A method for measuring the thickness accuracy of diamond epitaxial layer growth based on weighing method

Abstract

A method for measuring the thickness accuracy of diamond epitaxial layer growth based on a weighing method. The purpose of the present invention is to solve the problem that existing diamond thin drift layer measurement methods are difficult to accurately evaluate the thickness and growth rate of diamond epitaxial thin layers. Measurement method: 1. Polish the diamond substrate; 2. Place the polished diamond substrate in a strong oxidizing mixed acid to form an oxygen terminal, and then perform ultrasonic cleaning; 3. Use a high-precision balance to measure the weight of the diamond substrate and use a vernier caliper to measure the surface area of ​​the diamond substrate; 4. Clean the surface again; 5. Epitaxially grow a single crystal diamond layer on the surface of the diamond substrate; 6. Clean the surface three times; 7. Calculate the thickness of the epitaxially grown single crystal diamond layer. The present invention uses a high-precision balance to characterize and measure the thickness of the diamond epitaxial growth layer, which can achieve the measurement and control of ultra-thin diamond layers. The high-precision balance can achieve the measurement of ultra-thin diamond layers without damage and simply.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor power devices, and in particular relates to a method for measuring the thickness accuracy of a diamond epitaxial layer growth based on a weighing method. Background Art

[0002] Diamond has excellent electrical properties. The band gap width of diamond (5.47eV) is 5 times that of silicon (Si), and is also higher than other wide band gap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN). It has a low intrinsic carrier concentration (~10 -27 cm -3 ) and high breakdown field strength (10MV / cm); In addition, diamond has extremely high thermal conductivity (22W / cm·K), which is the semiconductor material with the highest thermal conductivity known so far. It has great application prospects in high temperature, high power and ultra-high voltage environments; Diamond also has high carrier mobility and hole mobility (3800cm 2 / Vs) and electron mobility (4500cm 2 / Vs) is also far higher than other semiconductor materials, leading to diamond being hailed as the "ultimate semiconductor." The rapid development of synthetic diamond, particularly the technology for growing diamond using microwave plasma chemical vapor deposition (MPCVD), has promoted its application in electronic devices. Before electronic devices can be fabricated using diamond, a high-quality functional layer must be epitaxially grown on its surface. The thickness of the drift layer, formed by this diamond epitaxial layer, is a key factor affecting the performance of diamond semiconductor electronic devices. The drift layer thickness typically ranges from tens of nanometers to tens of microns, making timely and accurate measurement of diamond growth thickness and growth rate particularly important. Through investigation, it was found that in current device research, thin diamond drift layers are usually grown according to long-term growth parameters in the literature, and the drift layer thickness is estimated based on the growth rate of known growth parameters. However, the drift layer growth is concentrated in the initial growth period of 10min-120min. Obviously, it is impossible to accurately obtain the drift layer thickness by estimating the long-term growth parameters. The drift layer thickness is mainly measured using a screw micrometer or a vernier caliper. Such methods have large errors and it is difficult to measure the drift layer thickness below 1μm. Alternatively, a Kelvin probe force microscope (KPFM) is used to measure the potential distribution of the diamond longitudinal section and the sample surface, and to determine the diamond epitaxial layer thickness based on the potential mutation point. This method is complex and costly, and can only measure the diamond epitaxial layer doped with heavy phosphorus (P). Currently known measurement methods cannot accurately evaluate the thickness and growth rate of diamond epitaxial thin layers. As a result, the growth thickness of diamond is difficult to precisely control, and the electrical properties of diamond devices are difficult to stabilize and regulate. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem that the existing diamond thin drift layer measurement method is difficult to accurately evaluate the diamond epitaxial thin layer thickness and growth rate, and it is difficult to use a spiral micrometer to measure the drift layer thickness below 1μm. Instead, a simple, easy-to-use, non-destructive testing method is provided to measure the thickness of the diamond thin epitaxial layer through a high-precision balance weighing method.

[0004] The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method of the present invention is implemented by the following steps:

[0005] Step 1: Surface smoothing:

[0006] polishing the surface of the diamond substrate to obtain a polished diamond substrate;

[0007] Step 2: Surface cleaning:

[0008] The polished diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminations on the surface of the diamond substrate. The substrate is then placed in plasma water and heated at 70-85°C to remove residual mixed acid on the diamond surface. After ultrasonic cleaning, a diamond substrate with oxygen terminations is obtained.

[0009] Step 3: Sample measurement:

[0010] First, the weight of the diamond substrate with oxygen terminals is measured using a high-precision balance, and then the length and width of the diamond substrate with oxygen terminals are measured using a vernier caliper to obtain the surface area S of the diamond substrate;

[0011] Step 4: Clean the surface again:

[0012] The diamond substrate with oxygen terminals is ultrasonically cleaned again using plasma water, anhydrous ethanol, and acetone in sequence to obtain a diamond substrate after secondary cleaning;

[0013] Step 5: Epitaxial growth:

[0014] placing the diamond substrate after the secondary cleaning on a molybdenum tray and placing them together on a sample stage of a microwave plasma chemical vapor deposition (MPCVD) apparatus, introducing a mixed gas of hydrogen and methane, and performing deposition under the conditions of a hydrogen flow rate of 100 sccm to 500 sccm, a methane flow rate of 1 sccm to 20 sccm, a diamond substrate temperature of 700° C. to 1100° C., a pressure of 50 mbar to 300 mbar, and a microwave power of 1000 W to 4000 W, to epitaxially grow a single crystal diamond layer on the surface of the diamond substrate, thereby obtaining a grown diamond substrate;

[0015] Step 6: Three-time surface cleaning:

[0016] The grown diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminals on the surface of the diamond substrate, and then placed in plasma water and heated at 70-85°C to remove the residual mixed acid on the diamond surface. After ultrasonic cleaning, a three-cleaned diamond substrate is obtained;

[0017] Step 7: Sample measurement:

[0018] The weight of the diamond substrate after three cleanings was measured using a high-precision balance. The weight difference between the diamond substrate after three cleanings and the diamond substrate with oxygen terminations was Δm. The standard average density of diamond is ρ. ava , calculated by the following formula,

[0019]

[0020] The thickness Δh of the epitaxially grown single-crystal diamond layer is thereby obtained.

[0021] The present invention provides a method for measuring the weight of a clean diamond before growth using a high-precision balance (1 part per 100,000 or greater), and using a vernier caliper and micrometer to measure the length, width, and thickness of the diamond, respectively. After the diamond substrate sample is cleaned, diamond is grown using a microwave plasma chemical vapor deposition (MPCVD) system. After growth, the sample is cleaned and measured again. The diamond growth thickness and growth rate are determined based on the weight difference before and after growth. This method is simple, easy to implement, and highly accurate. It can also accurately determine the diamond growth rate, which is of great significance for the controllable growth of diamond epitaxial layers.

[0022] The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method of the present invention has the following beneficial effects:

[0023] The use of a high-precision balance to characterize the thickness of diamond epitaxial growth layers enables the measurement and control of ultrathin diamond layers (<1μm). The high-precision balance allows for simple, non-destructive measurement of ultrathin diamond layers, providing a simple and accessible measurement method for the control and design of ultrathin functional epitaxial layers in diamond semiconductor devices. Finally, the relationship between the high-precision balance's test accuracy and the size of the diamond sample was studied. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of achieving single crystal diamond epitaxial growth on a diamond substrate in an embodiment;

[0025] Figure 2This is a photo of a high-precision balance used to measure the weight of diamonds in the examples;

[0026] Figure 3 Graph showing the relationship between the accuracy of the high-precision balance (one hundred thousandth) and the size of the diamond sample in the embodiment. DETAILED DESCRIPTION

[0027] Specific embodiment 1: The method for measuring the thickness accuracy of the diamond epitaxial layer growth based on the weighing method in this embodiment is implemented according to the following steps:

[0028] Step 1: Surface smoothing:

[0029] polishing the surface of the diamond substrate to obtain a polished diamond substrate;

[0030] Step 2: Surface cleaning:

[0031] The polished diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminations on the surface of the diamond substrate. The substrate is then placed in plasma water and heated at 70-85°C to remove residual mixed acid on the diamond surface. After ultrasonic cleaning, a diamond substrate with oxygen terminations is obtained.

[0032] Step 3: Sample measurement:

[0033] First, the weight of the diamond substrate with oxygen terminals is measured using a high-precision balance, and then the length and width of the diamond substrate with oxygen terminals are measured using a vernier caliper to obtain the surface area S of the diamond substrate;

[0034] Step 4: Clean the surface again:

[0035] The diamond substrate with oxygen terminals is ultrasonically cleaned again using plasma water, anhydrous ethanol, and acetone in sequence to obtain a diamond substrate after secondary cleaning;

[0036] Step 5: Epitaxial growth:

[0037] placing the diamond substrate after the secondary cleaning on a molybdenum tray and placing them together on a sample stage of a microwave plasma chemical vapor deposition (MPCVD) apparatus, introducing a mixed gas of hydrogen and methane, and performing deposition under the conditions of a hydrogen flow rate of 100 sccm to 500 sccm, a methane flow rate of 1 sccm to 20 sccm, a diamond substrate temperature of 700° C. to 1100° C., a pressure of 50 mbar to 300 mbar, and a microwave power of 1000 W to 4000 W, to epitaxially grow a single crystal diamond layer on the surface of the diamond substrate, thereby obtaining a grown diamond substrate;

[0038] Step 6: Three-time surface cleaning:

[0039] The grown diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminals on the surface of the diamond substrate, and then placed in plasma water and heated at 70-85°C to remove the residual mixed acid on the diamond surface. After ultrasonic cleaning, a three-cleaned diamond substrate is obtained;

[0040] Step 7: Sample measurement:

[0041] The weight of the diamond substrate after three cleanings was measured using a high-precision balance. The weight difference between the diamond substrate after three cleanings and the diamond substrate with oxygen terminations was Δm. The standard average density of diamond is ρ. ava , calculated by the following formula,

[0042]

[0043] The thickness Δh of the epitaxially grown single-crystal diamond layer is thereby obtained.

[0044] This embodiment grows diamonds through a microwave plasma chemical vapor deposition system (MPCVD), uses a high-precision balance to weigh the sample weight, uses a vernier caliper and a micrometer to measure the size of the sample, and obtains the growth thickness and growth rate based on the weight change before and after growth.

[0045] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the strong oxidizing mixed acid in step 2 is a mixture of 98.3% by mass concentrated sulfuric acid and 65% by mass concentrated nitric acid in a volume ratio of 3:1.

[0046] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that in step two, the polished diamond substrate is placed in a strong oxidizing mixed acid, heated at 230°C for 0.5h, and then heated to 350°C and continued to heat for 1.5h to form oxygen terminals on the surface of the diamond substrate.

[0047] Specific embodiment 4: The difference between this embodiment and specific embodiments 1 to 3 is that the ultrasonic cleaning described in step 2 is to use plasma water, anhydrous ethanol, and acetone for ultrasonic cleaning in sequence for 15 to 20 minutes respectively.

[0048] Specific embodiment 5: The difference between this embodiment and any one of specific embodiments 1 to 4 is that the accuracy of the high-precision balance in step 3 is one in 100,000.

[0049] Specific embodiment 6: The difference between this embodiment and any one of specific embodiments 1 to 5 is that in step 3, a high-precision balance is used to measure the weight of the diamond substrate with oxygen terminals, and the measurement is performed three times to obtain the average value.

[0050] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that in step five, the diamond substrate after secondary cleaning is etched pre-treated using hydrogen plasma for 5 to 30 minutes before epitaxial growth, and the hydrogen flow rate during etching is controlled to be 100 sccm to 500 sccm.

[0051] Specific embodiment eight: The difference between this embodiment and any of specific embodiments one to seven is that a mixed gas of hydrogen and methane is introduced in step five, and deposition is performed under the conditions of a hydrogen flow rate of 180 sccm to 240 sccm, a methane flow rate of 1 sccm to 6 sccm, a diamond substrate temperature of 800°C to 1000°C, a pressure of 100 mbar to 180 mbar, and a microwave power of 3200W to 3600W.

[0052] Specific embodiment 9: The difference between this embodiment and any one of specific embodiments 1 to 8 is that in step 6, the mixture is placed in plasma water and heated at 80-85° C. for 0.5 h.

[0053] Specific embodiment ten: This embodiment differs from specific embodiment six in that in step seven, a high-precision balance is used to measure the weight of the diamond substrate after three cleanings, and the average value is taken from the three measurements.

[0054] Example 1: The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method in this embodiment is implemented according to the following steps:

[0055] Step 1: Surface smoothing:

[0056] polishing the surface of the diamond substrate to obtain a polished diamond substrate;

[0057] Step 2: Surface cleaning:

[0058] The polished diamond substrate was placed in a strong oxidizing mixed acid mixture consisting of 98.3% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 3:1. The mixture was heated at 230°C for 0.5 h, then raised to 350°C and heated for 1.5 h to form oxygen terminations on the surface of the diamond substrate. The substrate was then placed in plasma water and heated at 85°C for 30 min to remove residual mixed acid on the diamond surface. The substrate was then ultrasonically cleaned in plasma water, anhydrous ethanol, and acetone for 15 min each to obtain a diamond substrate with oxygen terminations.

[0059] Step 3: Sample measurement:

[0060] First, use a high-precision balance to measure the weight of the diamond substrate with oxygen terminals, and take the average of the three measurements. Then, use a vernier caliper to measure the length and width of the diamond substrate with oxygen terminals. Finally, use a micrometer to measure the initial thickness of the diamond substrate with oxygen terminals. The initial dimensions of the diamond substrate are 5.04 mm * 5.04 mm * 0.5616 mm, and the initial weight is 0.04912 g.

[0061] Step 4: Clean the surface again:

[0062] The diamond substrate with oxygen terminals was ultrasonically cleaned again using plasma water, anhydrous ethanol, and acetone in sequence, each cleaning time being 15 minutes, to obtain a diamond substrate after secondary cleaning;

[0063] Step 5: Epitaxial growth:

[0064] The diamond substrate after the secondary cleaning was placed on a molybdenum tray and placed together on the sample stage of a microwave plasma chemical vapor deposition device (MPCVD). 200 sccm of hydrogen was first introduced for etching for 10 minutes, and then a mixture of hydrogen and methane was introduced. Deposition was performed for 1.5 hours (t) under the conditions of a hydrogen flow rate of 196 sccm, a methane flow rate of 4 sccm, a diamond substrate temperature of 830°C, a pressure of 108 mbar, and a microwave power of 2600 W. A single crystal diamond layer was epitaxially grown on the surface of the diamond substrate to obtain a grown diamond substrate.

[0065] Step 6: Three-time surface cleaning:

[0066] The grown diamond substrate was placed in a strong oxidizing mixed acid, heated at 230°C for 0.5 h, then heated to 350°C for a further 1.5 h to form oxygen terminations on the surface of the diamond substrate. The substrate was then placed in plasma water and heated at 85°C for 0.5 h to remove any residual mixed acid on the surface. The substrate was then ultrasonically cleaned in plasma water, anhydrous ethanol, and acetone for 15 min each, yielding a triple-cleaned diamond substrate.

[0067] Step 7: Sample measurement:

[0068] Use a high-precision balance to measure the weight of the diamond substrate after three cleanings. Take the average value of the three measurements. The weight difference between the diamond substrate after three cleanings and the diamond substrate with oxygen terminals is Δm. The density of diamond is known to be max =3.51554g / cm 3 , ρ min =3.51447g / cm 3 , ρ ava =3.51539g / cm 3 , calculated by the following formula,

[0069]

[0070] The thickness of the epitaxially grown single crystal diamond layer Δh is obtained, and the growth rate is calculated according to Formula calculation.

[0071] In this example, steps 2 through 7 were repeated for six rounds of growth. After each growth cycle, the weight of the diamond was measured using a high-precision balance. The average of the three measurements was taken. The weight difference before and after the growth cycle was obtained. The statistical data for each epitaxial growth cycle is shown in Table 1 below.

[0072] Table 1

[0073] Growth batches Growth time (h) Growth weight (g) Growth rate (μm / h) Growth thickness (μm) 1 1.5 0.00024 1.7918 2.6877 2 1.5 0.000256 1.9112 2.8668 3 1 0.00030 3.5496 3.5496 4 2 0.000524 2.9340 5.8680 5 2 0.000527 2.9508 5.9016 6 3 0.001144 4.2704 12.8112

[0074] To verify the reliability of the measured data, the sixth round of growth experiments was compared with the results of micrometer screw measurements. The diamond thickness obtained using a high-precision balance weighing method was 33.495 μm, while the thickness measured using a micrometer screw was 33.7 μm. This demonstrates the feasibility of this method for measuring thin layer thickness.

[0075] Example 2: The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method in this embodiment is implemented according to the following steps:

[0076] Step 1: Surface smoothing:

[0077] polishing the surface of the diamond substrate to obtain a polished diamond substrate;

[0078] Step 2: Surface cleaning:

[0079] The polished diamond substrate was placed in a strong oxidizing mixed acid mixture consisting of 98.3% concentrated sulfuric acid and 65% concentrated nitric acid in a volume ratio of 3:1. The mixture was heated at 230°C for 0.5 h, then raised to 350°C and heated for 1.5 h to form oxygen terminations on the surface of the diamond substrate. The substrate was then placed in plasma water and heated at 85°C for 30 min to remove residual mixed acid on the diamond surface. The substrate was then ultrasonically cleaned in plasma water, anhydrous ethanol, and acetone for 15 min each to obtain a diamond substrate with oxygen terminations.

[0080] Step 3: Sample measurement:

[0081] First, the weight of the diamond substrate with oxygen terminals was measured using a high-precision balance, and the average value was taken after three measurements. Then, the length and width of the diamond substrate with oxygen terminals were measured using a vernier caliper. Finally, the initial thickness of the diamond substrate with oxygen terminals was measured using a micrometer. The initial dimensions of the diamond substrate were 4.12 mm * 4.13 mm * 0.549 mm, and the initial weight was 0.03220 g.

[0082] Step 4: Clean the surface again:

[0083] The diamond substrate with oxygen terminals was ultrasonically cleaned again using plasma water, anhydrous ethanol, and acetone in sequence, each cleaning time being 15 minutes, to obtain a diamond substrate after secondary cleaning;

[0084] Step 5: Epitaxial growth:

[0085] The diamond substrate after the secondary cleaning was placed on a molybdenum tray and placed together on the sample stage of a microwave plasma chemical vapor deposition device (MPCVD). 200 sccm of hydrogen was first introduced for etching for 10 minutes, and then a mixture of hydrogen and methane was introduced for deposition for 1.5 hours under the conditions of a hydrogen flow rate of 196 sccm, a methane flow rate of 4 sccm, a diamond substrate temperature of 830°C, a pressure of 110 mbar, and a microwave power of 2700 W. A single crystal diamond layer was epitaxially grown on the surface of the diamond substrate to obtain a grown diamond substrate.

[0086] Step 6: Three-time surface cleaning:

[0087] The grown diamond substrate was placed in a strong oxidizing mixed acid, heated at 230°C for 0.5 h, then heated to 350°C for a further 1.5 h to form oxygen terminations on the surface of the diamond substrate. The substrate was then placed in plasma water and heated at 85°C for 0.5 h to remove any residual mixed acid on the surface. The substrate was then ultrasonically cleaned in plasma water, anhydrous ethanol, and acetone for 15 min each, yielding a triple-cleaned diamond substrate.

[0088] Step 7: Sample measurement:

[0089] Use a high-precision balance to measure the weight of the diamond substrate after three cleanings. Take the average value of the three measurements. The weight difference between the diamond substrate after three cleanings and the diamond substrate with oxygen terminals is Δm. The density of diamond is known to be max =3.51554g / cm 3 , ρ min =3.51447g / cm 3 , ρ ava =3.51539g / cm 3 , calculated by the following formula,

[0090]

[0091] The thickness Δh of the epitaxially grown single-crystal diamond layer is thereby obtained.

[0092] In this example, steps 2 through 7 were repeated for six rounds of growth. After each growth cycle, the weight of the diamond was measured using a high-precision balance. The average of the three measurements was taken. The weight difference before and after the growth cycle was obtained. The statistical data for each epitaxial growth cycle is shown in Table 2 below.

[0093] Table 2

[0094] Growth batches Growth time (h) Growth weight (g) Growth rate (μm / h) Growth thickness (μm) 1 0.5 0.00011 3.6779 1.8389 2 1 0.000227 3.7949 3.7949 3 2 0.000487 4.0708 8.1416 4 3 0.000836 4.6587 13.9761 5 1.5 0.000434 4.8370 7.3095 6 1.5 0.000473 5.2717 7.9075

[0095] To verify the reliability of the measured data, the sixth round of growth experiments was compared with the results of micrometer screw measurements. The diamond thickness obtained using a high-precision balance weighing method was 42.914 μm, while the micrometer screw measurement yielded a thickness of 42.75 μm. This demonstrates the feasibility of this method for measuring thin layer thickness.

[0096] According to the formula It can be seen that the measurement accuracy of diamond thickness by a high-precision balance is related to the area of ​​the diamond sample, and the relationship is as follows: Figure 3 As shown, the sample area is negatively correlated with the measurement accuracy. The test accuracy of Example 1 and Example 2 is 114nm and 178nm respectively. The difference between Example 2 and Example 1 is that the sample area is different. The results of the examples show that the present invention is feasible for testing different areas.

Claims

1. A method for measuring the thickness accuracy of diamond epitaxial layer growth based on weighing method, characterized in that The method for measuring the thickness accuracy of the diamond epitaxial layer growth is implemented according to the following steps: Step 1: Surface smoothing: polishing the surface of the diamond substrate to obtain a polished diamond substrate; Step 2: Surface cleaning: The polished diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminations on the surface of the diamond substrate. The substrate is then placed in plasma water and heated at 70-85°C to remove residual mixed acid on the diamond surface. After ultrasonic cleaning, a diamond substrate with oxygen terminations is obtained. Step 3: Sample measurement: First, the weight of the diamond substrate with oxygen terminals is measured using a high-precision balance, and then the length and width of the diamond substrate with oxygen terminals are measured using a vernier caliper to obtain the surface area S of the diamond substrate; Step 4: Clean the surface again: The diamond substrate with oxygen terminals is ultrasonically cleaned again using plasma water, anhydrous ethanol, and acetone in sequence to obtain a diamond substrate after secondary cleaning; Step 5: Epitaxial growth: Placing the diamond substrate after the secondary cleaning on a molybdenum holder and placing the substrate on a sample stage of a microwave plasma chemical vapor deposition apparatus, introducing a mixed gas of hydrogen and methane, and performing deposition under the conditions of a hydrogen flow rate of 100 sccm to 500 sccm, a methane flow rate of 1 sccm to 20 sccm, a diamond substrate temperature of 700° C. to 1100° C., a pressure of 50 mbar to 300 mbar, and a microwave power of 1000 W to 4000 W, to epitaxially grow a single crystal diamond layer on the surface of the diamond substrate, thereby obtaining a grown diamond substrate; Step 6: Three-time surface cleaning: The grown diamond substrate is placed in a strong oxidizing mixed acid, heated at 200-250°C for 0.4-0.6 hours, then heated to 330-370°C and continued to be heated for 1.4-1.8 hours to form oxygen terminals on the surface of the diamond substrate, and then placed in plasma water and heated at 70-85°C to remove the residual mixed acid on the diamond surface. After ultrasonic cleaning, a three-cleaned diamond substrate is obtained; Step 7: Sample measurement: The weight of the diamond substrate after three cleanings was measured using a high-precision balance. The weight difference between the diamond substrate after three cleanings and the diamond substrate with oxygen terminations was Δm. The standard average density of diamond is ρ. ava , calculated by the following formula, The thickness Δh of the epitaxially grown single-crystal diamond layer is thereby obtained.

2. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that The strong oxidizing mixed acid in step 2 is prepared by mixing concentrated sulfuric acid with a mass percentage of 98.3% and concentrated nitric acid with a mass percentage of 65% in a volume ratio of 3:

1.

3. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that In step 2, the polished diamond substrate is placed in a strong oxidizing mixed acid, heated at 230° C. for 0.5 h, and then heated to 350° C. for another 1.5 h to form oxygen terminals on the surface of the diamond substrate.

4. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that The ultrasonic cleaning described in step 2 is to use plasma water, anhydrous ethanol and acetone to ultrasonically clean for 15 to 20 minutes respectively.

5. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that The accuracy of the high-precision balance described in step 3 is one in one hundred thousand.

6. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that In step 3, a high-precision balance is used to measure the weight of the diamond substrate with oxygen terminals, and the weight is measured three times in total and the average value is taken.

7. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that In step five, before epitaxial growth, the diamond substrate after secondary cleaning is subjected to etching pretreatment using hydrogen plasma for 5 minutes to 30 minutes, and the hydrogen flow rate is controlled to be 100 sccm to 500 sccm during etching.

8. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that In step five, a mixed gas of hydrogen and methane is introduced, and deposition is performed under the conditions of a hydrogen flow rate of 180 sccm to 240 sccm, a methane flow rate of 1 sccm to 6 sccm, a diamond substrate temperature of 800°C to 1000°C, a pressure of 100 mbar to 180 mbar, and a microwave power of 3200W to 3600W.

9. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 1, characterized in that In step six, the sample is placed in plasma water and heated at 80-85° C. for 0.5 h.

10. The method for measuring the thickness accuracy of diamond epitaxial layer growth based on the weighing method according to claim 6, characterized in that In step seven, a high-precision balance is used to measure the weight of the diamond substrate after three cleanings, and the average value is obtained by measuring three times in total.

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