Holding table, processing device including same, and processing method

Abstract

To provide a new technique for preventing damage on a holding surface for a holding table that holds an ingot.SOLUTION: A laser processing device has a holding table 40 which suction-holds an ingot 3. On the holding surface 42, three or more support pins 44 for supporting the ingot, a plurality of pores 45 for suctioning the ingot, and an insertion hole 46 to which the support pin is inserted are formed. In the holding table 40, a flow channel 41a whose one end side communicates to a pneumatic chamber 41K and whose other end side is connected to an air suction source 52 or air supply source 54 in a freely switchable manner is formed. By supplying the air to the flow channel, the support pin is positioned at a protrusion support position, the ingot can be supported by the tip of the support pin, the flow channel is decompressed, the support pin is loosely positioned at a retreat position, the ingot 3 is supported on the holding surface and suction-held with the negative pressure acting on the plurality of pores 45.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a holding table having a holding surface that holds an ingot by suction, and a processing device equipped with the same, and more particularly to a technique for preventing damage to the holding surface. [Background technology]

[0002] Conventionally, as disclosed in Patent Documents 1 and 2, for example, a method of using a laser processing device instead of a conventional wire saw when slicing SiC wafers from a SiC ingot has been known. An ingot of a hard material such as SiC is held with its underside placed on the holding surface of a holding table, and a laser beam is irradiated from above and focused at a predetermined position to form a layer (separation layer) that serves as a starting point for dividing the ingot into wafers.

[0003] By using such a laser processing device, the cutting amount can be reduced compared to when cutting SiC wafers with a wire saw, and the processing speed can be increased, improving productivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-032771 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-223589 Summary of the Invention [Problem to be solved by the invention]

[0005] Ingots, for example, SiC, are heavy, weighing several kilograms for a 6-inch diameter ingot. Furthermore, when an ingot is made of a particularly hard material and has high hardness, there is a risk that when an operator places the ingot on the holding table, the corners of the ingot may come into contact with the holding surface of the holding table, scraping and damaging the holding surface.

[0006] If the holding surface of the holding table is worn down, the ingot cannot be held horizontally, which can cause problems such as the laser beam not being focused at the desired position and high-precision processing not being possible.

[0007] In view of the above problems, the present invention proposes a novel technique for preventing damage to the holding surface of a holding table that holds an ingot. [Means for solving the problem]

[0008] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0009] According to one aspect of the present invention, there is provided a holding table having a holding surface for suction-holding an ingot, wherein three or more support pins for supporting the ingot are provided on the holding surface so as to be movable forward and backward, and the holding surface is formed with a plurality of fine holes for suctioning the ingot and insertion holes into which the support pins are inserted, and the holding table is formed with flow channels whose one end communicates with the plurality of fine holes and with air pressure chambers at the rear ends of the support pins, respectively, and whose other end is switchably connected to an air suction source or an air supply source. By connecting the flow path to the air supply source and supplying air to the air pressure chamber, the tip of the support pin is positioned at a support position protruding from the holding surface, making it possible to support the ingot with the tip of the support pin, and by connecting the flow path to the air suction source and reducing the pressure in the air pressure chamber, the tip of the support pin is gently positioned at a retracted position where it is embedded in the insertion hole, and the ingot is supported by the holding surface and is suction-held on the holding surface by negative pressure acting on the multiple pores, resulting in a holding table.

[0010] According to another aspect of the present invention, the support pin is biased by an elastic member in a direction that moves it to a retracted position, and the support pin is positioned at the retracted position when air is not supplied to the air pressure chamber.

[0011] According to another aspect of the present invention, a processing apparatus includes a holding table.

[0012] According to one aspect of the present invention, there is provided a processing method for separating a wafer from an ingot, the processing method comprising: a support pin protruding step of protruding three or more support pins from a holding surface of a holding table; a step of placing the ingot on the tips of the support pins and supporting the ingot above the holding surface with the support pins; a holding step of slowly moving the support pins so as to embed them in the holding surface, placing the ingot on the holding surface, and suction-holding the ingot on the holding surface; and a laser irradiation step of focusing a laser beam at a predetermined height position on the ingot, and moving the holding table horizontally relative to the laser beam to form a separation layer in the ingot. [Effects of the Invention]

[0013] According to the configuration of the present invention, before the ingot is held on the holding surface, the ingot is placed on the tips of multiple support pins protruding from the holding surface, the ingot is supported by the support pins above the holding surface, and then the tips of the support pins are gently positioned to a retracted position where they are embedded in the holding surface, thereby holding the ingot on the holding surface. This prevents the ingot from colliding with the holding surface and damaging the holding surface during the process of holding the ingot on the holding table. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing an example of a laser processing device equipped with a holding table according to the present invention; [Figure 2] FIG. 2 is a plan view of a holding table according to the present invention. [Figure 3] 1A is a cross-sectional view illustrating the state of the support pin in a standby state, and FIG. 1B is a cross-sectional view illustrating the state in which the support pin is protruded. [Figure 4] FIG. 10 is a diagram illustrating a state in which the ingot is supported by the support pins. [Figure 5] FIG. 10 is a diagram illustrating a state in which an ingot is suction-held on a holding surface. [Figure 6] 1 is a flowchart illustrating each step of a processing method. [Figure 7] 10A to 10C are diagrams illustrating a laser irradiation step. DETAILED DESCRIPTION OF THE INVENTION

[0015] 1 is a diagram showing an example of a laser processing apparatus 1 equipped with a holding table 10 according to the present invention. The laser processing apparatus 1 has a laser beam irradiation mechanism 20 that irradiates a laser beam, and a holding table 40 that holds an ingot 3 on the upper surface.

[0016] The laser processing device 1 has a rectangular parallelepiped base 11, and on the upper surface of the base 11 is provided a movement mechanism 12 that feeds a holding table 40 for processing in the X-axis direction and indexes it in the Y-axis direction.

[0017] The movement mechanism 12 includes a Y-axis movement mechanism 12Y that moves the holding table 40 relative to the laser beam irradiation mechanism 20 in the Y-axis direction, and an X-axis movement mechanism 12X that moves the holding table 40 relative to the laser beam irradiation mechanism 20 in the X-axis direction.

[0018] The holding table 40 is provided so as to be rotatable (rotation in the θ direction) by a rotation axis extending in a direction perpendicular to a holding surface 42 of the holding table 40. The upper surface of the holding table 40 is connected to an air suction source 52 (FIG. 3(A)), which will be described in detail later, and is configured as the holding surface 42 that suction-holds the ingot 3.

[0019] A vertical wall 13 is provided on the base 11 behind the moving mechanism 12. An arm 14 protrudes horizontally from the front surface of the vertical wall 13, and a laser beam irradiation mechanism 20 is provided on the tip side of the arm 14 so as to face the holding table 40.

[0020] The laser beam irradiation mechanism 20 has a processing head 22. The arm unit 14 and the processing head 22 house an optical system of the laser beam irradiation mechanism 20. The optical system of the laser beam irradiation mechanism 20 includes an oscillator that generates a laser beam, a mirror that reflects the generated laser beam, and a focusing lens that focuses the laser beam on the ingot, and by focusing the laser beam at a predetermined position on the ingot 3, a separation layer is formed that serves as a starting point for dividing the ingot into wafers.

[0021] The arm 14 is supported on the upright wall 13 via a Z-axis movement mechanism 18, and as the arm 14 is moved in the Z-axis direction by the Z-axis movement mechanism 18, a processing head 22 disposed at the tip of the arm 14 moves in the Z-axis direction. An imaging camera 24 for capturing an image of the surface of the ingot 3 is provided on the side of the processing head 22.

[0022] In the above configuration, for example, if the ingot 3 is a SiC ingot, a laser beam having a wavelength that is transparent to SiC is focused at a predetermined height position on the ingot 3, and the holding table 40 is moved horizontally in the X and Y directions relative to the laser beam. As a result, a separation layer containing a mixture of carbon and silicon is formed at a predetermined height position within the ingot 3, and wafers are separated starting from this separation layer.

[0023] The ingot 3 is not limited to an SiC ingot, which has a hardness higher than that of the holding surface 42 of the holding table 40, but may be an ingot having a hardness lower than that of the holding surface 42 of the holding table 40. The present invention is effective for any type of ingot 3 in that it can prevent damage to the holding surface 42.

[0024] Next, the configuration of the holding table 40 shown in FIG. 2 and FIGS. 3(A) and (B) will be described. The holding table 40 is configured to have a base 41 and a plate 43 that is placed on the top of the base 41 and exposes the holding surface 42 .

[0025] The plate 43 is made of a disk-shaped porous material, and its upper surface forms a holding surface 42 that suction-holds the ingot 3. Six support pins 44, 44 that abut against the lower surface 3b (FIG. 4) of the ingot 3 and support the ingot 3 from below are provided on the holding surface 42 so as to be movable up and down.

[0026] In this embodiment, as shown in Figure 2, six support pins 44 are arranged circumferentially at equal intervals to stably hold the ingot 3, but the number of support pins 44 is not particularly limited as long as it is three or more and can support the ingot 3 horizontally.

[0027] As shown in Figures 2 and 3(A), the holding surface 42 is formed with a plurality of pores 45 that suck the lower surface 3b (Figure 4) of the ingot 3 and a plurality of insertion holes 46 into which the support pins 44 are respectively inserted.

[0028] In this embodiment, the pores 45 are formed by the plate 43 itself, which is made of a porous material, and negative pressure is generated in the pores 45 by suction through the flow path 41a of the base 41, so that the holding surface 42 is formed as a suction holding surface.

[0029] As shown in Figures 3(A) and (B), the flow path 41a is connected to an air suction source 52 via a control valve 51, and by opening the control valve 51, the holding surface 42 can function as a suction holding surface.

[0030] The flow path 41a is also connected to an air supply source 54 via a control valve 53, and by opening the control valve 53, positive pressure is generated on the holding surface 42, generating buoyancy in a direction that moves the ingot 3 away from the holding surface 42.

[0031] A cylinder portion 41s is formed in the base 41 of the holding table 40, and the piston portion 44s of the support pin 44 is slidably accommodated therein. An elastic member 55 is housed in the cylinder portion 41s and comes into contact with the upper side of the piston portion 44s of the support pin 44, urging the support pin 44 downward. The piston portion 44s is configured in a shaft shape, and the support pin 44 protrudes upward from the flat surface on the upper side thereof.

[0032] In the cylinder portion 41s, the space above the piston portion 44s is configured as a spring chamber 41b that houses an elastic member 55, and the space below the piston portion 44s is configured as an air pressure chamber 41k that supplies and exhausts air. The elastic member 55 is configured as, for example, a compression spring that surrounds the periphery of the support pin 44.

[0033] The lower end of the elastic member 55 abuts against the upper part of the piston portion 44s, urging the entire support pin 44 downward. As shown in Fig. 3(A), in a standby state where the ingot 3 is not supported, or as shown in Fig. 5, when the ingot 3 is held by the holding surface 42, the bias of the elastic member 55 causes the tip of the support pin 44 to enter completely into the insertion hole 46 and not protrude from the holding surface 42.

[0034] 3(A), in a standby state in which the ingot 3 is not supported, the support pins 44 are inserted into the insertion holes 46 by the elastic members 55, thereby making it possible to keep the holding surface 42 free of protrusions and preventing the support pins 44 from colliding with and damaging other components. In addition to the above configuration, the elastic members 55 may be omitted, or the elastic members 55 may be used to urge the support pins 44 in a direction in which they protrude from the holding surface 42.

[0035] 3B, the air pressure chamber 41k is connected to the flow path 41a, and when the control valve 53 is opened and connected to the air supply source 54, the pressure in the air pressure chamber 41k increases, pushing the piston 44s upward against the biasing force of the elastic member 55, causing the tip of the support pin 44 to protrude upward from the insertion hole 46.

[0036] 3(B) and 4, when the ingot 3 is carried into the holding table 40, air is supplied to the air pressure chamber 41k, causing the tip of the support pin 44 to protrude from the insertion hole 46. As a result, the support pin 44 is positioned at a support position where the tip protrudes from the holding surface 42, and the tip is ready to support the ingot 3.

[0037] 3(A), the air pressure chamber 41k of the cylinder portion 41s is connected to the flow path 41a, and when the control valve 53 is closed from the state of FIG. 4 and the control valve 51 is opened to connect the air pressure chamber 41k to the air suction source 52, the air pressure chamber 41k is reduced in pressure, and as shown in FIG. 5, the support pin 44 is gently positioned at a retracted position where its tip is embedded in the insertion hole 46 of the holding surface 42, and the ingot 3 is lowered so that the lower surface 3b is placed on the holding surface 42 and held by suction.

[0038] Next, a processing method using the holding table and processing device configured as described above will be described. Fig. 6 is a flowchart showing the steps of the processing method.

[0039] <Support pin protruding step> First, as shown in FIG. 3B, the control valve 53 is opened, air is supplied from the air supply source 54 to the air pressure chamber 41k, and the support pins 44 are caused to protrude from the holding surface 42 against the biasing force of the elastic member 55.

[0040] <Support Step> 4, the ingot 3 is placed on the tips of a plurality of support pins 44, and the ingot 3 is supported by the support pins 44 above the holding surface 42. Because the tips of the support pins 44 protrude from the holding surface 42, the ingot 3 can be supported by the support pins 44 without coming into contact with the holding surface 42. This prevents the ingot 3 from colliding with the holding surface 42 and damaging the holding surface 42.

[0041] The ingot 3 may be placed on the tip of the support pin 44 by an operator, or may be transported by a transport device and placed on the tip of the support pin 44. In either case, damage to the holding surface 42 by the ingot 3 can be avoided.

[0042] <Holding step> 5, the control valve 53 is closed to stop the supply of air from the air supply source 54 to the air pressure chamber 41k, and the control valve 51 is opened to reduce the pressure in the air pressure chamber 41k by the air suction source 52. As a result, the tips of the support pins 44 are gently drawn into the insertion holes 46, and the lower surface 3b of the ingot 3 is placed on the holding surface 42.

[0043] Furthermore, by opening the control valve 51, a negative pressure is also generated on the holding surface 42, and the lower surface 3b of the ingot 3 is held by suction on the holding surface.

[0044] <Laser irradiation step> 7, the laser beam L is focused at a predetermined height position on the ingot 3, and the holding table 40 is moved horizontally in the X and Y directions relative to the laser beam L. As a result, a separation layer B is formed at a predetermined height position within the ingot 3.

[0045] <Separation step> Next, as shown in Fig. 7, the upper portion of the separation layer B is separated as a wafer 2 in a separation device 70 having a suction holding pad 72 and carried out. The ingot 3 remaining after the separation of the wafer 2 has its upper surface ground or polished to be flattened. This flattening may be performed on the holding table 40 holding the ingot 3, or the suction holding of the holding table 40 may be released and the ingot 3 may be transported to another grinding device or the like for flattening. After flattening, the laser beam L is irradiated again to form the separation layer B.

[0046] The formation of separation layer B, separation of wafers 2, and flattening of the upper surface of ingot 3 are repeated until the ingot 3 reaches a predetermined thickness. After the ingot 3 reaches a predetermined thickness, control valve 53 is opened to supply air from air supply source 54 to holding surface 42 and air pressure chamber 41k, thereby generating positive pressure on holding surface 42 and lifting support pins 44 to peel off the remaining portion of ingot 3 from holding surface 42.

[0047] The present invention can be carried out as described above. That is, when the ingot 3 is carried in, before the ingot 3 is held on the holding surface 42, the ingot 3 is placed on the tips of multiple support pins 44 protruding from the holding surface 42, the ingot 3 is supported by the support pins above the holding surface 42, and then the tips of the support pins 44 are gently positioned at a retracted position where they are embedded in the holding surface 42, thereby holding the ingot 3 on the holding surface 42. This makes it possible to prevent the ingot 3 from damaging the holding surface 42 of the holding table 40 during the process of holding the ingot 3 on the holding table 40. [Explanation of symbols]

[0048] 1. Laser processing equipment 2 wafers 3 ingots 3b Bottom side 10 Holding table 11 Foundation 12 Moving mechanism 13 Vertical wall 14 Arm section 18 axis movement mechanism 20 Laser beam irradiation mechanism 22 Processing head 24 Imaging camera 40 Holding table 41 Base 41a Flow path 41b Spring chamber 41k Air Chamber 41s cylinder part 42 Holding surface 43 Plate 44 Support pin 44s piston part 45 pores 46 Insertion hole 51 Control valve 52 Air suction source 53 Control valve 54 Air supply source 55 Elastic member 70 Separation device 71 Adsorption holding pad B separation layer L laser beam

Claims

1. A holding table having a holding surface for suction-holding an ingot, Three or more support pins for supporting the ingot are provided on the holding surface so as to be movable forward and backward, The holding surface is formed with a plurality of small holes for sucking the ingot and insertion holes into which the support pins are respectively inserted, The holding table has: One end side communicates with the plurality of holes and the air pressure chamber at the rear end side of the support pin, A flow path is formed such that the other end side is switchably connected to an air suction source or an air supply source, by connecting the flow path to the air supply source and supplying air to the air pressure chamber, the tip of the support pin is positioned at a support position where it protrudes from the holding surface, and the tip of the support pin can support the ingot; By connecting the flow path to the air suction source and reducing the pressure in the air pressure chamber, the support pins are gently positioned at a retracted position where their tips are embedded in the insertion holes, and the ingot is supported by the holding surface, and the ingot is suction-held on the holding surface by negative pressure acting on the multiple pores.

2. The support pin is biased by an elastic member in a direction in which it moves to the retracted position, When air is not supplied to the air pressure chamber, the support pin is positioned at the retracted position.

2. The holding table according to claim 1.

3. A processing device comprising the holding table according to claim 1 or 2.

4. 1. A processing method for separating wafers from an ingot, comprising: a support pin protruding step of protruding three or more support pins from a holding surface of the holding table; placing an ingot on the tip of the support pin and supporting the ingot with the support pin above the holding surface; a holding step of slowly moving the support pins so as to be embedded in the holding surface, and placing the ingot on the holding surface to suction-hold the ingot on the holding surface; a laser irradiation step of focusing a laser beam at a predetermined height position of the ingot and horizontally moving the holding table relative to the laser beam to form a separation layer in the ingot; A processing method having the above structure.

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