Wafer processing method, ingot processing method and wafer

Abstract

To enable the formation of more devices.SOLUTION: A wafer processing method is a processing method for wafers made of semiconductor materials, and comprises a preparation step 2001 for preparing a wafer including a surface, a back surface, a side surface extending from the surface to the back surface, and a linear flat mirror surface section on the side surface indicating the wafer's crystal orientation, and a grinding step 1005 for Grinding the back surface of the wafer prepared in preparation step 2001 to form a recess and a protrusion surrounding the recess.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wafer processing method, an ingot processing method, and a wafer. [Background technology]

[0002] A wafer made of a semiconductor material has a notch, an orientation flat, or other notch formed on the periphery of the wafer as a mark indicating the crystal orientation of the wafer.

[0003] On the other hand, in order to facilitate handling after wafers have been ground and thinned, a technique has been widely adopted in the market in which the central region of the wafer is ground to form a recess, while the thickness of the outer periphery is left undisturbed to form a protrusion, which is then used as reinforcement (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-245172 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a notch or other cutout is formed in the wafer, the width of the convex portion must be set to be wider than the cutout in order for the convex portion to function as reinforcement, and there is a demand for forming wider concave portions in order to form more devices.

[0006] An object of the present invention is to provide a wafer processing method, an ingot processing method, and a wafer that can form more devices. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention is a method for processing a wafer made of a semiconductor material, characterized by comprising: a preparation step of preparing a wafer including a front surface, a back surface behind the front surface, and a side surface extending from the front surface to the back surface, the side surface having a flat mirror surface that indicates the crystal orientation of the wafer; and a grinding step of grinding the back surface of the wafer prepared in the preparation step to form a recess and a protrusion surrounding the recess.

[0008] In the wafer processing method, in the grinding step, the wafer may be ground without disposing a hard plate on the surface of the wafer.

[0009] The wafer processing method may include a detection step of detecting the flat mirror surface portion before or after performing the grinding step, and a storage step of storing the wafer in a wafer cassette after performing the detection step and the grinding step, in which the storage step stores the wafer in the wafer cassette with the flat mirror surface portion positioned in a predetermined orientation relative to the wafer cassette.

[0010] The ingot processing method of the present invention is a method for processing an ingot made of a semiconductor material, and is characterized by comprising: an orientation detection step for detecting the crystal orientation of the ingot; a linear flat mirror surface formation step for forming a linear flat mirror surface along the extension direction of the ingot based on the crystal orientation detected in the orientation detection step; a wafer formation step for separating a portion of the ingot to form a wafer after performing the linear flat mirror surface formation step; and a grinding step for grinding the back surface of the wafer to form a recess and to form a protrusion surrounding the recess.

[0011] The wafer of the present invention is a wafer that includes a front surface, a back surface behind the front surface, and a side surface extending from the front surface to the back surface, and is characterized in that the side surface has a flat mirror surface portion that indicates the crystal orientation of the wafer.

[0012] In the wafer, the width of the flat mirror surface portion may be 0.05 mm or more and 34.5 mm or less.

[0013] In the wafer, the side surface may be a straight line in a vertical cross section of the wafer, with a front side chamfer formed at the corner between the front surface and the side surface, and a back side chamfer formed at the corner between the back surface and the side surface.

[0014] In the wafer, the front side chamfer and the back side chamfer may each be formed in an arc shape extending from the front side to the side in a vertical cross section of the wafer, and also in an arc shape extending from the back side to the side.

[0015] The wafer may have a thickness of 900 μm or more.

[0016] In the wafer, the flat mirror surface portion may be formed in a line shape in a region extending from the front surface side to the back surface side of the side surface of the wafer. [Effects of the Invention]

[0017] The present invention has the advantage that more devices can be formed. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view schematically showing an ingot to be processed by the ingot processing method according to the first embodiment. [Figure 2] FIG. 2 is a flowchart showing the flow of the ingot processing method according to the first embodiment. [Figure 3] FIG. 3 is a perspective view schematically showing an example of the configuration of a laser processing device used in the wafer formation step of the ingot processing method shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG. [Figure 5]FIG. 5 is a cross-sectional view schematically showing a state in which a laser beam is irradiated onto an ingot in the wafer formation step of the ingot processing method shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view schematically illustrating adjacent separation layers formed within the ingot shown in FIG. [Figure 7] FIG. 7 is a side view schematically showing the orientation detection step of the ingot processing method shown in FIG. [Figure 8] FIG. 8 is a side view schematically showing the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 9] FIG. 9 is a side view schematically showing a modified example of the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 10] FIG. 10 is a plan view schematically showing the crystal orientation of a wafer on which a linear flat mirror surface portion is formed in the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 11] FIG. 11 is a perspective view schematically showing a wafer on which devices are formed in the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 12] FIG. 12 is a side view showing a portion XII in FIG. [Figure 13] FIG. 13 is a cross-sectional view of the wafer taken along line XIII-XIII in FIG. [Figure 14] FIG. 14 is a cross-sectional view showing a modification of the wafer shown in FIG. [Figure 15] FIG. 15 is a perspective view schematically showing an example of the configuration of a grinding device used in the grinding step and the like of the ingot processing method shown in FIG. [Figure 16] FIG. 16 is a side view schematically showing the configuration of the detection unit of the grinding machine shown in FIG. [Figure 17] FIG. 17 is a cross-sectional view schematically showing a state in which a holding table of a grinding device holds a wafer in the grinding step of the ingot processing method shown in FIG. [Figure 18]FIG. 18 is a cross-sectional view schematically showing a state in which a grinding unit of a grinding device grinds a wafer in the grinding step of the ingot processing method shown in FIG. [Figure 19] FIG. 19 is a front view schematically showing a wafer cassette containing wafers in the containing step of the ingot processing method shown in FIG. [Figure 20] FIG. 20 is a flowchart showing the flow of the ingot processing method according to the second embodiment. [Figure 21] FIG. 21 is a side view schematically showing the orientation detection step of the ingot processing method shown in FIG. [Figure 22] FIG. 22 is a side view schematically showing the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 23] FIG. 23 is a side view schematically showing a modified example of the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 24] FIG. 24 is a side view schematically showing another modified example of the linear flat mirror surface portion forming step in the ingot processing method shown in FIG. [Figure 25] FIG. 25 is a perspective view schematically showing the ingot after the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. [Figure 26] FIG. 26 is a plan view schematically showing the crystal orientation of an ingot on which a linear flat mirror surface portion is formed in the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0020] [Embodiment 1] An ingot processing method according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view schematically showing an ingot to be processed in the ingot processing method according to the first embodiment. Fig. 2 is a flowchart showing the flow of the ingot processing method according to the first embodiment.

[0021] (ingot) The ingot processing method according to the first embodiment is a method for processing an ingot 1 shown in Fig. 1. In the first embodiment, the ingot 1 to be processed by the ingot processing method according to the first embodiment is made of silicon and is formed into a cylindrical shape as a whole, as shown in Fig. 1. In the first embodiment, the ingot 1 is made of single crystal silicon, which is a semiconductor material. Note that, in the present invention, the semiconductor material constituting the ingot 1 is not limited to silicon.

[0022] As shown in Fig. 1, the ingot 1 has a first surface 2, which is a circular end face, a circular second surface 3 on the reverse side of the first surface 2, and an outer peripheral surface 4 that is continuous with the outer edges of the first surface 2 and the second surface 3. At least the first surface 2 of the ingot 1 has been subjected to grinding, polishing, and the like to form a mirror-like surface. Before being subjected to the ingot processing method according to embodiment 1, the ingot 1 does not have any crystal orientation. In embodiment 1, the first surface 2 is the (100) plane of the ingot 1.

[0023] As shown in FIG. 2, the ingot processing method according to the first embodiment includes a wafer formation step 1001, an orientation detection step 1002, a linear flat mirror surface formation step 1003, a detection step 1004, a grinding step 1005, and a storage step 1006.

[0024] (Wafer formation step) Fig. 3 is a perspective view schematically showing an example of the configuration of a laser processing device used in the wafer formation step of the ingot processing method shown in Fig. 2. Fig. 4 is a diagram showing an example of the configuration of a laser beam irradiation unit of the laser processing device shown in Fig. 3. In wafer formation step 1001, the laser processing device shown in Fig. 3 is used.

[0025] (Laser processing equipment) First, a description will be given of the laser processing apparatus 20. As shown in Fig. 3, the laser processing apparatus 20 includes a holding table 22, a laser beam irradiation unit 25, an imaging unit (not shown), and a control unit (not shown).

[0026] The holding table 22 is disk-shaped, and has a flat holding surface 23 formed of porous ceramic or the like along the horizontal direction for holding the ingot 1. The holding table 22 is also provided so as to be movable by moving units 28, 29 installed on the apparatus main body 21 between a processing area below the laser beam irradiation unit 25 and a carry-in / out area spaced from below the laser beam irradiation unit 25 where the ingot 1 is carried in and out.

[0027] The holding table 22 has a holding surface 23 connected to a vacuum suction source (not shown), and is sucked by the vacuum suction source to suck and hold the ingot 1 placed on the holding surface 23.

[0028] In the first embodiment, the holding table 22 is moved relative to the laser beam irradiation unit 25 by movement units 28 and 29 installed on the apparatus body 21. The holding table 22 is moved in the Y-axis direction parallel to the horizontal direction by a Y-axis movement unit 28 installed on the apparatus body 21. The Y-axis movement unit 28 is installed on the apparatus body 21 and moves a movement plate 24 on which an X-axis movement unit 29 is installed in the Y-axis direction, thereby moving the holding table 22 in the Y-axis direction.

[0029] Furthermore, the holding table 22 is moved in the X-axis direction, which is parallel to the horizontal direction and perpendicular to the Y-axis direction, by an X-axis movement unit 29 installed on the moving plate 24. The X-axis movement unit 29 is installed on the moving plate 24 and moves a second moving plate 27, on which a rotational movement unit 30 is installed, in the X-axis direction, thereby moving the holding table 22 in the X-axis direction.

[0030] Furthermore, the holding table 22 is rotated around an axis parallel to the Z-axis direction, which is parallel to the vertical direction, by the rotational movement unit 30. The rotational movement unit 30 is installed on the second moving plate 27 and supports the holding table 22, thereby rotating the holding table 22 around its axis.

[0031] The Y-axis moving unit 28 moves the X-axis moving unit 29, second moving plate 27, rotational moving unit 30, and holding table 22 together with the moving plate 24 in the Y-axis direction. The X-axis moving unit 29 moves the rotational moving unit 30 and holding table 22 together with the second moving plate 27 in the X-axis direction.

[0032] The Y-axis moving unit 28 and the X-axis moving unit 29 each include a well-known ball screw rotatably mounted about its axis, a well-known motor for rotating the ball screw about its axis, and a well-known guide rail for supporting the moving plates 24, 27 movably in the X-axis or Y-axis direction. The rotational moving unit 30 includes a well-known motor for rotating the holding table 22 about its axis.

[0033] 2, the laser beam irradiation unit 25 is provided at a portion on the tip of a support column 32 whose base end is supported by an erected column 31 erected from the end of the device body 21 in the Y-axis direction. The laser beam irradiation unit 25 is raised and lowered by an elevating unit 33 which raises and lowers the support column 32 attached to the erected column 31 in the Z-axis direction.

[0034] The lifting unit 33 raises and lowers part of the laser beam irradiation unit 25 in the Z-axis direction together with the support column 32. The lifting unit 33 includes a well-known ball screw that is rotatable about its axis, a well-known motor that rotates the ball screw about its axis, and a well-known guide rail that supports the support column 32 so that it can move in the Z-axis direction.

[0035] As shown in FIG. 4, the laser beam irradiation unit 25 includes a laser oscillator 252 that emits a laser beam 251, an attenuator 253, a spatial light modulator 254, a mirror 255, and an irradiation head 256.

[0036] The laser oscillator 252 has, for example, Nd:YAG or the like as a laser medium, and emits a pulsed laser beam 251 having a wavelength (for example, 1064 nm) that is transmitted through single crystal silicon. The attenuator 253 adjusts the laser beam 251 emitted by the laser oscillator 252 and supplies it to a spatial light modulator 254.

[0037] The spatial light modulator 254 branches the laser beam 251. In the first embodiment, for example, the spatial light modulator 254 branches the laser beam 251 so that the laser beam 251 emitted from an irradiation head 256 (described later) forms a plurality of (for example, five) focusing points arranged at equal intervals along the Y-axis direction.

[0038] The mirror 255 reflects the laser beam 251 branched by the spatial light modulator 254 toward the irradiation head 256. The irradiation head 256 houses a condenser lens (not shown) that condenses the laser beam 251. The irradiation head 256 emits the laser beam 251 condensed by the condenser lens toward the holding surface 23 of the holding table 22.

[0039] The imaging unit is disposed at the tip of the support column 32 in a position aligned in the X-axis direction with the irradiation head 256 of the laser beam irradiation unit 25. The imaging unit is equipped with an imaging element that images the area to be divided of the ingot 1 held on the holding table 22 before laser processing. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit images the ingot 1 held on the holding table 22 to obtain an image for performing alignment between the ingot 1 and the irradiation head 256 of the laser beam irradiation unit 25, and outputs the obtained image to the control unit.

[0040] The control unit controls each component of the laser processing apparatus 20 to cause the laser processing apparatus 20 to perform processing operations on the ingot 1. The control unit is a computer having an arithmetic processing device with a microprocessor such as a CPU (central processing unit), a storage device with memory such as a ROM (read only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 20 to each component of the laser processing apparatus 20 via the input / output interface device.

[0041] The control unit is connected to a display unit 34, which is configured with a liquid crystal display device or the like that displays the status of the machining operation, images, etc., and an input unit (not shown) that the operator uses to register machining content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit 34 and an external input device such as a keyboard.

[0042] Next, the wafer formation step 1001 will be described. Fig. 5 is a cross-sectional view schematically showing a state in which a laser beam is irradiated onto an ingot in the wafer formation step of the ingot processing method shown in Fig. 2. Fig. 6 is a cross-sectional view schematically showing adjacent peeling layers formed inside the ingot shown in Fig. 5.

[0043] The wafer forming step 1001 is a step of forming wafers 5 (shown in FIG. 1 etc.) by separating a portion of the ingot 1 on the first surface 2 side. In the first embodiment, in the wafer forming step 1001, a portion of the ingot 1 is separated as wafers 5, similar to JP 2023-27820 A.

[0044] Specifically, in the first embodiment, in the wafer forming step 1001, the laser processing device 20 is placed on the holding surface 23 of the holding table 22 with the second surface 3 side of the ingot 1 exposed, and the second surface 3 of the ingot 1 is suction-held on the holding surface 23 of the holding table 22. In the first embodiment, in the wafer forming step 1001, the laser processing device 20 sets the focal point to a predetermined depth according to the thickness of the wafer 5 separated from the first surface 2, and irradiates the ingot 1 with the laser beam 251 while moving the holding table 22 and the irradiation head 256 relatively in the X-axis direction.

[0045] Then, the laser beam 251 is branched and irradiated with each of its multiple focal points positioned inside the ingot 1. Then, modified regions 257 in which the crystal structure of the single crystal silicon is disrupted are formed inside the ingot 1, with each of the multiple focal points as the center. That is, a single irradiation of the laser beam 251 moving in the X-axis direction relative to the ingot 1 forms multiple modified regions 257 aligned along the Y-axis direction.

[0046] At this time, cracks 258 extend along a predetermined crystal plane from each of the multiple modified regions 257. As a result, a peeling layer 259 including the multiple modified regions 257 and the cracks 258 extending from each of the multiple modified regions 257 is formed inside the ingot 1.

[0047] In the first embodiment, in the wafer forming step 1001, when the laser processing device 20 forms a peeling layer 259 inside the ingot 1 over the entire length in the X-axis direction, the laser processing device 20 stops irradiating the laser beam 251 and moves the ingot 1 and the irradiation head 256 a predetermined distance in the Y-axis direction (hereinafter referred to as index feed). In the first embodiment, in the wafer forming step 1001, the laser processing device 20 repeats the operation of irradiating the laser beam 251 over the entire length of the ingot 1 in the X-axis direction and the index feed until the peeling layer 259 is formed over the entire position at a predetermined depth from the first surface 2 of the ingot 1, as shown in FIG.

[0048] In the first embodiment, in the wafer forming step 1001, once the peeling layer 259 is formed over the entire area of ​​the ingot 1 at a predetermined depth from the first surface 2, the first surface 2 and the second surface 3 are moved in a direction separating them, for example, by holding them by suction. Then, since the peeling layer 259 has been formed over the entire area of ​​the ingot 1 at a predetermined depth from the first surface 2, a portion of the ingot 1 on the first surface 2 side is separated as a wafer 5.

[0049] Wafers 5 separated from ingot 1 are subjected to grinding, polishing, etc. on a surface 7 separated from ingot 1. Furthermore, the ingot 1 is subjected to grinding, polishing, etc. on the surface from which wafers 5 are separated, and the separated surface is formed as a first surface 2, and then a portion of the ingot 1 is separated into wafers 5 until it reaches a predetermined thickness. Note that hereinafter, first surface 2 of wafer 5 will be referred to as the front surface, surface 7 of wafer 5 separated from ingot 1 will be referred to as the back surface behind front surface 2, and outer peripheral surface 4 of wafer 5 will be referred to as the side surface.

[0050] (Orientation detection step) Fig. 7 is a side view schematically showing the orientation detection step of the ingot processing method shown in Fig. 2. The orientation detection step 1002 is a step of detecting the crystal orientation of the wafer 5. The orientation detection step 1002 detects the crystal orientation of the wafer 5 in the same manner as in, for example, Japanese Patent Application Laid-Open No. 2000-266697.

[0051] Specifically, in the first embodiment, in the orientation detection step 1002, the detection and formation device 40 shown in FIG. 7 suction-holds the wafer 5 on a flat holding surface 42 of a disk-shaped turntable 41 that rotates about its axis and has a smaller diameter than the wafer 5. In the first embodiment, in the orientation detection step 1002, the detection and formation device 40 rotates the turntable 41 about its axis while directing X-rays 44 from the X-ray irradiation means 43 to the side surface 4 of the wafer 5 held on the turntable 41, and receives the reflected X-rays 44 with the X-ray receiving means 45. In the first embodiment, in the orientation detection step 1002, the detection and formation device 40 shown in FIG. 7 detects the crystal orientation of the wafer 5 from the intensity of the X-rays 44 received by the X-ray receiving means 45.

[0052] (Linear flat mirror surface forming step) FIG. 8 is a side view schematically showing the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 2. FIG. 9 is a side view schematically showing a modified linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 8. FIG. 10 is a plan view schematically showing the crystal orientation of a wafer on which a linear flat mirror surface portion is formed in the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 2. FIG. 11 is a perspective view schematically showing a wafer on which a device is formed in the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 2. FIG. 12 is a side view showing portion XII in FIG. 11. FIG. 13 is a cross-sectional view of the wafer taken along line XIII-XIII in FIG. 11. FIG. 14 is a cross-sectional view showing a modified example of the wafer shown in FIG. 13.

[0053] The linear flat mirror surface forming step 1003 is a step of forming a linear flat mirror surface 6 (corresponding to a flat mirror surface) along the thickness direction of the wafer 5, which is the elongation direction of the ingot 1, based on the crystal orientation of the wafer 5 detected in the orientation detecting step 1002. In the first embodiment, in the linear flat mirror surface forming step 1003, the detecting and forming device 40 positions a laser processing head 47 having a condenser 46 relative to a desired position on the side surface 4 of the wafer 5 based on the detected crystal orientation of the wafer 5, as shown in FIG.

[0054] In the first embodiment, in the linear flat mirror portion forming step 1003, the detection and formation device 40 positions the laser processing head 47 along the crystal orientation

[0011] of the wafer 5 that faces the (011) plane of the wafer 5. In the first embodiment, in the linear flat mirror portion forming step 1003, the detection and formation device 40 moves the wafer 5 held on the turntable 41 and the laser processing head 47 relatively in the thickness direction of the wafer 5, while irradiating a desired position on the side surface 4 of the wafer 5 with a laser beam 49 emitted from an oscillator 48 from the laser processing head 47 and having a wavelength that is absorbent for the wafer 5.

[0055] Thus, in embodiment 1, in the linear flat mirror surface portion forming step 1003, the detection and formation device 40 performs laser processing on the side surface 4 of the wafer 5 at a position along the (011) plane that is perpendicular to the crystal orientation

[0011] of the wafer 5, to form a linear flat mirror surface portion 6 that extends in the thickness direction of the wafer 5 over the entire length of the thickness direction at a position along the (011) plane of the side surface 4 of the wafer 5.

[0056] In addition, in the present invention, in the linear flat mirror surface portion forming step 1003, the detection and formation device 40 may, as shown in Figure 9, move the wafer 5 held on the rotating table 41 and the cutting blade 50 relatively in the thickness direction of the wafer 5, and cause the cutting blade 50 to cut into the side surface 4 of the wafer 5 at a desired position, thereby forming the linear flat mirror surface portion 6.

[0057] Thus, in the first embodiment, in the linear flat mirror surface portion forming step 1003, a linear flat mirror surface portion 6 is formed on the side surface 4 of the wafer 5 along the (011) plane, thereby forming the linear flat mirror surface portion 6 of the wafer 5 based on the crystal orientation of the wafer 5, and the linear flat mirror surface portion 6 is formed so that the linear flat mirror surface portion 6 and the crystal orientation of the wafer 5 have a predetermined positional relationship, as shown in FIG. 10 . Note that in the first embodiment, in the linear flat mirror surface portion forming step 1003, the linear flat mirror surface portion 6 is formed so that the crystal orientation of the wafer 5 and the linear flat mirror surface portion 6 have the positional relationship shown in FIG. 10 . In the present invention, it is sufficient that the linear flat mirror surface portion 6 has a fixed positional relationship with respect to the crystal orientation of the wafer 5, and the positional relationship between the linear flat mirror surface portion 6 formed in the linear flat mirror surface portion forming step 1003 and the crystal orientation of the wafer 5 is not limited to the example shown in FIG.

[0058] In the present invention, the linear flat mirror surface portion 6 may be formed by laser processing or the like after the wafer 5 separated from the ingot 1 has been subjected to laser processing to correct the outer diameter. In the present invention, the linear flat mirror surface portion 6 may be formed not over the entire thickness of the wafer 5 but over a portion of the thickness of the wafer 5 (it is desirable to form the linear flat mirror surface portion 6 from the surface 2 to a position closer to the surface 2 than the center of the thickness).

[0059] Thereafter, the wafer 5 is subjected to a process such as chamfering on the outer peripheral surface 4, and devices 8 are formed on the front surface 2 as shown in Fig. 11. The devices 8 are formed in areas defined by a plurality of mutually intersecting planned division lines 9 on the front surface 2. Note that in the present invention, after the crystal orientation of the wafer 5 is detected, the linear flat mirror surface portion 6 may be formed after the wafer 5 is chamfered.

[0060] The device 8 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor storage device).

[0061] In this way, a wafer 5 is obtained which includes a surface 2, a back surface 7 behind the surface 2, and a side surface 4 extending from the surface 2 to the back surface 7, and which has a linear flat mirror surface portion 6 on the side surface 4 which indicates the crystal orientation of the wafer 5, and in which the linear flat mirror surface portion 6 is formed in a line on the side surface 4 of the wafer 5 in the region from the surface 2 side to the back surface 7.

[0062] In the first embodiment, the width 10 (shown in FIG. 12) of the linear flat mirror surface portion 6 is 0.05 mm or more and 34.5 mm or less. The reason why the width 10 of the linear flat mirror surface portion 6 is 0.05 mm or more and 34.5 mm or less is that if the width 10 is less than 0.05 mm, the linear flat mirror surface portion 6 cannot be detected in the detection step 1004, and if the width exceeds 34.5 mm, the number of devices 8 formed on the surface 2 of the wafer 5 will be reduced undesirably in order to ensure the strength of the wafer 5 when the wafer 5 is ground in the grinding step 1005.

[0063] Furthermore, in the present invention, the width 10 of the linear flat mirror surface portion 6 is preferably 0.05 mm or more and 10 mm or less, and more preferably 0.05 mm or more and 5 mm or less. In short, it is desirable that the width 10 of the linear flat mirror surface portion 6 is as narrow as possible as long as it is 0.05 mm or more, in order to ensure the strength of the wafer 5 when grinding the wafer 5 in the grinding step 1005 and not reduce the number of devices 8 formed on the surface 2 of the wafer 5. In addition, in the first embodiment, the width 10 of the linear flat mirror surface portion 6 is 1 mm, and the thickness of the wafer 5 is 900 μm or more.

[0064] 13, the side surface 4 of the wafer 5 is straight in a vertical cross section passing through the axis of the wafer 5, and a front surface side chamfer 11 is formed at the corner between the front surface 2 and the side surface 4, and a back surface side chamfer 12 is formed at the corner between the back surface 7 and the side surface 4. These chamfers 11, 12 are formed in a tapered shape such that the diameter of the wafer 5 decreases toward the front surface 2 or the back surface 7 in the above-mentioned vertical cross section of the wafer 5. In the first embodiment, the chamfers 11, 12 are formed by C-chamfering of 0.2 mm or less.

[0065] In the present invention, the front side chamfer 11 and the back side chamfer 12 are each formed in an arc shape extending from the front side 2 to the side 4 in a vertical cross section of the wafer 5, as shown in Fig. 14, and may also be formed in an arc shape extending from the back side 7 to the side 4. In the case shown in Fig. 14, the chamfers 11 and 12 are formed by R-chamfering with a radius of 0.2 mm or less. In the case shown in Fig. 14, the chamfers 11 and 12 have a radius of curvature of, for example, less than half the thickness of the wafer 5 (because a radius of curvature of more than half the thickness of the wafer 5 results in a reduced number of devices 8, as in the conventional case), more preferably a radius of curvature of less than one-third the thickness of the wafer 5, or a radius of curvature of 1 / 100 or more (because a radius of curvature of less than 1 / 100 may cause damage to the wafer 5 during handling).

[0066] The aforementioned wafer formation step 1001, orientation detection step 1002, and linear flat mirror surface formation step 1003 constitute a preparation step 2001 for preparing a wafer 5 including a front surface 2, a back surface 7 behind the front surface 2, and a side surface 4 extending from the front surface 2 to the back surface 7, and having a linear flat mirror surface 6 on the side surface 4 that indicates the crystal orientation of the wafer 5.

[0067] (Grinding equipment) Fig. 15 is a perspective view schematically showing an example of the configuration of a grinding device used in the grinding step etc. of the ingot processing method shown in Fig. 2. Fig. 16 is a side view schematically showing the configuration of the detection unit of the grinding device shown in Fig. 15. In the detection step 1004, the grinding step 1005 and the storage step 1006, the grinding device 60 shown in Fig. 15 is used.

[0068] Next, the grinding device 60 will be described. As shown in Fig. 15, the grinding device 60 includes a device base 61, a turntable 62, for example, three holding tables 63 installed on the turntable 62, a rough grinding unit 64, a finish grinding unit 65, a cassette mounting table 66, a detection unit 67, a cleaning unit 68, and a control unit 69.

[0069] The turntable 62 is a disk-shaped table provided on the upper surface of the device base 61, and is rotatable about an axis parallel to the Z-axis direction in a horizontal plane, and is rotationally driven at a predetermined timing. The Z-axis direction is parallel to the vertical direction. On the turntable 62, for example, three holding tables 63 are arranged at equal intervals, for example, at a phase angle of 120 degrees. That is, the turntable 62 has a plurality of holding tables 63 arranged at equal angles (120 degrees in the first embodiment) in the circumferential direction.

[0070] The three holding tables 63 have upper surfaces made of a porous material such as porous ceramics, which serve as holding surfaces 70 on which wafers 5 are placed. The holding surfaces 70 of the holding tables 63 are connected to a suction source 632 via an on-off valve 631, and the holding surfaces 70 are sucked by the suction source 632, thereby suction-holding the wafers 5 placed on the holding surfaces 70 onto the holding surfaces 70.

[0071] During processing, the holding table 63 is rotated around an axis parallel to the Z-axis direction by a rotation mechanism. The holding table 63 is moved sequentially to a carry-in / out position 301, a rough grinding position 302, a finish grinding position 303, and again to the carry-in / out position 301 by the rotation of the turntable 62.

[0072] The loading / unloading position 301 is an area where the wafer 5 is loaded onto and unloaded from the holding table 63. The rough grinding position 302 is an area where the rough grinding unit 64 performs rough grinding (corresponding to processing) on ​​the wafer 5 held on the holding table 63. The finish grinding position 303 is an area where the finish grinding unit 65 performs finish grinding (corresponding to processing) on ​​the wafer 5 held on the holding table 63.

[0073] The rough grinding unit 64 is disposed above the holding table 63 positioned at the rough grinding position 302, and is a grinding unit equipped with a rough grinding grinding wheel 71 having a ring-shaped arrangement of grinding stones for rough grinding that roughly grinds the exposed back surface 7 of the wafer 5 held on the holding surface 70 of the holding table 63 at the rough grinding position 302.

[0074] The finish grinding unit 65 is disposed above the holding table 63 positioned at the rough grinding position 302, and is a grinding unit equipped with a finish grinding wheel 72 having a ring-shaped arrangement of grinding stones for finish grinding the back surface 7 of the wafer 5 held on the holding surface 70 of the holding table 63 at the finish grinding position 303.

[0075] In the grinding units 64, 65, grinding wheels 71, 72 can be attached to the lower ends of spindles that are rotated around axes parallel to the Z-axis direction by motors 73, 74. In the grinding units 64, 65, the grinding wheels 71, 72 are attached to the lower ends of the spindles, and the grinding stones of the grinding wheels 71, 72 are arranged opposite the holding surface 70 of the holding table 63. In the first embodiment, the outer diameter of the grinding stone portion consisting of multiple grinding stones of the grinding wheels 71, 72 is smaller than half the outer diameter of the wafer 5.

[0076] The grinding units 64, 65 perform rough grinding or finish grinding of the back surface 7 of the wafer 5 by rotating the spindle and grinding wheels 71, 72 around their axes using motors 73, 74 and supplying grinding water from a nozzle (not shown) to the back surface 7 of the wafer 5 held on the holding table 63 at the grinding positions 302, 303 while the grinding feed unit 75 moves the grinding wheel closer to the holding table 63 at a predetermined feed speed.

[0077] A grinding feed unit 75, which moves the grinding units 64, 65 in the Z-axis direction to move relatively closer to and away from the holding table 63, is mounted on an erect plate 76 erected from one end of the device base 61 in the X-axis direction, which is parallel to the horizontal direction. The grinding feed unit 75 includes a well-known ball screw rotatable about its axis, a well-known motor for rotating the ball screw about its axis, and well-known guide rails that support the spindle housings of the grinding units 64, 65 movably in the Z-axis direction.

[0078] In embodiment 1, the rough grinding unit 64 and the finish grinding unit 65 are arranged such that the axes which are the centers of rotation of the grinding wheels 71, 72 and the axis which is the center of rotation of the holding table 63 are parallel and spaced apart horizontally, and the grinding wheels pass over the center of the back surface 7 of the wafer 5 held on the holding table 63.

[0079] A wafer cassette 77 is placed on the cassette mounting table 66. The wafer cassette 77 is a container having a plurality of slots for accommodating a plurality of wafers 5. The wafer cassette 77 accommodates a plurality of wafers 5 before and after grinding. In the first embodiment, a pair of cassette mounting tables 66 are provided, and a wafer cassette 77 is placed on each of them. The cassette mounting tables 66 support the wafer cassettes 77 so that they can be raised and lowered along the Z-axis direction.

[0080] The detection unit 67 includes a holding table 78 on which the wafer 5 before grinding is temporarily placed after being removed from the wafer cassette 77. The detection unit 67 also includes the holding table 78 and an optical sensor 79, as shown in FIG.

[0081] The holding table 78 is mounted on the apparatus base 61 and has a disk shape. A flat holding surface 80 extending in the horizontal direction for holding the wafer 5 is formed from porous ceramic or the like. The holding table 78 is rotated about an axis parallel to the Z-axis direction by a motor 81 mounted on the apparatus base 61. The motor 81 has a built-in encoder capable of detecting the angle of the holding table 78. The encoder of the motor 81 outputs the detected angle of the holding table 78 to the control unit 69. The holding surface 80 of the holding table 78 is connected to a vacuum suction source (not shown), and is sucked by the vacuum suction source to suck and hold the wafer 5 placed on the holding surface 80.

[0082] The optical sensor 79 is installed on the apparatus base 61 and faces horizontally the side surface 4 of the wafer 5 held on the holding table 78. The optical sensor 79 includes a light-emitting unit that emits light toward the side surface 4 of the wafer 5 held on the holding table 78, a light-receiving unit that receives light reflected from the side surface 4, and a light-amount detecting unit that detects the amount of reflected light received by the light-receiving unit and outputs the detected amount of light to the control unit 69.

[0083] The cleaning unit 68 cleans the wafer 5 after grinding, and removes contamination such as processing debris adhering to the back surface 7 that has been ground and polished.

[0084] The grinding device 60 also includes a first transport unit 82 that removes the wafer 5 before grinding from the wafer cassette 77 and transports it to the holding table 78 of the detection unit 67, and transports the wafer 5 after grinding from the cleaning unit 68 to the holding table 78 of the detection unit 67, and further transports the wafer 5 from the holding table 78 of the detection unit 67 to the wafer cassette 77. The first transport unit 82 is, for example, a robot pick equipped with a U-shaped hand, and uses the U-shaped hand to suction-hold and transport the wafer 5.

[0085] The grinding device 60 also includes a second transfer unit 83 that transfers the wafer 5 before grinding on the holding table 78 of the detection unit 67 onto the holding table 63 located at the carry-in / out position 301, and a third transfer unit 84 that transfers the wafer 5 after grinding on the holding table 63 located at the carry-in / out position 301 to the cleaning unit 68. The transfer units 83 and 84 have suction pads that adsorb the wafer 5, and transport the wafer 5 by adsorbing and holding it on the suction pad.

[0086] The control unit 69 controls each of the above-mentioned constituent units constituting the grinding apparatus 60, causing the grinding apparatus 60 to perform processing operations on the wafer 5. The control unit 69 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having memory such as a ROM (read only memory) or RAM (random access memory), and an input / output interface device.

[0087] The arithmetic processing device of the control unit 69 performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs control signals for controlling the grinding device 60 to the above-mentioned components of the grinding device 60 via the input / output interface device. The control unit 69 is also connected to a display unit configured with a liquid crystal display device or the like for displaying the status and images of the processing operation, an input unit used by the operator when registering processing content information, and a notification unit for notifying the operator.

[0088] The input unit is composed of at least one of a touch panel provided on the display unit, a keyboard, etc. The notification unit notifies the operator by emitting at least one of sound, light, and a message on the touch panel.

[0089] (Detection step) Next, the detecting step 1004 will be described. In the first embodiment, the detecting step 1004 is a step of detecting the linear flat mirror surface portion 6 before the grinding step 1005 is performed. In the first embodiment, in the detecting step 1004, a tape 13 made of resin as a protective member is attached to the front surface 2 of the wafer 5, and the wafer 5 with the tape 13 attached is stored in the wafer cassette 77. At this time, the front surface 2 of the wafer 5 to which the tape 13 is attached is positioned downward, and the back surface 7 is exposed upward.

[0090] In embodiment 1, in the detection step 1004, a wafer cassette 77 containing a wafer 5 with tape 13 attached to its surface 2 is placed on the cassette mounting table 66, the operator registers the processing conditions in the control unit 69, and when the control unit 69 receives an instruction from the operator to start the processing operation, the grinding device 60 starts the processing operation.

[0091] In the first embodiment, in the detection step 1004, the control unit 69 of the grinding apparatus 60 rotates the spindles of the grinding units 64, 65 about their axes at the rotation speeds determined by the processing conditions. In the first embodiment, in the detection step 1004, the grinding apparatus 60 causes the first transport unit 82 to take out one wafer 5 from one of the wafer cassettes 77 and load it onto the holding table 78 of the detection unit 67.

[0092] In the first embodiment, in the detection step 1004, the grinding device 60 suction-holds the front surface 2 side of the wafer 5 on the holding surface 80 of the holding table 78 of the detection unit 67 via the tape 13, and while rotating the holding table 78, i.e., the wafer 5, about its axis by the motor 81, the light-emitting portion of the optical sensor 79 emits light and the reflected light is received by the light-receiving portion. In the first embodiment, in the detection step 1004, the grinding device 60 stops the rotation of the holding table 78 about its axis at the angle at which the amount of light is maximized based on the detection result from the light amount detection portion of the optical sensor 79 of the detection unit 67.

[0093] Thus, in the first embodiment, in the detecting step 1004, the grinding device 60 detects the linear flat mirror surface portion 6 by stopping the rotation of the holding table 78 about its axis at an angle where the amount of light is maximized based on the detection result of the light amount detecting portion of the optical sensor 79 of the detection unit 67, and positions the wafer 5 so that the linear flat mirror surface portion 6 is oriented in a predetermined direction relative to the second transport unit 83. Note that in the present invention, the detecting step 1004 may be performed after the grinding step 1005 has been performed.

[0094] (Grinding step) Next, the grinding step 1005 will be described. Fig. 17 is a cross-sectional view schematically showing a state in which a holding table of a grinding device holds a wafer in the grinding step of the ingot processing method shown in Fig. 2. Fig. 18 is a cross-sectional view schematically showing a state in which a grinding unit of the grinding device grinds a wafer in the grinding step of the ingot processing method shown in Fig. 2.

[0095] The grinding step 1005 is a step of grinding the back surface 7 of the wafer 5 prepared in the preparation step 2001 to form recesses 14 on the back surface 7 and to form protrusions 15 surrounding the recesses 14. In the first embodiment, in the grinding step 1005, the grinding device 60 stops suction holding of the wafer 5 on the holding table 78 of the detection unit 67.

[0096] In the grinding step 1005 in the first embodiment, the control unit 69 of the grinding apparatus 60 causes the suction pads of the second transport unit 83 to suck and hold the wafer 5 on the holding table 78 of the detection unit 67, and causes the second transport unit 83 to carry the wafer 5 onto the holding surface 70 of the holding table 63 located at the carry-in / out position 301. At this time, the second transport unit 83 carries the wafer 5 onto the holding table 63 so that the wafer 5 is oriented in a fixed direction relative to the holding table 63. In the grinding step 1005 in the first embodiment, as shown in FIG. 17 , the control unit 69 causes the wafer 5 to be sucked and held via the tape 13 on the holding surface 70 of the holding table 63 located at the carry-in / out position 301.

[0097] In the first embodiment, in the grinding step 1005, the control unit 69 of the grinding device 60 rotates the turntable 62 to transport the holding table 63, which holds the wafer 5 at the carry-in / out position 301, sequentially to the rough grinding position 302 and the finish grinding position 303. In the first embodiment, in the grinding step 1005, the grinding device 60 rotates the grinding wheels 71, 72 by the spindle and rotates the holding table 63 about its axis while supplying grinding water, as shown in Fig. 18 , and brings the grinding wheel into contact with the back surface 7 of the wafer 5 and approaches the holding table 63 at a predetermined feed rate, thereby sequentially performing rough grinding and finish grinding on the back surface 7 of the wafer 5 with the grinding wheel.

[0098] In the first embodiment, in the grinding step 1005, because the outer diameter of the grinding wheels 71, 72 is smaller than half the outer diameter of the wafer 5, annular convex portions 15 are formed leaving the outer edge of the back surface 7 of the wafer 5, and the inner periphery of the convex portion 15 is ground to form circular concave portions 14 in the inner periphery of the convex portion 15. In the first embodiment, in the grinding step 1005, the grinding device 60 grinds the back surface 7 of the wafer 5 with the grinding units 64, 65 until the thickness of the concave portion 14 reaches a predetermined thickness. After the grinding by the grinding units 64, 65 is completed, in the grinding step 1005, the grinding device 60 positions the ground wafer 5 at the carry-in / out position 301.

[0099] Thus, in the first embodiment, in the grinding step 1005, by adhering tape 13 made of resin to front surface 2 of wafer 5, wafer 5 is ground without disposing a hard plate on front surface 2 of wafer 5. In the first embodiment, the width of protrusion 15 in the radial direction of wafer 5 is 0.15% or more and 0.5% or less of the diameter of wafer 5. The reason why the width of protrusion 15 in the radial direction of wafer 5 is 0.15% or more and 0.5% or less of the diameter of wafer 5 is that if the width is less than 0.15% of the diameter of wafer 5, wafer 5 will be damaged during transportation, and if the width exceeds 0.5% of the diameter of wafer 5, the number of devices 8 will decrease.

[0100] (Containment Step) Fig. 19 is a front view schematically showing a wafer cassette containing wafers in the containing step of the ingot processing method shown in Fig. 2. The containing step 1006 is a step of containing wafers 5 in the wafer cassette 77 after the detection step 1004 and the grinding step 1005 have been performed.

[0101] In the first embodiment, in the storing step 1006, the grinding device 60 stops suction holding of the ground wafer 5 on the holding table 63 positioned at the carry-in / out position 301, and transports the wafer 5 from the holding table 63 positioned at the carry-in / out position to the cleaning unit 68 by the second transport unit 83. In the first embodiment, in the storing step 1006, the grinding device 60 cleans the wafer 5 in the cleaning unit 68, and transports the cleaned wafer 5 into the wafer cassette 77 by the first transport unit 82.

[0102] In the first embodiment, in the detecting step 1004 and the storing step 1006, the grinding apparatus 60 starts grinding or cleaning with the holding table 63 and the spinner table of the cleaning unit 68 always facing in the same direction throughout rough grinding, finish grinding, and cleaning in the cleaning unit 68, and stops in the same direction when grinding or cleaning is completed, so that the wafers 5 are transported in the grinding apparatus 60 always facing in the same direction and stored in the wafer cassette 77. For this reason, in the first embodiment, in the storing step 1006, the grinding apparatus 60 uses the first transport unit 82 to store the wafers 5 in the wafer cassette 77 so that the linear flat mirror surface portion 6 is located in the center of the wafer 5 in the width direction when viewed from the front of the opening of the wafer cassette 77 through which the wafers 5 are inserted and removed, as shown in FIG.

[0103] For this reason, in the first embodiment, in the storing step 1006, the grinding device 60 causes the linear flat mirror surface portions 6 of the wafers 5 stored in the wafer cassette 77 after grinding to overlap in the thickness direction of the wafers 5. Thus, in the storing step 1006, the wafers 5 are stored in the wafer cassette 77 with the linear flat mirror surface portions 6 positioned in a predetermined orientation relative to the wafer cassette 77. Note that the predetermined orientation for storing the wafers 5 after cutting in the wafer cassette 77 is not limited to the orientation shown in FIG.

[0104] Thus, in the detecting step 1004, the grinding step 1005, and the storing step 1006, the grinding device 60 detects the linear flat mirror surface portion 6 of the wafer 5, transports the wafer 5 by the turntable 62 to the rough grinding position 302, the finish grinding position 303, and the carry-in / out position 301 in that order, performs rough grinding and finish grinding on the wafer 5 in that order, cleans the wafer 5 in the cleaning unit 68, and stores it in the wafer cassette 77. In addition, every time the turntable 62 rotates 120 degrees, the grinding device 60 unloads the ground wafer 5 from the holding table 63 positioned at the carry-in / out position 301, loads the unground wafer 5 onto the holding table 63 positioned at the carry-in / out position 301, rough-grinds the unground wafer 5, and finish-grinds the rough-grinded wafer 5. When all the wafers 5 in the wafer cassette 77 have been ground, the grinding device 60 ends the processing operation.

[0105] The preparation step 2001, the detection step 1004, the grinding step 1005 and the accommodation step 1006 constitute the wafer processing method of the present invention.

[0106] In the wafer processing method and ingot processing method according to the first embodiment described above, since the wafer 5 has a linear flat mirror surface portion 6 on its side, the crystal orientation can be identified without forming a notch, orientation flat, or other notch. Furthermore, since the depth of the linear flat mirror surface portion 6 from the side surface 4 can be reduced more than with a notch, orientation flat, or other notch, it is possible to form a recess 14 that is wider than that of conventional wafers that have a notch, orientation flat, or other notch formed therein.

[0107] Furthermore, the wafer processing method and ingot processing method according to the first embodiment can form recesses 14 that are wider than those formed in conventional wafers, and therefore the number of devices 8 that can be formed can be increased.

[0108] As a result, the wafer processing method and ingot processing method according to the first embodiment have the effect of being able to form a larger number of devices 8.

[0109] Furthermore, currently, in the case of a large-diameter wafer, for example, 300 mm in diameter, the wafer is ground while fixed to a hard substrate because the wafer bends after grinding to form recesses 14. However, in the wafer processing method and ingot processing method according to embodiment 1, the side surface 4 of wafer 5 is linear in vertical cross section, front surface side chamfer 11 is formed at the corner with front surface 2, and back surface side chamfer 12 is formed at the corner with back surface 7. This prevents wafer 5 from bending after grinding step 1005 to form recesses 14, and allows grinding without fixing a hard substrate to wafer 5.

[0110] Furthermore, in the wafer processing method according to the first embodiment, the wafer 5 is placed in the wafer cassette 77 in a predetermined orientation in the placing step 1006, so that the step of detecting the orientation of the wafer 5 in the next step can be eliminated.

[0111] The wafer 5 according to the first embodiment has vertical side surfaces 4 and chamfered portions 11, 12 on the front and back surfaces 2, 7, so that the protrusions 15 function as reinforcement even when the width thereof is narrower than in conventional wafers that have arc-shaped chamfers extending from the front surface 2 to the back surface 7. Therefore, the wafer 5 according to the first embodiment can form wider recesses 14, and more devices 8 can be formed.

[0112] Furthermore, when the chamfered portions 11 and 12 of the wafer 5 according to the first embodiment are formed in an arc shape, the wafer 5 is less likely to be damaged during handling even if the radius of curvature of the chamfered portions 11 and 12 is set small.

[0113] Furthermore, since the wafer 5 according to the first embodiment has a thickness of 900 μm or more, it does not bend even after the grinding step 1005, and therefore a substrate is not required during the grinding step 1005.

[0114] [Embodiment 2] An ingot processing method according to the second embodiment will be described with reference to the drawings. FIG. 20 is a flowchart showing the flow of the ingot processing method according to the second embodiment. FIG. 21 is a side view schematically showing the orientation detection step of the ingot processing method shown in FIG. 20. FIG. 22 is a side view schematically showing the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 20. FIG. 23 is a side view schematically showing a modified linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 20. FIG. 24 is a side view schematically showing another modified linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 20. FIG. 25 is a perspective view schematically showing an ingot after the linear flat mirror surface portion forming step of the ingot processing method shown in FIG. 20. Fig. 26 is a plan view schematically showing the crystal orientation of an ingot on which a linear flat mirror surface portion is formed in the linear flat mirror surface portion forming step of the ingot processing method shown in Fig. 20. In Figs. 20, 21, 22, 23, 24, 25, and 26, the same parts as those in embodiment 1 are designated by the same reference numerals, and their description will be omitted.

[0115] As shown in Fig. 20, the ingot processing method according to the second embodiment is the same as that according to the first embodiment, except that the preparatory step 2001 of the wafer processing method is different from that of the first embodiment. As shown in Fig. 20, the ingot processing method according to the second embodiment, i.e., the preparatory step 2001 of the wafer processing method, performs an orientation detection step 1002, performs a linear flat mirror surface portion formation step 1003 after the orientation detection step 1002, and performs a wafer formation step 1001 after the linear flat mirror surface portion formation step 1003.

[0116] In the second embodiment, the orientation detection step 1002 is a step of detecting the crystal orientation of the ingot 1. In the second embodiment, the orientation detection step 1002 also detects the crystal orientation of the ingot 1, for example, in the same manner as in Japanese Patent Application Laid-Open No. 2000-266697.

[0117] Specifically, in the second embodiment, in the orientation detection step 1002, the detecting and forming device 40 shown in Fig. 21 suction-holds the second surface 3 of the ingot 1 on a flat holding surface 42 of a disk-shaped turntable 41 that rotates about its axis and has a smaller diameter than the ingot 1. In the first embodiment, in the orientation detection step 1002, the detecting and forming device 40 rotates the turntable 41 about its axis, causing X-rays 44 from the X-ray irradiation means 43 to be incident on the outer peripheral surface 4 of the ingot 1 held on the turntable 41, and receives the reflected X-rays 44 with the X-ray receiving means 45. In the second embodiment, in the orientation detection step 1002, the detecting and forming device 40 shown in Fig. 21 detects the crystal orientation of the ingot 1 from the intensity of the X-rays 44 received by the X-ray receiving means 45.

[0118] In the second embodiment, the linear flat mirror surface portion forming step 1003 is a step of forming a linear flat mirror surface portion 6 along the elongation (axial) direction of the ingot 1 based on the crystal orientation detected in the orientation detecting step 1002. In the second embodiment, in the linear flat mirror surface portion forming step 1003, the detecting and forming device 40 relatively moves the cutting blade 50 and the ingot 1 in the axial direction of the ingot 1 based on the detected crystal orientation of the ingot 1, as shown in Figures 22 and 23, and cuts the cutting blade 50 into the ingot 1 at a desired position on the outer peripheral surface 4 of the ingot 1 over the entire length thereof, thereby forming the linear flat mirror surface portion 6 over the entire length of the ingot 1.

[0119] In the second embodiment, in the linear flat mirror surface portion forming step 1003, the cutting blade 50 is caused to cut into the outer peripheral surface 4 of the ingot 1 at a position that corresponds to the (011) plane. At this time, the cutting edge of the cutting blade 50 may be parallel to the axis of the ingot 1, or may be perpendicular to the axis of the ingot 1. It is desirable that the cutting blade 50 has a cutting edge with a high grit size, such as #4000. In the present invention, in the linear flat mirror surface portion forming step 1003, after cutting with the cutting blade 50, the linear flat mirror surface portion 6 may be polished.

[0120] Furthermore, in the present invention, in the linear flat mirror surface portion forming step 1003 according to embodiment 2, as shown in FIG. 24, a laser beam 49 may be irradiated from a laser processing head 47 to a desired position on the outer peripheral surface 4 of the ingot 1 (in embodiment 2, a position along the (011) plane perpendicular to the crystal orientation

[0011] of the wafer 5) along the entire length of the ingot 1, thereby forming a linear flat mirror surface portion 6 along the entire length of the ingot 1.

[0121] Thus, in the second embodiment, in the linear flat mirror surface portion forming step 1003, a linear flat mirror surface portion 6 is formed over the entire length of the ingot 1 at a position that corresponds to the (011) plane on the outer peripheral surface 4 of the ingot 1, as shown in Fig. 25. Also, in the second embodiment, in the linear flat mirror surface portion forming step 1003, the linear flat mirror surface portion 6 of the ingot 1 is formed based on the crystal orientation of the ingot 1, so that the linear flat mirror surface portion 6 and the crystal orientation of the ingot 1 have a predetermined positional relationship, as shown in Fig. 26.

[0122] In the second embodiment, in the linear flat mirror surface portion forming step 1003, the linear flat mirror surface portion 6 is formed so that the crystal orientation of the ingot 1 and the linear flat mirror surface portion 6 have the positional relationship shown in Fig. 26. In the present invention, the positional relationship between the linear flat mirror surface portion 6 formed in the linear flat mirror surface portion forming step 1003 and the crystal orientation of the ingot 1 is not limited to the example shown in Fig. 26.

[0123] In the second embodiment, after the linear flat mirror portion forming step 1003, the wafer forming step 1001 is performed. For this reason, in the second embodiment, the wafer forming step 1001 is a step in which a portion of the ingot 1 is separated to form a wafer 5 after the linear flat mirror portion forming step 1003 is performed. In the second embodiment, the wafer forming step 1001 is a step in which a portion of the ingot 1 is separated to form a wafer 5, as in the first embodiment. Note that in the second embodiment, in the wafer forming step 1001, it is preferable to align the crystal orientation

[0010] of the ingot 1 held on the holding table 22 parallel to the X-axis direction of the laser processing apparatus 20, and to irradiate the ingot 1 with the laser beam 251 while moving the ingot 1 and the irradiation head 256 relatively along the X-axis direction, i.e., along the crystal orientation

[0010] .

[0124] In the second embodiment, the present invention may detect the linear flat mirror surface portion 6 in the wafer formation step 1001, and based on the position of the detected linear flat mirror surface portion 6, position the crystal orientation

[0010] of the ingot 1 parallel to the X-axis direction of the laser processing device 20. In the second embodiment, after the wafer formation step 1001, the detection step 1004, the grinding step 1005, and the accommodation step 1006 are performed in this order using the grinding device 60, as in the first embodiment.

[0125] In the wafer processing method and ingot processing method according to the second embodiment, since the wafer 5 has a linear flat mirror surface portion 6 on the side, the crystal orientation can be identified without forming a notch, orientation flat, or other cutout. This makes it possible to form a wider recess 14 than in conventional wafers that have cutouts such as a notch or orientation flat, and similar to the first embodiment, it is possible to form a larger number of devices 8.

[0126] Next, the effects of the ingot processing method, wafer processing method, and wafer 5 according to embodiment 1 were confirmed. In the confirmation, the presence or absence of damage to wafers 5 and the number of devices 8 were confirmed for present invention product 1, present invention product 2, present invention product 3, present invention product 4, present invention product 5, present invention product 6, present invention product 7, present invention product 8, present invention product 9, present invention product 10, comparative example 1, comparative example 2, and comparative example 3. The results are shown in Table 1 below.

[0127] [Table 1]

[0128] The wafers 5 of Products 1, 2, 3, 4, 5, 6, 7, 8, 9, Comparative Examples 1, 2, and 3 had a thickness of 900 μm and a diameter of 300 mm. Products 1, 2, 3, 4, 5, 6, 7, 8, and 9 of the present invention had side surfaces 4 and chamfered portions 11 and 12, while Products 1, 2, and 3 had arc-shaped chamfered portions on both the front surface 2 and the back surface 7.

[0129] In addition, the thickness of the recess 14 of the wafer 5 of Invention Product 1, Invention Product 2, Invention Product 3, Invention Product 4, Invention Product 5, Invention Product 6, Invention Product 7, Invention Product 8, Invention Product 9, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was set to 50 μm, the width of the protrusion 15 of the wafer 5 of Invention Product 1, Invention Product 2, Invention Product 3, Invention Product 4 and Comparative Example 1 was set to 0.15% of the diameter of the wafer 5, the width of the protrusion 15 of the wafer 5 of Invention Product 5, Invention Product 6, Invention Product 7, Invention Product 8, Invention Product 9 and Comparative Example 2 was set to 0.5% of the diameter of the wafer 5, and the width of the protrusion 15 of the wafer 5 of Comparative Example 3 was set to 0.7% of the diameter of the wafer 5.

[0130] The width 10 of the linear flat mirror surface portion 6 of the wafer 5 of present invention product 1 and present invention product 5 was 0.05 mm, the width 10 of the linear flat mirror surface portion 6 of the wafer 5 of present invention product 2 and present invention product 6 was 1.0 mm, the width 10 of the linear flat mirror surface portion 6 of the wafer 5 of present invention product 3 and present invention product 7 was 5.0 mm, the width 10 of the linear flat mirror surface portion 6 of the wafer 5 of present invention product 4 and present invention product 8 was 10.0 mm, and the width 10 of the linear flat mirror surface portion 6 of the wafer 5 of present invention product 9 was 34.5 mm, and the notch width, notch depth, and notch angle of comparison example 1, comparison example 2, and comparison example 3 were 2 mm, 1 mm, and 90 degrees.

[0131] According to Table 1, in the case of wafer 5 in Comparative Example 1, the convex portion 15 was broken during grinding, which did not serve as reinforcement and prevented damage to the wafer 5 during transport, and in the case of wafer 5 in Comparative Example 2, damage occurred during transport, whereas in the case of wafers 5 in present invention 1, present invention 2, present invention 3, present invention 4, present invention 5, present invention 6, present invention 7, present invention 8, present invention 9, and comparative example 3, no damage occurred during transport.

[0132] According to Table 1, the number of devices 8 on the wafer 5 of Comparative Example 3 was 621, while the number of devices 8 on the wafer 5 of Invention Products 1, 2, 3, and 4 was 636, and the number of devices 8 on the wafer 5 of Invention Products 5, 6, 7, 8, and 9 was 626.

[0133] Therefore, according to Table 1, it has become clear that the ingot processing method, wafer processing method, and wafer 5 according to embodiment 1 can form more devices 8 while suppressing damage to the wafer 5 during transportation by forming a linear flat mirror surface portion 6.

[0134] The present invention is not limited to the above-described embodiment, and can be implemented in various modifications without departing from the gist of the present invention. [Explanation of symbols]

[0135] 1 ingot 2 surface 4 Sides 5 wafers 6 Linear flat mirror surface section (flat mirror surface section) 7 Back side 10 width 11 Surface side chamfer 12 Back side chamfer 14 Recess 15 Convex part 77 Wafer Cassette 1001 Wafer formation step 1002 Direction detection steps 1003 Linear flat mirror surface forming step 1004 detection step 1005 Grinding Step 1006 Containment Step 2001 Preparation Steps

Claims

1. 1. A method for processing a wafer of semiconductor material, comprising: a preparation step of preparing a wafer including a front surface, a back surface behind the front surface, and a side surface extending from the front surface to the back surface, the side surface having a flat mirror surface portion indicating a crystal orientation of the wafer; a grinding step of grinding the back surface of the wafer prepared in the preparation step to form a recess and a protrusion surrounding the recess.

2. 2. The wafer processing method according to claim 1, wherein in the grinding step, the wafer is ground without disposing a hard plate on the surface of the wafer.

3. a detecting step of detecting the flat mirror surface portion before or after performing the grinding step; a storing step of storing the wafer in a wafer cassette after the detecting step and the grinding step are performed; 2. The wafer processing method according to claim 1, wherein in the storing step, the wafer is stored in the wafer cassette with the flat mirror surface portion positioned in a predetermined direction relative to the wafer cassette.

4. 1. A method for processing an ingot of semiconductor material, comprising: an orientation detection step of detecting the crystal orientation of the ingot; a linear flat mirror surface forming step of forming a linear flat mirror surface along the elongation direction of the ingot based on the crystal orientation detected in the orientation detecting step; a wafer forming step of forming a wafer by separating a part of the ingot after the linear flat mirror surface forming step is performed; a grinding step of grinding the back surface of the wafer to form a recess and a protrusion surrounding the recess.

5. A wafer, A wafer comprising a front surface, a back surface behind the front surface, and a side surface extending from the front surface to the back surface, the side surface having a flat mirror surface portion indicating the crystal orientation of the wafer.

6. 6. The wafer according to claim 5, wherein the width of the flat mirror surface portion is not less than 0.05 mm and not more than 34.5 mm.

7. 6. The wafer according to claim 5, wherein the side surface is a straight line in a vertical cross section of the wafer, and a front side chamfer is formed at a corner between the front surface and the side surface, and a back side chamfer is formed at a corner between the back surface and the side surface.

8. 8. The wafer according to claim 7, wherein the front side chamfer and the back side chamfer are each formed in an arc shape extending from the front side to the side surface and from the back side to the side surface in a vertical cross section of the wafer.

9. 6. The wafer according to claim 5, wherein the thickness of the wafer is 900 μm or more.

10. 6. The wafer according to claim 5, wherein the flat mirror surface portion is formed in a line in a region extending from the front surface side to the back surface side of the side surface of the wafer.

Images