Heteroepitaxial diamond film and preparation method and application thereof

Abstract

The invention provides a heteroepitaxial diamond film and a preparation method and application thereof, and the preparation method comprises the following steps: carrying out grinding and polishing treatment on a silicon wafer, then putting the silicon wafer into an MPCVD deposition device, and carrying out diamond vapor deposition to obtain a silicon-based diamond substrate; performing hydrogen plasma etching treatment on the silicon-based diamond substrate to obtain a silicon-based diamond substrate with a high diamond phase proportion; and the silicon-based diamond substrate with the high diamond phase proportion is put into an MPCVD device for continuous diamond vapor deposition, and the heteroepitaxial diamond film is obtained. The hydrogen plasma etching silicon-based diamond substrate prepared at low cost has a high diamond phase proportion, and a diamond film obtained by taking the hydrogen plasma etching silicon-based diamond substrate as a substrate for continuous epitaxy can effectively reduce the defect density and has excellent crystal quality.

Description

[0001] This application claims priority to patent application number 202410229902.6. The filing date of the prior application is February 29, 2024. The name of the invention is a heteroepitaxial diamond film and its preparation method. Technical Field

[0002] The invention belongs to the technical field of microwave plasma chemical vapor deposition and relates to a heteroepitaxial diamond film and a preparation method and application thereof. Background Art

[0003] Diamond is the ultimate semiconductor in the field of electronic power. It has the highest thermal conductivity, the highest breakdown electric field, and a wide bandgap. It has great application prospects in the field of electronic devices. Due to the limitation of the size of the diamond substrate, it is difficult to obtain large-sized diamonds by homoepitaxial growth, and the high preparation cost is not conducive to the development of industrialization. Heteroepitaxial growth is not limited by the size of the diamond substrate, and large-sized diamond epitaxial wafers can be obtained. However, heteroepitaxial growth has problems such as complex process, high cost, and difficulty in obtaining high-quality diamond films. If the quality of diamond films directly heteroepitaxially grown on silicon substrates can be improved and the heteroepitaxial process steps can be simplified, it can not only reduce costs, but also realize the preparation of large-sized high-quality silicon-based diamond films. However, at present, direct diamond heteroepitaxial growth on silicon substrates is often accompanied by the deposition of a high content of non-diamond phases, and even accompanied by the deposition of graphite phases. Summary of the invention

[0004] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a heteroepitaxial diamond film and a preparation method and application thereof. The present invention performs hydrogen plasma etching on a diamond film grown directly on a silicon substrate after grinding and polishing, and on a silicon-based diamond substrate with effectively reduced non-diamond phase content, performs secondary diamond epitaxy by adjusting the preparation process parameters to improve the quality of the diamond film, and further achieves the preparation of high-quality diamond film on the silicon substrate by periodically carrying out etching and adjusting the process parameters. The present invention effectively reduces the process complexity and cost of heteroepitaxial large-size diamond film, and can achieve the preparation of high-quality large-size silicon-based diamond film.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing a heteroepitaxial diamond film, the method comprising the following steps:

[0007] (1) grinding and polishing the silicon wafer, and then placing it in an MPCVD deposition device for diamond vapor deposition to obtain a silicon-based diamond substrate;

[0008] (2) performing hydrogen plasma etching on the silicon-based diamond substrate to obtain a silicon-based diamond substrate with a high diamond phase ratio;

[0009] (3) Placing the silicon-based diamond substrate with a high diamond phase ratio into an MPCVD device to continue diamond vapor deposition to obtain a heteroepitaxial diamond film.

[0010] Preferably, the gases used in the diamond vapor deposition in step (1) are hydrogen and methane.

[0011] Preferably, the flow rate of the hydrogen in step (1) is 100-1000sccm, for example, 100sccm, 150sccm, 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm, 900sccm, 950sccm, 1000sccm, and the flow rate of the methane is 1-100sccm, for example, 1sccm, 2sccm, 5sccm, 8sccm, 10sccm, 15sccm, 20sccm, 25sccm, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm or 100sccm.

[0012] Preferably, the gas flow ratio of methane and hydrogen in step (1) is 1:100 to 10:100, for example, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, 5.5:100, 6:100, 6.5:100, 7:100, 8:100, 9:100 or 10:100, etc.

[0013] Preferably, when the MPCVD deposition device in step (1) is operating, the microwave source has an operating power of 1000 W to 6000 W, for example, 1000 W, 1500 W, 1800 W, 2000 W, 2500 W, 2800 W, 3000 W, 3500 W, 4000 W, 4500 W, 5000 W, 5500 W or 6000 W. In the present invention, when the MPCVD deposition device is operating, the microwave source can ionize hydrogen and methane.

[0014] Preferably, the pressure during the diamond vapor deposition in step (1) is 30 torr to 200 torr, for example, 30 torr, 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 180 torr or 200 torr.

[0015] Preferably, the temperature of the diamond vapor deposition in step (1) is 700°C to 1100°C, for example, 700°C, 750°C, 800°C, 850°C, 880°C, 900°C, 950°C, 980°C, 1000°C, 1050°C or 1100°C.

[0016] Preferably, the time for the diamond vapor deposition in step (1) is 1-9 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or 9 hours.

[0017] The time of diamond vapor deposition cannot be too long to avoid excessive stress in the diamond film grown on silicon.

[0018] Preferably, the thickness of the diamond film in step (1) is 0.1-50 μm, for example 0.1 μm, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0019] In the present invention, during the hydrogen plasma etching in step (2), the introduction of methane gas is stopped and etching is performed using hydrogen plasma.

[0020] Preferably, the hydrogen flow rate during the hydrogen plasma etching in step (2) is 100-1000sccm, for example, 100sccm, 150sccm, 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm, 900sccm, 950sccm, 1000sccm.

[0021] Preferably, during the hydrogen plasma etching in step (2), the microwave source power of the MPCVD deposition device is 1000W to 6000W, for example, 1000W, 1500W, 1800W, 2000W, 2500W, 2800W, 3000W, 3500W, 4000W, 4500W, 5000W, 5500W or 6000W.

[0022] Preferably, the pressure during the hydrogen plasma etching in step (2) is 30 torr to 200 torr, for example, 30 torr, 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 180 torr or 200 torr.

[0023] Preferably, the temperature of the hydrogen plasma etching in step (2) is 700°C to 1100°C, for example, 700°C, 750°C, 800°C, 850°C, 880°C, 900°C, 950°C, 980°C, 1000°C, 1050°C or 1100°C.

[0024] Preferably, the hydrogen plasma etching time in step (2) is 10-240 min, for example, 10 min, 15 min, 20 min, 25 min, 40 min, 60 min, 80 min, 100 min, 120 min, 160 min, 180 min, 200 min, 220 min or 240 min.

[0025] Preferably, the gases used in the diamond vapor deposition in step (3) are hydrogen and methane.

[0026] Preferably, in step (3), the flow rate of hydrogen is 100-1000sccm, for example, 100sccm, 150sccm, 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, 850sccm, 900sccm, 950sccm, 1000sccm, and the flow rate of methane is 1-100sccm, for example, 1sccm, 2sccm, 5sccm, 8sccm, 10sccm, 15sccm, 20sccm, 25sccm, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm or 100sccm.

[0027] Preferably, the gas flow ratio of methane and hydrogen in step (3) is 1:100 to 10:100, for example, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, 5.5:100, 6:100, 6.5:100, 7:100, 8:100, 9:100 or 10:100, etc.

[0028] Preferably, the gas flow ratio of methane to hydrogen during the diamond vapor deposition in step (3) may be equal to or lower than the gas flow ratio of methane to hydrogen during the diamond vapor deposition in step (1).

[0029] Preferably, during the diamond vapor deposition in step (3), the microwave source power of the MPCVD deposition device is 1000W to 6000W, for example, 1000W, 1500W, 1800W, 2000W, 2500W, 2800W, 3000W, 3500W, 4000W, 4500W, 5000W, 5500W or 6000W.

[0030] Preferably, the pressure during the diamond vapor deposition in step (3) is 30 torr to 200 torr, for example, 30 torr, 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 180 torr or 200 torr.

[0031] Preferably, the temperature of the diamond vapor deposition in step (3) is 700°C to 1100°C, for example 700°C, 750°C, 800°C, 850°C, 880°C, 900°C, 950°C, 980°C, 1000°C, 1050°C or 1100°C.

[0032] Preferably, the time for the diamond vapor deposition in step (3) is 1-9 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or 9 hours.

[0033] In the present invention, the method for preparing the heteroepitaxial diamond film may further include repeating step (2) and step (3) at least once.

[0034] Preferably, the gas flow ratio of methane to hydrogen during each repeated diamond vapor deposition of step (3) may be equal to or lower than the gas flow ratio of methane to hydrogen during the previous diamond vapor deposition.

[0035] Step (2) and step (3) are repeated, that is, multiple-cycle growth is performed with etching and growth intervals.

[0036] During the initial growth, a high methane content can be used to increase the nucleation density of diamond nuclei on the silicon substrate, and the initial etching time also needs to be longer to effectively etch the non-diamond phase in the diamond film; when the methane concentration remains unchanged during the subsequent growth, the quality of the subsequent epitaxial diamond film can be improved because the non-diamond phase content of the diamond substrate before growth is reduced; when the methane concentration is reduced during the subsequent growth, the content of the non-diamond phase generated during the growth of the diamond film can be further reduced, and the subsequent etching time can also be reduced accordingly.

[0037] In another aspect, the present invention provides a heteroepitaxial diamond film prepared by the preparation method as described above.

[0038] The present invention can directly realize the nucleation growth of diamond on the ground and polished silicon substrate. The silicon-based diamond substrate prepared at low cost obtains a high diamond phase ratio after hydrogen plasma etching. The diamond film obtained by further epitaxial growth using the silicon-based diamond substrate as the substrate has a lower non-diamond phase content, which can effectively reduce the defect density of the diamond film and has excellent crystal quality.

[0039] In another aspect, the present invention provides the use of the heteroepitaxial diamond film as described above in the preparation of diamond films or semiconductor devices.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The hydrogen plasma etched silicon-based diamond substrate prepared at low cost in the present invention has a high diamond phase ratio. The heteroepitaxial diamond film obtained through the silicon-based diamond substrate with a high diamond phase ratio has a lower non-diamond phase content, can effectively reduce the defect density of the diamond film, and has excellent crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a Raman spectrum of diamond after the silicon-based diamond substrate in step (1) of Example 1 is etched with hydrogen plasma for different times;

[0043] Figure 2 It is a partial enlarged view of the Raman spectrum of diamond after the silicon-based diamond substrate in step (1) of Example 1 is etched with hydrogen plasma for different time periods;

[0044] Figure 3 yes Figure 2 Diamond phase (1332cm -1 ) and non-diamond phase (1500-1600cm -1 ) content ratio change diagram;

[0045] Figure 4 yes Figure 2 The Raman spectrum half-width change diagram of the diamond substrate after hydrogen plasma etching at different times;

[0046] Figure 5 The Raman spectrum of the diamond film after the diamond deposition in step (3) in Example 1;

[0047] Figure 6 This is a partial enlarged view of the Raman spectrum of the diamond film after the diamond deposition in step (3) in Example 1;

[0048] Figure 7 A graph showing the change in half-width of the Raman spectrum of the diamond film after the diamond deposition in step (3) in Example 1;

[0049] Figure 8 These are Raman spectra of diamond sample A after secondary epitaxy on the silicon-based diamond substrate without etching in Example 1, diamond sample F after secondary epitaxy after etching for 3 hours, diamond sample after secondary epitaxy in Example 2, and diamond sample after tertiary epitaxy in Example 3. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] Example 1

[0052] In this embodiment, a heteroepitaxial diamond film and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0053] Step 1: Diamond growth and hydrogen plasma etching are both carried out in an MPCVD deposition device. Six 1cm×1cm single-polished (111) silicon wafers are selected, ground and polished, and then placed in a chamber for direct diamond vapor deposition. The hydrogen flow rate in the vapor deposition is 500sccm, the methane flow rate is 10sccm, the chamber pressure, microwave power and growth temperature are 70Torr, 5000W and 900℃ respectively, the growth time (i.e., deposition time) is 9h, and the thickness of the grown diamond film is about 4.8μm.

[0054] Step 2: The prepared samples were then placed in an MPCVD device for hydrogen plasma etching, with a hydrogen flow rate of 400 sccm. The six samples were named A, B, C, D, E, and F. As a control group, sample A was not etched, and the etching times of samples BF were 20 min, 40 min, 60 min, 120 min, and 180 min, respectively. The chamber pressure, microwave power, and temperature during etching were 70 Torr, 5000 W, and 900 ° C, respectively.

[0055] Raman spectroscopy was used to characterize the half-width of the diamond Raman characteristic peak at different etching times and to analyze the changes in the content of diamond phase and non-diamond phase in the samples before and after hydrogen plasma treatment. Figure 1 and Figure 2 The following are the Raman spectra of six samples after different etching times. -1 Obvious diamond Raman characteristic peaks can be observed nearby, but not at 1580cm -1 1350cm -1The presence of graphite diffraction peaks was observed at 1500-1600cm -1 A faint broad peak is observed in the range of 2.147 W / m, which is generally used to characterize the content of non-diamond carbon.

[0056] In order to analyze the changes in the film surface phase, the area of ​​the diamond peak was divided by the area of ​​the non-diamond carbon peak to calculate the I under different etching times. diamond / I non-diamond The ratio of diamond phase to non-diamond phase can be analyzed based on this ratio. Figure 3 As shown in Figure 2, with the increase of hydrogen plasma etching time, I diamond / I non-diamond The ratio of I shows a trend of decreasing first and then increasing. When the etching time is 0-40min, I diamond / I non-diamond The ratio of I diamond / I non-diamond The ratio of continues to increase, indicating that the hydrogen plasma mainly etches the non-diamond phase during this period. Compared with the silicon-based diamond substrate prepared in step (1), that is, the unetched silicon-based diamond substrate, the hydrogen plasma etching for more than 60 min obtains a silicon-based diamond substrate with a high diamond phase ratio.

[0057] Figure 4 The changes of the half-width of the diamond Raman characteristic peak under different etching times were characterized. With the increase of etching time, the half-width of the diamond characteristic peak showed a trend of first rising and then falling. When the etching time was 0-40min, hydrogen plasma mainly etched the diamond phase, resulting in an increase in surface defects and a decrease in the ordered diamond domain, which in turn led to an increase in the half-width of the characteristic peak. When the etching time was above 40min, hydrogen plasma etching reduced the content of non-diamond phases related to defects, increased the ordered diamond domain, and then led to a decrease in the half-width of the characteristic peak and improved film quality. When the etching time was above 2h, the half-width of the Raman peak of the silicon-based diamond substrate was smaller than that of the silicon-based diamond substrate when it was not etched, indicating that appropriate hydrogen plasma etching can improve the quality of diamond films.

[0058] Among the samples etched by hydrogen plasma, the I diamond / I non-diamond The ratio is the highest, that is, sample F has the highest proportion of diamond phase and the best crystal quality.

[0059] Step 3: Continue to deposit diamond film on the silicon-based diamond film samples after different hydrogen etching times as above, with a hydrogen flow rate of 500 sccm, a methane flow rate of 10 sccm, a chamber pressure, a microwave power and a growth temperature of 70 Torr, 5000 W and 900°C respectively, and a growth time of 3 h.

[0060] like Figure 5 and Figure 6 As shown in Figure 2, the Raman spectrum of the secondary deposited diamond film shows that the diamond sample has extremely low non-diamond phase. Figure 7 Figure 3 shows the change in the half-width of the Raman characteristic peak of the secondary deposited diamond film. Compared with sample A which was directly deposited without etching, diamond sample D which was deposited again after hydrogen plasma etching for 60 minutes obtained a lower half-width of the Raman peak, and the half-width of the Raman peak of diamond samples E and F continued to decrease with the increase of etching time. This is because the hydrogen plasma etching treatment of the silicon-based diamond substrate for more than 60 minutes increases the diamond phase ratio of the silicon-based diamond substrate. Continuing to deposit a diamond film on it can effectively reduce the defect density of the subsequent epitaxial diamond film and improve the crystal quality of the film.

[0061] Example 2

[0062] Step 1 is the same as step 1 in Example 1;

[0063] Step 2 adopts hydrogen plasma etching for 180 min in step 2 of Example 1, and the rest is the same as step 2 of Example 1;

[0064] In step 3, the flow rate of methane is 8 sccm, the growth time is 4 h, and the rest is the same as step 3 in embodiment 1.

[0065] The Raman spectrum of the diamond sample after secondary epitaxy in Example 2 is as follows: Figure 8 As shown, compared with diamond sample A after secondary epitaxy on a silicon-based diamond substrate without etching and diamond sample F after secondary epitaxy after etching for 3 hours in Example 1, the Raman peak half-width of the diamond sample after secondary epitaxy in Example 2 becomes narrower, indicating that the crystal quality of the epitaxial diamond film is further improved.

[0066] Example 3

[0067] Step 1 is the same as step 1 in Example 1;

[0068] Step 2 adopts hydrogen plasma etching for 180 min in step 2 of Example 1, and the rest is the same as step 2 of Example 1;

[0069] In step 3, the flow rate of methane is 8 sccm, the growth time is 2.5 h, and the rest is the same as step 3 in embodiment 1;

[0070] In step 4, hydrogen plasma etching is performed for 120 min using step 2 in embodiment 1, and the rest is the same as step 2 in embodiment 1;

[0071] In step 5, the flow rate of methane is 6 sccm, the growth time is 2 h, and the rest is the same as step 3 in embodiment 1.

[0072] The Raman spectrum of the diamond sample after three epitaxy in Example 3 is as follows: Figure 8 As shown, compared with diamond sample A after secondary epitaxy on a silicon-based diamond substrate without etching, diamond sample F after secondary epitaxy after etching for 3 hours, and diamond sample after secondary epitaxy in Example 2, the Raman peak half-width of the diamond sample after tertiary epitaxy in Example 3 is further narrowed, indicating that it effectively reduces the defect density of the epitaxial diamond film and has excellent crystal quality.

[0073] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the heteroepitaxial diamond film and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a heteroepitaxial diamond film, characterized in that: The preparation method comprises the following steps: (1) grinding and polishing the silicon wafer, and then placing it in an MPCVD deposition device for diamond vapor deposition to obtain a silicon-based diamond substrate; (2) performing hydrogen plasma etching on the silicon-based diamond substrate to obtain a silicon-based diamond substrate with a high diamond phase ratio; (3) Placing the silicon-based diamond substrate with a high diamond phase ratio into an MPCVD device to continue diamond vapor deposition to obtain a heteroepitaxial diamond film.

2. The method for heteroepitaxial diamond film according to claim 1, characterized in that: The gases used in the diamond vapor deposition in step (1) are hydrogen and methane.

3. The method for preparing a heteroepitaxial diamond film according to claim 2, characterized in that: The flow rate of the hydrogen is 100-1000 sccm, and the flow rate of the methane is 1-100 sccm; Preferably, the gas flow ratio of methane to hydrogen is 1:100 to 10:100; Preferably, when the MPCVD deposition device in step (1) is operating, the microwave source operating power is 1000W to 6000W; Preferably, the pressure during the diamond vapor deposition in step (1) is 30 torr to 200 torr; Preferably, the temperature of the diamond vapor deposition in step (1) is 700° C. to 1100° C.; Preferably, the time for the diamond vapor deposition in step (1) is 1-9 hours.

4. The method for preparing a heteroepitaxial diamond film according to any one of claims 1 to 3, characterized in that: The thickness of the diamond film in step (1) is 0.1-50 μm.

5. The method for preparing a heteroepitaxial diamond film according to any one of claims 1 to 4, characterized in that: When performing the hydrogen plasma etching in step (2), the introduction of methane gas is stopped and etching is performed using hydrogen plasma; Preferably, the hydrogen flow rate during the hydrogen plasma etching in step (2) is 100-1000 sccm; Preferably, during the hydrogen plasma etching in step (2), the microwave source power of the MPCVD deposition device is 1000W to 6000W; Preferably, the pressure during the hydrogen plasma etching in step (2) is 30 torr to 200 torr; Preferably, the temperature of the hydrogen plasma etching in step (2) is 700° C. to 1100° C.; Preferably, the hydrogen plasma etching time in step (2) is 10-240 min.

6. The method for preparing a heteroepitaxial diamond film according to any one of claims 1 to 5, characterized in that: The gases used in the diamond vapor deposition in step (3) are hydrogen and methane.

7. The method for heteroepitaxial diamond film according to claim 6, characterized in that: The flow rate of the hydrogen is 100-1000 sccm, and the flow rate of the methane is 1-100 sccm.

8. The method for preparing a heteroepitaxial diamond film according to claim 6, characterized in that: The gas flow ratio of methane to hydrogen is 1:100 to 10:100; Preferably, the gas flow ratio of methane to hydrogen during the diamond vapor deposition in step (3) is equal to or lower than the gas flow ratio of methane to hydrogen during the diamond vapor deposition in step (1); Preferably, during the diamond vapor deposition in step (3), the microwave source power of the MPCVD deposition device is 1000W to 6000W; Preferably, the pressure during the diamond vapor deposition in step (3) is 30 torr to 200 torr; Preferably, the temperature of the diamond vapor deposition in step (3) is 700° C. to 1100° C.; Preferably, the time of the diamond vapor deposition in step (3) is 1-9 hours; Preferably, the method for preparing the heteroepitaxial diamond film may further include repeating step (2) and step (3) at least once; Preferably, the gas flow ratio of methane to hydrogen during each repeated diamond vapor deposition of step (3) is equal to or lower than the gas flow ratio of methane to hydrogen during the previous diamond vapor deposition.

9. The heteroepitaxial diamond film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the heteroepitaxial diamond film according to claim 9 in the preparation of diamond films or semiconductor devices.

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