SiC crystal ingot facet detection method and SiC crystal ingot facet processing method

Abstract

The invention relates to a SiC crystal ingot facet detection method and a SiC crystal ingot facet processing method. The SiC crystal ingot facet detection method comprises the following steps: establishing a delta omega-n linear model; determining the doping concentration nij through a delta omega-n linear model, associating the doping concentration nij, the detection image and the corresponding XY coordinate positions, and constructing a doping concentration distribution diagram of the surface layer of the workpiece; the processing method of the SiC crystal ingot comprises the steps that on the basis of a doping concentration distribution diagram and a preset n-P curve model, laser processing power Pij, a detection image and corresponding XY coordinate positions are associated, and a power distribution diagram of a workpiece modified layer is constructed; a processing laser beam is focused at a predetermined depth of the workpiece to perform internal modification, and a silicon carbide workpiece with a modified layer is obtained. The method has the advantages that the detection precision of the doping concentration of the crystal ingot is improved, the influence of abnormal values is small, lossless and accurate facet detection is realized, the processing consistency is improved, and the material loss of the modified layer is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device processing, and in particular to a method for detecting and processing facets of a SiC ingot. Background Art

[0002] Wide-bandgap semiconductor materials represented by SiC have excellent properties such as high thermal conductivity, strong anti-voltage breakdown ability, high saturated electron drift rate, strong chemical stability, radiation resistance, and high temperature resistance, making them highly favored in the fields of high frequency, high temperature, radiation resistance, high power, and high-density integrated electronic devices. Among the multiple processes from a SiC ingot to a qualified substrate wafer, the ingot cutting process is the main link causing SiC material loss. Currently, the ingot cutting technology mainly includes two methods: wire cutting and laser lift-off. Compared with the traditional wire cutting technology, the laser lift-off technology shows great development potential due to its high production efficiency and low consumable consumption. Its core lies in focusing the laser at a specific depth of the ingot to form a large-area modified region, and then performing the wafer lift-off work. During the growth of the ingot, due to different doping concentrations (carrier concentrations), facet regions and non-facet regions with different resistivity, refractive index, and energy absorption rate are formed. When the modification laser passes through the facet region and the non-facet region, the depth of its focal point is inconsistent, resulting in a low flatness of the lifted-off wafer and causing significant losses in the subsequent grinding and polishing processes. In addition, the non-uniform resistivity will cause a large mismatch between the SiC substrate wafer and the epitaxial layer grown on it. Therefore, the doping concentration is an important basic parameter characterizing the properties of semiconductor materials, and accurately measuring the carrier concentration of semiconductor materials has very important practical value.

[0003] Chinese Patent with the authorization announcement number CN110911268B discloses a method for generating a wafer, generating a SiC wafer from a SiC ingot, wherein the method for generating the wafer has the following steps: a flat surface forming step; a coordinate setting step, after implementing the flat surface forming step, detecting the facet region from the upper surface of the SiC ingot, and setting the X coordinate and Y coordinate of the boundary between the facet region and the non-facet region by setting the following two directions as the X-axis and Y-axis respectively: the inclination deviation angle of the c-plane relative to the upper surface of the SiC ingot, the X-axis is the direction perpendicular to the direction forming the deviation angle between the c-plane and the flat surface, and the Y-axis is the direction perpendicular to the X-axis; a machining feed step; a indexing feed step; and a lift-off step. The above method uses a photographing unit to photograph the upper surface of the ingot, and uses an image processing unit to perform binary processing on the captured image, so as to realize the discrimination between the facet region and the non-facet region. However, the ingot is relatively thick, and it is not easy to discriminate the facet region and the non-facet region by direct photographing, and errors are likely to occur during the implementation process.

[0004] A Chinese patent with the publication number CN115472515A discloses a method for processing an ingot. The method for processing the ingot has the following steps: a fluorescence detection step of irradiating the ingot with excitation light of a specified wavelength from above the ingot and detecting the number of photons of fluorescence generated from the upper surface of the ingot; a storage step of storing the distribution of the number of photons of fluorescence on the upper surface of the ingot detected by the fluorescence detection step as two-dimensional data in association with the XY coordinate positions on the XY plane perpendicular to the height direction of the ingot, and storing the position in the height direction of the ingot, i.e., the Z coordinate position, where the two-dimensional data is obtained, in association with the two-dimensional data; a laser beam irradiation step; and a wafer generation step. The above method uses a laser with a specific wavelength to irradiate the ingot, and judges the facet area by detecting the fluorescence intensity generated on the upper surface of the ingot. However, the laser power density used in the fluorescence detection step is relatively high, which easily causes damage to the surface of the ingot.

[0005] A Chinese patent with the publication number CN117316791A discloses a facet detection method, including: irradiating a first surface of an ingot with a laser beam to cause a peeling layer to be generated on the ingot; applying ultrasonic waves to the formed ingot based on an ultrasonic vibration assembly to obtain a wafer corresponding to the peeling layer; emitting a detection beam to the wafer based on a light source with a specific wavelength, and recording the light source emission intensity at the wafer receiving point; comparing the transmission intensity of the wafer and the light source emission intensity to obtain the transmittance of the wafer; positioning the facet area in the wafer and determining the position information corresponding to the facet area based on a preset transmittance threshold and the transmittance of the wafer; using the position information corresponding to the facet area as guiding information to update the laser processing conditions of the next wafer adjacent to the wafer, and performing peeling on the next wafer based on the laser processing conditions. The above method completes the detection of the first peeled wafer by comparing the transmission intensity of the wafer and the light source emission intensity, and then optimizes the laser processing conditions of the next wafer according to the position information corresponding to the facet area of the previous wafer. Laser energy fluctuations or other types of damage on the wafer surface will affect the measurement results, and there is also the problem of insufficient detection accuracy.

[0006] At present, an electrochemical capacitance-voltage (C-V) carrier concentration longitudinal distribution measuring instrument is often selected to measure the longitudinal carrier concentration distribution. The four-probe method and the Hall measurement method are used to directly measure the average carrier concentration of the material. By measuring the far-infrared reflection spectrum, the phonon vibration parameters, the plasma oscillation frequency, and the damping constant of the crystal can also be obtained, and the carrier concentration can be obtained therefrom. Among them, the measurement results of the C-V method are affected by factors such as the depletion layer hypothesis, the junction manufacturing technology, and leakage. Both the four-probe method and the Hall measurement method require ohmic contact between the electrode and the standard sample to be measured, and factors such as the size, shape, test current, and probe pressure of the standard sample will bring large errors. Wang Guanghong et al. studied the carrier concentration of n-type 4H- and 6H-SiC crystals through Raman spectroscopy. Raman scattering is a non-destructive research method, and the research results further confirm that for n-type 4H- and 6H-SiC crystals, the carrier concentration of the relevant materials can be accurately given by analyzing the line shape of the LOPC mode. However, the above method directly establishes a curve fitting equation through the plasma frequency and the carrier concentration, and its model is complex and not convenient for rapid analysis and decision-making. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the first object of the present invention is to provide a method for detecting the facets of a SiC ingot, which has the advantages of improving the detection accuracy of the doping concentration of the ingot, being less affected by outliers, and realizing non-destructive and accurate facet detection.

[0008] The second object of the present invention is to provide a method for processing a SiC ingot, which avoids the phenomenon of inconsistent depths and completion of the modified layers of the ingot caused by uneven doping concentrations, and has the advantages of improving processing consistency and reducing material loss of the modified layers.

[0009] To achieve the above first object, the present invention provides the following technical solutions: A method for detecting the facets of a SiC ingot, comprising the following steps, S11 Provide a plurality of silicon carbide standard samples with different doping concentrations n, and obtain the Raman characteristic peak frequencies ω of these standard samples n , make a difference calculation with the Raman characteristic peak frequency ω of one of the standard samples n as a reference, and determine the relative Raman shift Δω, and then establish a Δω-n linear model of the relative Raman shift Δω and the doping concentration n based on the least squares method; S12 Provide a silicon carbide workpiece, and based on a preset Raman detection scanning path, obtain the Raman characteristic peak frequencies ω of different detection points on the surface layer of the workpiece i , detection images, and the XY coordinate positions (X i , Y j ) on the XY plane perpendicular to the height direction of the workpiece, and then determine the doping concentration n through the Δω-n linear modelij and associate these doping concentrations n ij , the detected images, and the corresponding XY coordinate positions to construct a doping concentration distribution map of the surface layer of the workpiece.

[0010] Among them, the Raman characteristic peak frequency ω n where n≥0 in it corresponds to the doping concentration n; i and j are integers ≥0, and their maximum values respectively correspond to the number of detection points in the X and Y directions.

[0011] Furthermore, in the S11, the Raman characteristic peak frequency ω n is obtained by performing Raman detection in the longitudinal optical phonon - plasmon coupling (LOPC) mode.

[0012] Still further, in the S11, provide an undoped silicon carbide standard and multiple silicon carbide standards with other doping concentrations n', and obtain the Raman characteristic peak frequencies ω 0 and ω n' , calculate the difference using the Raman characteristic peak frequencies ω 0 and ω n' , and determine the relative Raman shift Δω, and then establish a Δω - n linear model of the relative Raman shift Δω and the doping concentration n based on the least squares method.

[0013] Still further, in the S11, the detection laser of the Raman detection laser is a continuous laser, the laser wavelength is 450 - 1000 nm, the laser detection power is adjustable from 0 to 500 mW, and the beam quality factor M 2 <1.2, and the wavelength drift <10 pm.

[0014] Even further, in the S11, the fitting function of the Δω - n linear model is n = k 1 Δω + b 1 , k 1 = 1.00×10 17 ~1.50×10 17 , b 1 = 0~1.

[0015] Most further, in the S11, the fitting function of the Δω - n linear model is n = 1.27×10 17 Δω (R = 99%).

[0016] Furthermore, in the S12, after determining the doping concentration n ij through the Δω - n linear model, first associate these doping concentrations n ij , and the corresponding XY coordinate positions into two - dimensional data (X i , Y j, n ij ), and then associate the two-dimensional data (X i , Y j , n ij ) with the detection image to form image data, and construct a doping concentration distribution map of the workpiece surface layer.

[0017] Further, in the S12, the Raman characteristic peak frequency ω ij is obtained by performing Raman detection in the longitudinal optical phonon-plasma coupling (LOPC) mode.

[0018] Still further, in the S12, the detection laser of the Raman detection laser is a continuous laser, the laser wavelength is 450 - 1000 nm, the laser detection power is adjustable from 0 to 500 mW, and the beam quality factor M 2 < 1.2, and the wavelength drift < 10 pm.

[0019] Further, in the S12, obtain the Z-axis coordinate positions (Z ij ) of different detection points on the workpiece surface layer, associate these Z-axis coordinate positions and the corresponding XY coordinate positions, and construct a topography distribution map of the workpiece surface layer.

[0020] To achieve the above second object, the present invention provides the following technical solutions: A processing method for a SiC ingot, including the following steps, S1 provides a silicon carbide workpiece, and constructs a doping concentration distribution map of the workpiece surface layer according to the above-mentioned facet detection method; S2 is based on the doping concentration distribution map obtained in S1 and the n-P curve model between the preset doping concentration n and the laser processing power P, and determines the laser processing power P ij of different detection points on the workpiece surface layer, and associate these laser processing powers P ij , the detection image, and the corresponding XY coordinate positions, and construct a power distribution map of the workpiece modified layer; S3 is based on the power distribution map obtained in S2, focuses the processing laser beam on a predetermined depth of the workpiece for internal modification, and makes the workpiece and the focal point move relative to each other approximately in the XY direction to obtain a silicon carbide workpiece with a modified layer.

[0021] Further, in the S2, the processing laser beam of the processing laser is a pulsed laser, the laser pulse width is 200 fs - 10 ns, the laser wavelength is 400 - 1100 nm, and the laser energy is 0.01 - 1500 mJ.

[0022] Still further, in the S2, the fitting function of the n-P curve model is P = k 2e [n / (1.18×10^18)] + b 2 , k 2 = 0.10 to 1.00, b 2 = 0 to 1.

[0023] Furthermore, in the step S2, the fitting function of the n - P curve model is P = 0.57e [n / (1.18×10^18)] (R = 99%). Among them, the fitting function of the n - P curve model can also be expressed as P = 0.57exp[n / (1.18×10 18 )].

[0024] Furthermore, in the step S3, the relative moving speed between the workpiece and the focal point is 5 to 5000 mm / s.

[0025] Furthermore, in the step S3, the Z - axis coordinate positions (Z ij ) of different detection points on the surface layer of the workpiece are obtained in advance, and these Z - axis coordinate positions and the corresponding XY coordinate positions are associated to construct the topography distribution map of the surface layer of the workpiece, and then the Z - axis coordinate position of the focusing objective lens of the processing laser beam corresponding to different detection points on the surface layer of the workpiece is determined, so that the workpiece and the focal point move relatively approximately in the XY direction.

[0026] In summary, the beneficial technical effects of the present invention are as follows: 1. The small - face detection method of the present invention uses a low - power laser with photon energy far lower than the band - gap energy of silicon carbide to generate Raman signals, and establishes a relationship model between the doping concentration (carrier concentration) and the Raman characteristic peak frequency shift (Raman shift). The Raman shift depends on the change of molecular vibration energy levels and has high specificity. Due to this specificity, the Raman shift is not affected by laser wavelength, energy fluctuation, and background noise. Therefore, by detecting the Raman shift, the doping concentration value of the ingot can be accurately determined, and the interference of background noises such as laser scattered light and fluorescence signals on the Raman characteristic peak can be avoided, realizing non - destructive and accurate measurement; 2. The processing method of the present invention synchronously optimizes the parameters of the processing laser according to the doping concentration at the detection point of the ingot, avoids the phenomenon of inconsistent depth and completion of the modified layer of the ingot caused by uneven doping concentration, improves the peeling quality of the wafer, reduces material loss, and thus improves the overall production efficiency and product quality; 3. The present invention also uses the three - dimensional coordinate positions of the detection points to construct the topography information of the ingot surface, so as to adjust the processing depth in real time according to the topography undulation of the surface layer of the ingot during the laser processing process, that is, to adjust the Z - axis coordinate position of the focusing objective lens of the processing laser beam, so that the workpiece and the focal point move relatively approximately in the XY direction, and finally the processing depth of the wafer tends to be consistent. This method can significantly improve the processing accuracy and quality of the wafer and further improve the production efficiency. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a silicon carbide workpiece according to Embodiment 1 of the present invention.

[0028] Figure 2 It is a Raman spectrogram of two silicon carbide standards with different doping concentrations according to Embodiment 2 of the present invention.

[0029] Figure 3 It is a fitting function graph between the relative Raman frequency shift Δω and the doping concentration n according to Embodiment 2 of the present invention.

[0030] Figure 4 It is a schematic diagram of the Raman detection scanning path of the workpiece surface layer according to Embodiment 3 of the present invention.

[0031] Figure 5 It is a fitting function graph between the doping concentration n and the laser processing power P according to Embodiment 5 of the present invention. Detailed Embodiments

[0032] In order to make the technical means, creative features, achieved purposes and functions of the present invention clearer and easier to understand, the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0033] Embodiment 1: Refer to Figure 1 , a method for detecting the facets of a SiC ingot disclosed in the present invention, includes the following steps S11 Provide a plurality of silicon carbide standards with different doping concentrations n, and obtain the Raman characteristic peak frequencies ω n of these standards. Calculate the difference with the Raman characteristic peak frequency ω n of one of the standards as a reference, and determine the relative Raman frequency shift Δω. Then, based on the least squares method, establish a Δω-n linear model of the relative Raman frequency shift Δω and the doping concentration n; S12 Provide a silicon carbide workpiece. Based on a preset Raman detection scanning path, obtain the Raman characteristic peak frequencies ω i of different detection points on the workpiece surface layer, the detection images, and the XY coordinate positions (X i , Y j ) on the XY plane perpendicular to the height direction of the workpiece. Then, determine the doping concentration n ij through the Δω-n linear model, and associate these doping concentrations n ij , the detection images, and the corresponding XY coordinate positions to construct a doping concentration distribution map of the workpiece surface layer.

[0034] The present invention also discloses a method for processing a SiC ingot, including the following steps S1 provides a silicon carbide workpiece and constructs a doping concentration distribution map of the workpiece surface layer according to the above-mentioned facet detection method; S2 determines the laser processing power P of different detection points on the workpiece surface layer based on the doping concentration distribution map obtained in S1 and the n-P curve model between the preset doping concentration n and the laser processing power P, ij and associates these laser processing powers P ij with the detection images and the corresponding XY coordinate positions to construct a power distribution map of the workpiece modified layer; S3 performs internal modification by focusing the processing laser beam on a predetermined depth of the workpiece based on the power distribution map obtained in S2, and relatively moves the workpiece and the focal point approximately in the XY direction to obtain a silicon carbide workpiece with a modified layer.

[0035] Example 2: Refer to Figure 2 and Figure 3 , which is a facet detection method for a SiC ingot disclosed by the present invention. The difference from Example 1 is that in S11, an undoped silicon carbide standard and multiple silicon carbide standards with other doping concentrations n' are provided, and Raman detection is performed in the longitudinal optical phonon-plasma coupling (LOPC) mode to obtain the Raman characteristic peak frequencies ω 0 and ω n' of these standards. The difference between the Raman characteristic peak frequencies ω 0 and ω n' is calculated, and the relative Raman shift Δω is determined. Furthermore, a Δω-n linear model between the relative Raman shift Δω and the doping concentration n is established based on the least squares method, and its fitting function is n = 1.27×10 17 Δω (R = 99%). Among them, the detection laser of the Raman detection laser is a continuous laser, the laser wavelength is 450-1000 nm, the laser detection power is adjustable from 0 to 500 mW, and the beam quality factor M 2 < 1.2, and the wavelength drift < 10 pm.

[0036] Example 3: Refer to Figure 4 , which is a facet detection method for a SiC ingot disclosed by the present invention. The difference from Example 2 is that in S12, a silicon carbide workpiece is provided, and based on the preset Raman detection scanning path I→II→III→IV→V→VI→VII→VIII→IX, the Raman characteristic peak frequencies ω i , the detection images, and the XY coordinate positions (X i , Y j ) on the XY plane perpendicular to the height direction of the workpiece are obtained. Furthermore, after determining the doping concentration n ij through the Δω-n linear model, these doping concentrations n ij, and associated with the corresponding XY coordinate positions to form two-dimensional data (X i , Y j , n ij ). Then, the two-dimensional data (X i , Y j , n ij ) is associated with the detected image to form image data, and a doping concentration distribution map of the workpiece surface layer is constructed. Among them, the detection laser of the Raman detection laser is a continuous laser, the laser wavelength is 450 - 1000 nm, the laser detection power is adjustable from 0 to 500 mW, the beam quality factor M 2 < 1.2, and the wavelength drift < 10 pm.

[0037] Example 4: A method for detecting facets of a SiC ingot disclosed by the present invention. The difference from Example 3 is that in S12, the Z-axis coordinate positions (Z ij ) of different detection points on the workpiece surface layer are obtained, and these Z-axis coordinate positions and the corresponding XY coordinate positions are associated to form three-dimensional data (X i , Y j , Z ij ), and a topography distribution map of the workpiece surface layer is constructed.

[0038] Example 5: Referring to Figure 5 , a method for processing a SiC ingot disclosed by the present invention. The difference from Example 4 is that in S2, based on the doping concentration distribution map obtained in S1 and the n - P curve model between the preset doping concentration n and the laser processing power P, whose fitting function is P = 0.57e [n / (1.18×10^18)] (R = 99%), the laser processing power P ij of different detection points on the workpiece surface layer is determined, and these laser processing powers P ij , the detected image, and the corresponding XY coordinate positions are associated to construct a power distribution map of the workpiece modified layer (X i , Y j , P ij ). Among them, the processing laser beam of the processing laser is a pulsed laser, the laser pulse width is 200 fs - 10 ns, the laser wavelength is 400 - 1100 nm, and the laser energy is 0.01 - 1500 mJ.

[0039] Example 6: A method for processing a SiC ingot disclosed by the present invention. The difference from Example 5 is that in S3, based on the topography distribution map obtained in S1 and the power distribution map obtained in S2, the processing laser beam is focused on a predetermined depth d of the workpiece for internal modification, not only guiding the processing laser beam to move along a fixed scanning path in the XY plane with optimal laser parameters, but also determining the focusing objective Z-axis coordinate positions of the processing laser beam corresponding to different detection points on the workpiece surface layer for real-time adjustment (Xi ,Y j ,Z ij ,P ij ), so that the workpiece and the focus approximately move relative to each other in the XY direction, that is, the processing laser beam is always focused at the d depth and forms modified particles along a fixed scanning path, and finally a silicon carbide workpiece with a modified layer is obtained.

[0040] Taking multiple detection points (from left to right) on a straight line passing through the facet region as an example, the two-dimensional data corresponding to the doping concentration distribution map obtained according to Embodiment 3 and the power distribution map obtained according to Embodiment 5 are shown in Table 1 below.

[0041] Table 1 Detection position <![CDATA[XY coordinate position (X i , Y j )]]> <![CDATA[Raman characteristic peak frequency ω ij (cm -1 )]]> <![CDATA[Relative Raman frequency shift Δω(ω 0 = 964 cm -1 )]]> <![CDATA[Doping concentration n (×10 17 cm -3 )]]> Processing laser power (W) Non-faceted area <![CDATA[X 1 ,Y 1 > 980.79 16.69 21.20 3.51 Faceted area <![CDATA[X 2 ,Y 1 > 982.18 18.08 22.96 4.03 Faceted area <![CDATA[X 3 ,Y 1 > 984.07 19.97 25.36 4.89 Faceted area <![CDATA[X 4 ,Y 1 > 983.03 18.93 24.04 4.45 Non-faceted area <![CDATA[X 5 ,Y 1 > 981.32 17.22 21.87 3.71 Non-faceted area <![CDATA[X 6 ,Y 1 > 981.37 17.27 21.93 3.73 Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for detecting a small face of a SiC ingot, characterized in that: The following steps are included: S11 provides multiple silicon carbide standards with different doping concentrations n, and obtains the Raman characteristic peak frequencies ω of these standards. n , taking the Raman characteristic peak frequency ω of one of the standards n The difference is calculated as the reference, and the relative Raman frequency shift Δω is determined, and then a Δω-n linear model of the relative Raman frequency shift Δω and the doping concentration n is established based on the least square method; S12 provides a silicon carbide workpiece, and obtains the Raman characteristic peak frequency ω of different detection points on the surface layer of the workpiece based on a preset Raman detection scanning path. i , the detection image, and the XY coordinate position (X i , Y j ), and then determine the doping concentration n through the Δω-n linear model ij , and these doping concentrations n ij , the detection image, and the corresponding XY coordinate positions to construct a doping concentration distribution map of the surface layer of the workpiece.

2. A method for detecting a small facet of a SiC ingot according to claim 1, characterized in that: In S11, the Raman characteristic peak frequency ω n Obtained by Raman detection in longitudinal optical phonon-plasmon coupling mode.

3. A method for detecting a small facet of a SiC ingot according to claim 2, characterized in that: In the step S11, an undoped silicon carbide standard product and a plurality of silicon carbide standards with other doping concentrations n' are provided, and the Raman characteristic peak frequencies ω0 and ω1 of these standards are obtained. n' , with Raman characteristic peak frequencies ω0 and ω n' The difference calculation is performed and the relative Raman frequency shift Δω is determined, and then a Δω-n linear model of the relative Raman frequency shift Δω and the doping concentration n is established based on the least squares method.

4. A method for detecting a small facet of a SiC ingot according to claim 2, characterized in that: In S11 and S12, the detection laser of the Raman detection laser is a continuous laser with a laser wavelength of 450-1000 nm, a laser detection power adjustable between 0 and 500 mW, and a beam quality factor M 2 <1.2, wavelength drift <10pm.

5. A method for detecting a small facet of a SiC ingot according to claim 4, characterized in that: In S11, the fitting function of the Δω-n linear model is n=k1Δω+b1, k1=1.00×10 17 ~1.50×10 17 , b1=0~1.

6. A method for processing a SiC ingot, characterized in that: The following steps are included: S1 provides a silicon carbide workpiece, and constructs a doping concentration distribution map of the surface layer of the workpiece according to the small face detection method described in any one of claims 1 to 5; S2 determines the laser processing power P at different detection points on the surface layer of the workpiece based on the doping concentration distribution diagram obtained in S1 and the nP curve model between the preset doping concentration n and the laser processing power P. ij , and these laser processing powers P ij , the detection image, and the corresponding XY coordinate position to construct a power distribution diagram of the modified layer of the workpiece; S3 focuses the processing laser beam on a predetermined depth of the workpiece based on the power distribution diagram obtained in S2 to perform internal modification, and makes the workpiece and the focus point move relatively in the XY direction approximately to obtain a silicon carbide workpiece with a modified layer.

7. A method for processing a SiC ingot according to claim 6, characterized in that: In S2, the processing laser beam of the processing laser is a pulse laser, the laser pulse width is 200fs~10ns, the laser wavelength is 400~1100nm, and the laser energy is 0.01~1500mJ.

8. A method for processing a SiC ingot according to claim 7, characterized in that: In S2, the fitting function of the nP curve model is P=k2e [n / (1.18×10^18)] +b2, k2=0.10~1.00, b2=0~1.

9. A method for processing a SiC ingot according to claim 6, characterized in that: In S3, the relative moving speed between the workpiece and the focal point is 5-5000 mm / s.

10. The method for processing a SiC ingot according to claim 6, characterized in that: In S3, the Z-axis coordinate positions (Z ij ), these Z-axis coordinate positions and the corresponding XY coordinate positions are associated to construct a morphology distribution map of the workpiece surface layer, and then the Z-axis coordinate position of the focusing objective lens of the processing laser beam corresponding to different detection points on the workpiece surface layer is determined, so that the workpiece and the focusing point can be moved relative to each other approximately in the XY direction.

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