Method for measuring depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method

Abstract

The invention relates to the technical field of epitaxial wafer growth, in particular to a method for measuring 4H-SiC epitaxial layer doping concentration depth distribution through an Hg-CV probe method, and the method comprises the steps: determining the relation of the measurement depth along with the change of a bias voltage for a finished 4H-SiC epitaxial wafer, and determining the bias voltage; the 4H-SiC epitaxial layer to be measured is divided into n measurement areas from top to bottom in sequence, and the thickness of each measurement area is the measurement depth corresponding to the determined bias voltage; n substrates are prepared and named in sequence; sequentially growing epitaxial layers of which the film thickness is the thickness of the measurement area of the mark number on the substrate according to the mark number of the substrate, and carrying out Hg-CV characterization to obtain depth distribution; overlapping doping concentration depth distribution results represented by Hg-CV on all substrates to obtain a complete depth distribution curve of the whole epitaxial layer; and comparing and verifying the overlapping and splicing result with an SIMS test result. According to the invention, the doping concentration distribution of the epitaxial layer can be detected in real time on a common epitaxial factory line.

Description

Technical Field

[0001] The invention relates to the technical field of epitaxial wafer growth, and in particular to a method for measuring the depth distribution of doping concentration of a 4H-SiC epitaxial layer by a Hg-CV probe method. Background Art

[0002] As one of the two heroes of the third-generation semiconductor materials, silicon carbide has been industrialized in the field of power devices and has even become the hottest "new darling" in the entire industry. Looking at the domestic and international silicon carbide material industry chain, new construction, expansion, and production projects are emerging in an endless stream.

[0003] The epitaxial link is crucial in the entire silicon carbide power device industry chain. It is like a bridge that connects the substrate material and the chip manufacturing process. The conventional characterization parameters of 4H-SiC homoepitaxial wafers mainly include: defects, film thickness, doping concentration, surface roughness, surface shape (surface flatness) and other characterization techniques, such as: SIMS (secondary ion mass spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), etc. The characterization method of doping concentration usually uses a Hg-CV probe, and the commonly used equipment is Semilab's MCV 530, MCV 2200, and CnCV (non-contact equipment). The test equipment automatically calculates the epitaxial doping concentration in the depletion region based on the CV test curve of the sample, and gives the depth distribution of the doping concentration with the film thickness.

[0004] The Hg-CV method is very convenient to measure the doping concentration of the 4H-SiC epitaxial layer and will not damage the sample. However, this concentration test method also has certain limitations. When the bias voltage is set at -5V~-20V, the Hg-CV method can only characterize the doping concentration distribution of the surface layer at a depth of about 1.6um. The thickness of the commonly used epitaxial layer is 5um-12um. The conventional Hg-CV test cannot achieve the characterization of the doping concentration depth distribution of the entire epitaxial layer. That is, under the bias voltage that the test system can provide, the depletion layer depth is limited, and it is difficult to achieve the accurate measurement of the longitudinal distribution of the doping concentration of the complete epitaxial layer with the thickness. SIMS (secondary ion mass spectrometry) is required. The SIMS method can achieve the depth distribution characterization of the doping concentration of the entire structure of the epitaxial layer with the change of film thickness. However, this method also has certain limitations, such as: 1) destructive testing, 2) expensive equipment and high testing costs, 3) it is impossible to perform real-time testing on the production line, and it is generally outsourced to a third-party testing agency.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0006] The first object of the present invention is to provide a non-destructive, convenient and practical method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method, so as to overcome the shortcomings of the existing Hg-CV method and SIMS test.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: A method for measuring the depth distribution of doping concentration of a 4H-SiC epitaxial layer using a Hg-CV probe method comprises the following steps: S01: For the finished 4H-SiC epitaxial wafer, single-point measurement is performed under different bias conditions to determine the relationship between the measurement depth and the bias voltage, and the bias voltage is determined based on the measurement results; As a preferred embodiment, in step S01, a film with a thickness of 10 um and a doping concentration of 1.0E16 atoms / cm 3 The 4H-SiC epitaxial wafer is measured at a single point under different bias conditions; among them, when the Hg-CV bias is -5~-20 V, the measurement depth is 1.5 um; when the Hg-CV bias is -5~-50 V, the measurement depth is 2.3 um; when the Hg-CV bias is -5~-100 V, the measurement depth is 3.2 um; when the Hg-CV bias is -5~-150 V, the measurement depth is 3.7 um; when the Hg-CV bias is -5~-200 V, the measurement depth is 3.8 um. It can be seen that within the bias range of -5~-150 V, the measurement depth gradually increases from 1.5 um to 3.7 um. When the bias continues to increase to -200 V, the measurement depth does not change significantly, so the subsequent steps of the present invention adopt the Hg-CV bias setting of -5~-150 V.

[0008] Preferably, in step S01, the relationship between the measured depth and the bias voltage is: y=−0.0001x 2 −0.0337x+0.8728; Where y is the measurement depth in µm and x is the Hg-CV bias in V.

[0009] S02: Divide the 4H-SiC epitaxial layer to be measured into N measurement areas from top to bottom, where N is an integer greater than 2; the thickness of each measurement area is the measurement depth corresponding to the bias voltage determined in step S01; the sum of the thicknesses of the N measurement areas is the thickness of the 4H-SiC epitaxial layer to be measured; Furthermore, the thickness of each measurement area should not exceed the effective measurement depth of Hg-CV to ensure the accuracy of the doping concentration of each layer. Preferably, in step S02, the thickness of the 4H-SiC epitaxial layer to be measured is 10.5 µm, the bias voltage is determined to be -5~-150 V, and the 4H-SiC epitaxial layer to be measured is divided into three measurement areas from top to bottom.

[0010] S03: preparing N substrates, which are named substrate 1, substrate 2, ... substrate n in sequence; Preferably, in step S03, three substrates are prepared, which are named substrate 1, substrate 2, and substrate 3 respectively.

[0011] S04: growing an epitaxial layer having a thickness of 1 portion of the thickness of the measuring area on substrate 1 and performing Hg-CV characterization to obtain a depth distribution, growing an epitaxial layer having a thickness of 2 portions of the thickness of the measuring area on substrate 2 and performing Hg-CV characterization to obtain a depth distribution, ... growing an epitaxial layer having a thickness of N portions of the thickness of the measuring area on substrate n and performing Hg-CV characterization to obtain a depth distribution; In this step, when growing epitaxial layers of different thicknesses on different substrates, the growth parameters (temperature, pressure, reaction gas flow) of each layer are exactly the same, ensuring that the surface characteristics of each layer (such as doping uniformity, defect density, etc.) are relatively consistent, reducing test errors.

[0012] Preferably, in step S04, a film with a thickness of 3.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on the substrate 1. 3 The epitaxial layer 1 is characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 1 from top to bottom to a depth of 3.5 µm.

[0013] Preferably, in step S04, a film with a thickness of 7 μm and a doping concentration of 1.0E16 atoms / cm is grown on the substrate 2. 3 The epitaxial layer 2 was characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 2 from top to bottom to a depth of 3.5 µm.

[0014] Preferably, in step S04, a film with a thickness of 10.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on the substrate 3. 3 The epitaxial layer 3 is characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 3 from top to bottom to a depth of 3.5 µm.

[0015] In this step, the bias voltage measured for each substrate is unified to ensure that the test results of epitaxial layers of different thicknesses are superimposable under the same measurement conditions.

[0016] S05: superimposing the doping concentration depth distribution results characterized by Hg-CV on the substrate 1, substrate 2, ... substrate n to obtain a complete depth distribution curve of the entire epitaxial layer; Preferably, in step S05, when data is spliced, the measurement results of each substrate need to be depth aligned and spliced ​​segment by segment. The measurement range of each layer should start from the surface of the layer and end at its corresponding measurement depth. When splicing, the results of multiple substrates are superimposed layer by layer according to the depth, and the doping concentration data of each layer is seamlessly connected. Specifically, the doping concentration depth distribution result of substrate 1 is used as the initial part, and the doping concentration depth distribution results on substrates 2 and 3 are sequentially spliced ​​as independent data segments according to the depth to generate a complete curve of doping concentration changing with thickness. At different depth points, the depth corresponding to each measurement point needs to be accurately marked.

[0017] In this step, the boundary between the epitaxial layer thickness and the measured depth of each substrate needs special processing. When stitching data, some boundary areas may have large measurement errors (for example, inaccurate concentration at the depth boundary of a layer). During the stitching process, smoothing algorithms such as Spline interpolation and linear interpolation can be used to smooth the stitching points between different layers to eliminate jumps caused by small measurement differences between different substrates.

[0018] Epitaxial layers of different thicknesses are grown on multiple substrates, and the growth and measurement process of each substrate is independent, avoiding the problems of interlayer diffusion and interface effects. The thickness and doping distribution of the epitaxial layer on each substrate are more controllable, and there is no influence of interlayer materials or interfaces, which provides a more stable foundation for subsequent data splicing.

[0019] S06: Compare the stacking results with the SIMS test results to verify the accuracy and consistency of the method.

[0020] Preferably, in step S06, the stitched data needs to be compared with known high-precision test results such as SIMS to calibrate the data accuracy; if there is an obvious deviation, it is adjusted by adjusting the test or stitching parameters until the stitching curve accurately reflects the depth distribution of the actual doping concentration.

[0021] In summary, the present invention has the following beneficial effects: (1) The present invention uses the Hg-CV probe method to replace the traditional SIMS (secondary ion mass spectrometry) measurement method. The Hg-CV probe method is combined with the step-by-step measurement of multiple substrates to effectively solve the problem that a single Hg-CV test cannot cover the depth distribution of thick epitaxial layers. Through reasonable bias setting and data splicing, a complete doping concentration depth distribution curve is obtained, thereby achieving high-precision measurement results. The doping concentration distribution of the epitaxial layer can be detected in real time on a general epitaxial plant line. This not only simplifies the detection process, but also reduces the expensive cost of third-party SIMS detection, greatly reducing production costs.

[0022] (2) The present invention divides the epitaxial layer into regions of different thicknesses during measurement, and independently grows and tests on multiple substrates at the same time, thus avoiding the complexity of multiple growth and measurement of a single substrate. This makes the overall process more efficient, and the accuracy and consistency of the data can be verified by comparing and calibrating the spliced ​​measurement results with high-precision test results such as SIMS. This ensures the reliability of the measurement and provides a basis for subsequent data correction, ensuring the physical consistency and accuracy of the final measurement results.

[0023] (3) The present invention flexibly adjusts the bias voltage and the thickness of the measurement area according to the thickness of the epitaxial layer, and has high adjustability and adaptability. This flexibility makes the solution suitable for epitaxial layer detection requirements of different thicknesses, doping concentrations and target processes, and can be applied to thicker epitaxial layer measurements, with good scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments in the records of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The doping concentration depth curve of the 4H-SiC epitaxial layer under the bias setting of -5 to -20 V in step S01 of the present invention; Figure 2 The doping concentration depth curve of the 4H-SiC epitaxial layer under the bias setting of -5 to -50 V in step S01 of the present invention; Figure 3 The doping concentration depth curve of the 4H-SiC epitaxial layer under the bias setting of -5 to -100 V in step S01 of the present invention; Figure 4 The doping concentration depth curve of the 4H-SiC epitaxial layer under the bias setting of -5 to -150 V in step S01 of the present invention; Figure 5The doping concentration depth curve of the 4H-SiC epitaxial layer under the bias setting of -5 to -200 V in step S01 of the present invention; Figure 6 Schematic diagram of epitaxial layer growth and characterization in step S04 of an embodiment of the present invention; Figure 7 The doping concentration depth distribution result measured by Hg-CV on the epitaxial layer 1 in step S04 of the embodiment of the present invention; Figure 8 The doping concentration depth distribution result measured by Hg-CV on the epitaxial layer 2 in step S04 of the embodiment of the present invention; Fig. 9 The doping concentration depth distribution result measured by Hg-CV on the epitaxial layer 3 in step S04 of the embodiment of the present invention; Fig.10 The depth distribution of doping concentration of the 4H-SiC epitaxial layer obtained by stacking by the Hg-CV method of the present invention; Fig.11 The SIMS method is used in the comparative example to obtain the depth distribution of doping concentration of the 4H-SiC epitaxial layer. DETAILED DESCRIPTION

[0026] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a method for measuring the depth distribution of doping concentration of a 4H-SiC epitaxial layer by a Hg-CV probe method proposed in the present invention, its specific implementation method, characteristics and effects are described in detail as follows.

[0027] A method for measuring the depth distribution of doping concentration of a 4H-SiC epitaxial layer using a Hg-CV probe method comprises the following steps: S01: For the finished 4H-SiC epitaxial wafer, single-point measurement is performed under different bias conditions to determine the relationship between the measurement depth and the bias voltage, and the bias voltage is determined based on the measurement results; like Figures 1 to 5 As shown, in step S01, a film with a thickness of 10 um and a doping concentration of 1.0E16 atoms / cm 3The 4H-SiC epitaxial wafer is measured at a single point under different bias conditions; among them, when the Hg-CV bias is -5~-20 V, the measurement depth is 1.5 um; when the Hg-CV bias is -5~-50 V, the measurement depth is 2.3 um; when the Hg-CV bias is -5~-100 V, the measurement depth is 3.2 um; when the Hg-CV bias is -5~-150 V, the measurement depth is 3.7 um; when the Hg-CV bias is -5~-200 V, the measurement depth is 3.8 um. It can be seen that within the bias range of -5~-150 V, the measurement depth gradually increases from 1.5 um to 3.7 um. When the bias continues to increase to -200 V, the measurement depth does not change significantly, so the subsequent steps of the present invention adopt the Hg-CV bias setting of -5~-150 V.

[0028] Preferably, in step S01, the relationship between the measured depth and the bias voltage is: y=−0.0001x 2 −0.0337x+0.8728; Where y is the measurement depth in µm and x is the Hg-CV bias in V.

[0029] S02: Divide the 4H-SiC epitaxial layer to be measured into N measurement areas from top to bottom, where N is an integer greater than 2; the thickness of each measurement area is the measurement depth corresponding to the bias voltage determined in step S01; the sum of the thicknesses of the N measurement areas is the thickness of the 4H-SiC epitaxial layer to be measured; Further, the thickness of each measurement area should not exceed the effective measurement depth of Hg-CV to ensure the accuracy of the doping concentration of each layer. Preferably, in step S02, the thickness of the 4H-SiC epitaxial layer to be measured is 10.5 μm, the bias voltage is determined to be -5~-150 V, and the 4H-SiC epitaxial layer to be measured is divided into 3 measurement areas from top to bottom. The present invention divides the epitaxial layer into regions of different thicknesses during measurement, and independently grows and tests multiple substrates at the same time, thereby avoiding the complexity of multiple growths and measurements of a single substrate. The overall process is made more efficient, and the accuracy and consistency of the data can be verified by comparing and calibrating the spliced ​​measurement results with high-precision test results such as SIMS. The reliability of the measurement is guaranteed, and a basis is provided for subsequent data correction to ensure the physical consistency and accuracy of the final measurement results.

[0030] S03: preparing N substrates, which are named substrate 1, substrate 2, ... substrate n in sequence; Preferably, in step S03, three substrates are prepared, which are named substrate 1, substrate 2, and substrate 3 respectively.

[0031] S04: growing an epitaxial layer having a thickness of 1 portion of the thickness of the measuring area on substrate 1 and performing Hg-CV characterization to obtain a depth distribution, growing an epitaxial layer having a thickness of 2 portions of the thickness of the measuring area on substrate 2 and performing Hg-CV characterization to obtain a depth distribution, ... growing an epitaxial layer having a thickness of N portions of the thickness of the measuring area on substrate n and performing Hg-CV characterization to obtain a depth distribution; like Figure 6~Figure 9 As shown, in this step, when epitaxial layers of different thicknesses are grown on different substrates, the growth parameters (temperature, pressure, reaction gas flow) of each layer are exactly the same, ensuring that the surface characteristics of each layer (such as doping uniformity, defect density, etc.) are consistent, thereby reducing test errors.

[0032] Specific as Figure 7 As shown, in step S04, a film with a thickness of 3.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on substrate 1. 3 The epitaxial layer 1 is characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 1 from top to bottom to a depth of 3.5 µm.

[0033] like Figure 8 As shown, in step S04, a film with a thickness of 7 μm and a doping concentration of 1.0E16 atoms / cm is grown on substrate 2. 3 The epitaxial layer 2 was characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 2 from top to bottom to a depth of 3.5 µm.

[0034] like Fig. 9 As shown, in step S04, a film with a thickness of 10.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on the substrate 3. 3 The epitaxial layer 3 is characterized by Hg-CV to obtain the doping distribution of the epitaxial layer 3 from top to bottom to a depth of 3.5 µm.

[0035] In this step, the bias voltage measured for each substrate is unified to ensure that the test results of epitaxial layers of different thicknesses are superimposable under the same measurement conditions.

[0036] S05: Fig.10 As shown, the Hg-CV doping concentration depth distribution results on the substrate 1, substrate 2, ... substrate n are superimposed to obtain a complete depth distribution curve of the entire epitaxial layer; Preferably, in step S05, when data is spliced, the measurement results of each substrate need to be depth aligned and spliced ​​segment by segment. The measurement range of each layer should start from the surface of the layer and end at its corresponding measurement depth. When splicing, the results of multiple substrates are superimposed layer by layer according to the depth, and the doping concentration data of each layer is seamlessly connected. Specifically, the doping concentration depth distribution result of substrate 1 is used as the initial part, and the doping concentration depth distribution results on substrates 2 and 3 are sequentially spliced ​​as independent data segments according to the depth to generate a complete curve of doping concentration changing with thickness. At different depth points, the depth corresponding to each measurement point needs to be accurately marked.

[0037] In this step, the boundary between the epitaxial layer thickness and the measured depth of each substrate needs special processing. When stitching data, some boundary areas may have large measurement errors (for example, inaccurate concentration at the depth boundary of a layer). During the stitching process, smoothing algorithms such as Spline interpolation and linear interpolation can be used to smooth the stitching points between different layers to eliminate jumps caused by small measurement differences between different substrates.

[0038] Epitaxial layers of different thicknesses are grown on multiple substrates, and the growth and measurement process of each substrate is independent, avoiding the problems of interlayer diffusion and interface effects. The thickness and doping distribution of the epitaxial layer on each substrate are more controllable, and there is no influence of interlayer materials or interfaces, which provides a more stable foundation for subsequent data splicing.

[0039] S06: Compare the stacking results with the SIMS test results to verify the accuracy and consistency of the method.

[0040] like Fig.10 and Fig.11 In step S06, the spliced ​​data needs to be compared with known high-precision test results such as SIMS to calibrate the data accuracy; if there is an obvious deviation, it is adjusted by adjusting the test or splicing parameters until the splicing curve accurately reflects the depth distribution of the actual doping concentration.

[0041] The present invention uses the Hg-CV probe method to replace the traditional SIMS (secondary ion mass spectrometry) measurement method, and adopts the Hg-CV probe method combined with the step-by-step measurement of multiple substrates, which can effectively solve the problem that a single Hg-CV test cannot cover the depth distribution of thick epitaxial layers. Through reasonable bias setting and data splicing, a complete doping concentration depth distribution curve is obtained, thereby achieving high-precision measurement results. The doping concentration distribution of the epitaxial layer can be detected in real time on a general epitaxial plant line. This not only simplifies the detection process, but also reduces the expensive cost of third-party SIMS detection, greatly reducing production costs.

[0042] The present invention can flexibly adjust the bias voltage and the thickness of the measurement area according to the thickness of the epitaxial layer, and has high adjustability and adaptability. This flexibility makes the solution suitable for epitaxial layer detection requirements of different thicknesses, doping concentrations and target processes, and can be applied to thicker epitaxial layer measurements, with good scalability.

[0043] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for measuring the depth distribution of doping concentration of a 4H-SiC epitaxial layer using a Hg-CV probe method, characterized in that: The steps include: S01: For the finished 4H-SiC epitaxial wafer, single-point measurement is performed under different bias conditions to determine the relationship between the measurement depth and the bias voltage, and the bias voltage is determined based on the measurement results; S02: Divide the 4H-SiC epitaxial layer to be measured into N measurement areas from top to bottom, where N is an integer greater than 2; the thickness of each measurement area is the measurement depth corresponding to the bias voltage determined in step S01; the sum of the thicknesses of the N measurement areas is the thickness of the 4H-SiC epitaxial layer to be measured; S03: prepare N substrates, which are named substrate 1, substrate 2, ... substrate n in sequence; S04: growing an epitaxial layer having a thickness of 1 portion of the thickness of the measuring area on substrate 1 and performing Hg-CV characterization to obtain a depth distribution, growing an epitaxial layer having a thickness of 2 portions of the thickness of the measuring area on substrate 2 and performing Hg-CV characterization to obtain a depth distribution, ... growing an epitaxial layer having a thickness of N portions of the thickness of the measuring area on substrate n and performing Hg-CV characterization to obtain a depth distribution; S05: superimposing the Hg-CV doping concentration depth distribution results on the substrate 1, substrate 2, ... substrate n to obtain a complete depth distribution curve of the entire epitaxial layer; S06: Compare the stacking results with the SIMS test results to verify the accuracy and consistency of the method.

2. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 1, characterized in that: In step S01, a film with a thickness of 10 um and a doping concentration of 1.0E16 atoms / cm is selected. 3 The 4H-SiC epitaxial wafer was measured at different bias conditions. When the Hg-CV bias was -5~-20 V, the measurement depth was 1.5 um. When the Hg-CV bias was -5~-50 V, the measurement depth was 2.3 um. When the Hg-CV bias was -5~-100 V, the measurement depth was 3.2 um. When the Hg-CV bias was -5~-150 V, the measurement depth was 3.7 um. When the Hg-CV bias was -5~-200 V, the measurement depth was 3.8 um.

3. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 2, characterized in that: In step S01, the relationship between the measured depth and the bias voltage is: y=−0.0001x 2 −0.0337x+0.8728; Where y is the measurement depth in µm and x is the Hg-CV bias in V.

4. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 2, characterized in that: In step S02, the thickness of the 4H-SiC epitaxial layer to be measured is 10.5 µm, the bias voltage is determined to be -5~-150 V, and the 4H-SiC epitaxial layer to be measured is divided into three measurement areas from top to bottom.

5. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 4, characterized in that: In step S03, three substrates are prepared, which are named substrate 1, substrate 2, and substrate 3 respectively.

6. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 5, characterized in that: In step S04, a film with a thickness of 3.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on substrate 1. 3 The epitaxial layer was characterized by Hg-CV to obtain the doping profile of the epitaxial layer from top to bottom to a depth of 3.5 µm.

7. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 6, characterized in that: In step S04, a film with a thickness of 7 μm and a doping concentration of 1.0E16 atoms / cm is grown on substrate 2. 3 The epitaxial layer was characterized by Hg-CV to obtain the doping profile of the epitaxial layer from top to bottom to a depth of 3.5 µm.

8. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 7, characterized in that: In step S04, a film with a thickness of 10.5 μm and a doping concentration of 1.0E16 atoms / cm is grown on substrate 3. 3 The epitaxial layer was characterized by Hg-CV to obtain the doping profile of the epitaxial layer from top to bottom to a depth of 3.5 µm.

9. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 8, characterized in that: In step S05, the doping concentration depth distribution result of substrate 1 is taken as the initial part, and the doping concentration depth distribution results on substrate 2 and substrate 3 are sequentially spliced ​​as independent data segments according to depth to generate a complete curve of doping concentration changing with thickness.

10. The method for measuring the depth distribution of doping concentration of 4H-SiC epitaxial layer by Hg-CV probe method according to claim 9, characterized in that: In step S06, the stitched data needs to be compared with known high-precision test results such as SIMS to calibrate the data accuracy; if there is an obvious deviation, it is adjusted by adjusting the test or stitching parameters until the stitching curve accurately reflects the depth distribution of the actual doping concentration.

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