surface of the carrier body.

  On the other hand, in the case of a DLC thin film on a conventional carrier body surface that has been mirror-finished, since the incidence of damage is increased by using the mirror surface, the residual stress during film formation is limited to 0.5 MPa or less (for example, Patent Document 3). In this respect, when the peened layer is formed according to the method of the present invention, such a restriction is eliminated. As a result, in forming the DLC thin film, not only the plasma CVD method but also many methods such as an ionization vapor deposition method, an arc ion plating method, and a plasma booster method can be adopted.

(B) In the case of a shot peened layer formed on the surface of the carrier body, the bonding area with the DLC thin film formed thereon is expanded, so that the adhesion strength of the thin film is increased, and a load such as some deformation, tension, compression, etc. Also, it becomes difficult to peel off. In particular, after shot peening treatment, when the blasting treatment that sprays finer abrasive particles on the treated surface is made into a composite groove where large and small uneven layers overlap, the effects of both are combined. Therefore, the adhesion of the DLC film is further improved. In this case, the shot peening process mainly prevents deformation and “twisting” of the carrier body, and the blasting process strongly receives the adhesion improving effect of the DLC film.

(C) Since the time required for the shot peening processing is shorter than the case where the surface of the carrier body is mirror-polished, in addition to the improvement in work efficiency, before the carrier with the DLC thin film is reused. It can also be applied as a process (can also be used for a process of removing old DLC thin film).

(3) About carrier main body (base material) The following thing can be considered as a carrier main body for raising the effect of the shot peening processing mentioned above. For example, various stainless steels such as SUS304, titanium and titanium alloys, aluminum and alloys thereof, special steels such as SK steel, SKH steel, and SUJ steel are particularly suitable.

(4) DLC Thin Film Coating Method A method and apparatus for coating a DLC thin film on the surface of a carrier body having a shot peening layer will be specifically described. In the present invention, the DLC thin film can be formed by any one of an ionized vapor deposition method, an arc ion plating method, a plasma booster method, and a high frequency / high voltage pulse superposition type plasma CVD method (hereinafter simply referred to as “plasma CVD method”). Is possible. However, the following description will explain the plasma CVD method.

  FIG. 5 is a schematic diagram of a plasma CVD apparatus used for coating a DLC thin film on the surface of a carrier body on which a shot peening layer has been formed through the above-described processing. The plasma CVD apparatus mainly includes a grounded reaction vessel 41, a high voltage pulse generating power source 44 for applying a high voltage pulse in the reaction vessel 41, and an object to be processed (hereinafter referred to as a “carrier body”) 42. In addition to a plasma generating power source 45 for generating unitary hydrogen-based gas plasma around it, a superimposing device 46 for simultaneously applying both a high-voltage pulse and a high-frequency voltage to the conductor 43 and the carrier body 42, It is interposed between the high voltage pulse generation power supply 44 and the plasma generation power supply 45. The conductor 43 and the carrier main body 42 are connected to the superimposing device 46 via the high voltage introducing portion 49.

  This plasma CVD apparatus includes a gas introducing device (not shown) for introducing an organic gas for film formation into the reaction vessel 41 and a vacuum device (not shown) for evacuating the reaction vessel 41, respectively. It is connected to the reaction vessel 41 via valves 47a and 47b.

  In order to form a DLC thin film on the surface of the object to be processed using this plasma CVD apparatus, first, the carrier body 42 is installed at a predetermined position in the reaction vessel 41, and the vacuum device is operated to operate the reaction vessel 41. After the inside air is discharged and deaerated, an organic gas is introduced into the reaction vessel 41 by a gas introduction device.

  Next, high frequency power from the plasma generating power supply 45 is applied to the carrier body 42. Since the reaction vessel 41 is in an electrically neutral state by the ground wire 48, the carrier main body 42 generates positive ions in a relatively negative plasma around the negatively charged carrier main body 42. It will be.

  When a high voltage pulse (negative high voltage pulse) from the high voltage pulse generator 44 is applied to the carrier body 42, positive ions in the organic introduction gas plasma are attracted and adsorbed on the surface of the carrier body 42. . By such treatment, a DLC thin film is generated and formed on the surface of the carrier body 42. That is, in the reaction vessel 41, a DLC thin film consisting of amorphous carbon hydrogen solids mainly composed of carbon and hydrogen is vapor-deposited around the carrier body 42 to cover the surface of the processing body 42. It is considered that a film is formed as described above.

  The inventors of the present invention use the plasma CVD apparatus to form a DLC thin film layer made of an amorphous carbon hydrogen solid formed on the surface of the object through the following processes (a) to (d). I guess.

(A) ionization of the introduced hydrocarbon gas (neutral particles called radicals also exist),
(B) Ions and radicals changed from the hydrocarbon gas impact impact the surface of the carrier body 42 to which a negative voltage is applied,
(C) C—H having a low binding energy is cut by the energy at the time of collision, and then activated C and H are polymerized by repeating the polymerization reaction to form an amorphous state mainly composed of carbon and hydrogen. Vapor deposition of carbon hydrogen solids of
(D) When the reaction (c) occurs, a DLC thin film composed of a deposited layer of amorphous carbon hydrogen solids is formed on the surface of the carrier body 42.

In this apparatus, the carrier body 42 can be ion-implanted by changing the output power of the high voltage pulse generating power supply 44 as shown in the following (a) to (d). .
(A) When ion implantation is focused on: 10 to 40 kV
(B) When performing both ion implantation and film formation: 5 to 20 kV
(C) When only film formation is performed: several hundred V to several kV
(D) When focusing on sputtering, etc .: several hundred V to several kV

In the high voltage pulse generation source 44,
Pulse width: 1 μsec to 10 msec
Number of pulses: It is also possible to repeat one to a plurality of pulses.

  Further, the output frequency of the high frequency power of the plasma generating power supply 45 can be changed in the range of several tens of kHz to several GHz.

  As the organic gas for film formation introduced into the reaction vessel 41 of this plasma CVD processing apparatus, a hydrocarbon gas composed of carbon and hydrogen as shown in the following (a) to (c) is used.

(I) Gas phase state at room temperature (18 ° C.) CH ₄ , CH ₂ CH ₂ , C ₂ H ₂ , CH ₃ CH ₂ CH ₃ , CH ₃ CH ₂ CH ₂ CH ₃
(B) Liquid phase at normal temperature C ₆ H ₅ CH ₃ , C ₆ H ₅ CH ₂ CH, C ₆ H ₄ (CH ₃ ) ₂ , CH ₃ (CH ₂ ) ₄ CH ₃ , C ₆ H ₁₂ ,
C ₆ H ₄ Cl

  The gas introduced into the reaction vessel 41 in the gas phase at normal temperature can be introduced into the reaction vessel 41 as it is, but the compound in the liquid phase is heated to gasify it. A DLC thin film can be formed by supplying gas (vapor) into the reaction vessel 41.

(5) DLC thin film formed under the present invention The DLC thin film formed on the carrier surface provided with the shot peening layer as described above has the following characteristics.
(A) Ratio of carbon and hydrogen content constituting the DLC thin film The DLC thin film is hard and excellent in wear resistance, but lacks flexibility. For this reason, when the carrier body is made of a large and thin metal, etc., and a plurality of holes of various sizes are provided, if the DLC thin film is coated, the carrier body is greatly deformed when it is carried Cracks may occur in the DLC thin film with poor ductility and sometimes peel off. As a countermeasure, in the present invention, attention is paid to the ratio of carbon and hydrogen constituting the DLC thin film, and in particular, the DLC thin film is resistant to wear by controlling the hydrogen content to 12 to 30 atomic% (at%) of the whole. It was decided to give flexibility as well as sex. Specifically, the hydrogen content contained in the DLC thin film was 12 to 30 atomic% (at%), and the balance was the carbon content. Formation of the DLC thin film having such a composition can be accomplished by mixing compounds having different hydrogen contents in the hydrocarbon-based gas for film formation.

(B) Surface properties of DLC thin film In the present invention, even the DLC thin film can exhibit sufficient corrosion resistance and wear resistance, and at the same time can be given flexibility, and can be sufficiently practical as a carrier for polishing silicon wafers. is there.

Example 1
In this example, DLC thin films with different film thicknesses are formed directly on the surface of the SK steel substrate that has been mirror-finished and on the shot peened layer that has been finished to various surface roughnesses by shot peening. did. Subsequently, these test pieces were subjected to a salt spray test to investigate the surface roughness of the substrate and the corrosion resistance of the DLC thin film.

(1) Test base material The test base material was SK steel (SK60 annealing material), and a test piece having a width of 50 mm, a length of 70 mm, and a thickness of 2 mm was prepared from this base material. Then, the surface roughness about what performed the following pre-processing with respect to the whole surface of the test piece is shown.
(A) The shot peening process was performed with a roughness of Ra: 0.15 to 1.55 μm, Rz: 1.55 to 8.55 μm.
In this treatment, glass beads having a particle size range of 2 to 20 μm are used as spherical shots and sprayed using compressed air of 0.3 MPa. In addition, about some test pieces, what performed the blasting process by a SiC particle after the shot peening process was prepared.
(B) For reference, the following experiment for mirror finishing was performed.
(A) Electropolishing Ra: 0.01 to 0.013 μm Rz: 0.14 μm to 0.16 μm
(B) Buffing Ra: 0.013 to 0.015 μm Rz: 0.20 to 0.29 μm
(2) Formation method and film thickness of DLC thin film A plasma CVD method was used to form the DLC thin film, and a DLC thin film having a thickness of 0.5 to 20 μm was formed on all the test pieces.
(3) Test Method and Conditions The test piece on which the DLC thin film was formed was subjected to the salt spray test specified in JIS Z2371 for 96 hours, and the presence or absence of red rust generated on the DLC thin film surface after the test was investigated.
(4) Test results The test results are summarized in Table 2. As is clear from this result, in the DLC thin film of the test piece formed on the substrate roughened by the shot peening processing according to the method of the present invention, the DLC thin film is affected by the surface roughness and is thinner than the Ra value or the Rz value. The thin films (No. 1, 2, 3, 4, 5, 6) had insufficient corrosion resistance and red rust was observed. However, even when the DLC thin film on the shot peened layer was formed thicker than the Rz value of the surface roughness (No. 1 to 6), it was confirmed that red rust was not generated and sufficient corrosion resistance was exhibited.
DLC thin film specimens formed on the surfaces of the electropolished surfaces (Nos. 7 and 8) and buffed surfaces (Nos. 9 and 10) used as reference examples were found to have red rust even when they were 0.5 μm thick. There wasn't.

  From this, as in the case of electrolytic polishing and buff polishing in the mirror state shown as a reference example, even when the shot peening processing of the present invention is performed, the thickness is at least larger than the Rz roughness value and is 20 μm or less. When the DLC thin film was formed, the corrosion resistance of the film was found to be the same as that of the conventional mirror surface and completely inferior.

  As described above, when the roughness of the substrate surface is set to Ra: 0.15 to 1.55 μm and Rz: 1.55 to 8.55 μm by the shot peening processing, the thickness of the DLC thin film is 2.0 to 20 μm. It was found that when the film thickness was within the range and the film thickness was larger than the Rz value, film formation without elution of the base material component was possible.

(Example 2)
In this example, a DLC thin film with varying hydrogen content was formed on the surface of a stainless steel (SUS304) substrate, and the resistance to bending deformation and subsequent changes in corrosion resistance were investigated.

(1) Properties of the test substrate and DLC thin film The test sample was stainless steel (SUS304), and a test piece having a size of width 15 mm × length 70 mm × thickness 1.8 mm was prepared from this substrate. Thereafter, the entire surface of the test substrate is subjected to a shot peening process, and a roughening process of Ra: 0.16 to 1.02 μm and Rz: 1.58 to 2.99 μm is performed, and the shot peening process is performed. A test piece having a hydrogen content in the layer of 5 to 50 atomic% and the balance being a carbon component was formed to a thickness of 3.5 μm.
(2) Test method and conditions The test piece on which the DLC thin film was formed was subjected to bending deformation at 180 ° (U-bend shape), and the appearance of the DLC in the bent portion was observed with a 20-fold magnifier. Further, the bending test piece after the observation was immersed in a 10% HCl aqueous solution and allowed to stand at a room temperature of 21 ° C. for 48 hours, and a change in color tone due to ions eluted in the HCl aqueous solution was examined.
(3) Test results Table 3 summarizes the test results. As is clear from this test result, the DLC film with a small hydrogen content (test piece No. 1, 2, 3) generates cracks when it is deformed to 1800, or has a small area but is locally There was a drop in the membrane. It was confirmed that these DLC thin films lack flexibility. On the other hand, when the test piece after the bending test is immersed in 10% HCl, the cracked DLC thin film (No. 3) is obtained from a base material of stainless steel to metal ions (iron as a main component and a small amount of C
(including r and Ni), and the aqueous HCl solution changed from colorless and transparent to yellowish green.
On the other hand, the HCl aqueous solution in which the DLC thin film (No. 4 to 8) containing 1.5 to 59 atomic% of hydrogen content is immersed is colorless and transparent, and is flexible even when subjected to 900 deformation. It was found that the film having the initial state was maintained.
However, as the hydrogen content in the DLC thin film increases, it becomes softer and quality control becomes more difficult. Therefore, in the present invention, the hydrogen content in the range of 13 to 30 atomic% is adopted.

(Example 3)
In this example, the DLC thin film was formed by various methods on the entire surface of the test piece subjected to the shot peening process according to the present invention and the surface of the SK steel base material mirror-finished by buffing. Subsequently, the 180 ° bending test and the salt spray test were performed on the test piece, and the resistance to the bending deformation and the corrosion resistance of the DLC thin film were investigated.

(1) Test base material and its surface treatment The test base material was SK steel (SK60 annealed material), and a test piece having a width of 15 mm, a length of 70 mm and a thickness of 1.8 mm was prepared from this base material. Thereafter, buffing and shot peening were performed on the entire surface of the test piece. The roughness after each treatment was as follows.
(A) Surface roughness of buffed surface Ra: 0.02-0.08 μm Rz: 0.66-0.81 μm
(B) Surface roughness of shot peened layer Ra: 0.15 to 1.12 μm Rz: 1.58 to 4.10 μm
(2) Test method of DLC thin film The test piece on which the DLC thin film was formed was bent at 180 ° from the center (U-bend shape), and the appearance of the DLC thin film at the bent portion was observed with a 20 × magnifier. . Further, the test piece after observation was exposed to the salt spray test specified in JIS Z2371 for 96 hours, and the change in the DLC thin film was examined.
(4) Test results Table 4 summarizes the test results. As is clear from the test results, the surface of the test piece was buffed and a DLC thin film was formed thereon (Nos. 1, 3, 5, and 7). Thin film peeling was also observed. However, only the DLC thin film formed by plasma CVD of N0.7 had very few cracks and good adhesion to the substrate.

  On the other hand, according to the results of the salt spray test carried out after the bending test, it was observed that all the test pieces in which cracks and delamination were observed in the DLC thin film generated red rust, the cracks reached the base material and the anticorrosive action disappeared It was done. On the other hand, the test piece that maintained a healthy state even in the bending test exhibited excellent corrosion resistance without generating red rust in the salt spray test. From this result, it was confirmed that the DLC thin film according to the present invention is not limited to the plasma CVD method and can be applied to other existing DLC thin film forming methods.

Example 4
In this example, stainless steel (SUS304) is used as a base material, and the surface is buffed (polished), and the shot peening layer and the shot peening layer according to the present invention are further blasted. The adhesion strength of the DLC thin film formed was evaluated.

(1) Test base material and pretreatment A test piece having a width of 25 mm, a length of 30 mm, and a thickness of 3 mm was cut out from SUS304 steel as the test base material, and the following pretreatment was performed.
(A) Buffing (polishing): Ra: 0.01 to 0.014 μm Rz: 0.11 to 0.15 μm
(B) Shot peening layer: Ra: 1.05-1.45 μm Rz: 4.80-5.8 μm
(C) Blast processing layer after shot peening: Ra: 1.25 to 1.88 μm Rz: 5.55 to 6.0 μm
(2) DLC Thin Film Formation Method and Film Thickness For the formation of the DLC thin film, a plasma CVD method was used, and a DLC film having a thickness of 7 μm was formed on all the pretreatment test pieces. Incidentally, the hydrogen content in the DLC thin film is 18 atomic% and the balance is carbon.
(3) Test method For the adhesion strength of the DLC thin film to the substrate, a drawing test (scratch test), which is widely used as an adhesion test of the coating film, was used. That is, a straight cut was made on the DLC thin film with a diamond needle loaded with a constant load, and the adhesion strength was determined based on whether or not the DLC thin film was peeled off at that time.
(4) Test results The test results are shown in FIG. This photograph shows the appearance of the DLC thin film after a scratch test with a diamond needle. When the DLC thin film is directly formed on the polishing surface, there are a large number of peeled portions of the DLC thin film along the scratches, indicating that the adhesion strength of the thin film is low. On the other hand, the DLC thin film formed on the surface subjected to the shot peening processing or the blast processing on the surface of the DLC film is excellent in that no scratches are observed due to diamond needles but peeling of the thin film is not recognized. It was confirmed to have adhesion strength.

(Example 5)
In this example, an experiment was conducted to qualitatively investigate the rigidity improvement of the carrier body pretreated by the shot peening process.

(1) Test base material and test piece Stainless steel (SUS304) was used as the test base material, and a test piece having a width of 30 mm, a length of 200 mm, and a thickness of 1 mm was cut out.
(2) Blasting process for test piece The following shot peening process was performed on one side of the test piece, and electrolytically polished stainless steel (SUS304) was used as a test piece for comparison.
(B) Surface roughness Ra of the base material surface by shot peening processing: 0.15 to 1.05 μm, Rz: 1.55 to 5.95 μm (b) Ra: 0.013 μm, Rz: 016 μm mirror-finished (3) Test method As shown in FIG. 7, various test specimens were fixed at one end of the test piece, and 1000 g of weight was placed on one tip. The change width of the tip of the test piece depending on the weight was measured.
(4) Test results The test results are summarized in Table 8. As is clear from this result, the test pieces roughened by the shot peening process (Nos. 1 to 4) have a smaller displacement width and are less likely to be deformed than the mirror-finished test pieces of the comparative example. Was recognized.

(Example 6)
In this example, an Si wafer having a diameter of 200 m and a thickness of 0.5 mm was polished using the carrier body having the shape shown in FIG. 1, and the effect of the DLC thin film according to the present invention was investigated. The following pretreatment and DLC thin film were formed on the entire surface of the carrier body.

(1) Properties of pre-treatment and DLC thin film according to the present invention The surface of the carrier body is roughened to Ra: 0.15-0.98 μm, Rz: 1.52-4.95 μm by shot peening processing. Thereafter, a DLC thin film containing a hydrogen content of 18 atomic% was formed thereon to a thickness of 5 μm.
(2) Pretreatment of comparative example and properties of DLC thin film After buffing the surface of the carrier body to a mirror surface of Ra: 0.02-0.10 μm, Rz: 0.11-0.16 μm, A DLC thin film was formed to a thickness of 5 μm. The hydrogen content in the DLC thin film is 15 atomic%, and the balance is carbon.
(3) Test results As a result of polishing a silicon wafer using a water slurry abrasive containing colloidal silica as an abrasive, the surface of the silicon wafer was reduced to 0 when the carrier body formed with the DLC thin film of the present invention was used. It took about 20 minutes to finish to 0.01 μm or less, but it took 58 minutes for the carrier body coated with the DLC thin film of the comparative example.

  The DLC thin film formation technology that uses the peening process according to the present invention as a pretreatment is not limited to polishing semiconductor wafers such as Si and GAP, but can be applied to polishing liquid crystal display glass and hard disks. is there.

It is a top view of the metal carrier main body for silicon wafer polishing. It is a SEM photograph of the processing surface which performed various pretreatments to the carrier body surface. It is the rough surface of the surface which carried out the peening process of the metal carrier main body, and the blasting process after a peening process, and the cross-sectional schematic diagram of the DLC thin film formed on it, (a) is the surface after a shot peening process When the DLC thin film is formed, (b) is a case where the DLC thin film is formed on the surface subjected to the blast processing after the shot peening processing. It is a schematic diagram which shows the skewness value (Rsk) in the surface roughness display of a shot peening process layer. It is the schematic of the plasma CVD apparatus for forming a DLC thin film in the carrier main body for grinding | polishing of a silicon wafer. It is an enlarged photograph which shows the DLC thin film surface state after a scratch test part. (A) DLC thin film was formed on the polished surface, (b) on the shot peened layer, (c) on the shot peened layer, and further on the blasted surface. It is the external appearance after a scratch test. It is the schematic of the condition which tested the rigidity of SUS304 steel which carried out the shot peening process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon wafer holding hole 2 Abrasive supply hole 3 Peripheral tooth 4 Outgoing hole 5 Carrier surface 21 forming DLC thin film Carrier body 22 Concavity and convexity layer 23 Protruding portion 24 Processing influence layer 25 generated during shot peening processing DLC thin film 41 Reaction vessel 42 Object to be treated (carrier body)
43 conductor 44 high voltage pulse generation source 45 plasma generation source 46 superposition device 47a, 47b valve 48 ground wire 49 high voltage introduction terminal

Claims (14)

A carrier for holding an object to be polished, wherein a metal carrier body having a shot peening layer on the surface is coated with a DLC thin film via the shot peening layer. The shot peening layer is a layer that is an uneven layer formed by a spherical depression obtained by spraying a spherical shot, and at the same time, is a layer that has become a processing-influenced layer in which at least one of compressive residual stress or work hardening has occurred. The carrier for holding an object to be polished according to claim 1, wherein: The shot peening layer is a layer whose surface roughness is adjusted in a range of 0.15 to 1.50 μm in Ra value and 1.55 to 6.0 μm in Rz value. 3. A carrier for holding an object to be polished according to 1 or 2. The shot peening layer is a layer formed by superimposing a fine roughened layer formed by spraying square grinding particles finer than a shot in the uneven layer on the surface thereof. The carrier for holding an object to be polished according to any one of claims 1 to 3. The carrier for holding an object to be polished according to any one of claims 1 to 4, wherein the shot peening layer has a surface roughness Rsk value of less than ± 1. 6. The carrier for holding an object to be polished according to claim 1, wherein the DLC thin film has a film thickness that exceeds the roughness Rz of the shot peening layer and is 20 μm or less. 7. The carrier for holding an object to be polished according to claim 1, wherein the DLC thin film is a film having a hydrogen content of 13 to 30 atomic% and the balance being carbon. The metal carrier body is made of one or more kinds of metals / alloys selected from special steels such as aluminum alloy, titanium alloy, stainless steel, SK steel, and SKH steel. The carrier for holding an object to be polished according to any one of the above. A shot peening layer consisting of a concavo-convex layer formed by a spherical depression is formed by spraying a shot made of spherical particles on the surface of a metal carrier body, and a DLC thin film is coated on the surface of the shot peening layer A method for producing a carrier for holding an object to be polished, characterized by comprising: A shot peening layer is formed by spraying shots made of spherical particles on the surface of the metal carrier body, and then, the surface of the shot peening layer is finely sprayed with square grinding particles smaller than the shot grains. Forming a roughening layer, and then coating a DLC film on the surface of the shot peening layer including the roughening layer. Method. The shot or abrasive particles are sprayed by using compressed air of 0.21 to 0.5 MPa, and the shot and the abrasive particles are sprayed from the direction of 60 to 90 ° with respect to the surface of the metal carrier body. The method for producing a carrier for holding an object to be polished according to claim 9, wherein the method is performed. The shot peening layer is obtained by spraying a shot made of any one or more spherical particles selected from casting, stainless steel, high speed steel, cemented carbide, glass, ceramics, and a spherical depression on the surface of the carrier body. 11. The fine concavo-convex layer formed by the above-mentioned method, and at the same time, it is a layer that has become a work-affected layer in which at least one of addition of compressive residual stress and work hardening is developed. A method for producing a carrier for holding an object to be polished as described in 1. 11. The method for manufacturing a carrier for holding an object to be polished according to claim 9, wherein the DLC thin film has a hydrogen content of 13 to 30 atomic% and the balance is made of carbon. 14. The DLC thin film is formed by coating the surface of a carrier body by any one of a plasma CVD method, a sputtering method, and an ion plating method. A method for manufacturing a carrier for holding an object to be polished.

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