JP2016015463A - METHOD FOR PROCESSING SiC MATERIAL AND SiC MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing an SiC material capable of appropriately cutting a material without complicating a laser irradiation device, and capable of suppressing the degradation of crystal quality, and to provide a SiC material.SOLUTION: A method for processing an SiC material includes: an altered region formation step of irradiating an SiC material, in which an absorbing layer and a non-absorbing layer with a lower absorption coefficient at a predetermined wavelength than the absorbing layer are laminated, with a laser beam of the predetermined wavelength having a convergent beam point set to the absorbing layer, thereby allowing the absorbing layer to absorb the laser beam to form an altered region; and a peeling step of peeling the non-absorbing layer from the altered region in the absorbing layer. In the method, the laser beam is allowed to be adequately absorbed at the absorbing layer.

Description

  The present invention relates to a method for processing a SiC material and a SiC material.

  In general, the SiC material is cut mechanically using a wire saw or the like. However, since SiC has a high hardness, there is a problem in that processing using a wire saw or the like results in processing at a low speed and throughput is reduced.

  In order to solve this problem, a SiC material cutting method in which a modified region is formed inside by irradiating a pulse laser beam along a planned cutting surface of the SiC material, and the SiC material is cut along the planned cutting surface. Has been proposed (see Patent Document 1). In the method described in Patent Document 1, the laser light is relatively moved along a predetermined line in a state where the condensing point is aligned on the planned cutting surface inside the SiC material.

JP 2002-184724 A

  However, in the method described in Patent Document 1, since the cutting plane is determined by the locus of the condensing point that moves relative to the SiC material, high accuracy is required for laser beam position control, and the laser irradiation apparatus is There was a problem of becoming complicated. Further, when the modified region is formed in the SiC material, there is also a problem that the quality of the crystal is deteriorated because the laser energy is absorbed in the crystal immediately below the condensing point.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately cut a material without complicating a laser irradiation apparatus and to suppress deterioration in crystal quality. An object of the present invention is to provide an SiC material processing method and an SiC material.

  In order to achieve the above object, in the present invention, a focusing point is set in the absorption layer for an SiC material in which an absorption layer and a non-absorption layer having a smaller absorption coefficient at a predetermined wavelength than the absorption layer are laminated. By irradiating the laser beam of the predetermined wavelength, the modified layer forming step of forming the altered region by absorbing the laser beam in the absorbing layer, and peeling the non-absorbing layer from the altered region of the absorbing layer And an exfoliating step. A method of processing a SiC material is provided.

  In the SiC material processing method, the absorption layer may have a larger absolute value of the difference between the donor impurity concentration and the acceptor impurity concentration than the non-absorption layer.

  In the SiC material processing method, the absorbing layer and the non-absorbing layer may both be n-type SiC.

  Moreover, in this invention, the SiC material by which the absorption layer and the non-absorption layer whose absorption coefficient of a predetermined wavelength is smaller than the said absorption layer was laminated | stacked is provided.

  In the SiC material, the absorption layer may have a larger absolute value of the difference between the donor impurity concentration and the acceptor impurity concentration than the non-absorption layer.

  In the SiC material, both the absorbing layer and the non-absorbing layer may be n-type SiC.

  According to the SiC material processing method and the SiC material of the present invention, the material can be accurately cut without complicating the laser irradiation apparatus, and the deterioration of the crystal quality can be suppressed.

FIG. 1 is a schematic perspective view of a SiC laminate showing an embodiment of the present invention. FIG. 2 is a schematic explanatory diagram of the laser irradiation apparatus. FIG. 3 is a flowchart showing a method for processing a SiC material. 4A and 4B show the growth process of the SiC material, where FIG. 4A shows a state in which the first absorption layer is formed on the seed crystal substrate, and FIG. 4B shows the first non-absorption layer on the first absorption layer. (C) shows a state in which the second absorption layer is formed on the first non-absorption layer. FIG. 5 shows the growth process of the SiC material, (a) shows a state where the second non-absorbing layer is formed on the second absorbing layer, and (b) shows n sets of absorbing layers on the seed crystal substrate. And the state which formed the non-absorbing layer is shown. FIG. 6 is a graph showing the relationship between the wavelength and the absorption coefficient for the sample body A, the sample body B, and the sample body C. FIG. 7 is a graph showing the relationship between the wavelength and the absorption coefficient for sample body B, sample body D, sample body E, sample body F, sample body G, sample body H, sample body I, sample body J, and sample body K. It is. FIGS. 8A and 8B are explanatory diagrams of the energy absorption process and the peeling process, in which FIG. 8A shows a state in which a laser beam is focused on the nth absorption layer, and FIG. 8B shows an nth nonabsorption layer. The state after peeling is shown. FIG. 9 is an explanatory diagram of an energy absorption process and a peeling process, where (a) shows a state in which a laser beam is focused on the second absorption layer, and (a) shows the first absorption layer. It shows a state in which the laser is irradiated with the focus. FIG. 10 is a plan view of a SiC material showing a portion where the altered region is formed. FIG. 11 is a plan view of a SiC material showing a portion where the altered region is formed.

1 to 11 show an embodiment of the present invention, and FIG. 1 is a schematic perspective view of a SiC material.
As shown in FIG. 1, the SiC laminate 1 is formed in a cylindrical shape and has an absorption layer 210, 230, 250 having a relatively large absorption coefficient for a laser having a predetermined wavelength, and a predetermined wavelength than the absorption layers 210, 230, 250. Non-absorbing layers 220, 240, and 260 having a small absorption coefficient are alternately stacked on the seed crystal substrate 110. In this embodiment, the SiC laminated body 1 consists of 6H type SiC, and can make a diameter into 3 inches, for example. Each absorption layer 210, 230, 250 is used as a sacrificial layer that absorbs laser light during laser processing. The non-absorbing layers 220, 240, and 260 are peeled off from the absorbing layers 210, 230, and 250 after laser processing, and are used as, for example, a substrate of a semiconductor device.

  The interfaces between the absorbing layers 210, 230, 250 and the non-absorbing layers 220, 240, 260 form an off-angle angle with the c-plane orthogonal to the c-axis of 6H-type SiC. Therefore, by cutting the SiC laminated body 1 along the interface between the absorbing layers 210, 230, 250 and the non-absorbing layers 220, 240, 260, an SiC substrate having a main surface that forms an off-angle with respect to the c-plane is obtained. Can be manufactured. The off angle is, for example, about 4 ° and includes the case of 0 °. When the off-angle is 0 °, the interface is parallel to the c-plane.

FIG. 2 is a schematic explanatory diagram of the laser irradiation apparatus.
As shown in FIG. 2, the laser irradiation apparatus 300 includes a laser oscillator 310 that oscillates a laser beam, a mirror 320 that changes the direction of the oscillated laser beam, an optical lens 330 that focuses the laser beam, And a stage 340 that supports the SiC laminated body 1 to be irradiated. Although a particularly fine optical system is not shown in FIG. 2, the laser irradiation apparatus 300 can adjust the focal position, adjust the beam shape, correct aberrations, and the like. In addition, the laser irradiation apparatus 300 includes a housing 350 that maintains the laser beam path in a vacuum state. In the present embodiment, the laser irradiation apparatus 300 is used to irradiate the 6H-type SiC SiC laminated body 1 with laser light, thereby forming an altered region inside the laser light, and cutting the SiC laminated body 1.

  The altered region formed in the present embodiment refers to a region in which physical properties such as density, refractive index, and mechanical strength are different from the surroundings. The altered region can be, for example, a melt-treated region, a crack region, a dielectric breakdown region, a refractive index change region, or a region where these are mixed. Further, the altered region may be a region where the density of the altered region is changed as compared with the density of the unmodified region, or a region where lattice defects are formed. In addition, the altered region may be formed continuously or intermittently. Further, the altered region may be in the form of rows or dots. In addition, a crack may be formed starting from the altered region.

  In addition, the area where the density of the melt treatment area, the refractive index change area, the modified area has changed compared to the density of the non-modified area, and the area where lattice defects are formed are further included in these areas and the modified areas. In some cases, cracks (microcracks) are included in the boundary between the non-modified region and the non-modified region. The included crack may be formed over the entire surface of the modified region, or may be formed in only a part or a plurality of parts.

  The laser oscillator 310 can use a second harmonic of a YAG laser or the like. The beam emitted from the laser oscillator 310 is reflected by the mirror 320 and its direction is changed. A plurality of mirrors 320 are provided to change the direction of the laser light. The optical lens 330 is positioned above the stage 340 and focuses laser light incident on the SiC laminated body 1.

  Stage 340 is moved in the x direction and / or y direction by a moving means (not shown), and moves SiC stack 1 placed thereon. Furthermore, the stage 340 may be rotatable about the z direction. That is, the SiC laminated body 1 can be moved relative to the laser light, whereby a processed surface by the laser light can be formed at a predetermined depth of the SiC laminated body 1. The laser light is irradiated through the seed crystal substrate 110 and the non-absorbing layers 220, 240, 260 and is absorbed by the absorbing layers 210, 230, 250.

  The laser beam is particularly absorbed in the vicinity of the light condensing point in the SiC laminated body 1, and thereby an altered region is formed in the SiC laminated body 1. In the present embodiment, the condensing points are set in the absorption layers 210, 230, and 250 in the laser irradiation apparatus 300. If the laser energy is absorbed by each of the absorption layers 210, 230, and 250, it is not necessary that the focal point and the position of each of the absorption layers 210, 230, and 250 match. For example, the condensing point may be set at a position deeper than the absorption layers 210, 230, and 250. Since the absorption layers 210, 230, and 250 have a larger absorption coefficient than the non-absorption layers 220, 240, and 260, the laser light is applied to the absorption layers 210, 230, and 250 even if the condensing point is slightly shifted in the depth direction. Can be absorbed accurately.

  In the present embodiment, the laser light is relatively moved along a predetermined line in a state where the condensing points are aligned with the absorption layers 210, 230, and 250 inside the SiC laminated body 1. As a result, altered regions are formed in the absorption layers 210, 230, and 250. Note that the direction in which the laser light is relatively moved is not limited to a straight line, and may be moved in a curved line, for example.

  Further, in the present embodiment, linear altered regions are formed by performing one-pulse shots along the absorption layers 210, 230, and 250 at predetermined intervals. A processing spot is formed in the portion where the one-pulse shot is performed, and examples of such a processing spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least two of these.

Next, a processing method of the SiC material will be described with reference to FIG. FIG. 3 is a flowchart showing a method for processing a SiC material.
As shown in FIG. 3, this SiC material processing method includes a first absorption layer growth step S1, a first non-absorption layer growth step S2, a second absorption layer growth step S3, and a second non-absorption layer growth step S3. It includes an absorption layer growth step S4, an nth absorption layer growth step S5, an nth non-absorption layer growth step S6, an energy absorption step S7, and a peeling step S8. Here, n is the number of pairs of the absorbing layer and the non-absorbing layer formed on the seed crystal substrate. In FIG. 3, n is an integer of 3 or more. Here, although the manufacturing method of the SiC laminated body 1 is arbitrary, it can be manufactured by growing a SiC crystal by, for example, a sublimation method or a chemical vapor deposition method. At this time, the concentration of nitrogen in the SiC laminate 1 can be arbitrarily set by appropriately adjusting the partial pressure of the nitrogen gas (N ₂ ) in the atmosphere during crystal growth.

  4A and 4B show the growth process of the SiC material, where FIG. 4A shows a state in which the first absorption layer is formed on the seed crystal substrate, and FIG. 4B shows the first non-absorption layer on the first absorption layer. (C) shows a state in which the second absorption layer is formed on the first non-absorption layer. FIG. 5 shows the growth process of the SiC material, (a) shows a state where the second non-absorbing layer is formed on the second absorbing layer, and (b) shows n sets of absorbing layers on the seed crystal substrate. And the state which formed the non-absorbing layer is shown.

In the present embodiment, as shown in FIG. 4A, first, the first absorption layer 210 is grown on the seed crystal substrate 110 (first absorption layer growth step: S1). In the present embodiment, N ₂ gas is added to the atmospheric gas during crystal growth, and the first absorption layer 210 contains a relatively high concentration of N as an impurity element. The thickness of the first absorption layer 210 is, for example, 10 μm to 50 μm. The first absorption layer 210 may function as a light absorption layer in the energy absorption step S7, and the thickness, impurity concentration, and the like are arbitrary as long as the first absorption layer 210 functions as a light absorption layer.

Next, as shown in FIG. 4B, the first non-absorbing layer 220 is grown on the first absorbing layer 210 (first non-absorbing layer growth step: S2). In the present embodiment, N ₂ gas is added to the atmosphere gas during crystal growth, and the first non-absorbing layer 220 contains a relatively low concentration of N as an impurity element. The thickness of the first non-absorbing layer 220 is, for example, 200 μm to 300 μm.

  Further, as shown in FIG. 4C, a second absorption layer 230 is grown on the first non-absorption layer 220 under the same conditions as the first absorption layer 210 (second absorption layer growth). Step: S3). Furthermore, as shown in FIG. 5A, a second non-absorbing layer 240 is grown on the second absorbing layer 230 under the same conditions as the first non-absorbing layer 220 (second non-absorbing layer 220). Absorbing layer growth step: S4). In this way, the absorbing layer and the non-absorbing layer are alternately stacked in this order, and as shown in FIG. 5B, the n-th absorbing layer 250 and the n-th non-absorbing layer 260 are stacked (the first layer). n absorption layer growth step: S5, nth non-absorption layer growth step: S6). Thereby, the SiC material laminated body 1 by which the some absorption layer and non-absorption layer on the seed crystal substrate 110 were laminated | stacked is produced.

  Next, each absorption layer 210, 230, 250 absorbs laser energy (energy absorption step: S7). In the present embodiment, in the energy absorption process, a light condensing point is set in the absorption layer for the SiC material in which the absorption layer and the non-absorption layer having a smaller absorption coefficient at a predetermined wavelength than the absorption layer are stacked. By irradiating a laser beam having a predetermined wavelength, an altered region forming step is performed in which the absorptive layer absorbs the laser beam to form an altered region. The laser light is irradiated through the seed crystal substrate 110 or the non-absorbing layers 220, 240, 260 and is absorbed by the absorbing layers 210, 230, 250. The impurity concentration of the absorption layers 210, 230, and 250 is adjusted so that the laser absorption coefficient is larger than that of the non-absorption layers 220, 240, and 260.

Here, for a plurality of sample bodies, the relationship between the wavelength and the absorption coefficient was actually measured at room temperature.
FIG. 6 is a graph showing the relationship between the wavelength and the absorption coefficient for the sample body A, the sample body B, and the sample body C. The sample body A was p-type SiC doped with Al, and the concentration of Al was set to 1.5 × 10 ¹⁹ / cm ³ . The sample body B is undoped n-type SiC. The sample body C was n-type SiC doped with Al and N, and the Al concentration was 4 × 10 ¹⁸ / cm ³ and the N concentration was 5.5 × 10 ¹⁸ / cm ³ . As shown in FIG. 6, the sample body A that is p-type SiC has a significantly larger absorption coefficient in the region of 420 nm or more than the sample body B and sample body C that are n-type SiC. If the combination has a difference in absorption coefficient, an absorption layer and a non-absorption layer can be obtained, but it is advantageous for processing that the difference in absorption coefficient is remarkably large. The sample body C is fluorescent SiC that emits blue light when excited by near ultraviolet light.

FIG. 7 is a graph showing the relationship between the wavelength and the absorption coefficient for sample body B, sample body D, sample body E, sample body F, sample body G, sample body H, sample body I, sample body J, and sample body K. It is. In FIG. 7, the letter “sample body” is omitted, and the letters “B”, “D”, “E”, “F”, “G”, “H”, “I”, “J”, “K” is shown. The sample body D was p-type SiC doped with B, and the concentration of B was 5 × 10 ¹⁸ / cm ³ . The sample body E was n-type SiC doped with B and N, and the concentration of B was 6 × 10 ¹⁷ / cm ³ and the concentration of N was 1 × 10 ¹⁹ / cm ³ . The sample body F was n-type SiC doped with B and N, and the concentration of B was 4 × 10 ¹⁷ / cm ³ and the concentration of N was 2.6 × 10 ¹⁸ / cm ³ . The sample body G was n-type SiC doped with B and N, and the concentration of B was 8.95 × 10 ¹⁷ / cm ³ and the concentration of N was 2.5 × 10 ¹⁸ / cm ³ . The sample body H was n-type SiC doped with N, and the concentration of N was 5.4 × 10 ¹⁸ / cm ³ . Further, the sample body I was n-type SiC doped with N, and the concentration of N was set to 7.7 × 10 ¹⁸ / cm ³ . The sample body J was n-type SiC doped with N, and the concentration of N was set to 1.2 × 10 ¹⁹ / cm ³ . The sample body K was n-type SiC doped with N, and the concentration of N was 1.4 × 10 ¹⁹ / cm ³ . As shown in FIG. 10, p-type SiC has a significantly larger absorption coefficient in a region of 450 nm or more than n-type SiC. Moreover, even between n-type SiCs, the difference in absorption coefficient can be made relatively large.

Sample body E, sample body F, sample body G, sample body H, sample body I, sample body J, and sample body K are all compared in the absorption coefficient between the region of 450 nm to 580 nm and the region of 680 nm or more. Low. Therefore, it is preferable that the wavelength of the laser is 450 nm or more and 580 nm or less or 680 nm or more because the difference in absorption coefficient from p-type SiC increases. Even in the region of more than 580 nm and less than 680 nm, although the absorption coefficients of the sample body E, the sample body H, the sample body I, the sample body J, and the sample body K are relatively high, The absorption coefficient is relatively low. This is thought to be due to the difference in concentration _{N A} of the acceptor impurity concentration _{N D} of the donor impurity of each sample body _(N D -N _A), the difference _(N D -N _A) is the sample body E 9.4 × 10 ¹⁸ / cm ³ , Sample F is 2.2 × 10 ¹⁸ / cm ³ , Sample G is 1.6 × 10 ¹⁸ / cm ³ , and Sample H is 5.4 × 10 ¹⁸ / cm 3. ^3. Sample body I is 7.7 × 10 ¹⁸ / cm ³³ , sample body J is 1.2 × 10 ¹⁹ / cm ³ , and sample body K is 1.4 × 10 ¹⁹ / cm ³ . Therefore, if the difference between the concentration _{N A} of the acceptor impurity concentration _{N D} of the donor impurities _(N D -N _A) and 2.2 × ¹⁰ 18 / cm ³ or less, preferably Nari low absorption coefficient in the entire wavelength region . Further, by adjusting the difference in density N _A of the acceptor impurity concentration N _D of the donor impurities (N D _{-N A),} even at a SiC material between the n-type to increase the difference in absorption coefficient it can. Further, even in SiC material between the p-type, it is possible to increase the difference in absorption coefficient by adjusting the difference between the concentration N _A and the donor impurity concentration N _D of the acceptor impurities (N A _{-N D)} it can. That is, the absorption layer only needs to have a larger absolute value of the difference between the donor impurity concentration and the acceptor impurity concentration than the non-absorption layer.

  Specifically, the absorption coefficient of the absorption layer is preferably 1 / cm or less, and the absorption coefficient of the non-absorption layer is preferably 10 / cm or more. When a large difference in absorption coefficient cannot be secured, it is preferable to increase the power density of the laser beam by narrowing the beam or to process the material temperature at a temperature at which the difference in absorption coefficient becomes larger.

  FIGS. 8A and 8B are explanatory diagrams of the energy absorption process and the peeling process, in which FIG. 8A shows a state in which a laser beam is focused on the nth absorption layer, and FIG. 8B shows an nth nonabsorption layer. The state after peeling is shown. FIG. 9 is an explanatory diagram of an energy absorption process and a peeling process, where (a) shows a state in which a laser beam is focused on the second absorption layer, and (a) shows the first absorption layer. It shows a state in which the laser is irradiated with the focus.

  In peeling off the non-absorbing layers 220, 240, and 260, first, as shown in FIG. 8A, the condensing point of the laser beam is aligned with the n-th absorbing layer 250 farthest from the seed crystal substrate 110, The n-th absorption layer 250 absorbs the laser light through the n non-absorption layer 260 to form a modified region. As shown in FIG. 8A, when the laser light is incident on the SiC stacked body 1 from the non-absorbing layer 260 side, the non-absorbing layer 260 is prevented from being blocked by the roughness of the incident surface. It is preferable to polish the surface. Also, when laser light is incident on the SiC laminate 1 from the seed crystal substrate 110 side, the back surface (growth of the seed crystal substrate 110) is prevented so that the incident surface is not disturbed by the rough incident surface. It is preferable to polish the surface opposite to the surface. When laser light is incident on the SiC laminate 1 from the seed crystal substrate 110 side, the back surface of the seed crystal substrate 110 has less waviness and is flat compared to the surface of the non-absorbing layer 260. It is possible to suppress variations in the laser condensing state depending on the incident position.

  In the present embodiment, the altered region 12 is formed by linearly moving the condensing point of the laser beam. That is, as shown in FIG. 10, a plurality of linear alteration regions 12 parallel to each other are arranged at a predetermined interval. Here, FIG. 10 is a plan view of the SiC material showing the part where the altered region is formed. The interval between the altered regions 12 is set to a pitch such that cracks generated from the altered region 12 extend along the c-plane of the 6H-type SiC crystal. This pitch is such a pitch that cracks generated from the altered region 12 extend the longest in the direction along the c-plane as compared to other directions, and the crack extending from the altered region 12 along the c-plane is the SiC laminate 1. The pitch is preferably generated in the above. Specifically, such a pitch is 10 μm or more and 500 μm or less. In particular, when the pitch between the altered regions 12 is 50 μm or less, it is easy to form cracks continuously. If the pitch is smaller than 10 μm, it is necessary to increase the number of times of laser light irradiation on the entire cutting plane, which is not preferable because the throughput is lowered. The c-plane crack may occur only in the SiC laminated body 1 or may reach the side surface 6 of the SiC laminated body 1.

  Further, in the present embodiment, each altered region 12 is a pulse laser beam, and thus is formed as a set of altered spots formed by one pulse shot. Specifically, the linearly altered regions 12 are formed by continuously forming adjacent altered spots such that a part of them overlap each other. It should be noted that the altered spots can be formed at intervals so that adjacent altered spots do not overlap each other.

  Note that the altered region 12 may have a curved shape as shown in FIG. 11 in addition to the linear shape as shown in FIG. In FIG. 11, the altered region 12 is formed in a spiral shape. In addition, the altered region 12 may be concentric with a predetermined interval.

  After the altered region 12 is formed in this manner, the seed crystal substrate 110 side of the SiC stack 1 is fixed, and a force is applied to the n-th non-absorbing layer 260 side in a direction away from the seed crystal substrate 110 side. Thereby, a crack progresses so that c plane cracks in absorption layer 250 may be connected, and SiC layered product 1 is cut. Thereby, as shown in FIG. 8B, the n-th non-absorbing layer 260 is peeled from the seed crystal substrate 110 side (peeling step: S8). After peeling, it is desirable to remove the remainder of the absorption layer 250 from the non-absorption layer 260 side and the seed crystal substrate 110 side by polishing or the like. In particular, if the interface between the absorbing layer 250 and the non-absorbing layer 260 is not parallel to the c-plane, the peeled surface becomes jagged, so it is preferable to achieve planarization while removing the remaining portion of the absorbing layer 250 by polishing or the like.

  In cutting the SiC laminated body 1, the c-plane crack does not necessarily have to occur in the absorption layer 250, and an altered region is formed by laser processing, which is caused by mechanical or thermal load or chemical treatment. The non-absorbing layer 260 may be peeled off.

  Thus, the non-absorbing layer is sequentially peeled from the side opposite to the seed crystal substrate 110. Then, as shown in FIG. 9A, the second absorption layer 230 absorbs the laser light to form the altered region, and then the second non-absorption layer 240 is peeled off, as shown in FIG. 9B. All the non-absorbing layers 220, 240, 260 are peeled off from the seed crystal substrate 110 side by peeling the first non-absorbing layer 220 after the first absorbing layer 210 absorbs the laser beam to form the altered region. Is done. Each time the non-absorbing layer is peeled off, it is preferable to polish the exposed surface on the seed crystal substrate 110 side to expose the next non-absorbing layer while removing the absorbing layer remaining on the seed crystal substrate 110 side. In this way, the seed crystal substrate 110 from which all the non-absorbing layers 220, 240, and 260 have been peeled can be reused.

  According to the processing method of the SiC material of the present embodiment, the absorption layers 210, 230, 250 are formed adjacent to the seed crystal substrate 110 and the non-absorption layers 220, 240, 260, and the laser light is absorbed by the absorption layers 210, 230, By making it absorb to 250, the altered region 12 can be formed to a uniform depth. That is, even if the condensing point of the laser beam is slightly deviated from the set position, the absorption layers 210, 230, and 250 can absorb energy accurately. Therefore, high accuracy is not required for laser beam position control, and the configuration of the laser irradiation apparatus 300 can be made relatively simple.

  Further, since the laser light is reliably absorbed by the absorption layers 210, 230, and 250, the energy of the laser is applied to the crystal of the seed crystal substrate 110 or the non-absorption layers 220 and 240 immediately below the absorption layers 210, 230, and 250. It is hardly absorbed. Thereby, the fall of the crystal quality of the seed crystal substrate 110 or the non-absorption layer 220,240 can be suppressed.

  Furthermore, since the absorption coefficient of the absorption layers 210, 230, and 250 is large, laser light with a relatively low power density can be used, and damage to the crystals immediately below the absorption layers 210, 230, and 250 can be reduced. it can. Therefore, this also can suppress a decrease in crystal quality of the seed crystal substrate 110 or the non-absorbing layers 220 and 240.

  Furthermore, since the absorption layers 210, 230, and 250 may be of a thickness that can absorb the laser, the thickness can be drastically reduced as compared with the thickness of the cutting allowance in the case of separation with a wire saw and peeling. Therefore, the yield when manufacturing the SiC material can be dramatically improved. For example, when the SiC material is mechanically divided using a wire saw, a cutting allowance of about 400 μm is necessary, but each of the absorption layers 210, 230, 250 can be made about 10 μm of about 1/40. .

  In the above embodiment, the difference in the absorption coefficient is shown by adjusting the impurity concentration. However, the absorption coefficient may be changed by a method other than adjusting the impurity concentration. For example, by introducing hydrogen gas during material growth to form a passivation, the carrier concentration in the material can be lowered and the absorption coefficient can be reduced. Therefore, hydrogen gas is not introduced during growth of the absorption layer and is not absorbed. It is conceivable that hydrogen gas is introduced during the growth of the layer.

  Moreover, in the said embodiment, although both the absorption layer and the non-absorption layer showed what is n-type SiC, if the difference of the absorption coefficient of each SiC layer can be made comparatively large, it will be irrespective of a conductivity type. Of course, it can be an absorption layer and a non-absorption layer. For example, the non-absorbing layer may be p-type fluorescent SiC by donor-acceptor pair emission having a relatively large absorption coefficient, and the absorbing layer may be n-type SiC having a relatively small absorption coefficient.

DESCRIPTION OF SYMBOLS 1 SiC laminated body 110 Seed crystal substrate 210 1st absorption layer 220 1st non-absorption layer 230 2nd absorption layer 240 2nd non-absorption layer 250 nth absorption layer 260 nth non-absorption layer 300 Laser irradiation Device 310 Laser oscillator 320 Mirror 330 Optical lens 340 Stage 350 Housing

Claims (6)

Irradiate a laser beam having a predetermined wavelength with a condensing point on the absorption layer to a SiC material in which an absorption layer and a non-absorption layer having a smaller absorption coefficient at a predetermined wavelength than the absorption layer are stacked. A modified region forming step of forming the modified region by absorbing the laser light in the absorption layer,
A peeling step of peeling the non-absorbing layer from the altered region of the absorbing layer.   The SiC material processing method according to claim 1, wherein the absorption layer has a larger absolute value of a difference between a donor impurity concentration and an acceptor impurity concentration than the non-absorption layer.   The SiC material processing method according to claim 2, wherein the absorbing layer and the non-absorbing layer are both n-type SiC.   A SiC material in which an absorption layer and a non-absorption layer having a smaller absorption coefficient at a predetermined wavelength than the absorption layer are laminated.   The SiC material according to claim 4, wherein the absorption layer has a larger absolute value of a difference between a donor impurity concentration and an acceptor impurity concentration than the non-absorption layer.   The SiC material according to claim 5, wherein both the absorbing layer and the non-absorbing layer are n-type SiC.

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