JP2006210488A - Method and device for mechanochemical polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly efficiently work a compound semiconductor wafer of high hardness whose thickness is not more than 500 μm without damaging it, and to realize mechanochemical polishing with which surface roughness in a substrate is uniformly finished. <P>SOLUTION: In a mechanochemical polishing method, powder of one of oxides in chrome oxide, magnesium oxide, iron oxide and aluminum oxide is used as an abrasive grain, and the semiconductor wafer is polished as a material to be polished. A polishing plate 1 is formed of an elastic material whose shore hardness is 80 to 90. At least two kinds of grooves are formed in a polishing face of the polishing plate 1 which is brought into contact with the material to be polished. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to mechanochemical polishing, and more particularly to a polishing technique using oxide abrasive grains as abrasive grains.

  Power devices with low electrical energy loss and high performance directly contribute to a significant reduction in power consumption, and are used in many fields. Currently, a power device using a silicon wafer is used. However, due to material characteristics of silicon, there is a limit to further improving the performance of the power device by performing fine processing on silicon. In particular, since silicon cannot be used under conditions such as high temperatures, materials that replace silicon have become necessary.

  For example, SiC (silicon carbide) is an alternative material for silicon, but the forbidden band width of SiC is three times that of silicon, so that it can be used under higher temperature conditions than silicon. In addition, since the electric breakdown field is about 10 times that of silicon, it can be downsized. Furthermore, the thermal conductivity is about three times that of silicon, and there is an advantage that it is excellent in heat dissipation and is easily cooled. Since SiC has excellent characteristics as described above, the SiC substrate is attracting attention as a semiconductor substrate for power devices that replaces the silicon substrate.

By the way, in order to use a SiC substrate as a power device, it is necessary to polish the surface. As the final polishing method, a polishing method using a polishing with diamond abrasive grains or a suspension containing SiO ₂ (colloidal silica) is currently generally used. However, the MCP (mechanical chemical polishing) polishing method using chromium oxide abrasive grains having a higher processing rate has recently been attracting attention. It is disclosed that this construction method causes the processing to proceed by causing a solid phase reaction between the object to be polished and the abrasive grains (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 7-80770 JP 2001-205555 A

  In order to cause the above solid-phase reaction, it is necessary to bring the material to be polished and the polishing surface plate into contact with each other with a pressure of a certain level or more. However, the thickness of the workpiece in the final polishing process is generally 500 μm or less, and in addition, high hardness materials such as SiC are used in the lapping process, slicing process, and grinding process, which are the previous processes. Since it is difficult to finish the flatness of BOW or the like with high accuracy, a BOW shape of 10 to 30 μm is almost obtained even on a 2-inch substrate, and the workpiece in such a state is disclosed in Patent Document 1 described above. As shown, when pressed against a polishing surface plate using a material having a Vickers hardness of 1000 to 2000 at a high pressure, an elementary problem of damage to the substrate occurs before realizing the high-precision polishing that is the original purpose. High risk.

  The BOW used here is an international standard used as an index representing the shape of a semiconductor substrate. Briefly, the BOW is an arbitrary standard on the wafer surface when the wafer is in a free state (a state in which the back surface is not attracted or bonded). The shortest distance between the plane passing through three points and the center point of the wafer surface.

  In addition, as described in the above-mentioned Patent Document 2, it is thought that the substrate breakage can be reduced by using a polishing cloth made of a fiber material or a resin material as a polishing surface plate. It can be said that there is a difficulty in the processing rate regarded as the most problematic. Further, in long-time processing, it is predicted that the processing rate will be significantly reduced due to wear of the soft abrasive cloth.

  In order to solve the above-mentioned problems, the mechanochemical polishing method of the present invention is a mechanochemical polishing method for polishing a semiconductor wafer as a material to be polished using an oxide powder as abrasive grains. It is made of an elastic material having a hardness of 80 to 90, and has at least two kinds of grooves on the polishing surface of the polishing surface plate that comes into contact with the material to be polished.

  Further, the mechanochemical polishing method of the present invention is a mechanochemical polishing method in which an oxide powder is used as an abrasive grain to polish a semiconductor wafer as a material to be polished. The polishing surface plate has a Shore hardness of 80 to 90. After having been lapped and bonded to a common tool in order to keep the wafer at a predetermined flatness, which is made of an elastic material and has at least two kinds of grooves on the polishing surface side of the polishing surface plate that comes into contact with the material to be polished The wafer is polished.

  Further, the mechanochemical polishing apparatus of the present invention is a mechanochemical polishing apparatus that uses an oxide powder as abrasive grains to polish a semiconductor wafer as a material to be polished, and has a polishing surface plate with a Shore hardness of 80 to 90. The polishing surface of the polishing surface plate made of an elastic material and in contact with the material to be polished has at least two kinds of grooves.

  As described above, according to the present invention, a compound semiconductor wafer having a thickness of 500 μm or less can be processed with high efficiency without being damaged, and the surface roughness in the substrate can be finished uniformly.

  Hereinafter, embodiments of a mechanochemical polishing method and a mechanochemical polishing apparatus for a compound semiconductor substrate according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of a mechanochemical polishing apparatus in the present embodiment. The polishing surface plate 1 is fixed to a polishing table 2 that can rotate at a predetermined rotational speed, and can be driven to rotate counterclockwise in conjunction with the polishing table 2. The workpiece 3 is adsorbed and fixed to the polishing head 5 in a state where the workpiece 3 is bonded and fixed to the tool 4 shared with the previous process (this embodiment will be described later). The polishing head 5 can be driven to rotate in the same direction as that of the polishing table 2 in a state where the workpiece 3 is pressed against the polishing surface plate 1 with a predetermined pressure.

  A brush 7 is fixed to the tip of the brushing head 6 and can be driven to rotate while in contact with the polishing surface plate 1. The abrasive abrasive powder 8 is sprinkled in a predetermined amount by the operator near the position 9 on the polishing surface plate 1, and is transferred to the position of the brush 7 when the polishing surface plate 1 rotates counterclockwise. The Then, the polishing platen 1 further rotates counterclockwise in a state of being uniformly diffused on the polishing platen 1 by the brush 7, thereby contacting the workpiece 3.

  On the polishing platen 1, powdered abrasive particles are dispersed and the free abrasive particles produced by the dispersed abrasive particles are added to the fixed abrasive particles produced by the abrasive particles held on the polishing platen 1. Furthermore, the processing rate can be improved. In this case, as a countermeasure against clogging of the polishing surface plate 1, clogging is prevented by mounting a resin brush 7 on the polishing apparatus and brushing the polishing surface plate 1 at the same time as polishing.

  Further, the polishing surface plate 1 is formed with a first spiral groove for promoting polishing of the workpiece, and the abrasive grains arranged in the crests of the groove are connected to the polishing surface plate 1 and the surface to be polished. A liberation action is generated between the workpiece 3 and the polishing of the workpiece is promoted. When excess abrasive grains leaked from the crests of the grooves are discharged to the valleys of the second grooves that are deeper than the depth of the first grooves formed to discharge the abrasive grains, and are brought into contact with the brush 7 again. In addition, the bristle of the brush 7 enters the groove and is dug up to prevent clogging of the groove.

  That is, even when the abrasive grains on the surface are worn, a decrease in the processing rate can be prevented by deriving new abrasive grains in the inner layer. The surface of the polishing surface plate is provided with spiral grooves for the purpose of preventing the object to be polished from adhering to the polishing surface plate, improving the processing pressure, and discharging used abrasive grains. .

  FIG. 2A is an external view of the polishing surface plate 1 in the present embodiment.

  The shape was a disk shape with a diameter of 200 mm and a thickness of 10 mm, urethane rubber was used as the material, and the Shore hardness was 80-90. In the urethane rubber, abrasive grains are kneaded in advance. As a result, there are abrasive grains with abrasive grains held by urethane rubber on the surface of the polishing platen, enabling processing without supplying abrasives, and when the abrasive grains on the surface are worn However, a decrease in the processing rate can be prevented by deriving new abrasive grains in the inner layer.

  In this embodiment, urethane rubber whose hardness is relatively easy to adjust is used, but the same effect can be predicted with fluororubber. In this example, chromium oxide (III) having a particle size of 1.6 μm was contained in the urethane rubber at a ratio of about 60%. In this embodiment, chromium oxide was used as the abrasive grains to be contained in the polishing surface plate and the abrasive grains to be dispersed. However, similar effects can be obtained with oxide abrasive grains such as iron oxide, magnesium oxide, and aluminum oxide. The surface of the polishing surface plate 1 was grooved using a facing device. A diamond tool having a nose radius of 0.3 mm was used as a facing tool.

  The groove shape that can be formed by using a facing device is spiral and concentric, and the effect is considered to be the same, but due to the processing principle of the facing device, it takes a longer time to form a concentric circle than a spiral. The spiral was selected to have Specifically, facing means that a diamond cutting tool is brought into contact with the vicinity of the center of the polishing surface plate while the polishing surface plate is rotated at a constant speed, and the groove machining is performed by moving the polishing plate at a constant speed toward the outer periphery of the polishing surface plate. The groove depth is determined by the contact depth between the diamond tool and the polishing surface plate, and the groove pitch is determined by the relationship between the number of rotations of the polishing surface plate and the moving speed of the diamond tool. It becomes a continuous spiral shape to the outer periphery.

  When making this concentric circle, with the diamond bite in contact with the polishing platen, rotate the polishing platen once to form the first groove, and then move the diamond bite by the required pitch. Then, the second groove is formed by further rotating the polishing surface plate once, which takes much time compared to the former. In addition, as an apparatus capable of forming grooves, a typical milling machine can be used as a processing machine, and a grid-like groove can be formed. However, a fine groove such as the first groove in this embodiment can be used. Formation is considered difficult due to the limit of miniaturization of the end mill, which is a processing tool.

  FIG. 2B is a detailed view of the groove shape. The grooves X were produced for the purpose of discharging unnecessary abrasive grains, and the pitch was 2.5 mm and the depth was 0.25 μm. The groove Y was produced for the purpose of holding the abrasive grains, and the pitch was 0.5 mm and the depth was 0.08 μm. The groove shape is not limited to this specification, but it is known that when the groove X is not present or too shallow, clogging occurs and the processing rate is drastically reduced. Further, it can be said that the groove Y needs to be optimized depending on the type and particle size of the abrasive grains.

  The purpose of the grooves X and Y will be further explained. If a polishing surface plate that does not have any grooves is used, the abrasive grains are not retained, so that the abrasive particles only slide between the workpiece and the polishing surface plate. It is clear that processing does not progress. Therefore, the groove Y is required. Next, in the case where only the groove Y is produced and there is no groove X, the abrasive grains are in contact with the entire polished surface of the workpiece, so as to obtain a necessary processing pressure (load ÷ workpiece area). Requires a considerable load. That is, since the processing pressure is applied to the entire portion where the groove Y exists, a large weight is required to obtain a desired processing rate. Therefore, when processing is possible with an appropriate load, a second groove having a certain depth, such as the groove X, is required.

  FIG. 3 is an external view of the brush 7 used in this embodiment. The brush material was nylon resin, and the average brush diameter was 80 μm. Regarding the brush diameter, it is necessary to select the optimum size according to the groove shape of the polishing surface plate. If it is larger than the groove shape, naturally the abrasive grains in the groove cannot be scraped, and conversely it is too thin The removal ability decreases.

  The purpose of the brush 7 is to prevent clogging of the abrasive grains in the grooves, and the abrasive grains swept from the grooves by the brush 7 in order to prevent the abrasive grains from remaining in the grooves and being compressed. Will perform the polishing operation again as loose abrasive grains.

  Next, the brush setting method was adjusted using the brush height adjusting microhead 18 in FIG. Specifically, the brush height adjustment microhead 18 is adjusted while visually confirming the position where the most advanced portion of the brush 7 is in contact with the surface of the polishing surface plate, and then the scale of the brush height adjustment microhead 18 is adjusted. Was used, and the brush 7 was moved 0.5 mm toward the polishing surface plate. As a result, the tip of the brush 7 reaches the groove of the polishing surface plate, and the abrasive grains in the groove can be scraped out. The sweeping of the abrasive grains by the brush 7 is just an image of plowing the field with mulberry in agricultural work, and it is important that the abrasive grains act as rolling abrasive grains between the workpiece and the polishing surface plate.

  FIG. 4 illustrates a method for adhering the workpiece 3 to the shared tool 4 in this embodiment. The common tool 4 uses alumina, which has a low coefficient of thermal expansion and is relatively easy to machine, as a material, and has a thickness of 52 mm that is slightly larger than the outer shape of the 2-inch SiC wafer used as a workpiece in this example. The shape was a cylinder of 8 mm. The adhesive surface of the shared tool 4 was finished to a surface roughness Ra = 5 μm and a surface profile within 2 μm by a surface grinding machine and a surface polishing machine.

  Furthermore, the groove | channel 10 for discharging | emitting the excess of the adhesive agent used at the time of adhesion | attachment, or discharging the bubble mixed in the adhesive agent was provided in the cross shape so that it may cross | intersect at the center point of the shared tool 4. FIG. The width of the groove was 1 mm and the depth was 0.5 mm. The common tool was placed with the adhesive surface facing upward on a hot plate 11 set at 120 ° C., and a few grams of thermosetting adhesive 12 (shift wax) was applied to the adhesive surface, and the entire adhesive surface was extended with a cotton swab. Then, place the workpiece 3 gently and rub against the common tool 4 while pressing the surface of the workpiece with a finger wearing a heat-resistant glove to remove excess adhesive or bubbles in the groove 10 provided in the common tool 4 or the workpiece. Ringing, which is an operation for discharging to the outer periphery of the object 3, was performed. After the ringing, fluororesin guides 12 were arranged at three positions of 120 degrees so that the workpiece 3 would not protrude from the outermost periphery of the shared tool 4 and a 4 kg weight 14 was placed on both sides of the silicon rubber 13. Thereafter, the hot plate 11 was turned off and the common tool 4 was allowed to stand at room temperature for about one hour to cure the adhesive.

  FIG. 5 shows the result of measuring the surface profile of the workpiece 3 after bonding using a surface roughness meter. The surface profile here refers to the two-dimensional shape of the workpiece surface of the workpiece. More specifically, as shown in FIG. 10, it refers to the two-dimensional shape of the wafer surface when the cross section of the wafer is cut along a line XX passing through the center point of the wafer that is the workpiece.

  When a parallel flat substrate with guaranteed flatness was applied to a tool with guaranteed flatness with a sufficient application load, the surface profile should theoretically be flat, but this was used in this example. Since the flatness of the 2-inch SiC wafer is poor as described above, the surface profile after bonding has a BOW shape of about 20 μm. When the workpiece in this state is pressed against an inelastic body such as a ceramic polishing surface plate having a Vickers hardness of about 1000, it can be easily imagined that there is a high risk of substrate damage.

  Further, even when processing is performed using the elastic polishing surface plate of the present invention, it is considered that there is a difference between the processing pressure at the convex portion of the surface profile and the processing pressure at the concave portion, and it is difficult to perform uniform processing on the entire surface of the substrate. Therefore, in the present invention, uniform processing on the entire surface of the substrate was realized by shifting to the mechanochemical polishing step with the surface profile temporarily corrected within 2 μm by the method described below. Here, the expression “temporary correction” means that the surface profile is realized only in a state of being attached to the shared tool 4 and may be deteriorated by a difference in processing stress after peeling from the shared tool. know.

  FIG. 6 is a schematic view of a single-sided lapping apparatus used for improving the surface profile of the present invention. The single-sided wrapping apparatus used was a general desktop type. The lapping platen 15 was made of copper and rotated counterclockwise at 50 rpm. The surface of the lapping platen 15 was finished with a facing device or the like within a flatness of 1 μm, and diamond slurry (particle size 2 to 4 μm) embedded in the lapping platen surface was used as fixed abrasive grains. As the slurry, a particle diameter of 2 to 4 μm of diamond slurry was used, and 1 drop per second was dropped on a lapping platen. Lapping is a processing method for transferring the shape of a polisher (here, lapping platen) to a workpiece.

  In this example, while diamond slurry rolls between the lapping surface plate finished with a flatness within 1 μm and the work piece, diamond is embedded as fixed abrasive grains on the lapping surface plate side. However, since the workpiece side is made of a softer material than diamond, the convex part of the surface is slowly scraped by the influence of the rolling diamond while tracing the shape of the polishing platen, and finally the lapping constant The board and workpiece are approaching the same shape. That is, the surface shape of the lapping surface plate is transferred to the workpiece side. If the flatness of the lapping platen is ensured within 1 μm, the flatness of the workpiece can be corrected to the same extent.

  Subsequently, the workpiece is mounted on the apparatus. As described above, the workpiece 3 is in a BOW state of about 20 μm in a state of being bonded to the common tool 4. The workpiece 3 and the common tool 4 in this state are arranged on the lapping surface plate so that the machining surface is in contact with the lapping surface plate, and the driving roller 17 of the jig forced drive device 16 is in contact with the outer periphery of the common tool 4. set. By operating the jig forced drive device 16, the drive roller rotates and the shared tool 4 rotates in conjunction with it. In this embodiment, the rotation was performed counterclockwise at a rotation speed of 50 rpm. The processing load was 100 g.

  After the start of processing, the shared tool 4 was unloaded every hour, and the surface profile was measured to confirm whether there was any uneven scraping. When uneven shaving occurred, the movable weight 16 was set on the outer periphery of the shared tool 4 on the side where the machining amount was small, and was corrected. In the case of a BOW shape of about 20 μm, a surface profile within 2 μm as shown in FIG. 7 could be obtained after processing for about 10 hours. Thereafter, the work piece 3 held in a surface profile of 2 μm or less (which is still adhered to the common tool 4) is cleaned by ultrasonic cleaning or the like, mounted on a mechanochemical polishing apparatus, and mechanochemical polishing is performed. Will be implemented.

  Examples of the mechanochemical polishing method for a compound semiconductor substrate in the present invention will be described in more detail. As a workpiece, an SiC single crystal wafer having an outer shape of 2 inches and a thickness of 250 μm and having a surface profile kept within 2 μm in advance was used.

  Further, as described above, since a hard material such as SiC is difficult to finish with a high degree of flatness such as BOW in the lapping process, slicing process, and grinding process, which are the previous processes, it is 10 even on a 2-inch substrate. In most cases, it becomes a BOW shape of ˜30 μm. When the polishing surface plate of the present invention is used in such a BOW state, the polishing pressure is not uniform in the substrate even if it is not damaged. This leads to non-uniform surface roughness that is most important in the final polishing process. In the present invention, a common processing tool 4 (hereinafter referred to as a shared tool) is used in the lapping step and final polishing step using diamond abrasive grains, which are the previous steps, and the workpiece 3 is temporarily attached to the shared tool 4. In the bonded state, the flatness of the work surface of the work piece 3 is temporarily secured with high accuracy within 2 μm, and this is dealt with. Here, it is expressed that the flatness is temporarily secured because the workpiece 3 is distorted by the influence of the processing stress when it is removed from the common tool 4, and a high-precision flatness within 2 μm is obtained. It is because it cannot be maintained.

  In order to confirm the effect of the present invention, four substrates of the same size were prepared with the flatness within 2 μm maintained with a shared tool, and four types of experiments were performed by changing the conditions of mechanochemical polishing. It was. Experiment (1) is a case where a chromium oxide polishing surface plate having a Shore hardness of 80 to 90 in the present invention is used. Experiment (2) is when a non-woven fabric made of resin fibers is used as the polishing surface plate. Experiment (3) is when using a chromium oxide polishing surface plate with a Shore hardness of 70-80. Experiment (4) is when an alumina surface plate having a Vickers hardness of 1000 or more is used. Vickers hardness is a standard that represents the hardness of metals and ceramics. The processing conditions other than the polishing surface plate in the above four types of experiments were all the same.

As the settings of the polishing apparatus, the number of rotations of the polishing platen was 20 rpm, the number of rotations of the processing head was 30 rpm, and the processing pressure was 350 g / cm ² . Further, chromium oxide abrasive grains having a particle size of 1 μm were sprinkled on the polishing surface plate as a free abrasive grain on the polishing surface plate before processing several tens of grams, and subsequent additional spraying was not performed. The result of processing for 20 hours under the above conditions is shown in FIG. With respect to the processing rate in FIG. 8A, the change in weight before and after processing was measured using an electronic balance with a resolution of 0.1 mg, and converted into processing dimensions per unit time.

  Moreover, about the surface roughness Ra in FIG.8 (b), the measurement of 5 points | pieces shown in FIG. 9 was performed using the surface shape inspection apparatus by the general optical interference fringe measuring method. As can be seen from the experimental results, in the experiment (1) which is an embodiment of the present invention, the highest processing rate among the four types can be obtained, and the surface roughness is uniform at 5 points of measurement. Finished. With regard to the processing rate, it can be said that further improvement is possible by increasing the number of rotations of the polishing platen and the polishing head or increasing the polishing pressure. In the experiment (2), although it can be said that the result is good as in the example in the present invention, it can be said that the processing rate is still difficult. In addition, the nonwoven fabric after processing is severely worn, and it seems difficult to operate continuously for more than 20 hours under the present processing conditions. In the experiment (3), the processing is not performed at all, and it is considered that the polishing pressure is absorbed by the polishing platen because the polishing platen is too elastic.

  Regarding experiment (4), a number of chips and cracks occurred near the outer periphery of the substrate within a few minutes after the start of processing, and the experiment was stopped.

  The mechanochemical polishing method for compound semiconductor wafers according to the present invention is capable of safely and efficiently performing mechanochemical polishing of thin wafers of 500 μm or less compared to conventional processing methods, and is very useful as a method for manufacturing compound semiconductor wafers. is there.

Schematic configuration diagram of a mechanochemical polishing apparatus in an embodiment of the present invention The figure for demonstrating the polishing surface plate in the Example of this invention typically The figure for demonstrating typically the brush in the Example of this invention. The figure explaining the adhesion method of the shared tool and a workpiece in the Example of this invention The figure which shows the surface profile after the workpiece | work adhesion | attachment in the Example of this invention. 1 is a schematic configuration diagram of a lapping apparatus used for improving a surface profile in an embodiment of the present invention. The figure which shows the state after the surface profile improvement in the Example of this invention. The figure explaining the experimental result in the Example of this invention The figure explaining the measurement location of the surface roughness in the Example of this invention The figure explaining the surface profile in the Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing surface plate 2 Polishing table 3 Workpiece 4 Shared tool 5 Polishing head 6 Brushing head 7 Brush 8 Polishing abrasive powder 9 Abrasive dispersion position 10 Groove 11 Hot plate 12 Guide 13 Silicone rubber 14 Weight 15 Lapping surface plate 16 Forced drive device 17 Drive roller 18 Micro head for brush height adjustment

Claims (12)

In the mechanochemical polishing method for polishing a semiconductor wafer, which is a material to be polished, using oxide powder as abrasive grains,
A mechanochemical polishing method comprising: a polishing surface plate made of an elastic material having a Shore hardness of 80 to 90, and having at least two kinds of grooves on a polishing surface of the polishing surface plate in contact with the material to be polished. The mechanochemical polishing method according to claim 1, wherein the oxide is any one of chromium oxide, magnesium oxide, iron oxide, and aluminum oxide. The mechanochemical polishing method according to claim 1, wherein the elastic material of the polishing surface plate is made of urethane rubber or fluororubber. 4. The mechanochemical polishing according to claim 3, wherein the abrasive grains are kneaded in advance in urethane rubber or fluororubber in order to hold the oxide abrasive grains on the surface of the polishing platen. Method. The first groove formed on the polishing surface side of the polishing surface plate is a groove formed in a spiral shape for the purpose of holding abrasive grains, and the second groove is a groove than the first groove. 2. The mechanochemical polishing method according to claim 1, wherein the mechanochemical polishing method is formed in a spiral shape for obtaining a predetermined processing rate and discharging a large amount of excessive abrasive grains. In order to prevent clogging due to abrasive grains being polished in a groove formed on the polishing surface plate, a brush in contact with the surface of the polishing surface plate is disposed, and the abrasive particles in the groove are swept out. The mechanochemical polishing method according to claim 5, wherein: In the mechanochemical polishing method for polishing a semiconductor wafer, which is a material to be polished, using oxide powder as abrasive grains,
The polishing surface plate is made of an elastic material having a Shore hardness of 80 to 90, and has at least two kinds of grooves on the polishing surface side of the polishing surface plate that comes into contact with the material to be polished.
A mechanochemical polishing method comprising polishing a wafer after being bonded and lapped to a common tool in order to keep the wafer at a predetermined flatness. The mechanochemical polishing method according to claim 7, wherein the wafer is polished in a state where the flatness of the wafer is maintained within 2 μm. The mechanochemical polishing method according to claim 8, wherein the oxide is any one of chromium oxide, magnesium oxide, iron oxide, and aluminum oxide. In a mechanochemical polishing apparatus that polishes a semiconductor wafer that is a material to be polished, using oxide powder as abrasive grains,
A mechanochemical polishing apparatus comprising a polishing surface plate made of an elastic material having a Shore hardness of 80 to 90, and having at least two kinds of grooves on a polishing surface of the polishing surface plate contacting the material to be polished. 11. The mechanochemical polishing apparatus according to claim 10, wherein the oxide is any one of chromium oxide, magnesium oxide, iron oxide, and aluminum oxide. The mechanochemical polishing apparatus according to claim 11, wherein the elastic material of the polishing surface plate is made of urethane rubber or fluororubber.

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