JP2013035144A - Method and apparatus for coring sapphire single crystal ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coring a cylindrical block of crystal orientation having a desired angle with an a-axis of a crystal direction using a core drill from a sapphire single crystal ingot without damaging a tip portion of a core drill blade tip part.SOLUTION: The method for coring the sapphire single crystal ingot forms a flat reference surface to be placed on a table in the ingot as well as a flat worked surface in parallel to the reference surface, presses and fixes the worked surface by a pressing device at a location which does not interfere with coring operation by core bits after placing the reference surface without fixing on the table, abuts the blade tip part of the core bits with the worked surface, and feeds at low speed at the beginning, increasing the feeing speed after the predetermined amount of cut to perform constant high speed feeding, and reducing the feeding speed toward the end of the coring operation.

Description

  The present invention relates to a coring method and apparatus for hollowing out a cylindrical block from a sapphire single crystal ingot using a core drill.

  A wafer to be a sapphire substrate is usually obtained by slicing a cylindrical block cut from a sapphire single crystal ingot to a certain thickness. Patent Document 1 listed below discloses a CZ method (Czochralski method) or an EFG method. A coring method that uses a core drill from a sapphire single crystal ingot obtained by (Edge-defined Film-fed. Growth Method) etc. to feed a cylindrical core bit at a feed rate of 2 to 10 mm / min to hollow out a cylindrical block. In the coring method using a core drill, a cylindrical block having a good cross-sectional accuracy close to a perfect circle can be obtained easily and in a short time by a single coring operation.

  In Patent Document 1 below, in order to manufacture a wafer having a desired crystal orientation, a predetermined angle or a c-axis direction orthogonal to the a-axis is formed with respect to the a-axis which is the crystal growth direction of the sapphire single crystal ingot. A coring method is disclosed in which a cylindrical block having a crystal orientation different from that of a sapphire single crystal ingot is cut out by drilling.

JP2008-971

As shown in FIG. 1, a sapphire single crystal ingot grown by the Kilopros method is generally bullet-shaped and has a cross section perpendicular to the crystal growth direction a, and the cross section in the c-axis direction indicated by the alternate long and short dash line is substantially circular. It has an irregular shape that changes in direction.
On the other hand, a sapphire single crystal ingot grown by the CZ method has a crystal growth direction of a c-axis indicated by a one-dot chain line as shown in FIG. 2, and a cross section perpendicular to the c-axis has a substantially hexagonal shape.

  In any ingot, for example, when a cylindrical block in the c-axis direction is manufactured using a core drill, a reference plane parallel to the a-axis is created by machining, and then the ingot at the time of coring is prepared. The reference surface is precisely polished so that the orientation becomes the desired orientation, then the reference surface is applied to the plate under the core drill, and the sapphire single crystal ingot is fixed with an adhesive to perform coring. Therefore, it is not easy to accurately cut the target position. That is, when cutting into the ingot, as shown in FIG. 3, when a part of the cutting edge portion 2 of the core bit 1 constituting the core drill hits an inclined or curved portion of the ingot 3, the cutting edge portion 2 escapes or shakes in the direction of the arrow in the figure. It becomes easy to do. Moreover, since sapphire has high hardness and is brittle with low toughness, the ingot is easily chipped or cracked or cracked easily due to the aforementioned blurring of the cutting edge.

  The ingot fixed by the adhesive can stably perform the coring operation, but it takes time for the adhesive to harden, and even if the folding angle reference surface is precisely polished, the ingot is interposed by the intervening adhesive. The azimuth may be shifted from the desired azimuth. After coring, the ingot and the hollow cylindrical block must be removed from the plate, but in order to remove the adhesive, it must be boiled in hot water, which takes time and takes a long time. Become.

  In coring work, the positioning of the core bit edge with respect to the ingot at the start of cutting is conventionally performed by visual inspection, and the feed at the start is a low speed of 0.1 to 0.3 mm / min. In general, a part or all of the cutting edge of the core bit is cut into the projecting ingot, and it takes time until the cutting is stabilized.

  The present invention relates to a method and apparatus capable of coring a cylindrical block having a crystal orientation having a desired angle with the a-axis in the crystal direction from a sapphire single crystal ingot without causing damage to the core drill cutting edge. The purpose is to provide.

  The invention according to claim 1 uses a core drill, feeds a cylindrical core bit constituting the core drill with a feed motor, coring a sapphire single crystal ingot installed on a table, and sets a desired angle with the crystal direction. A method of manufacturing a cylindrical block having a crystal orientation having a flat reference surface to be placed on a table in the ingot, a flat processed surface parallel to the reference surface, and a reference surface After mounting without fixing on the table, press and fix the processing surface that faces upward with a presser device at a location that does not interfere with the coring work by the core bit, and then apply the cutting edge of the core bit to the processing surface, Start at a low speed, increase the feed speed after cutting a predetermined amount to a constant high speed feed, and reduce the feed speed near the end of coring work. And features.

  The invention according to claim 2 is an apparatus for carrying out the invention according to claim 1, wherein a core bit having a cutting edge portion made of a diamond abrasive tip at the tip, and a rotation driving device for rotationally driving the core bit, A core drill having a feed motor and having a feed device that feeds the core bit in the vertical direction; a presser device that presses a processed surface of the ingot placed on the table at a location that does not interfere with the coring operation by the core bit; and a core bit After detecting the cutting start reference position by the detecting means for detecting whether or not the cutting edge portion has reached the cutting start reference position to the ingot, the measuring means for measuring the feed amount of the cutting edge portion at the time of cutting The vertical position of the blade edge part is obtained from the feed amount measured by the measuring means, and the vertical position of the obtained blade edge part is close to the machining surface Until the set upper position is reached, the rotational speed of the feed motor is controlled at a low speed, and when the upper position is reached, the rotational speed of the feed motor is increased to a high speed set number and maintained at the set number, And a control device that controls the number of revolutions of the feed motor so that a low-speed feed is achieved when the vertical position of the cutting edge obtained from the feed amount reaches a lower position set near the table.

The invention according to claim 3 is the invention according to claim 2, wherein the presser device is passed through the shaft center of the core bit and has a hollow presser bar having a presser at its lower end, and a presser for lowering the presser bar. The presser bar has an opening in the core bit, and the dressing powder supplied from the outside into the presser bar is discharged into the core bit through the opening,
The invention according to claim 4 is the invention according to claim 2 or 3, wherein the table on which the ingot is placed is xy-controlled, and positioning means is provided for aligning the mark marked on the ingot with the axis of the core bit. It is characterized by that.

  According to the first aspect of the present invention, since the processed surface of the ingot is flat, it is easy to press with the pressing device, and the ingot on the table is pressed with the pressing device, so that the reference surface is adhesive as in the conventional method. The ingot can be fixed without adhering to the plate, so the time and time required for the adhesive to solidify and to remove the adhesive as in the conventional method using an adhesive are not required, and the time is reduced accordingly. When the workability is improved and the orientation of the ingot does not deviate from the desired orientation as in the case where an adhesive is interposed, the upper part of the ingot has a mountain shape. Is cut into the ingot, and it takes a relatively long time for the low-speed feed required for the cutting state to be stabilized. Stable when cut even mm, to reduce the time of low-speed feed has the effect of such that it is possible to further shorten the time required for coring operations.

According to the invention relating to claim 2, the feeding during the coring operation of the invention relating to claim 1 can be automated.
According to the invention of claim 3, during the coring operation, when the sharpness of the core bit is reduced, conventionally, the rotation of the core bit was temporarily stopped and the dressing powder was put into the ingot cutting portion. The dressing powder can be supplied into the core bit through the presser bar without stopping the core bit.

  According to the fourth aspect of the present invention, the ingot placed on the table can be accurately positioned without visual observation.

Schematic of an ingot created by the Kilopros method. Schematic of the ingot created by the CZ method. Explanatory drawing when a core bit blade edge | tip part contacts the inclination part of an ingot. The schematic diagram of this apparatus. The front view of a core drill unit. The schematic of the ingot in which a reference surface and a process surface are formed. Schematic which installed the ingot on the table. Schematic which shows another aspect which installed the ingot on the table. Schematic which shows the state which fixed the ingot with the presser. Schematic which shows the state which put the pressure sensitive sheet on the processing surface of the ingot at the time of a work start. Schematic which shows the state which fixed the ingot with the pressing tool and the fixing tool. Schematic when injecting cooling water and dressing powder.

Hereinafter, an apparatus for performing a coring operation of a sapphire crystal ingot according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 4 shows a schematic diagram of the entire coring apparatus, and FIG. 5 shows a core drill unit of the coring apparatus. The core drill unit includes a cutting edge portion 11 made of a diamond abrasive grain tip at the tip. The core bit 12 is removably attached to a lower end of a hollow main shaft 15 that is rotationally driven by a drive motor 13 via a gear transmission device 14 so as to be rotationally driven around a vertical axis. It has become.

  The core bit 12 is also moved up and down along the vertical axis by a feed mechanism 17 having a feed motor 16, and the feed mechanism 17 is a ball screw (not shown) that is rotationally driven by the feed motor 16. 5 has a guide rail 18 provided in parallel with the ball screw on the front side of the ball screw, and a bracket 19 having a nut (not shown) supported by the guide rail 18 so as to be movable up and down and screwed to the ball screw. The bracket 19 rotatably supports the main shaft 15 in a cylindrical body 20 fixed to the bracket 19 and moves up and down integrally with the main shaft 15 in the vertical axis direction.

  A hollow presser bar 21 that constitutes a presser device together with a pressing means described later, for example, a spring device, a pneumatic or a hydraulic cylinder 22, is passed through the shaft center of the main shaft 15 so as to be able to move up and down, and the presser bar 21 protrudes upward. At the upper end of the part, it is connected to the piston rod 23 of the hydraulic cylinder 22 as the push-down means constituting a part of the core drill unit, and ascends and descends as the piston rod 23 advances and retracts, and protrudes from the main shaft 15 into the core bit. An opening 25 for discharging dressing powder and cooling water is provided at the lower part, and a presser 24 is attached to the lower end. As shown in FIG. 4, a dressing powder supply line 27 and a cooling water, for example, tap water supply line 28 are connected to the upper end of the presser bar 21, and the supply line 27 is connected to a compressed air source such as a compressor. A hopper 29 and a solenoid valve 31 into which dressing powder is put are provided on the line 27, and when the solenoid valve 31 is opened, compressed air from the compressed air source passes through the line 27 and accompanies the dressing powder in the hopper. It is supplied to the presser bar 21. When the electromagnetic valve 31 is closed, the supply of the dressing powder is stopped.

  When tap water is used as the cooling water, the supply line 28 is connected to a faucet, and an electromagnetic valve 32 is provided on the line. The cooling water is supplied or stopped by opening and closing the electromagnetic valve 32. The bracket 19 also has a pair of laser line markers 34 arranged at an angle of 90 ° (only one laser line marker 34 is shown in the figure, and other laser line markers are not shown). The sapphire crystal ingot 35 is irradiated with a linear laser beam from each laser line marker 34, and the intersection of the laser beams is displayed.

  On the base 37 of the core drill unit, as shown in FIG. 5, a table 38 comprising a table 38a movable in the y direction and a table 38b movable in the x direction below the table 38a is installed. The shaft motor 41 and a ball screw or pinion rack mechanism (not shown) are sent in the y direction of the arrow, and the table 38b is sent in the x axis direction by an x axis motor 42 and a ball screw or pinion rack mechanism (not shown). Yes.

  The control device 44 includes a CPU, a ROM for storing a feed control program, a program for ingot positioning, a calculation formula for calculating the vertical position of the core bit cutting edge from the rotational speed of the feed motor 16, and the like. The entire system is constituted by a personal computer comprising a RAM and the like for temporarily measuring the number of rotations and measuring values measured by an encoder 45 (FIG. 4) as a means for measuring the amount of feed, and other various data. . A function for controlling the y-axis motor 41 and the x-axis motor 42 (both the motors 41 and 42 can be started and stopped by operating a manual button without using the control device 44, respectively. A function for ON / OFF control of the switching valves 43a and 43b of the hydraulic cylinder, a function for ON / OFF control of the electromagnetic valves 31 and 32, a drive motor 13 and a feed motor 16 for rotationally driving the core bit 12. , A function of calculating the feed amount of the core bit cutting edge 11 from the accumulated value of the rotational speed read from the encoder 45 of the feed motor 16, and a detecting means placed on the processing surface at the upper end of the ingot 35 A function for obtaining a distance from a detection signal from a sensing sheet (to be described later) constituting the workpiece to the processed surface of the ingot 35, and The height of the ingot 35 is calculated from the distance to the ingot processing surface and the distance to the table 38 on which the ingot 35 is placed, and is set close to the processing surface, for example, 1 to 2 mm from the processing surface, so that the incision is stable. Until reaching the position, for example, an ultra-low speed feed of 0.05 to 0.1 mm / min is set, and when the core bit cutting edge 11 reaches the upper place, for example, a high speed feed of 5 to 10 mm / min is set near the end of cutting. When reaching the lower position, for example, a function of controlling the feed motor 16 so as to achieve a low speed feed of 0.1 to 0.3 mm / min, and a function of controlling the opening and closing of the electromagnetic valves 31 and 32 by an external input means And have.

The present apparatus is configured as described above, and the coring operation for hollowing out the cylindrical block from the sapphire single crystal ingot is performed as follows. The following shows an example using an ingot 35 created by the Cyprus method as an ingot.
First, an ingot 35 is formed by machining a reference surface parallel to the crystal growth direction a and a machining surface parallel to the reference surface (FIG. 6), and the plate 47 is placed on the table 35 with the reference surface facing downward. For example, instead of placing the plate 47 through a carbon plate (FIG. 7), as shown in FIG. 8, an annular groove 46 for escaping the cutting edge 11 may be formed in the table 35 as shown in FIG. .

  Next, a mark corresponding to the center point of the circular cross section of the cylindrical block to be collected from the ingot 35 is marked. This marking is done, for example, by punching in or by magic or other writing instruments.

  After marking, the y-axis motor 41 and the x-axis motor 42 are operated to start and stop by a button operation so that the intersection of the orthogonal lines applied on the ingot by the pair of laser line markers 34 matches the mark. Xy control of the tables 38a and 38b is performed.

  Positioning is performed by matching the mark marked on the ingot 35 with the intersection of the laser line markers 34. Therefore, the center of the circular cross section of the cylindrical block to be sampled from the sapphire single crystal ingot 35 is the rotation center of the core bit. The positioning means for positioning the ingot so as to be positioned at the position is constituted by the marking, the laser line marker 34, the y-axis motor 41, the x-axis motor 42, etc., but the ingot positioning means is limited to this. Any known means can be used.

Next, the switching valves 43a and 43b of the hydraulic cylinder 22 are switched by an input from an external input means (not shown) to the control device 44, the presser bar 21 is pressed down to press the presser 24 at the lower end of the presser bar against the work surface of the ingot 35, The ingot 35 on the table is fixed (FIG. 9). After fixing, a sensing means 51 for detecting whether or not the cutting edge portion 11 has reached the cutting start reference position, for example, a sensing sheet 51 which is made of a copper plate which is not easily damaged even when the cutting edge portion 11 hits, and which is energized when the cutting edge of the core bit comes into contact. Is placed on the processing surface of the ingot 35 on the table 38, and a coring start button (not shown) of the control device 44 is pushed. Then, the feed motor 16 is activated, and the core bit 12 is lowered along the guide rail 18. The core bit 12 is lowered until the cutting edge portion 11 reaches the sensing sheet 51 (FIG. 10) and the energization of the sensing sheet 51 is output to the control device 44. When the output is performed, the control device 44 performs the cutting edge. It is determined that the section 11 has reached the cutting start reference position, and the feed amount at this time is calculated from the cumulative value of the encoder 45 that has read the rotational speed of the feed motor 16. Then, the height of the ingot 35 is obtained by subtracting the thickness of the sensing sheet 51 from the distance between the cutting edge portion 11 located at the top dead center and the table 38 that has been obtained in advance.
In response to the output from the sensing sheet 51, the controller 44 also reverses the feed motor 16 once by a predetermined amount and lifts the core bit cutting edge 11 slightly during the set time.

  When the cutting edge portion 11 of the core bit 12 is slightly lifted, the pressure sensitive sheet 51 is removed from the processed surface of the ingot 35. When the set time elapses, the control device 44 controls the feed motor 16 and lowers the core bit 12 to the cut start reference position (by the way, this reference position is obtained by adding the thickness of the sensing sheet 51 to the machining surface of the ingot). Let The feed speed of the core bit 12 is high up to the cut start reference position, and when it reaches the cut start reference position, the feed motor 16 is controlled to an extremely low speed. Ultra-low speed feed is performed until the cutting edge 11 reaches the upper position set to 1 to 2 mm, for example, from the machining surface, and when it reaches the upper position, it is switched to high speed feed. Thereafter, this high-speed feed is maintained. This high-speed feed is performed until the vertical position of the cutting edge portion 11 obtained from the feed amount reaches a lower position set to, for example, 1 to 2 mm from the reference surface, and when it reaches the lower position, the low-speed feed is switched.

  In FIG. 11, a is a section where ultra-low speed feed is performed from the machining surface to the upper position, b is a section where low speed feed is performed from the lower position to the reference surface, and a section between a and b is a section where high speed feed is performed. ing.

  When the cutting edge 11 reaches the carbon plate 47 at the end of coring, the feed motor 16 is stopped. During this time, when visually observing the reduction in sharpness, the control device 44 opens the electromagnetic valves 31 and 32 through the input from the external input means (not shown) to pass the dressing powder and cooling water into the presser bar 21, It discharges toward the periphery from the opening 25 into the core bit. The discharged cooling water and powder enter the cut groove to cool the blade edge and perform dressing (FIG. 12). As a result, coring can be performed continuously. Instead of visually injecting the cooling water and the powder, the torque of the feed motor 16 and / or the drive motor 13 is measured, and when the measured value or the rate of change thereof reaches a set value, the control device 44 controls the solenoid valve. 31 and 32 may be controlled to inject cooling water and powder. In this case, cooling water and powder can be automatically injected.

  In the above-described embodiment, the sensing sheet 51 is placed on the ingot, and the vertical positioning of the cutting edge portion 11 at the start of cutting is performed at a position where the core bit cutting edge portion 11 contacts the sensing sheet 51, and the core bit 12 is temporarily placed at the position. After slightly raising and lowering again, the operation of sending the core bit 12 from the position at an ultra-low speed is automatically performed. However, the core bit 12 is moved at an ultra-low speed from the once raised position above the cut start reference position. It may be sent (although the working time slightly increases), the core bit is suddenly lowered by the eye without performing the positioning operation of the core bit cutting edge portion 11 as described above, and sent immediately before contacting the ingot 35. It is not impossible to stop and position and then perform the automatic operation as described above. The task of positioning temporarily stopped just before contact with the ingot 35 is difficult to fine adjustment, if the core bit cutting edges 11 mistakenly contacts the ingot 35, the cutting edge portion 11 is easily damaged.

  As described above, the ingot 35 on the table is fixed by the presser 24. In addition to the presser 24, a fixer 53 as shown in FIGS. 8, 11, and 12 is provided, and the ingot 35 is provided by the fixer 53. It is desirable to press and fix the periphery. The cylindrical block that is hollowed out at the end of coring is edged with the surrounding ingot 35. However, even if the block is fixed by the presser 24, the edged ingot 35 is not fixed. is there. As described above, the presser device is composed of the presser 24, but the fixing member 53 may or may not be included in the presser device.

  The fixture 53 includes a shaft 54 that is vertically attached to the table 38, a presser portion 58 that is slidably attached to the shaft 54, and a presser plate 56 and a presser portion 58 that are attached to the upper end of the shaft. It consists of a spring 57 attached to the shaft 54 between them.

  At the time of coring, as shown in FIG. 5, it is desirable to provide an enclosure 55 surrounding the ingot 35 on the table so that dust is not scattered.

  In the above embodiment, an ingot created by the Kilopros method is used as an ingot. However, when an ingot created by the CZ method is used as shown in FIG. 2, an alternate long and short dash line in the a-axis direction perpendicular to the crystal growth direction c The reference surface and the processed surface indicated by are formed in the same manner.

11. · Cutting edge 12 · · Core bit 13 · · Drive motor 15 · Spindle 16 · · Feed motor 21 · · Presser bar 22 · · Hydraulic cylinder 24 · · Presser 25 · · Opening 34 · · Laser marker 35 · · Ingot 38 .. Table 44.. Control device 47.. Carbon plate 51.. Pressure sensitive sheet 53.

Claims (4)

  Using a core drill, a cylindrical core bit constituting the core drill is sent by a feed motor, and a sapphire single crystal ingot placed on a table is cored, and a cylindrical block having a crystal orientation and a desired angle is obtained. A method of manufacturing, wherein a flat reference surface to be placed on a table is created on the ingot, a flat processed surface parallel to the reference surface is created, and the reference surface is mounted without being fixed on the table. After that, the machined surface is pressed and fixed by a holding device at a place where it does not interfere with the coring work by the core bit, and then the cutting edge of the core bit is applied to the machined surface. A sapphire single crystal ingot characterized by increasing the speed to a constant high-speed feed and reducing the feed speed near the end of the coring operation. How to coring a cylindrical block from.   A core drill having a cutting edge portion made of a diamond abrasive grain tip, a rotation driving device for rotationally driving the core bit, a feeding motor, and a feeding device for feeding the core bit in the vertical direction; A pressing device for pressing the processing surface of the ingot placed on the core bit at a location that does not interfere with the coring operation by the core bit, and a detecting means for detecting whether or not the core bit cutting edge has reached the incision start reference position to the ingot. Then, after detecting the cutting start reference position by the measuring means for measuring the feed amount of the cutting edge portion at the time of cutting, the vertical position of the cutting edge portion is obtained from the feeding amount measured by the measuring means, Controls the rotation speed of the feed motor at a low speed until the vertical position of the cutting edge reaches the upper position set near the machining surface. When the upper position is reached, the number of rotations of the feed motor is increased to a set number of high speeds and maintained at the set number, and the vertical position of the blade edge portion obtained from the feed amount is set to the lower position set near the table. The apparatus for carrying out the coring method according to claim 1, further comprising a control device that controls the rotational speed of the feed motor so as to achieve low-speed feed when reaching.   The presser device has a hollow presser bar that is passed through the core of the core bit and has a presser at the lower end, and a presser device that presses down the presser bar, and the presser bar has an opening in the core bit, 3. The apparatus according to claim 2, wherein the dressing powder supplied from the outside into the presser bar is discharged into the core bit through the opening.   4. The apparatus according to claim 2, further comprising positioning means for performing xy control on a table on which the ingot is placed and aligning the mark marked on the ingot with the axis of the core bit.