CN114589421A - Method for processing SiC ingot and laser processing device - Google Patents

Abstract

The invention provides a method for processing a SiC ingot and a laser processing device, wherein the method for processing the SiC ingot can form a proper stripping belt in the SiC ingot at any height. The method for processing the SiC ingot comprises the following steps: a separation band forming step of positioning a converging point of a processing laser beam having a wavelength that is transparent to the SiC ingot at a depth corresponding to a thickness of a wafer to be produced, and irradiating the SiC ingot with the processing laser beam to form a band-shaped separation band composed of cracks; a reflected light detection step of irradiating the separation zone with an inspection laser beam having a wavelength which is transmissive to the SiC ingot and is reflected at the crack of the separation zone, and detecting the intensity of the reflected light reflected at the crack; and a processing laser beam output adjustment step of adjusting the output of the processing laser beam so that the intensity of the reflected light detected in the reflected light detection step falls within a predetermined range.

Description

SiC ingot processing method and laser processing device

technical field

The present invention relates to a processing method and a laser processing device of a SiC ingot.

Background technique

Devices such as ICs, LSIs, and LEDs are formed by laminating a functional layer on the front surface of a wafer made of Si (silicon), Al ₂ O ₃ (sapphire), etc., and dividing the functional layer by a plurality of intersecting planned dividing lines. of. In addition, power devices, LEDs, etc. are formed by laminating a functional layer on the front surface of a wafer made of single crystal SiC (silicon carbide) and dividing the functional layer by a plurality of intersecting lines to be divided. The wafer on which the device is formed is processed by a cutting device or a laser processing device on the lines to be divided to be divided into individual device chips, and each of the divided device chips is used in electronic equipment such as mobile phones and personal computers.

The wafer on which the device is formed is generally produced by thinly cutting a cylindrical semiconductor ingot with a wire dicing machine. A mirror surface is finished by grinding the front and back surfaces of the cut wafer (for example, see Patent Document 1). However, when the semiconductor ingot is cut with a wire dicing machine and the front and back surfaces of the cut wafer are ground, most (70 to 80%) of the semiconductor ingot is discarded, which is uneconomical. In particular, SiC ingots have high hardness, are difficult to cut by a wire dicing machine, and require a considerable amount of time, resulting in poor productivity and high unit price of semiconductor ingots, which pose a problem in efficiently producing wafers.

Therefore, the present applicant has proposed a technique in which a condensing point of a laser beam having a wavelength that is transparent to single crystal SiC is positioned inside a SiC ingot, and the SiC ingot is irradiated with the laser beam to form peeling on the plane to be cut. The wafer is peeled from the SiC ingot along the plane to be cut where the peeling tape is formed (for example, see Patent Document 2).

Patent Document 1: Japanese Patent Laid-Open No. 2000-94221

Patent Document 2: Japanese Patent Laid-Open No. 2016-111143

However, as the SiC ingot grows, the crystal structure becomes uniform. Therefore, when the exfoliation band is formed at the first grown portion, the irradiated SiC ingot needs to be increased compared to the case where the exfoliation band is formed at the last grown portion. As for the energy of the laser beam, there is a problem that the energy of the laser beam for forming an appropriate peeling tape varies depending on the height (axial position) of the SiC ingot.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a processing method and a laser processing apparatus of a SiC ingot, which can form a suitable peeling tape in a SiC ingot at any height.

According to one aspect of the present invention, there is provided a method for processing a SiC ingot, wherein the method for processing a SiC ingot includes a step of forming a stripping tape perpendicular to a direction in which an off angle is formed between the end face and the c-plane of the SiC ingot The direction in which the c-plane is inclined with respect to the end face of the SiC ingot is referred to as the X-axis direction, and the direction perpendicular to the X-axis direction is referred to as the Y-axis direction, while the laser beam for processing having a wavelength that is transparent to the SiC ingot The light condensing point is positioned at a depth corresponding to the thickness of the wafer to be produced, the SiC ingot is irradiated with the laser beam for processing, and the SiC ingot and the condensing point are relatively processed in the X-axis direction. A strip-shaped peeling tape is formed, and the peeling tape is obtained by extending the part where the crack is separated into Si and C from SiC along the c-plane; in the indexing feeding process, the SiC ingot and the light-converging point are The Y-axis direction is relatively indexed and fed to arrange the peeling tapes in parallel in the Y-axis direction; in the reflected light detection step, the peeling tape is irradiated with the SiC ingot that is transparent to the an inspection laser beam having a wavelength reflected at a crack to detect the intensity of the reflected light reflected at the crack; and a processing laser beam output adjustment step of adjusting the intensity of the reflected light detected by the reflected light detection step The output of the laser beam for processing is adjusted so as to be within a predetermined range.

Preferably, the processing method of the SiC ingot further includes a flat surface forming step of grinding the end surface of the SiC ingot to form a flat surface before the peeling tape forming step.

According to another aspect of the present invention, there is provided a laser processing apparatus for forming a peeling tape in a SiC ingot, wherein the laser processing apparatus includes: a chuck table that holds the SiC ingot; and a laser beam irradiation unit that A concentrator is included, and a direction perpendicular to a direction forming an off-angle between an end face of the SiC ingot and a c-plane relative to the end face of the SiC ingot held by the chuck table is taken as the X-axis direction Inclination, the direction perpendicular to the X-axis direction is defined as the Y-axis direction, and the concentrator positions the condensing point of the processing laser beam having a wavelength transparent to the SiC ingot corresponding to the thickness of the wafer to be produced The SiC ingot is irradiated with the laser beam for processing at the depth of the SiC ingot, and the laser beam irradiating unit forms a strip-shaped peeling belt obtained by extending the portion where the crack is separated from SiC into Si and C along the c-plane ; X-axis feeding mechanism, which performs processing and feeding relative to the chuck table and the condenser in the X-axis direction; Y-axis feeding mechanism, which is the chuck table and the condenser. The indexing feed is relatively performed in the Y-axis direction; the reflected light detection unit irradiates the peeling tape with a laser light for inspection of a wavelength that is transparent to the SiC ingot and is reflected at the crack of the peeling tape, detecting the intensity of the reflected light reflected at the crack; and a control unit that adjusts the output of the processing laser beam so that the intensity of the reflected light detected by the reflected light detecting unit falls within a predetermined range.

According to the processing method of the SiC ingot of the present invention, a suitable peeling band can be formed in the SiC ingot at any height.

According to the laser processing apparatus of this invention, like the processing method of a SiC ingot, a suitable peeling tape can be formed in an arbitrary height in a SiC ingot.

Description of drawings

FIG. 1 is a perspective view of a laser processing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a part of the configuration of the laser processing apparatus shown in FIG. 1 .

FIG. 3( a ) is a front view of the SiC ingot, and FIG. 3( b ) is a plan view of the SiC ingot.

FIG. 4 is a perspective view showing a state in which a flat surface forming step is performed.

FIG. 5( a ) is a perspective view showing a state in which a release tape forming step is performed, and FIG. 5( b ) is a cross-sectional view showing a state in which a release tape forming process is performed.

FIG. 6 is a perspective view showing a state in which a reflected light detection step is performed.

FIG. 7 is a perspective view showing a state in which a peeling step is performed.

Label description

2: Laser processing device; 4: Holding unit; 6: Condenser; 8: Laser light irradiation unit; 10: X-axis feed mechanism; 12: Y-axis feed mechanism; 14: Reflected light detection unit; 16: Control Cell; 86: SiC ingot; 100: Parts of SiC separated into Si and C; 102: Crack; 104: Stripping tape; 106: Wafer; LB1: Pulsed laser light for processing; LB2: Pulsed laser light for inspection.

Detailed ways

Hereinafter, preferred embodiments of the SiC ingot processing method and laser processing apparatus of the present invention will be described with reference to the accompanying drawings.

First, a laser processing apparatus according to an embodiment of the present invention will be described with reference to FIG. 1 . The laser processing apparatus denoted by reference numeral 2 as a whole includes at least: a holding unit 4 which holds a SiC ingot; and a laser light irradiation unit 8 which has a concentrator 6 which will transmit the SiC ingot with a wavelength of light. The laser beam is irradiated to the SiC ingot with the condensing point of the laser beam for processing positioned at a depth corresponding to the thickness of the wafer to be produced, and the laser beam irradiation unit 8 forms and separates the cracks from the SiC into Si (silicon) and C (carbon). A strip-shaped peeling tape obtained by extending the part of the 3D along the c-plane; the X-axis feeding mechanism 10, which feeds the holding unit 4 and the condenser 6 in the X-axis direction relative to each other; the Y-axis feeding mechanism 12 , which index and feed the holding unit 4 and the concentrator 6 relative to the Y-axis direction; the reflected light detection unit 14, which irradiates the peeling tape, which is transparent to the SiC ingot and reflects at the crack of the peeling tape and the control unit 16 (refer to FIG. 2 ) for making the intensity of the reflected light detected by the reflected light detection unit 14 within a predetermined range The output of the laser light for processing is adjusted in the internal way. In addition, the X-axis direction is the direction indicated by the arrow X in FIG. 1 , and the Y-axis direction is the direction indicated by the arrow Y in FIG. 1 , which is a direction perpendicular to the X-axis direction. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

As shown in FIG. 1 , the holding unit 4 includes an X-axis movable plate 20 mounted on the base 18 movably in the X-axis direction, and mounted on the X-axis movable plate 20 movably in the Y-axis direction the Y-axis movable plate 22; a circular holding table 24 rotatably mounted on the upper surface of the Y-axis movable plate 22; and a holding table motor (not shown) that rotates the holding table 24 .

The laser beam irradiation unit 8 includes a casing 26 extending upward from the upper surface of the base 18 and then extending substantially horizontally. As shown in FIG. 2 , the casing 26 includes a laser oscillator 28 for oscillating a pulsed laser light for processing having a wavelength transparent to the SiC ingot, and an attenuator 30 for oscillating the laser light emitted from the laser oscillator 28 The output of the pulsed laser beam LB1 for processing is adjusted; and the reflection mirror 32 reflects the pulsed laser beam LB1 for processing whose output is adjusted by the attenuator 30 and guides it to the condenser 6 .

As shown in FIG. 1 , the condenser 6 of the laser light irradiation unit 8 is mounted on the lower surface of the front end of the housing 26 . In addition, the laser beam irradiation unit 8 includes a condensing point position adjustment unit (not shown). For example, the condensing point position adjustment unit may have a ball screw connected to the concentrator 6 and extending in the vertical direction, and a motor for rotating the ball screw. The position in the vertical direction of the converging point of the emitted processing pulsed laser beam LB1 is adjusted.

In addition, the c-plane is inclined with respect to the end face of the SiC ingot held by the holding unit 4, and the direction perpendicular to the direction in which the offset angle is formed between the end face of the SiC ingot and the c-plane is referred to as the X-axis direction, and the direction perpendicular to the X-axis direction is referred to as Y. In the axial direction, the concentrator 6 locates the condensing point of the pulsed laser beam LB1 for processing having a wavelength transparent to the SiC ingot at a depth corresponding to the thickness of the wafer to be produced, and irradiates the SiC ingot with the pulsed laser beam for processing. LB1.

As shown in FIG. 1 , on the lower surface of the front end of the casing 26 , the imaging unit 3 for capturing the image of the SiC ingot held by the holding unit 4 is mounted at a distance from the condenser 6 in the X-axis direction. In addition, on the upper surface of the casing 26, a display unit 36 that displays an image captured by the imaging unit 34 is arranged.

The X-axis feed mechanism 10 includes a ball screw 38 extending in the X-axis direction along the upper surface of the base 18 , and a motor 40 for rotating the ball screw 38 . A nut portion (not shown) of the ball screw 38 is coupled to the X-axis movable plate 20 . In addition, the X-axis feed mechanism 10 uses the ball screw 38 to convert the rotational motion of the motor 40 into linear motion and transmits it to the X-axis movable plate 20 , and the X-axis movable plate 20 faces along the guide rail 18 a on the base 18 . The processing feed is relatively performed in the X-axis direction with respect to the condenser 6 .

The Y-axis feed mechanism 12 includes a ball screw 42 extending in the Y-axis direction along the upper surface of the X-axis movable plate 20 , and a motor 44 for rotating the ball screw 42 . A nut portion (not shown) of the ball screw 42 is coupled to the Y-axis movable plate 22 . In addition, the Y-axis feed mechanism 12 uses the ball screw 42 to convert the rotational motion of the motor 44 into linear motion and transmits it to the Y-axis movable plate 22, so that the Y-axis movable plate 22 is moved along the X-axis movable plate 20. The guide rail 20a is indexed and fed relative to the condenser 6 in the Y-axis direction.

Continuing the description with reference to FIG. 1 , the reflected light detection unit 14 includes a light emitter 46 and a light receiver 48 , both of which are mounted on the lower surface of the front end of the housing 26 . The light-emitting device 46 includes: a laser oscillator (not shown) that oscillates a pulsed laser light for inspection having a wavelength that is transparent to the SiC ingot and reflected at the crack of the peeling tape; and an irradiator (not shown), It irradiates the SiC ingot with the pulsed laser beam LB2 for inspection radiated from the laser oscillator. The light receiver 48 may be constituted by a photodiode or the like.

Both the emitter 46 and the receiver 48 are movable in the X-axis direction, the Y-axis direction, and the vertical direction, and the angle of the emitter 46 and the angle of the receiver 48 (both are angles relative to the end face of the SiC ingot) are changed. composed in a free manner. Thereby, the incident angle θ of the pulsed laser beam LB2 for inspection with respect to the end face of the SiC ingot can be adjusted, and the light receiver 48 can be detected in the optical path of the pulsed laser beam LB2 for inspection reflected at the crack of the peeling tape. The position of the light-receiving surface is adjusted (see Figure 6).

The control unit 16 constituted by a computer includes: a central processing unit (CPU) that performs arithmetic processing according to a control program; a read-only memory (ROM) that stores the control program and the like; RAM) (neither are shown).

As shown in FIG. 2 , the control unit 16 is electrically connected to the light receiver 48 , and transmits a signal related to the intensity of the reflected light detected by the light receiver 48 from the light receiver 48 to the control unit 16 . In addition, the control unit 16 is also electrically connected to the attenuator 30 of the laser light irradiation unit 8 . Then, the control unit 16 controls the attenuator 30 according to the intensity of the reflected light transmitted from the light receiver 48 so that the intensity of the reflected light detected by the light receiver 48 falls within a predetermined range (for example, the voltage output from the light receiver 48 The output of the processing pulse laser beam LB1 is adjusted so that the signal is in the range of 1V to 1.2V).

The above-mentioned predetermined range is a range in which a peeling tape can be appropriately formed inside the SiC ingot, and the wafer can be appropriately peeled off from the SiC ingot, and is appropriately set based on the results of experiments performed in advance and the like. When the intensity of the reflected light is less than the lower limit of the above-specified range, there is a fear that the cracks in the peeling tape will not grow sufficiently, and the wafer may not be properly peeled from the SiC ingot. Therefore, when the intensity of the reflected light is less than the lower limit of the predetermined range, the control unit 16 controls the attenuator 30 to increase the output of the processing pulsed laser beam LB1 so that the intensity of the reflected light falls within the predetermined range.

On the other hand, when the intensity of the reflected light detected by the light receiver 48 exceeds the upper limit value of the predetermined range, the wafer can be appropriately peeled off from the SiC ingot, but cracks in the peeling tape grow beyond what is required, and the After the SiC ingot peels off the wafer, the amount of grinding increases when the peeled surface of the SiC ingot and the peeled surface of the wafer are ground and flattened, and the loss of the raw material increases. Therefore, when the intensity of the reflected light exceeds the upper limit of the predetermined range, the control unit 16 controls the attenuator 30 to reduce the output of the processing pulsed laser beam LB1 so that the intensity of the reflected light falls within the predetermined range.

As shown in FIG. 1 , the laser processing apparatus 2 of the present embodiment further includes a peeling unit 50 that peels off the wafer from the SiC ingot using the peeling tape as a starting point, and a grinding unit 52 that grinds the end face of the SiC ingot to This end surface is formed as a flat surface.

The peeling unit 50 includes: a casing 54 arranged at the end portion of the guide rail 18a on the base 18; an arm 56 extending in the X-axis direction from a base end supported by the casing 54 in a lifting and lowering manner; and an arm lifting unit ( Not shown), which raises and lowers the arm 56 . The arm raising/lowering unit may have a configuration including a ball screw that is coupled to the arm 56 and extends in the vertical direction, and a motor that rotates the ball screw. A motor 58 is attached to the front end of the arm 56 , and the suction sheet 60 is rotatably connected to the lower surface of the motor 58 around an axis extending in the vertical direction. A plurality of suction holes (not shown) are formed on the lower surface of the suction sheet 60, and the suction sheet 60 is connected to a suction unit (not shown). In addition, an ultrasonic vibration imparting unit (not shown) for imparting ultrasonic vibration to the lower surface of the adsorption sheet 60 is incorporated in the adsorption sheet 60 .

The grinding unit 52 includes: an attachment wall 62 connected to the casing 26 ; a lift plate 64 mounted on one surface of the attachment wall 62 so as to be able to move up and down; and a lift unit 66 for raising and lowering the lift plate 64 . The elevating unit 66 includes a ball screw 68 extending in the vertical direction along one surface of the attachment wall 62 and a motor 70 for rotating the ball screw 68 . A nut portion (not shown) of the ball screw 68 is connected to the lift plate 64 . In the elevating unit 66 , the rotational motion of the motor 70 is converted into linear motion by the ball screw 68 and transmitted to the elevating plate 64 , and the elevating plate 64 is moved up and down along the guide rail 62 a attached to one surface of the mounting wall 62 . .

A support wall 72 protruding in the Y-axis direction is fixed to one surface of the lift plate 64 . The main shaft 74 is rotatably supported by the support wall 72 around an axis extending in the vertical direction, and a main shaft motor 76 that rotates the main shaft 74 is mounted on the upper surface of the support wall 72 . 1 and 4 , a disc-shaped grinding wheel mounting seat 78 is fixed to the lower end of the main shaft 74 , and an annular grinding wheel 82 is fixed to the lower surface of the grinding wheel mounting seat 78 by bolts 80 . To the outer peripheral edge part of the lower surface of the grinding wheel 82 , a plurality of grinding tools 84 arranged annularly at intervals in the circumferential direction are fixed.

A cylindrical SiC ingot 86 formed of SiC is shown in FIG. 3 . The SiC ingot 86 has: a first end face 88 in a circular shape; a second end face 90 in a circular shape on the side opposite to the first end face 88; a peripheral face 92 between the first end face 88 and the second end face 90; The c-axis (<0001> direction) of the first end face 88 to the second end face 90; and the c-plane ({0001}-plane) perpendicular to the c-axis.

In the SiC ingot 86, the c-plane is inclined with respect to the first end face 88 (the c-axis is inclined with respect to the vertical line 94 of the first end face 88), and the first end face 88 and the c-plane form an off-angle α (for example, α=1 degree, 3 degrees, 6 degrees). The direction in which the deviation angle α will be formed is shown by arrow A in FIG. 3 . In addition, on the peripheral surface 92 of the SiC ingot 86, a rectangular first orientation plane 96 and a second orientation plane 98 each representing a crystal orientation are formed. The first orientation plane 96 is parallel to the direction A forming the deviation angle α, and the second orientation plane 98 is perpendicular to the direction A forming the deviation angle α. As shown in FIG. 3( b ), when viewed from above, the length L2 of the second alignment plane 98 is shorter than the length L1 of the first alignment plane 96 ( L2 < L1 ).

Next, a preferred embodiment of the processing method of the SiC ingot of the present invention will be described, and here, the processing method of the SiC ingot using the above-described laser processing apparatus 2 will be described. In the processing method of the SiC ingot of the present embodiment, first, the SiC ingot 86 is fixed on the holding table 24 with a suitable adhesive (for example, an epoxy-based adhesive) with the second end face 90 facing downward. on the surface. In addition, a plurality of suction holes may be formed on the upper surface of the holding table 24 to generate an attractive force on the upper surface of the holding table 24 to suck and hold the SiC ingot 86 .

After the SiC ingot 86 is fixed on the holding table 24 , except when the end surface of the SiC ingot 86 is already formed flat, a flat surface forming step is performed to grind the end surface of the SiC ingot 86 to form a flat surface.

In the flat surface forming step, first, the holding table 24 is positioned below the grinding wheel 82 of the grinding unit 52 by the X-axis feed mechanism 10 . Next, as shown in FIG. 4 , the holding table 24 is rotated at a predetermined rotational speed (for example, 300 rpm) counterclockwise when viewed from above by the holding table motor. In addition, the spindle 74 is rotated at a predetermined rotational speed (for example, 6000 rpm) counterclockwise when viewed from above by the spindle motor 76 . Next, the spindle 74 is lowered by the elevating unit 66 , and the grinding wheel 84 is brought into contact with the first end surface 88 of the SiC ingot 86 . After that, the spindle 74 is lowered at a predetermined grinding feed rate (for example, 0.1 μm/s). As a result, the first end face 88 of the SiC ingot 86 can be ground to form a flat face to such an extent that it does not interfere with the incidence of the laser beam.

After the SiC ingot 86 is held by the upper surface of the holding table 24 , a peeling tape forming step is performed, and the direction perpendicular to the direction A in which the deviation angle α is formed by the end face and the c-plane of the SiC ingot 86 is defined as the X-axis direction , the c-plane is inclined with respect to the end face of the SiC ingot 86 , and the direction perpendicular to the X-axis direction is defined as the Y-axis direction, and the light-converging point of the processing pulsed laser beam LB1 having a wavelength transparent to the SiC ingot 86 is positioned While irradiating the SiC ingot 86 with the pulsed laser beam LB1 for processing at a depth corresponding to the thickness of the wafer to be produced, the SiC ingot 86 and the light-converging point are relatively fed in the X-axis direction to form a strip-shaped peeling. The peeling tape is obtained by extending the portion where the crack is separated from SiC into Si and C along the c-plane.

In the peeling tape forming step, first, the SiC ingot 86 is imaged by the imaging unit 34 from above the SiC ingot 86 . Next, based on the image of the SiC ingot 86 captured by the imaging unit 34 , the holding table 24 is moved and rotated by the X-axis feeding mechanism 10 , the Y-axis feeding mechanism 12 , and the holding table motor, whereby the SiC ingot 86 is moved and rotated. The orientation is adjusted to a predetermined orientation, and the positions of the SiC ingot 86 and the condenser 6 on the XY plane are adjusted. When the orientation of the SiC ingot 86 is adjusted to a predetermined orientation, as shown in FIG. 5( a ), the second orientation plane 98 is aligned with the X-axis direction so that the direction perpendicular to the direction A forming the deviation angle α is The X-axis direction coincides, and the direction A forming the deviation angle α is made to coincide with the Y-axis direction.

Next, the concentrator 6 is moved up and down by the condensing point position adjustment means, and the condensing point FP1 (see FIG. 5( b )) of the pulsed laser beam LB1 for processing is positioned from the first end face 88 of the SiC ingot 86 to the desired position. The thickness of the resulting wafer corresponds to the depth. Next, the holding table 24 is fed by the X-axis feed mechanism 10 along the X-axis direction (which corresponds to the direction perpendicular to the direction A that forms the deviation angle α) at a predetermined machining feed rate, while the holding table 24 is moved from the The optical device 6 irradiates the SiC ingot 86 with the pulsed laser beam LB1 for processing having a wavelength that is transparent to the SiC ingot 86 . As a result, as shown in FIG. 5( b ), SiC is separated into Si and C by the irradiation of the processing pulsed laser beam LB1 , and the processing pulsed laser beam LB1 irradiated next is absorbed by the previously formed C to cause the SiC to be interlocked. It is separated into Si and C, and a peeling tape 104 is formed along the X-axis direction in which the part 100 where the crack 102 is separated from SiC into Si and C is extended along the c-plane.

Such a release tape forming step can be performed under the following conditions, for example. Here, the following defocus is the amount of movement when the condenser 6 is moved toward the upper surface of the SiC ingot 86 from the state where the converging point FP1 of the processing pulsed laser beam LB1 is positioned on the upper surface of the SiC ingot 86 .

Wavelength of pulsed laser light for processing: 1064nm

Average output: 7W～16W

Repetition rate: 30kHz

Pulse width: 3ns

Processing feed rate: 165mm/s

Defocus: 188μm

The position of the peeling tape from the upper surface of the SiC ingot: 500 μm

In addition, while performing the peeling tape forming step, a reflected light detection step is performed in which the peeling tape 104 is irradiated with laser light for inspection having a wavelength that is transparent to the SiC ingot 86 and is reflected at the cracks 102 of the peeling tape 104 . The intensity of the reflected light reflected at the crack 102 is detected.

6 , in the reflected light detection step, the converging point FP2 of the pulsed laser beam LB2 for inspection irradiated from the light emitter 46 is positioned at the crack of the peeling tape 104 formed by the irradiation of the pulsed laser beam LB1 for processing. 102. When adjusting the position of the light emitter 46 , it is preferable to set the incident angle θ of the pulsed laser beam LB2 for inspection with respect to the first end face 88 of the SiC ingot 86 to Brewster's angle. As a result, the ratio of the pulsed laser beam LB2 for inspection irradiated to the SiC ingot 86 is increased without being reflected on the first end face 88 of the SiC ingot 86 but incident on the inside of the SiC ingot 86 , so that it is possible to increase the rate of formation in the SiC ingot 86 . The detection accuracy of the reflected light reflected on the crack 102 of the peeling tape 104 inside the SiC ingot 86 occurred. In addition, the light-receiving surface of the light receiver 48 is positioned in the optical path of the reflected light of the pulsed laser beam LB2 for inspection, which has been reflected at the crack 102 of the peeling tape 104 .

Then, while the holding table 24 is processed and fed in the X-axis direction, the SiC ingot 86 is irradiated with the pulsed laser beam LB1 for processing to form the peeling tape 104, and the crack 102 of the formed peeling tape 104 is irradiated and inspected. Use pulsed laser light LB2. In this way, the light receiver 48 detects the reflected light of the pulsed laser beam LB2 for inspection reflected at the crack 102 of the peeling tape 104, and a signal related to the intensity of the reflected light detected by the light receiver 48 is sent to the control unit 16.

Such a reflected light detection step can be performed under the following conditions, for example.

Wavelength of pulsed laser light for inspection: 1064nm

Average output: 0.1W

Repetition rate: 10kHz

Pulse width: 10ns

Processing feed rate: 165mm/s

In addition, while performing the peeling tape forming step and the reflected light detection step, a processing laser beam output adjustment step of adjusting the processing laser light output so that the intensity of the reflected light detected by the reflected light detection step falls within a predetermined range is performed. The output of the pulsed laser light LB1. That is, the peeling tape 104 is formed by irradiation of the pulsed laser beam LB1 for processing, and the reflected light of the pulsed laser beam LB2 for inspection is detected while irradiating the crack 102 of the formed peeling tape 104 with the pulsed laser beam LB2 for inspection. The output of the pulsed laser beam LB1 for processing is adjusted.

In the processing laser beam output adjustment step, the control unit 16 controls the attenuator 30 to adjust the output of the processing pulse laser beam LB1 so that the intensity of the reflected light detected by the light receiver 48 falls within a predetermined range. When the intensity of the reflected light detected by the light receiver 48 is less than the lower limit value of the predetermined range, the output of the pulsed laser beam LB1 for processing is increased, for example, by about 1W to 6W. On the other hand, when the intensity of the reflected light detected by the light receiver 48 exceeds the upper limit value of the predetermined range, the output of the processing pulsed laser beam LB1 is reduced by, for example, about 1W to 6W.

Next, an index feeding process is performed, and the SiC ingot 86 and the light-converging point FP1 are indexed and fed to face each other in the Y-axis direction, and the release tapes 104 are arranged side by side in the Y-axis direction. In the index feeding step, the holding table 24 is moved by the Y-axis feeding mechanism 12 to feed the SiC ingot by a predetermined indexing feed amount Li in the Y-axis direction corresponding to the direction A in which the deviation angle α is formed. 86 is relatively indexed with respect to the condensing point FP1.

Then, by alternately repeating the above-described release tape forming step and the index feeding, as shown in FIG. 5 , the release tape 104 extending in the X-axis direction is spaced apart in the Y-axis direction by a predetermined interval of the indexing feed amount Li Set side by side. However, by setting the indexing feed amount Li within a range not exceeding the width of the cracks 102 and overlapping the cracks 102 of the peeling tapes 104 adjacent to each other in the Y-axis direction when viewed from the top-bottom direction, the following peeling is facilitated. In the process, peeling of the wafer is performed. In addition, after the output of the pulsed laser beam LB1 for processing is adjusted so that the intensity of the reflected light falls within a predetermined range, the reflected light detection step and the processing need not be performed at the same depth of the SiC ingot 86 . Laser light output adjustment process.

After a plurality of peeling tapes 104 are formed inside the SiC ingot 86 (at a depth corresponding to the thickness of the wafer to be produced), a peeling step is performed to peel the wafer from the SiC ingot 86 using the peeling tape 104 as a starting point.

In the peeling process, first, the holding table 24 is positioned below the suction sheet 60 of the peeling unit 50 by the X-axis feed mechanism 10 . Next, the arm 56 is lowered by the arm elevating means, and as shown in FIG. 7 , the lower surface of the suction sheet 60 is brought into close contact with the first end surface 88 of the SiC ingot 86 . Next, the suction unit is operated, and the lower surface of the suction sheet 60 is suctioned to the first end face 88 of the SiC ingot 86 . Next, the ultrasonic vibration imparting unit is operated to impart ultrasonic vibration to the lower surface of the suction sheet 60 , and the suction sheet 60 is rotated by the motor 58 . Thereby, the wafer 106 can be peeled off from the peeling tape 104 as a starting point.

After the peeling step is performed, the flat surface forming step, the peeling tape forming step, the reflected light detection step, the processing laser beam output adjustment step, the index feeding step, and the peeling step are repeated as described above. The ingot 86 produces a plurality of wafers 106 .

As described above, in the present embodiment, the inspection pulse laser beam LB2 is irradiated to the crack 102 of the peeling tape 104 to detect the intensity of the reflected light reflected at the crack 102, and the intensity of the reflected light to be detected falls within a predetermined range. Since the output of the pulsed laser beam LB1 for processing is adjusted in an internal manner, an appropriate peeling tape 104 can be formed at any height in the SiC ingot 86 .

In addition, in the present embodiment, an example in which the release tape forming step, the reflected light detection step, and the processing laser beam output adjustment step are performed simultaneously has been described, but these steps may be performed separately. That is, a peeling tape forming step may be performed, a reflected light detection step may be performed next, and a processing laser beam output adjustment step may be performed next.

Claims (3)

1. a processing method of a SiC ingot, wherein, The processing method of this SiC ingot includes the following steps: In the peeling tape forming step, the direction perpendicular to the direction in which the off angle is formed by the end face of the SiC ingot and the c-plane which is inclined with respect to the end face of the SiC ingot is the X-axis direction, and the direction perpendicular to the X-axis direction is As the Y-axis direction, the SiC ingot is irradiated with the processing laser beam while positioning the condensing point of the processing laser beam having a wavelength transparent to the SiC ingot at a depth corresponding to the thickness of the wafer to be produced, While the SiC ingot and the light-converging point are relatively fed in the X-axis direction, a strip-shaped peeling tape is formed along the c-plane at the portion where the cracks are separated from SiC into Si and C. extended; indexing and feeding process, the SiC ingot and the light-converging point are relatively indexed and fed in the Y-axis direction to arrange the peeling tape side by side in the Y-axis direction; A reflected light detection step of irradiating the peeling tape with laser light for inspection having a wavelength that is transparent to the SiC ingot and reflected at the crack in the peeling tape, and detects the intensity of the reflected light reflected at the crack ;as well as The processing laser beam output adjustment step adjusts the output of the processing laser beam so that the intensity of the reflected light detected in the reflected light detection step falls within a predetermined range. 2. The processing method of SiC ingot according to claim 1, wherein, The processing method of the SiC ingot further includes a flat surface forming step of grinding the end surface of the SiC ingot to form a flat surface before the peeling tape forming step. 3. A laser processing apparatus that forms a peeling tape in a SiC ingot, wherein, The laser processing device has: A chuck table, which holds the SiC ingot; A laser beam irradiation unit including a condenser, and a direction perpendicular to a direction in which an off angle is formed between an end face of the SiC ingot and a c-plane held by the chuck table as the X-axis direction The end face of the SiC ingot is inclined, and the direction perpendicular to the X-axis direction is taken as the Y-axis direction, and the concentrator locates the condensing point of the laser beam for processing with a wavelength that is transparent to the SiC ingot at the same point as the desired direction. The SiC ingot is irradiated with the laser beam for processing at a depth corresponding to the thickness of the generated wafer, and the laser beam irradiation unit forms a strip-shaped peeling belt along the portion where the cracks are separated from the SiC into Si and C. The c-plane is extended; X-axis feeding mechanism, which relatively performs processing and feeding of the chuck table and the condenser in the X-axis direction; Y-axis feeding mechanism, which performs indexing feeding of the chuck table and the condenser in the Y-axis direction relatively; A reflected light detection unit that irradiates the peeling tape with a laser light for inspection of a wavelength that is transparent to the SiC ingot and reflected at a crack of the peeling tape, and detects the intensity of the reflected light reflected at the crack; as well as A control unit that adjusts the output of the processing laser beam so that the intensity of the reflected light detected by the reflected light detection unit falls within a predetermined range.

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