JP2013240867A - Surface polishing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface polishing plate that performs high speed polishing with diamond abrasive grains with sharp outer shapes, and performs mirror surface processing by automatically supplying abrasive grains with chemically polishing action at a predetermined timing.SOLUTION: Diamond abrasive grains 18 or the like are entirely dispersed, embedded and solidified in a porous plate 16 having multiple continuous bubbles 24 communicated from one side surface 20 to the another side surface 22. A liquid 26 with viscosity that does not naturally flow down by the gravity force in the continuous bubbles 24 at a room temperature, in which abrasive grains 28 that mechanically and chemically polish an acting surface 32 of a polished material 30 is mixed, is used to impregnate the continuous bubbles 24. The liquid 26 is softened by heat generated when the polished material 30 is polished or heat supplied from the outside to increase fluidity, and is flowed to the acting surface 32 of the acting abrasive grains 30 along with a chemical abrasive 28. Grain sizes of the abrasive grains 28 with chemical polishing action are not less than grain sizes of the diamond abrasive grains 18.

Description

  The present invention relates to a surface polishing plate, a surface polishing apparatus, and a surface polishing method used for mirror processing of a surface of a silicon wafer or the like.

  When mirror polishing a silicon wafer or the like, a grindstone is pressed against the surface of the material to be polished and rubbed. In order to realize polishing processing with high flatness in a short time, a surface polishing plate having a wide effective area has been developed (see Patent Document 1).

Japanese Patent No. 4737689

The known prior art has the following problems to be solved.
When polishing a material to be polished quickly, it is preferable to use diamond grains having a sharp outer shape. On the other hand, it is preferable to use a chemical abrasive for mirror polishing of the material to be polished. For this reason, the operation | work which replaces | exchanges a surface polishing board in the first half and the latter half of a grinding | polishing process, or replaces the abrasive grain to be used is requested | required. There is a limit to shortening the time for the polishing process in such an operation, and complicated control is required even when it is automated.
In order to solve the above-described problems, the present invention provides a surface polishing plate that performs high-speed polishing with sharply shaped diamond abrasive grains and that is automatically supplied with a chemical abrasive at a predetermined timing to perform a mirror surface treatment. Another object is to provide a surface polishing apparatus and a surface polishing method.

The following configurations are means for solving the above-described problems.
<Configuration 1>
The first abrasive grains having a hard and mechanically sharp outer surface are dispersed and embedded throughout to be solidified, and a porous plate having a large number of open cells extending from one surface to the other surface is obtained at room temperature. A liquid having a viscosity that does not naturally flow down from one surface of the plate toward the other surface by gravity, and includes second abrasive grains that mechanically and chemically polish the working surface of the material to be polished. And the liquid is softened by heat generated when the material to be polished is polished or heat supplied from the outside to increase fluidity, and the second Surface polishing characterized in that it is a liquid that flows to the work surface of the material to be polished together with abrasive grains, and the particle diameter of the second abrasive grains is greater than or equal to the particle diameter of the first abrasive grains. Board.

<Configuration 2>
The first abrasive grains having a hard and mechanically sharp outer surface are dispersed and embedded throughout to form a porous plate having a large number of open cells extending from one surface to the other surface. And a liquid having a viscosity that does not naturally flow down by gravity from the one surface of the porous plate to the other surface at room temperature, and a device that polishes the material to be polished with the first abrasive grains. A mixture of second abrasive grains having a grain size equal to or larger than that of the first abrasive grains and mechanically and chemically polishing the working surface of the material to be polished is contained in the open cell. The liquid is softened by the heat generated when the material to be polished or the heat supplied from the outside is softened in the state of impregnating the material to be polished, and the material to be polished together with the second abrasive grains. For chemically polishing the working surface of the material to be polished Surface polishing apparatus characterized by comprising a.

<Configuration 3>
The first abrasive grains having a hard and mechanically sharp outer surface are dispersed and embedded throughout to form a porous plate having a large number of open cells extending from one surface to the other surface. A liquid having a viscosity such that the material to be polished is polished with the first abrasive grains and does not naturally flow down from the one surface of the porous plate toward the other surface at room temperature. A mixture of second abrasive grains having a grain size equal to or larger than that of the first abrasive grains and mechanically and chemically polishing the working surface of the material to be polished. So that the liquid is softened by heat generated when polishing the material to be polished or heat supplied from the outside to improve fluidity, and together with the second abrasive grains, the working surface of the material to be polished To chemically polish the working surface of the material to be polished. Surface polishing method and butterflies.

<Configuration 4>
The surface polishing method according to Configuration 3, wherein the working surface of the material to be polished is chemically polished by the second abrasive particles flowing out to the working surface of the material to be polished, and the porous plate A surface polishing method characterized in that clogging of the other surface of the porous plate is prevented by chemically reacting with a foreign substance adhering to the other surface and the other surface.

The working surface of the material to be polished is polished at high speed with diamond abrasive grains. With the heat generated in this polishing, the liquid flows to the working surface together with the chemical polishing agent, and chemical polishing is started. Thereafter, the chemical abrasive starts mirror polishing.
The chemical abrasive not only mirrors the working surface of the material to be polished, but also chemically reacts with the other surface of the porous plate facing the working surface of the material to be polished. Thereby, diamond abrasive grains are easily separated from the other surface of the porous plate, and further, there is an effect of preventing clogging of the other surface of the porous plate and maintaining the polishing performance.

It is a partial expanded cross-sectional view which shows the structure of the porous board 16 of this invention. It is a partial expanded cross-sectional view which shows the state at the time of the grinding | polishing process start of the porous board 16 of this invention. It is a partial expanded cross-sectional view which shows the state at the time of the mirror polishing process of the porous board 16 of this invention. It is an Example front view of the porous board grinding | polishing apparatus of this invention. It is a front view of the slurry system polishing apparatus of a comparative example. It is a strength comparison figure (1) of the silicon wafer chip by the difference in a processing system. It is intensity | strength comparison figure (2) of the silicon wafer chip | tip by the difference in a processing system. It is a surface roughness comparison figure of the silicon wafer chip by the difference in a processing system. It is explanatory drawing of the experiment example which verifies the clogging complete effect of this invention.

  First, the structure of the porous plate 16 of the present invention and the outline of the polishing process will be described with reference to FIGS. Each of these drawings is an enlarged view of a cross section of a portion where the porous plate 16 and the material to be polished 30 are in contact with each other. Therefore, only a part of the porous plate 16 and the material to be polished 30 appears in the drawing. The diamond abrasive grains 18, the abrasive grains 28 having a chemical polishing action, and the open cells 24 in the figure do not necessarily accurately indicate the shape and state of the actual object, but are simply illustrated for convenience of explanation.

  As shown in FIG. 1, the porous plate 16 is obtained by dispersing and embedding diamond abrasive grains 18 throughout and solidifying them. The porous plate 16 may be a sintered ceramic. Alternatively, diamond abrasive grains 18 may be kneaded into a synthetic resin and solidified. Ceramic grains and diamond abrasive grains 18 may be mixed and solidified with an adhesive.

  The diamond abrasive grains 18 are chemically stable abrasives that mechanically sharply and rapidly polish the workpiece 30. It is suitable for quickly polishing and flattening the working surface 32 of the material 30 to be polished. The abrasive grains embedded in the porous plate 16 may be hard and mechanically sharp, such as zirconia or silicon carbide (SiC). In the above description of <Configuration>, the abrasive grains embedded in the porous plate 16 are expressed as first abrasive grains. The material to be polished 30 is, for example, a silicon wafer. Surface polishing is used to eliminate defects and increase the strength.

  The porous plate 16 has a large number of open cells 24 extending from one surface 20 to the other surface 22. The liquid 26 is impregnated here. The liquid 26 is adjusted so as to have a viscosity that does not naturally flow down from one surface 20 to the other surface 22 of the porous plate 16 at room temperature. For example, agar, cellulose, petrolatum or grease can be used. Furthermore, food thickeners such as carrageenan and CMC (carboxymethylcellulose) can be used. Moreover, the polyethylene glycol currently used for toothpaste can also be used. Food and other materials are safe and do not pollute the environment even if they are disposed of in sewage.

  In the liquid 26, abrasive grains 28 having a chemical polishing action for mechanically and chemically polishing the material to be polished 30 are mixed. The liquid 26 is impregnated in the open cells 24 of the porous plate 16. The abrasive grains 28 having a chemical polishing action are, for example, abrasive grains such as ceria, mica, and iron oxide. The abrasive 28 having a chemical polishing function has a function of mechanically scraping and polishing the material 30 to be polished, and chemically reacting with the working surface 32 of the material 30 to be mirror-finished. it can. What reacts to adsorb | suck and peel off a part of to-be-polished material 30 is preferable. In the description of the above <configuration>, it is expressed as the second abrasive grain. The first abrasive grains only need to be harder and mechanically sharper than the second abrasive grains. In addition, a liquid having no chemical polishing action such as a small amount of diamond abrasive grains may be mixed in the liquid.

  The liquid 26 is softened by the heat generated when the diamond abrasive grains 18 are pressed against the working surface 32 of the material 30 to polish the material 30 to increase the fluidity, and the abrasive particles 28 having a chemical polishing action. At the same time, it flows out to the working surface 32 of the material 30 to be polished. Note that the liquid 26 may be forcibly softened by applying heat from the outside at a predetermined timing.

  As shown in FIG. 2, at the beginning of polishing, diamond abrasive grains 18 exposed on the other surface 22 of the porous plate 16 are pressed against the working surface 32 of the material to be polished 30, and the working surface 32 of the material to be polished 30. Is polished until a certain flatness is obtained. When the working surface 32 of the material to be polished 30 reaches a certain flatness, a large number of diamond abrasive grains 18 sandwiched between the other surface 22 of the porous plate 16 and the working surface 32 of the material to be polished 30 are porous. Friction between the other surface 22 of the material plate 16 and the working surface 32 of the material to be polished 30 increases, and heat is generated to a temperature at which the liquid 26 is softened.

  The grain size of the abrasive grains 28 having a chemical polishing action is greater than or equal to the grain size of the diamond abrasive grains 18. Note that abrasive grains 28 having a chemical polishing action that is less than the grain diameter of the diamond abrasive grains 18 may be mixed in part.

  As shown in FIG. 3, when the softened liquid 26 and the abrasive grains 28 having a chemical polishing action flow between the other face 22 of the porous plate 16 and the action face 32 of the material to be polished 30, the particle size becomes large. The abrasive grains 28 having a chemical polishing action come into strong contact with the working surface 32 of the material 30 to be polished. As a result, the working surface 32 of the workpiece 30 is mirror-finished by the chemical reaction of the abrasive grains 28 having a chemical polishing action. Since the temperature rises due to frictional heat between the porous plate 16, the abrasive grains 28 having a chemical polishing action, and the working surface 32 of the material to be polished 30, the chemical reaction is also promoted.

  The chemical reaction of the abrasive grains 28 having a chemical polishing action is not limited to the mirror treatment of the working surface 32 of the material 30 to be polished. The abrasive grains 28 having a chemical polishing action also act on the other surface 22 of the porous plate 16. When the abrasive grains 28 having a chemical polishing action act on the other surface 22 of the porous plate 16, the diamond abrasive particles 18 easily fall off from the other surface 22 of the porous plate 16.

  That is, in the polishing process, new diamond abrasive grains 18 are successively supplied from the other surface 22 of the porous plate 16 onto the working surface 32 of the material to be polished 30, and the polishing ability by the diamond abrasive grains 18 is maintained.

  Furthermore, clogging may occur due to adhesion of used abrasive grains or scraps of the material to be polished 30 to the other surface 22 of the porous plate 16. The abrasive grains 28 having a chemical polishing action act on these and have a function of preventing clogging of the other surface 22 of the porous plate 16.

  Although there is a method of preventing clogging to some extent by flowing a large amount of slurry 44, it is not always effective. Clogging is particularly likely to occur when the amount of the slurry 44 is small or when dry polishing is performed without flowing the slurry 44. The clogging prevention effect by the abrasive grains 28 having a chemical polishing action is effective in such a case. Hereinafter, embodiments of the present invention will be described in detail for each example.

  As an example, a surface polishing apparatus 14 as shown in FIG. 4 is used. The material to be polished 30 is adsorbed and fixed to the upper surface of the fixing table 38. It is a silicon wafer having a thickness of 80 μm and a diameter of 300 mm. The surface polishing plate 12 is pressed against the upper surface, and the surface polishing plate 12 is driven to rotate in the direction of the arrow 40 for polishing. The surface polishing plate 12 is a porous ceramic plate which is sintered by mixing diamond abrasive grains having an average particle size of 0.65 to 0.89 nm. The surface polishing plate 12 was impregnated with a liquid mixed with ceria abrasive grains. The average particle size of the ceria abrasive grains is 2 μm. Agar was used as the liquid as a thickener. The gelation start temperature is 40 degrees Celsius. The same experiment was conducted on a 50 μm thick silicon wafer.

Comparative Example 1

  As a comparative example, an apparatus as shown in FIG. 5 is used. A silicon wafer 36 is fixed to the lower surface of the holder 42 by suction. A polishing cloth 46 is fixed to the upper surface of the turntable 48. The slurry 44 is dropped on the polishing cloth 46. The turntable 48 is rotationally driven in the direction of arrow 50 to polish the silicon wafer 36. The silicon wafer 36 is a silicon wafer having the same shape as that used in the first embodiment. The slurry 44 was mixed with diamond abrasive grains having an average particle diameter of 0.65 to 0.89 nm. The polishing time was the same for 2 minutes.

  FIG. 6 shows that when the silicon wafer having a thickness of 80 μm is observed, in the apparatus of Example 1, any part of the silicon wafer can be uniformly polished to substantially the same strength. On the other hand, in the case of the comparative example, the intensity varies greatly depending on the location of the silicon wafer, and it seems that the entire surface is not mirror-polished uniformly. As can be seen from FIG. 7, when the silicon wafer having a thickness of 50 μm is observed, the apparatus of Example 1 has a larger variation than that of the thickness of 80 μm, but has the same strength and can be polished well. On the other hand, in the case of the comparative example, a part with insufficient strength occurs.

  FIG. 8 compares the surface roughness after polishing. This is a result of inspection of a silicon wafer having a thickness of 50 μm. It can be seen that the surface roughness in the vicinity of the center of the comparative example is rougher than that of Example 1 compared to that of Example 1. This is in good agreement with the results of FIG. As a result, it was demonstrated that the apparatus using the surface polishing plate according to the present invention can perform better mirror polishing in a shorter time than before. In the case of the comparative example, it goes without saying that the target mirror polishing can be realized and the target strength can be obtained by continuing the polishing for a longer time.

  The clogging prevention effect will be described with reference to FIG. When the silicon wafer 36 was polished by the dry polishing method using the surface polishing plate of Example 1 above for 2 minutes with the apparatus shown in FIG. 4 was compared with the case where the polishing was performed for the same time using only diamond abrasive grains. . When the surface polishing plate of Example 1 is used, the change in rotational torque in the direction of arrow 40 is relatively small. This is because clogging is prevented and the polishing performance does not change significantly. On the other hand, when only diamond abrasive grains are used, clogging progresses and the polishing ability decreases, and the rotational torque gradually decreases. That is, it was demonstrated that the surface polishing plate of the present invention has an extremely excellent clogging prevention function.

DESCRIPTION OF SYMBOLS 12 Surface polishing plate 14 Surface polishing apparatus 16 Porous board 18 Diamond abrasive grain 20 One surface 22 The other surface 24 Open-cell 26 Liquid 28 Chemical abrasive | polishing agent 30 To-be-polished material 32 Working surface 36 Silicon wafer 38 Fixing stand 40 Arrow 42 Holder 44 Slurry 46 Polishing cloth 48 Turntable 50 Arrow

Claims (4)

A first abrasive grain having a hard and mechanically sharp outer surface is dispersed and embedded throughout to be solidified, and a porous plate having a large number of open cells from one surface to the other surface,
A liquid having a viscosity that does not naturally flow down from one surface of the porous plate to the other surface of the porous plate at room temperature, and mechanically and chemically polishes the working surface of the material to be polished. Impregnated with the above-mentioned continuous bubbles,
The liquid is softened by heat generated when the material to be polished is polished or heat supplied from the outside to increase fluidity, and the liquid flows out to the work surface of the material to be polished together with the second abrasive grains. Because
The surface polishing plate, wherein the particle size of the second abrasive grains is greater than or equal to the particle size of the first abrasive grains. The first abrasive grains having a hard and mechanically sharp outer surface are dispersed and embedded throughout to form a porous plate having a large number of open cells extending from one surface to the other surface. An apparatus for polishing the material to be polished with the first abrasive grains,
A liquid having a viscosity that does not naturally flow down from one surface of the porous plate to the other surface of the porous plate at room temperature, and has a particle size equal to or larger than the particle size of the first abrasive grain. Heat generated when the material to be polished is polished while the continuous bubbles are impregnated with second abrasive grains that mechanically and chemically polish the working surface of the abrasive. The liquid is softened by the heat supplied from the surface to improve the fluidity, and flows together with the second abrasive grains onto the working surface of the material to be polished, thereby chemically polishing the working surface of the material to be polished. A surface polishing apparatus comprising the apparatus. The first abrasive grains having a hard and mechanically sharp outer surface are dispersed and embedded throughout to form a porous plate having a large number of open cells extending from one surface to the other surface. And polishing the material to be polished with the first abrasive grains,
A liquid having a viscosity that does not naturally flow down from one surface of the porous plate to the other surface of the porous plate at room temperature, and has a particle size equal to or larger than the particle size of the first abrasive grain. What is mixed with the second abrasive grains for mechanically and chemically polishing the working surface of the material to be polished is impregnated in the open cell,
The liquid is softened by heat generated when the material to be polished or heat supplied from the outside is softened to increase fluidity, and flowed to the working surface of the material to be polished together with the second abrasive grains. A surface polishing method comprising chemically polishing a working surface of the material to be polished. The surface polishing method according to claim 3,
The second abrasive grains that have flowed out to the working surface of the material to be polished chemically polish the working surface of the material to be polished and adhere to the other surface and the other surface of the porous plate. A surface polishing method characterized in that clogging of the other surface of the porous plate is prevented by chemically reacting with a foreign substance.

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