JP2013169610A - High hardness material working method and working device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high hardness material working method eliminating the problems of heat resistance and clogging of a grindstone.SOLUTION: A working method making a high hardness material touch a rotating polishing tool while rotating the high hardness material comprises the steps of: heating the high hardness material to a temperature higher than a predetermined working temperature at a position different from a machined part so as to become the working temperature at that machined part and thereby forming a softened layer with a hardness lower than a surface layer of the high hardness material; working the high hardness material by making the polishing tool rotate at a speed such that the temperature of the polishing tool which rises due to heat input from the high hardness material at machined part to the polishing tool becomes no more than a heat resistance temperature of the polishing tool while making the high hardness material touch the polishing tool; cooling the polishing tool at a position which is different from the machined part; and washing the polishing tool at a position which is different from the machined part.

Description

  The present invention relates to a method for processing a high hardness material, and more particularly to a method suitable for surface polishing of a SiC single crystal wafer.

  Conventionally, a wafer processing method is known in which a wafer is formed by cutting an ingot, and the surface of the wafer is polished and flattened. For example, when processing using a high-hardness material such as SiC as a wafer, the high-hardness material has a high processing resistance. Therefore, in order to satisfy a predetermined processing accuracy, it is necessary to perform processing at a low processing speed. As a result, the processing efficiency is lowered.

  When polishing and flattening the surface of a high-hardness wafer, etc., it is known to improve the processing efficiency by forming a modified layer with low hardness on the surface layer of the wafer and polishing the modified layer. ing.

  Patent Document 1 discloses a wafer processing method in which a modified layer is formed by applying heat to a portion to be polished while rotating the wafer, and the portion of the wafer to which heat is applied is polished with a polishing tool. Yes.

JP 2011-249449 A

  In the method of heating and processing the processed portion of the high hardness material, the following problems occur.

  The first is a problem of heat resistance of the grinding wheel. It is necessary to process a high-hardness material with abrasive grains having a hardness equal to or higher than the hardness of the workpiece. For example, when the workpiece is SiC, it is necessary to use diamond abrasive grains or cBN abrasive grains. The hardness decreases when diamond abrasive grains are 600 ° C or higher and cBN abrasive grains are 1280 ° C or higher. Therefore, in order to realize the process of heating and processing the processed part of high-hardness material, the heat input to the cutting tool is reduced. There is a need to.

  The second is a problem of processing deterioration due to clogging due to a dry process. Usually, in grinding, in order to prevent the workability from being deteriorated due to clogging of the grindstone by chips, the processing is performed while applying the processing liquid, and the chips are discharged. However, in the method of heating and processing the processed portion of the high-hardness material, it is necessary to perform processing by a dry process in order to heat the processed portion to about 1200 ° C. and stabilize the temperature. The liquid cannot be supplied, and the processing is likely to deteriorate due to clogging.

  The third problem is a heating method. For example, SiC has very good thermal conductivity and high cooling performance. Therefore, even if the surface is heated to a predetermined temperature, the surface is immediately cooled to lower the temperature, and the softening effect by heating is reduced.

  The present inventors diligently studied a method for solving the above problem.

  As a result, it has been found that the first problem can be solved by increasing the rotational speed of the grindstone and further cooling it at a part different from the processed part. In other words, the grindstone has heat input from the heated work material due to heat conduction, but the work material and the abrasive grains are rotated at a high speed so that the amount of heat input is smaller than the heat resistant temperature of the abrasive grains. To reduce contact time. Moreover, the temperature which rose by the heat input by contact cools in the position different from a process part, and returns to normal temperature.

  It has been found that the second problem can be solved by performing cleaning at a position different from the processing part. As described above, the abrasive grains are cooled at a position different from the processed part and returned to room temperature, so that the abrasive grains can be cleaned. As the cleaning method, vapor cleaning, high-pressure cleaning, cleaning with an ultrasonic superposition processing liquid, or the like can be used.

  As for the third problem, the heating source for heating the workpiece is set to a temperature higher than a predetermined temperature, and heat loss due to thermal diffusion and heat conduction is taken into consideration so that the processing portion has a predetermined temperature. I found out that it can be solved.

The present invention is a method of processing a high-hardness material made based on the above knowledge while abutting while rotating a polishing tool,
Heating the high hardness material to a temperature higher than the processing temperature at a position different from the processing portion so that the processing portion has a predetermined processing temperature, and forming a softened layer having a low hardness on the surface layer of the high hardness material ,
While rotating the polishing tool at a speed such that the temperature of the polishing tool that rises due to heat input from the high-hardness material to the polishing tool in the processing section is equal to or lower than the heat-resistant temperature of the polishing tool, A process of processing a high hardness material in contact with
A step of cooling the polishing tool at a position different from the processing part;
The polishing tool includes a step of cleaning the polishing tool at a position different from the processing portion.

  According to the present invention, the problem of the heat resistance and clogging of the grindstone can be solved, and the high-hardness workpiece can be heated and softened to a high temperature, so that the processing time can be shortened. It becomes possible to improve the processing efficiency of the high hardness material.

It is a figure which shows the outline | summary of the processing method of this invention, (a) is an upper surface schematic diagram, (b) is a cross-sectional schematic diagram.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with a workpiece as a SiC single crystal wafer and a grindstone abrasive as cBN with reference to the drawings.

  1A and 1B are diagrams showing an outline of a processing method of the present invention. FIG. 1A is a schematic view of a processing apparatus as viewed from above, and FIG. 1B is a schematic view of a cross section AA ′ in FIG. is there. 1 includes a rotary stage 16, a polishing tool (grinding stone) 21, a polishing wheel 26, a rotary shaft 27, a heating device 31, a cooling / cleaning device 41, a temperature detection device 51, a processing resistance detection device 61, and a control. A device (not shown) is provided.

  The SiC single crystal wafer that is the workpiece 11 is fixed to a rotation stage 16 having a rotation mechanism (not shown). The workpiece 11 is processed by bringing the workpiece 11 fixed to the rotary stage 16 into contact with the rotating polishing tool 21.

  The polishing tool 21 is configured by using, for example, a grindstone, and processes the surface of the workpiece 11 by contacting the workpiece 11 while rotating. In FIG. 1, the workpiece 11 and the grindstone 21 are both shown to rotate counterclockwise, but the rotation direction is not limited to this.

  A heating device 31 is provided at a position different from the processing unit 12 where the workpiece 11 is in contact with the rotating grindstone 21, and the workpiece 11 is heated to a predetermined processing temperature by the processing unit 12. A softened layer with reduced hardness is formed on the surface layer of the workpiece 11. The heating device 31 that is a heating source is preferably disposed immediately before the processing portion 12 in the rotation direction of the workpiece 11. That is, it is preferable to arrange the workpiece 11 heated by the heating device 31 at a position where it is processed immediately after being heated.

  When the grindstone of the grindstone 21 is cBN, the heat-resistant temperature of cBN is 1280 ° C. Therefore, the output of the heating device 31, the heating area, and the heating position are set so that the temperature of the SiC wafer in the processing unit 12 is about 1200 ° C. To the processing part 12 is set.

  Since SiC is a material that has good thermal conductivity and is easily cooled even when heated, the heating by the heating device 31 is set at a position higher than SiC 1200 ° C. at the position of the heating device 31.

  The hardness of SiC is about Hv 2500, but when heated to about 1200 ° C., a softened layer with reduced hardness is formed on the surface layer. This is considered to be because the molecular bonding force is relaxed by heating.

  As a heating method used in the heating device 31, a method such as dielectric heating, induction heating, thermal radiation, or the like that can be heated up to about 3000 ° C. is preferable. In the case of thermal radiation, it is preferable to use a heating hot wall made of carbon having a heat resistant temperature of 3400 ° C.

  When the workpiece 11 is SiC, the cooling property is very high, and when heated locally, it is difficult to raise the temperature to a predetermined temperature. Therefore, the heating device 31 preferably has a certain heating area.

  By heating the workpiece 11 by the heating device 31 and reducing the hardness of the surface layer, the processing can be speeded up, and the processing efficiency is increased.

  The workpiece 11 and the grindstone 21 are rotated at a high speed so that the grindstone 21 is not softened due to a temperature rise due to heat input from the workpiece 11 heated to a high temperature.

  The grindstone 21 is cooled and cleaned by a cooling / cleaning device 41 at a position different from the processing unit 12. As the cooling / cleaning means, vapor cleaning / cooling, high-pressure cleaning, cleaning / cooling with ultrasonic superimposing coolant, and the like can be used.

  The temperature detection device 51 is disposed above the workpiece 11. For the temperature detection device 51, for example, a radiation thermometer can be used. The temperature detection device 51 detects the temperature of the workpiece 11 in the processing unit 12 and transmits the detected temperature to the control device.

  For example, a torque meter or the like can be used for the machining resistance detection device 61. The processing resistance detection device 61 detects a resistance value transmitted to the grinding wheel 26 and the rotating shaft 27 that rotate the grinding wheel 21 via the grinding stone 21 when the grinding stone 21 contacts the workpiece 11 and / or. The resistance value transmitted to the rotary stage 16 via the workpiece 11 is detected, and the detected resistance value is transmitted to the control device.

  The control device controls the output of the heating device 31 according to the temperature detected by the temperature detection device 51 and the processing resistance detected by the processing resistance detection device 61. Specifically, when the detected temperature is lower than a preset threshold value or when the machining resistance is higher than a preset threshold value, the output of the heating device 31 is increased and the amount of heat given to the workpiece 11 is increased. Enlarge.

  The temperature detection device 51, the processing resistance detection device 61, and the control device are not necessarily provided. However, by providing these devices and appropriately controlling the heating device 31, a desired region of the workpiece 11 can be reliably obtained. Since it can be softened, the high hardness material can be processed more efficiently.

  Although the embodiment of the present invention has been described with a specific example, the present invention is not limited to the description of the embodiment of the present invention. It goes without saying that various modified embodiments are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Processing apparatus 11 Work material 12 Processing part 16 Rotation stage 21 Abrasive tool (grinding stone)
26 Polishing wheel 27 Rotating shaft 31 Heating device 41 Cooling / cleaning device 51 Temperature detection device 61 Processing resistance detection device

Claims (5)

While rotating a high hardness material, it is a method of contacting and processing a rotating polishing tool,
Heating the high hardness material to a temperature higher than the processing temperature at a position different from the processing portion so that the processing portion has a predetermined processing temperature, and forming a softened layer having a low hardness on the surface layer of the high hardness material ,
While rotating the polishing tool at a speed such that the temperature of the polishing tool that rises due to heat input from the high-hardness material to the polishing tool in the processing section is equal to or lower than the heat-resistant temperature of the polishing tool, A process of processing a high hardness material in contact with
A step of cooling the polishing tool at a position different from the processing part;
A method for processing a high-hardness material, comprising a step of cleaning the polishing tool at a position different from a processing portion.   2. The high hardness according to claim 1, wherein a temperature and a processing resistance of the high hardness material are detected at a processing portion, and an output of a heating source for heating the high hardness material is controlled according to the detected value. Material processing method.   The method of processing a high-hardness material according to claim 1 or 2, wherein the heating of the high-hardness material is performed by dielectric heating, induction heating, or thermal radiation.   The method for processing a high hardness material according to any one of claims 1 to 3, wherein the high hardness material is SiC and the polishing tool is cBN. A processing device for processing while contacting a rotating polishing tool while rotating a high hardness material,
A heating device for heating the high-hardness material at a position different from the processing part;
A cooling device for cooling the polishing tool at a position different from the processing part;
A processing apparatus for a high-hardness material, comprising: a cleaning device for cleaning the polishing tool at a position different from a processing section.

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