JP2022150811A - Manufacturing method of single-crystal silicon carbide substrate - Google Patents

Abstract

To provide a new manufacturing method of a single-crystal silicon carbide substrate which can be adopted when the amount to be removed is small and the cost required for processing can be kept low.SOLUTION: A manufacturing method of a single-crystal silicon carbide substrate includes a laser beam irradiation step of irradiating a first surface side of a single crystal silicon carbide substrate with a pulsed laser beam having a wavelength of 9 μm to 11 μm, and a grinding step of grinding the single crystal silicon carbide substrate, In the laser beam irradiation step, a region to be irradiated with the pulsed laser beam is moved on the first surface such that an irradiated region on a first surface of a pulsed laser beam with which the single crystal silicon carbide substrate is irradiated, and an irradiated region on the first surface of a pulsed laser beam with which the single crystal silicon carbide substrate is irradiated next partially overlap, a portion including the irradiated region of the single crystal silicon carbide substrate is heated by irradiation with the pulsed laser beam, thereby separating and removing the heated portion from the remaining portion of the single crystal silicon carbide substrate.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method for processing a single crystal silicon carbide substrate.

2. Description of the Related Art In order to realize small and light device chips, there are increasing opportunities to process thin semiconductor substrates (semiconductor wafers) on which devices such as integrated circuits are provided on the front side. For example, the front side of the semiconductor substrate is held by a chuck table, and while the grinding wheel and the chuck table to which a grinding wheel for grinding containing abrasive grains is fixed are mutually rotated, the grinding wheel is pressed against the back surface of the semiconductor substrate. This semiconductor substrate can be thinned by grinding.

By the way, a power electronics device represented by an inverter incorporates a semiconductor element called a power device suitable for power control. This power device uses, for example, a substrate made of single crystal silicon carbide (SiC) (hereinafter referred to as a single crystal silicon carbide substrate), which is advantageous in terms of high withstand voltage and low loss compared to single crystal silicon (Si) or the like. manufactured by

On the other hand, since single-crystal silicon carbide is very hard, grinding a single-crystal silicon carbide substrate by the method described above results in significant wear of the whetstone. Therefore, in recent years, a plurality of regions at a predetermined depth from the surface of the single-crystal silicon carbide substrate are modified with a laser beam, and the single-crystal silicon carbide substrate is divided into two thin sheets with a plane containing the plurality of regions as a boundary. A technique for separating into single-crystal silicon carbide substrates has been proposed (see Patent Document 1, for example).

A region modified by a laser beam is more fragile than other regions, and cracks occur between two adjacent modified regions. can be easily separated into two sheets and thinned with a small force. In other words, since the amount (thickness) to be removed by subsequent grinding is reduced, the consumption of the grindstone can be reduced.

JP 2017-28072 A

However, with the technique described above, it is difficult to modify a shallow position of less than 100 μm from the surface of the single crystal silicon carbide substrate and separate the single crystal silicon carbide substrate into two at this shallow position. Therefore, for example, when the amount to be removed from the single-crystal silicon carbide substrate is small (that is, when the boundary for separation should be arranged at a position close to the surface), the above technique could not be adopted.

In addition, in the above-described technique, the consumption of the grindstone can be suppressed to a low level, but in the process of reforming the single-crystal silicon carbide substrate with a laser beam, and by applying force, the single-crystal silicon carbide substrate is separated into two pieces. A new process is required. Therefore, from the viewpoint of processing costs, etc., a more advantageous technique has been desired.

The present invention has been made in view of such problems, and its object is to provide a new unit that can be used when the amount to be removed is small (when the thickness to be removed is small) and the cost required for processing can be kept low. An object of the present invention is to provide a method for processing a crystalline silicon carbide substrate.

According to one aspect of the present invention, the invention comprises a first surface and a second surface located on the opposite side of the first surface, and with respect to the first surface and the second surface A method for processing a single-crystal silicon carbide substrate used for processing a single-crystal silicon carbide substrate having c-axes intersecting, wherein the single-crystal silicon carbide substrate is irradiated with a pulsed laser beam having a wavelength of 9 μm to 11 μm. a step of irradiating a laser beam to the first surface side; and rotating a grinding wheel including a grindstone for grinding against the first surface side of the single crystal silicon carbide substrate irradiated with the pulsed laser beam. and a grinding step of grinding the single-crystal silicon carbide substrate by bringing a grindstone into contact with the first surface of the pulsed laser beam with which the single-crystal silicon carbide substrate is irradiated in the laser beam irradiation step. is scheduled to be irradiated with the pulsed laser beam so that part of the irradiated region of and the irradiated region on the first surface of the pulsed laser beam with which the single-crystal silicon carbide substrate is next irradiated overlaps. A region is moved on the first surface, and a portion including the irradiated region of the single crystal silicon carbide substrate is heated by irradiation with the pulsed laser beam, so that the heated portion is transferred to the single crystal silicon carbide substrate. A method for processing a single crystal silicon carbide substrate is provided in which the substrate is peeled off from the remaining portion of the substrate.

Preferably, in the laser beam irradiation step, the single crystal silicon carbide substrate is irradiated with the pulsed laser beam under the condition that the depth of the portion is less than 30 μm from the first surface.

Preferably, the second surface of the single-crystal silicon carbide substrate has a device region including a plurality of devices and an outer peripheral surplus region surrounding the device region, and in the laser beam irradiation step, the single-crystal irradiating a region of the silicon carbide substrate on the side of the first surface located opposite to the device region with the pulsed laser beam, and in the grinding step, the first surface of the single-crystal silicon carbide substrate; The side region is ground to form a disk-shaped thin plate portion and an annular thick plate portion surrounding the thin plate portion.

In the single-crystal silicon carbide substrate processing method according to one aspect of the present invention, when irradiating the single-crystal silicon carbide substrate with the pulse laser beam, the pulse laser beam is applied so that the regions to be irradiated with the pulse laser beam partially overlap. By moving the planned irradiation region and heating the portion including the irradiated region of the single crystal silicon carbide substrate by irradiating the pulsed laser beam, the heated portion is separated from the remaining portion of the single crystal silicon carbide substrate and removed. do.

Therefore, the size of the removed portion of the single-crystal silicon carbide substrate can be easily adjusted simply by changing the irradiation conditions of the pulsed laser beam. That is, even when the amount to be removed is small (when the thickness to be removed is small), the single crystal silicon carbide substrate processing method according to one aspect of the present invention can be employed.

In addition, the heated portion of the single-crystal silicon carbide substrate is naturally peeled off due to the heating caused by the irradiation of the pulsed laser beam. In addition to the substrate, there is no need to strip the heated site. Therefore, the cost required for processing can be kept low as compared with the conventional method in which it is necessary to apply force after irradiating the laser beam.

FIG. 1 is a perspective view showing an example of a single crystal silicon carbide substrate. FIG. 2 is a side view showing an example of a single crystal silicon carbide substrate. FIG. 3 is a perspective view showing an example of a laser processing device. FIG. 4 is a perspective view showing how a single crystal silicon carbide substrate is held by a chuck table. FIG. 5 is a perspective view showing how a single-crystal silicon carbide substrate is irradiated with a pulsed laser beam. FIG. 6 is a plan view showing an example of a region to be irradiated with a pulsed laser beam. FIG. 7 is a cross-sectional view showing an example of a portion heated by a pulsed laser beam. FIG. 8 is a cross-sectional view showing an example of a single-crystal silicon carbide substrate from which the heated portion is removed. FIG. 9 is a perspective view showing an example of a grinding device. FIG. 10 is a perspective view showing how the single-crystal silicon carbide substrate is ground.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a single crystal silicon carbide substrate 11 processed by a method for processing a single crystal silicon carbide substrate according to the present embodiment, and FIG. 2 shows an example of the single crystal silicon carbide substrate 11. It is a side view. As shown in FIGS. 1 and 2, single-crystal silicon carbide substrate 11 is a disk-shaped wafer made of hexagonal single-crystal silicon carbide (SiC).

Single-crystal silicon carbide substrate 11 has a circular first surface 11a and a circular second surface 11b located on the opposite side of first surface 11a and substantially parallel to first surface 11a. , is equipped with A first orientation flat 13a and a second orientation flat, which are substantially linear when viewed from a direction perpendicular to the first surface 11a (or the second surface 11b), are provided on the outer peripheral portion of the single-crystal silicon carbide substrate 11. 13b are formed.

The extending direction of the first orientation flat 13a and the extending direction of the second orientation flat 13b are substantially perpendicular to each other. Also, the length of the first orientation flat 13a in the direction parallel to the first surface 11a is longer than the length of the second orientation flat 13b in the direction parallel to the first surface 11a.

The c-axis 15 of single-crystal silicon carbide forming the single-crystal silicon carbide substrate 11 is oriented in the direction of the second orientation flat 13b with respect to the perpendicular to the first surface 11a (the perpendicular to the second surface 11b) 17. angle (called the off-angle). That is, the c-plane 19 perpendicular to the c-axis 15 also forms an angle α with respect to the first plane 11a and the second plane 11b. α is typically 4°. However, α can be freely set within the range of 1° to 6°.

Second surface 11b of single-crystal silicon carbide substrate 11 is divided into, for example, a substantially circular device region and an outer peripheral surplus region surrounding the device region. The device area is further partitioned into a plurality of small areas by a plurality of crossing streets (division lines), and devices such as power MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are formed in each small area. It is That is, the device region includes multiple devices.

There are no restrictions on the type, number, shape, structure, size, arrangement, etc. of devices formed on single-crystal silicon carbide substrate 11 . In the present embodiment, the single-crystal silicon carbide substrate 11 having the device formed on the second surface 11b is used as the workpiece. It can also be applied to single crystal silicon carbide substrate 11 .

In the method for processing a single crystal silicon carbide substrate according to the present embodiment, single crystal silicon carbide substrate 11 is processed from the first surface 11a side to be thin. Specifically, first, the single-crystal silicon carbide substrate 11 is irradiated with a pulsed laser beam having a wavelength of 9 μm to 11 μm toward the first surface 11a (laser beam irradiation step).

FIG. 3 is a perspective view showing an example of the laser processing device 2 used in this embodiment. In addition, in FIG. 3, some components of the laser processing apparatus 2 are shown as functional blocks. Also, the X1-axis direction (processing feed direction), the Y1-axis direction (indexing feed direction), and the Z1-axis direction (vertical direction) used in the following description are perpendicular to each other.

As shown in FIG. 3, the laser processing apparatus 2 includes a base 4 on which each component is mounted. A horizontal movement mechanism (processing feed mechanism, index feed mechanism) 6 is arranged on the upper surface of the base 4 . The horizontal movement mechanism 6 includes a pair of Y1-axis guide rails 8 fixed to the upper surface of the base 4 and substantially parallel to the Y1-axis direction. A Y1-axis moving plate 10 is attached to the Y1-axis guide rail 8 so as to be slidable along the Y1-axis direction.

A nut portion (not shown) forming a ball screw is provided on the lower surface side of the Y1-axis moving plate 10 . A screw shaft 12 substantially parallel to the Y1-axis guide rail 8 is rotatably connected to the nut portion. A Y1-axis pulse motor 14 is connected to one end of the screw shaft 12 . When the screw shaft 12 is rotated by the Y1-axis pulse motor 14, the Y1-axis moving plate 10 moves along the Y1-axis guide rail 8 in the Y1-axis direction.

A pair of X1-axis guide rails 16 that are substantially parallel to the X1-axis direction are provided on the upper surface of the Y1-axis moving plate 10 . An X1-axis moving plate 18 is attached to the X1-axis guide rail 16 so as to be slidable along the X1-axis direction. A nut portion (not shown) forming a ball screw is provided on the lower surface side of the X1-axis moving plate 18 .

A screw shaft 20 substantially parallel to the X1-axis guide rail 16 is rotatably connected to the nut portion. An X1-axis pulse motor 22 is connected to one end of the screw shaft 20 . When the screw shaft 20 is rotated by the X1-axis pulse motor 22, the X1-axis moving plate 18 moves along the X1-axis guide rail 16 in the X1-axis direction.

A cylindrical table base 24 is arranged on the upper surface side of the X1-axis movement plate 18 . A chuck table (holding table) 26 used for holding single-crystal silicon carbide substrate 11 as a workpiece is arranged above table base 24 . A rotary drive source (not shown) such as a motor is connected to the lower portion of the table base 24 .

The chuck table 26 rotates around a rotation axis substantially parallel to the Z1-axis direction by the force generated from this rotational drive source. Further, the table base 24 and the chuck table 26 are moved in the X1-axis direction and the Y1-axis direction by the above-described horizontal movement mechanism 6 (processing feed, indexing feed).

It is assumed that this laser processing apparatus 2 processes single-crystal silicon carbide substrate 11 supported by annular frame 23 via tape 21 . In other words, before the pulsed laser beam is applied to the first surface 11a of the single crystal silicon carbide substrate 11 by the laser processing apparatus 2, the single crystal silicon carbide substrate is formed on the second surface 11b side of the single crystal silicon carbide substrate 11. A tape 21 having a larger diameter than 11 is applied.

An annular frame 23 configured to surround single-crystal silicon carbide substrate 11 is fixed to the outer peripheral portion of tape 21 . Of course, in the method for processing a single-crystal silicon carbide substrate according to the present invention, the pulse laser beam may be applied to the single-crystal silicon carbide substrate 11 in a state in which the tape 21 is not attached or the single-crystal silicon carbide substrate 11 is not supported by the frame 23 . .

A portion of the upper surface of chuck table 26 is made of, for example, a porous material, and is in contact with tape 21 (single crystal silicon carbide substrate 11 when tape 21 is not attached) to hold single crystal silicon carbide substrate 11 thereon. It functions as a holding surface 26a for holding. The holding surface 26a is substantially parallel to the X1-axis direction and the Y1-axis direction.

Further, the holding surface 26a is connected to a suction source (not shown) such as a vacuum pump through a channel (not shown) provided inside the chuck table 26 or the like. Four clamps 28 capable of fixing an annular frame 23 supporting single-crystal silicon carbide substrate 11 are provided around chuck table 26 .

A support structure 30 having a side surface substantially perpendicular to the X1-axis direction is provided in a region on one side of the horizontal movement mechanism 6 in the Y1-axis direction. A vertical movement mechanism (height adjustment mechanism) 32 is arranged on the side surface of the support structure 30 . The vertical movement mechanism 32 includes a pair of Z1-axis guide rails 34 fixed to the side surfaces of the support structure 30 and substantially parallel to the Z1-axis direction. A Z1-axis moving plate 36 is attached to the Z1-axis guide rail 34 so as to be slidable along the Z1-axis direction.

A nut portion (not shown) forming a ball screw is provided on the back side of the Z1-axis movement plate 36 (on the side of the Z1-axis guide rail 34). A screw shaft (not shown) substantially parallel to the Z1-axis guide rail 34 is rotatably connected to the nut portion. A Z1-axis pulse motor 38 is connected to one end of the screw shaft. When the Z1-axis pulse motor 38 rotates the screw shaft, the Z1-axis moving plate 36 moves along the Z1-axis guide rail 34 in the Z1-axis direction.

A support 40 is fixed to the surface side of the Z1-axis movement plate 36, and a part of the laser beam irradiation unit 42 is supported by the support 40. As shown in FIG. The laser beam irradiation unit 42 includes, for example, a laser oscillator (not shown) fixed to the base 4, a tubular housing 44 supported by the support 40 and elongated in the Y1-axis direction, and an end portion of the housing 44 (Y1-axis an irradiation head 46 provided at the other end of the direction).

The laser oscillator uses, for example, carbon dioxide gas as a laser medium, generates a high-output pulsed laser beam suitable for processing the single-crystal silicon carbide substrate 11, and radiates it toward the housing 44 side. In this embodiment, this laser oscillator generates a pulsed laser beam having a wavelength (10.6 μm) that is absorbed by the single-crystal silicon carbide substrate 11 . Single crystal silicon carbide has an absorption band at 9 μm to 11 μm.

The housing 44 accommodates a part of the optical system that constitutes the laser beam irradiation unit 42 and guides the pulsed laser beam emitted from the laser oscillator to the irradiation head 46 at the end. Another part of the optical system that constitutes the laser beam irradiation unit 42 is accommodated in the irradiation head 46 . For example, the irradiation head 46 changes the course of the pulsed laser beam guided from the housing 44 downward by an optical element such as a mirror, and converges the light at a predetermined height position on the chuck table 26 side with a condensing lens. .

A camera (imaging unit) 48 fixed to the housing 44 is arranged in a region on one side of the irradiation head 46 in the X1-axis direction. The camera 48 includes a two-dimensional optical sensor such as a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor sensitive to visible light, and is held by the chuck table 26. It is used when imaging the single crystal silicon carbide substrate 11 or the like.

The housing 44 and the irradiation head 46 of the laser beam irradiation unit 42 are moved in the Z1-axis direction by the vertical movement mechanism 32 together with the camera 48 described above. That is, the vertical movement mechanism 32 moves components such as optical elements and lenses provided in the irradiation head 46 in a direction substantially perpendicular to the holding surface 26 a of the chuck table 26 .

In this embodiment, the case where the laser oscillator is fixed to the base 4 has been described as an example, but the laser oscillator is supported by the vertical movement mechanism 32 together with the housing 44 and the like, and can move in the Z1-axis direction. It may be configured as follows. Further, an actuator or the like may be provided in the irradiation head 46 so that only the lens inside the irradiation head 46 can be independently moved in the Z1-axis direction.

The top of the base 4 is covered with a cover (not shown) that can accommodate each component. A touch screen (input/output device) 50 serving as a user interface is arranged on the side surface of this cover. For example, various conditions applied when processing single crystal silicon carbide substrate 11 are input to this touch screen 50 . Note that instead of the touch screen 50 in which the display device (output device) and the input device are integrated, a display device (output device) such as a liquid crystal display and an input device such as a keyboard and a mouse may be provided. good.

Components such as the horizontal movement mechanism 6 , the vertical movement mechanism 32 , the laser beam irradiation unit 42 , the camera 48 , the touch screen 50 and the like are each connected to a control unit 52 . Control unit 52 controls each component described above in accordance with a series of steps required for processing single crystal silicon carbide substrate 11 .

The control unit 52 is configured by a computer including, for example, a processing device such as a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a hard disk drive or flash memory. be done. The functions of the control unit 52 are realized by operating the processing device and the like according to the software stored in the auxiliary storage device. However, the control unit 52 may be realized only by hardware.

When irradiating the first surface 11a of the single crystal silicon carbide substrate 11 with the pulse laser beam, first, the second surface 11b side of the single crystal silicon carbide substrate 11 is moved by the chuck table 26 of the laser processing apparatus 2 described above. Hold. Specifically, for example, single-crystal silicon carbide substrate 11 is placed on chuck table 26 so that tape 21 attached to second surface 11b of single-crystal silicon carbide substrate 11 is brought into contact with holding surface 26a of chuck table 26 . put it on

Then, the negative pressure of the suction source is applied to the holding surface 26 a of the chuck table 26 . Thereby, the second surface 11b side of single crystal silicon carbide substrate 11 is held by chuck table 26 via tape 21, and first surface 11a is exposed upward. The frame 23 attached to the tape 21 is fixed by four clamps 28. As shown in FIG. FIG. 4 is a perspective view showing how single crystal silicon carbide substrate 11 is placed on chuck table 26 . 4, the tape 21, the frame 23, the clamp 28, etc. are omitted for convenience of explanation.

After holding the second surface 11b side of the single-crystal silicon carbide substrate 11 by the chuck table 26, a pulse laser generated using carbon dioxide gas as a medium is applied to the exposed first surface 11a of the single-crystal silicon carbide substrate 11. A beam (a pulsed laser beam with a wavelength of 9 μm to 11 μm) is applied. FIG. 5 is a perspective view showing how single-crystal silicon carbide substrate 11 is irradiated with pulsed laser beam 31 . Note that the tape 21, the frame 23, the clamp 28, and the like are omitted in FIG. 5 as well.

Specifically, for example, the chuck table 26 and the chuck table 26 are arranged so that the irradiation target region 46 a of the pulsed laser beam 31 located directly below the irradiation head 46 is arranged on the first surface 11 a of the single-crystal silicon carbide substrate 11 . The positional relationship with the irradiation head 46 is adjusted by the horizontal movement mechanism 6 or the like. Then, a pulsed laser beam 31 generated by a laser oscillator is emitted toward this planned irradiation region 46a. As a result, the pulsed laser beam 31 is applied to a portion (irradiated region) of the first surface 11a which overlaps with the irradiation planned region 46a.

As described above, in the present embodiment, pulsed laser beam 31 having a wavelength that is absorbed by single-crystal silicon carbide substrate 11 is used. Therefore, most of the pulsed laser beam 31 irradiated to the irradiated region of the first surface 11a is absorbed by the single-crystal silicon carbide substrate 11 and converted into heat. Thereby, a portion of single-crystal silicon carbide substrate 11 including the irradiated region is rapidly heated and then rapidly cooled.

The laser oscillator of the laser beam irradiation unit 42 is configured to generate the pulse laser beam 31 at a predetermined repetition frequency. Therefore, by operating the horizontal movement mechanism 6 while generating the pulse laser beam 31 by the laser oscillator to move the irradiation planned area 46a of the pulse laser beam 31 with respect to the first surface 11a, the first surface 11a A pulsed laser beam 31 can be applied to a plurality of different portions (irradiated regions) on the upper surface.

6 is a plan view showing an example of a region 11c to be irradiated with the pulse laser beam 31, and FIG. 7 is a cross-sectional view showing an example of a portion 11d heated by the pulse laser beam 31. As shown in FIG. As shown in FIGS. 6 and 7, in the present embodiment, the irradiated region 11c on the first surface 11a of the pulsed laser beam 31 with which the single-crystal silicon carbide substrate 11 is irradiated at a certain timing, and the irradiated region 11c at the next timing. A part of the irradiated region 11c on the first surface 11a of the pulsed laser beam 31 with which the single-crystal silicon carbide substrate 11 is irradiated is overlapped.

That is, the irradiated area 11c on the first surface 11a of the pulsed laser beam 31 and the irradiated area 11c on the first surface 11a of the pulsed laser beam 31 to be irradiated next are partially overlapped. , the irradiation target region 46a of the pulse laser beam 31 is moved on the first surface 11a according to the repetition frequency of the pulse laser beam 31, the size of the region 11c to be irradiated, and the like. Thereby, heated portion 11d including irradiated region 11c can be separated and removed from remaining portion 11e of single-crystal silicon carbide substrate 11 .

FIG. 8 is a cross-sectional view showing an example of single crystal silicon carbide substrate 11 from which heated portion 11d is removed. The reason why the portion 11d heated by the above method is peeled well is that the thermal gradient caused by the thermal expansion and thermal contraction of each portion 11d and the partial overlapping of the adjacent irradiated regions 11c causes the portion 11d to be separated. and the portion 11e. Thus, by removing heated portion 11d and substantially thinning single-crystal silicon carbide substrate 11, the amount to be removed by later grinding can be reduced.

Single-crystal silicon carbide substrate 11 has the property of being easily cleaved along c-plane 19 perpendicular to c-axis 15 . Therefore, it is considered that the cracks described above mainly extend in the direction along c-plane 19 of single-crystal silicon carbide substrate 11 . Therefore, it can also be said that the heated portion 11d is separated mainly along the c-plane 19 at the boundary with the portion 11e.

Conditions for irradiation with pulsed laser beam 31 can be arbitrarily set and changed according to the amount (thickness) to be removed from single-crystal silicon carbide substrate 11 . However, if the portion 11d heated by the irradiation of the pulse laser beam 31 becomes too large, cracks are less likely to occur at the boundary between this portion 11d and the remaining portion 11e. Therefore, it is desirable to irradiate the single-crystal silicon carbide substrate 11 with the pulse laser beam 31 under the condition that the depth of the portion 11d is less than 30 μm from the first surface 11a.

On the other hand, if portion 11d becomes too small, the amount to be removed by later grinding cannot be sufficiently reduced, and the significance of irradiating single-crystal silicon carbide substrate 11 with a pulsed laser beam decreases. Therefore, it is desirable to irradiate the single-crystal silicon carbide substrate 11 with the pulse laser beam 31 under the condition that the depth of the portion 11d is 2 μm or more from the first surface 11a.

More specifically, the output of the pulse laser beam 31 is set to, for example, 120 W to 130 W, and the repetition frequency is set to, for example, 1 kHz to 200 kHz. Further, the speed of moving the planned irradiation region 46a with respect to the first surface 11a is set to, for example, 200 mm/s, and the size (diameter) of the irradiated region 11c is set to, for example, 100 μm to 200 μm. When such conditions are applied, portion 11d having a depth of about 20 μm from first surface 11a can be removed from single crystal silicon carbide substrate 11 .

For example, substantially the entire first surface 11a of the single-crystal silicon carbide substrate 11 is irradiated with the pulse laser beam 31, and when the entire single-crystal silicon carbide substrate 11 becomes substantially thin, the irradiation of the pulse laser beam 31 is terminated. . In this embodiment, the planned irradiation region 46a is linearly moved with respect to the first surface 11a, but the planned irradiation region 46a may be moved in a curved line with respect to the first surface 11a. . For example, the planned irradiation region 46a can be moved so as to draw a spiral trajectory.

After the first surface 11a side of the single crystal silicon carbide substrate 11 is irradiated with the pulse laser beam 31 and the heated portion 11d is removed, the first surface 11a side of the single crystal silicon carbide substrate 11 is ground. (grinding step). FIG. 9 is a perspective view showing the grinding device 102 used in this embodiment. The X2-axis direction (front-rear direction), the Y2-axis direction (left-right direction), and the Z2-axis direction (vertical direction) used in the following description are perpendicular to each other.

As shown in FIG. 9, the grinding device 102 has a base 104 on which each component is mounted. A columnar support structure 106 is provided at the rear end of the base 104 . The upper surface of the base 104 is formed with an opening 104a elongated in the X2-axis direction. A ball screw type X2-axis movement mechanism 108 is arranged in the opening 104a.

The X2-axis movement mechanism 108 has an X2-axis movement table (not shown), and moves this X2-axis movement table in the X-axis direction. A first cover 110a is arranged above the X2-axis moving table. Accordion-shaped second covers 110b are connected to the front and rear of the first cover 110a. Thereby, the upper part of the X2-axis movement mechanism 108 is covered with the first cover 110a and the second cover 110b. An operation panel 112 is provided in front of the opening 104a for use in inputting grinding conditions and the like.

A chuck table (holding table) 114 used to hold the single-crystal silicon carbide substrate 11 is provided above the X2-axis movement table so as to be exposed above the first cover 110a. A portion of the upper surface of chuck table 114 is made of, for example, a porous material, and functions as holding surface 114 a for holding single crystal silicon carbide substrate 11 . The holding surface 114a has, for example, a shape corresponding to the side surface of a cone, and is connected to a suction source (not shown) such as a vacuum pump through a channel (not shown) provided inside the chuck table 114. there is

The chuck table 114 is connected to a rotational drive source (not shown) such as a motor, and rotates parallel to the Z2 axis so that the apex of the holding surface 114a corresponding to the apex of the cone is the center of rotation. It rotates around an axis of rotation that is slightly tilted with respect to the axis, or the Z2 axis direction. Further, the chuck table 114 is moved in the X2-axis direction together with the X2-axis moving table by the X2-axis moving mechanism 108 described above.

A Z2-axis movement mechanism 116 is provided on the front surface of the support structure 106 . The Z2-axis movement mechanism 116 includes a pair of Z2-axis guide rails 118 substantially parallel to the Z2-axis direction, and a Z2-axis movement plate 120 is attached to the Z2-axis guide rails 118 in a slidable manner. there is A nut portion (not shown) constituting a ball screw is provided on the rear surface side (rear surface side) of the Z2-axis movement plate 120, and this nut portion has a screw shaft substantially parallel to the Z2-axis guide rail 118. 122 are rotatably connected.

A Z2-axis pulse motor 124 is connected to one end of the screw shaft 122 . By rotating the screw shaft 122 with the Z2-axis pulse motor 124, the Z2-axis moving plate 120 moves along the Z2-axis guide rail 118 in the Z2-axis direction. A front surface (surface) of the Z2-axis movement plate 120 is provided with a support 126 projecting forward.

Support 126 supports a grinding unit 128 for grinding single crystal silicon carbide substrate 11 . Grinding unit 128 includes a spindle housing 130 secured to support 126 . A spindle 132 serving as a rotation shaft is rotatably accommodated in the spindle housing 130 .

A lower end of the spindle 132 is exposed outside the spindle housing 130 . A disk-shaped mount 134 is provided at the lower end of the spindle 132 . A plurality of holes (not shown) passing through the mount 134 in the thickness direction are provided in the outer peripheral portion of the mount 134, and a bolt 136 or the like is inserted into each hole. A disk-shaped grinding wheel 138 having approximately the same diameter as the mount 134 is fixed to the lower surface of the mount 134 by bolts 136 or the like.

The grinding wheel 138 includes a disk-shaped (annular) wheel base 140 (FIG. 10) made of stainless steel, aluminum, or the like. The wheel base 140 has an upper surface and a lower surface that are generally parallel to each other, and a circular opening that penetrates the wheel base 140 from the upper surface to the lower surface is formed in the center. Further, inside the wheel base 140, a flow path is provided for downwardly supplying a liquid (processing liquid) such as pure water.

A plurality of grindstones 142 for grinding, which are made by dispersing abrasive grains such as diamond and cBN (cubic boron nitride) in a binder such as resin or metal, are arranged in a ring on the lower surface of the wheel base 140 . The type (material) of the binder constituting grindstone 142 and the material, size, etc. of the abrasive grains are adjusted in accordance with required flatness and the like so that single crystal silicon carbide substrate 11 can be appropriately ground.

When first surface 11a side of single crystal silicon carbide substrate 11 is ground, first, second surface 11b side of single crystal silicon carbide substrate 11 is held by chuck table 114 of grinding apparatus 102 described above. Specifically, for example, single-crystal silicon carbide substrate 11 is placed on chuck table 114 so that tape 21 attached to second surface 11b of single-crystal silicon carbide substrate 11 is brought into contact with holding surface 114a of chuck table 114 . put it on

Then, the negative pressure of the suction source is applied to the holding surface 114 a of the chuck table 114 . Thereby, the second surface 11b side of single crystal silicon carbide substrate 11 is held by chuck table 114 via tape 21, and first surface 11a is exposed upward. Incidentally, before placing single-crystal silicon carbide substrate 11 on chuck table 114 , tape 21 is cut along the outer edge of single-crystal silicon carbide substrate 11 to separate single-crystal silicon carbide substrate 11 from frame 23 . good.

After holding the second surface 11b side of single crystal silicon carbide substrate 11 by chuck table 114, grindstone 142 is brought into contact with the exposed first surface 11a side of single crystal silicon carbide substrate 11 to perform single crystal carbonization. A silicon substrate 11 is ground. FIG. 10 is a perspective view showing how single crystal silicon carbide substrate 11 is ground.

Specifically, first, the X2-axis movement mechanism 108 is operated to move the chuck table 114 directly below the grinding wheel 138 . Next, the chuck table 114 and the grinding wheel 138 are rotated in predetermined directions at predetermined rotation speeds. The rotation speed of the chuck table 114 is, for example, 10 rpm to 300 rpm, and the rotation speed of the grinding wheel 138 is, for example, 1000 rpm to 7000 rpm. However, the number of rotations of the chuck table 114 and the number of rotations of the grinding wheel 138 are not limited to these.

Then, while supplying a liquid (working fluid) to single-crystal silicon carbide substrate 11 on chuck table 114 through the channel of wheel base 140 or the like, grindstone 142 is applied to first surface 11a of single-crystal silicon carbide substrate 11 . Grinding wheel 138 is lowered at a predetermined speed so as to press against it. As a result, as shown in FIG. 10 , single crystal silicon carbide substrate 11 can be thinned by grinding single crystal silicon carbide substrate 11 on the side of first surface 11 a with grindstone 142 .

The speed at which the grinding wheel 138 is lowered is, for example, 0.1 μm/s to 5.0 μm/s, and the liquid supply rate is, for example, 1.0 L/min to 10.0 L/min. However, the speed at which the grinding wheel 138 is lowered and the amount of liquid supplied are not limited to these. At the timing when single-crystal silicon carbide substrate 11 has been processed to a predetermined finished thickness, grinding wheel 138 is stopped from descending to finish grinding single-crystal silicon carbide substrate 11 .

In the method for processing a single-crystal silicon carbide substrate according to the present embodiment, when the single-crystal silicon carbide substrate 11 is irradiated with the pulse laser beam 31, the pulse laser beam 31 is irradiated so that the irradiated region 11c of the pulse laser beam 31 partially overlaps. By moving the irradiation planned region 46a of the beam 31 and heating the portion 11d including the irradiated region 11c of the single crystal silicon carbide substrate 11 by the irradiation of the pulse laser beam 31, the heated portion 11d is heated to the single crystal silicon carbide substrate. 11 is removed by peeling from the remaining portion 11e.

Therefore, the amount (thickness) to be removed by subsequent grinding can be reduced, and wear of the grindstone 142 can be suppressed. Further, the size of the removed portion 11d of the single-crystal silicon carbide substrate 11 can be easily adjusted only by changing the irradiation conditions of the pulsed laser beam 31 . That is, even when the amount to be removed is small (when the thickness to be removed is small), the method for processing a single crystal silicon carbide substrate according to the present embodiment can be employed.

Furthermore, the heated portion 11d of the single-crystal silicon carbide substrate 11 is naturally peeled off due to the heating caused by the irradiation of the pulsed laser beam 31. Therefore, after the irradiation of the pulsed laser beam 31, the peeling force is applied. In addition to single-crystal silicon carbide substrate 11, there is no need to separate heated portion 11d. Therefore, the cost required for processing can be kept low as compared with the conventional method in which it is necessary to apply force after irradiating the laser beam.

It should be noted that the present invention is not limited to the description of the above-described embodiment and can be implemented with various modifications. For example, in the above-described embodiment, both the laser processing device 2 and the grinding device 102 are used to process the single crystal silicon carbide substrate 11. Single-crystal silicon carbide substrate 11 may be processed using a composite apparatus.

Further, in the above-described embodiment, an example of processing the entire first surface 11a side of single-crystal silicon carbide substrate 11 has been described. The invention works. For example, only the region on the first surface 11a side located on the opposite side of the device region is irradiated with the pulsed laser beam 31, and then only the region on the first surface 11a side irradiated with the pulsed laser beam 31 can also be ground. In this case, a disk-shaped thin plate portion and an annular thick plate portion surrounding the thin plate portion are formed.

In addition, the structures, methods, and the like according to the above-described embodiments and modifications can be modified without departing from the scope of the present invention.

11: single-crystal silicon carbide substrate 11a: first surface 11b: second surface 11c: irradiated region 11d: portion 11e: portion 13a: first orientation flat 13b: second orientation flat 15: c-axis 17: Perpendicular line 19: c plane 21: tape 23: frame 31: pulse laser beam 2: laser processing device 4: base 6: horizontal movement mechanism 8: Y1 axis guide rail 10: Y1 axis movement plate 12: screw shaft 14: Y1 axis Pulse motor 16 : X1-axis guide rail 18 : X1-axis movement plate 20 : Screw shaft 22 : X1-axis pulse motor 24 : Table base 26 : Chuck table 26a : Holding surface 28 : Clamp 30 : Support structure 32 : Vertical movement mechanism 34 : Z1-axis guide rail 36 : Z1-axis moving plate 38 : Z1-axis pulse motor 40 : Support 42 : Laser beam irradiation unit 44 : Housing 46 : Irradiation head 46a : Planned irradiation area 48 : Camera 50 : Touch screen 52 : Control unit 102: grinding device 104: base 104a: opening 106: support structure 108: X2-axis movement mechanism 110a: first cover 110b: second cover 112: operation panel 114: chuck table 114a: holding surface 116: Z2-axis movement mechanism 118: Z2-axis guide rail 120: Z2-axis moving plate 122: Screw shaft 124: Z2-axis pulse motor 126: Supporting tool 128: Grinding unit 130: Spindle housing 132: Spindle 134: Mount 136: Bolt 138: Grinding wheel 140: Wheel Base 142: grindstone

Claims (3)

Single-crystal silicon carbide comprising a first surface and a second surface located on the opposite side of the first surface, wherein the c-axis intersects the first surface and the second surface A method for processing a single crystal silicon carbide substrate used for processing a substrate, comprising:
a laser beam irradiation step of irradiating the first surface side of the single crystal silicon carbide substrate with a pulsed laser beam having a wavelength of 9 μm to 11 μm;
A grinding wheel including a grindstone for grinding is brought into contact with the first surface side of the single-crystal silicon carbide substrate irradiated with the pulsed laser beam while the grindstone is rotated, so that the single-crystal silicon carbide substrate is ground. a grinding step of grinding;
In the laser beam irradiation step, an irradiated region on the first surface of the pulsed laser beam with which the single-crystal silicon carbide substrate is irradiated, and the pulsed laser beam with which the single-crystal silicon carbide substrate is next irradiated. The region to be irradiated with the pulsed laser beam is moved on the first surface so that a portion of the region to be irradiated with the pulsed laser beam overlaps with the region to be irradiated on the first surface of, and the single crystal is irradiated with the pulsed laser beam A method of processing a single crystal silicon carbide substrate, wherein a portion of a silicon carbide substrate including an irradiated region is heated to separate and remove the heated portion from the remaining portion of the single crystal silicon carbide substrate. 2. The single crystal silicon carbide substrate according to claim 1, wherein in the laser beam irradiation step, the pulsed laser beam is applied to the single crystal silicon carbide substrate under the condition that the depth of the portion is less than 30 μm from the first surface. Substrate processing method. the second surface of the single-crystal silicon carbide substrate has a device region including a plurality of devices and an outer peripheral surplus region surrounding the device region;
In the laser beam irradiation step, a region of the single crystal silicon carbide substrate on the first surface side located opposite to the device region is irradiated with the pulsed laser beam,
2. In the grinding step, a region of the single-crystal silicon carbide substrate on the first surface side is ground to form a disk-shaped thin plate portion and to form an annular thick plate portion surrounding the thin plate portion. 3. The method for processing a single crystal silicon carbide substrate according to claim 2.

Images