Screening method of diamond substrate

Abstract

The invention provides a diamond substrate screening method, which can be applied to the technical field of single crystal diamond material preparation, and comprises the following steps: carrying out crystal quality screening on diamond substrates, and selecting substrates meeting preset crystal quality to obtain a first screened substrate; performing stress state screening on the first screening substrate, and selecting a substrate meeting a preset stress state to obtain a second screening substrate; performing optical quality screening on the second screening substrate, and selecting a substrate meeting the preset optical quality to obtain a third screening substrate; performing surface quality screening on the third screening substrate, and selecting the substrate meeting the preset surface quality to obtain a fourth screening substrate; and crystal face deviation angle screening is conducted on the fourth screening substrate, the substrate meeting the preset crystal face deviation angle is selected, the target diamond substrate is obtained, and screening is completed. The epitaxial crystal quality of the CVD monocrystal diamond is improved by comprehensively evaluating substrate attributes such as crystal quality, stress state, defect distribution and surface quality.

Description

Technical Field

[0001] The present invention relates to the technical field of single-crystal diamond material preparation, and more particularly to a method for screening diamond substrates. Background Art

[0002] Single-crystal diamond is regarded as an ideal candidate material for next-generation semiconductor materials due to its ultra-wide bandgap, high carrier mobility, high carrier saturation drift velocity, high critical breakdown field strength, ultra-high thermal conductivity, excellent anti-irradiation characteristics, and the stability of physical and chemical properties. Currently, chemical vapor deposition (CVD) epitaxial growth is the mainstream technology for preparing large-size and high-quality single-crystal diamond. Among them, high-pressure high-temperature (HPHT) diamond is usually selected as the substrate in CVD homoepitaxy. However, existing HPHT substrate screening technologies mostly rely on single-parameter screening of substrates, ignoring the combined effects of various factors such as crystal quality, surface roughness, lattice stress, optical quality, defect density, and impurity distribution. In summary, there is an urgent need to develop a multi-parameter collaborative and highly sensitive HPHT substrate screening method to improve the quality and yield of CVD epitaxial diamond. Summary of the Invention

[0003] (I) Technical Problems to be Solved

[0004] In view of the above problems, the present invention provides a method for screening diamond substrates. By comprehensively evaluating substrate properties such as crystal quality, stress state, optical quality, defect distribution, surface quality, and substrate tilt angle, the problems of high defect transfer rate and unstable epitaxial layer quality caused by single-parameter optimization in traditional screening technologies are solved, thereby improving the epitaxial crystal quality of CVD single-crystal diamond.

[0005] (II) Technical Solutions

[0006] In view of the above technical problems, an embodiment of the present invention provides a method for screening diamond substrates.

[0007] According to the first aspect of the present invention, a screening method for diamond substrates is provided. According to the quality requirements for diamond substrates, a screening method for diamond substrates is designed. The method includes: A screening method for diamond substrates, characterized in that according to the quality requirements for diamond substrates, a screening method for diamond substrates is designed. The method includes: S1. Screen the crystal quality of the diamond substrate, including using an X-ray diffractometer to measure the rocking curve of the growth crystal plane. The screening conditions are: if the substrate is the (100) crystal plane, the full width at half maximum (FWHM) of the (400) rocking curve ≤ 300 arcsec; if the substrate is the (111) crystal plane, the FWHM of the (111) rocking curve ≤ 200 arcsec; if the substrate is other crystal planes, the FWHM of the rocking curve ≤ 300 arcsec, to obtain the first screened substrate; S2. Screen the stress state of the first screened substrate, including detecting the diamond characteristic peak through a Raman spectrometer, and screening the substrate with a Raman peak FWHM ≤ 3.0 cm -1 to obtain the second screened substrate; S3. Screen the optical quality of the second screened substrate, including using a deep ultraviolet photoluminescence spectrometer (excited at 177 nm) and a cathodoluminescence spectrometer to locate the free exciton recombination emission peak (B1, 5.27 eV) and the dislocation-related defect peak (A band, 2.90 eV), combining the standard sample spectrum to determine the defect type and density, and determining the defect distribution through spectral scanning imaging technology, and selecting the diamond substrate that meets the preset optical quality to obtain the third screened substrate; S4. Screen the surface quality of the third screened substrate, including observing with an optical microscope with an objective lens of ≥ 50 times to determine no visible defects; scanning with an atomic force microscope in an area of ≥ 5 × 5 μm 2 to limit the surface roughness Ra ≤ 5 nm to obtain the fourth screened substrate; and S5. Screen the substrate tilt angle of the fourth screened substrate, including using an X-ray single crystal orientator to measure the substrate tilt angle, and screening the substrate that meets the predetermined tilt angle to obtain the target diamond substrate, thus completing the screening.

[0008] In some exemplary embodiments, in step S1, if the X-ray diffractometer uses the copper target Kα1 line and the (400) characteristic peak used when measuring the (100) crystal plane is at 2θ = 119.497°, the screening condition is that the FWHM of the characteristic peak rocking curve is less than or equal to 250 arcsec.

[0009] In some exemplary embodiments, in step S1, if the X-ray diffractometer uses the copper target Kα1 line and the (111) characteristic peak used when measuring the (111) crystal plane is at 2θ = 43.931°, the screening condition is that the FWHM of the characteristic peak rocking curve is less than or equal to 150 arcsec.

[0010] In some exemplary embodiments, in step S2, the typical diamond characteristic peak is located at 1332 - 1333 cm -1and between; and there are no relevant peaks of graphite inclusions or amorphous carbon phase at the 1350 cm -1 position and the 1580 cm -1 position.

[0011] In some exemplary embodiments, in step S3, at least one free exciton recombination luminescence peak is detected near the diamond band edge at the 5.27 eV position, called the B1 peak; the typical dislocation-related defect peak is located at the 2.90 eV position, and due to the relatively large width of the typical dislocation-related defect peak, it is called the A band.

[0012] In some exemplary embodiments, in step S3, during the spectral test, the test temperature is not greater than 12 K to obtain obvious spectral peaks; and there are no other impurity-related peaks with relatively high intensities in the entire spectral range (about 1.2 - 6.7 eV).

[0013] In some exemplary embodiments, in step S3, the quality of the substrate is judged by the ratio of the intensity of the B1 peak to the intensity of the A band. A substrate with an intensity ratio greater than or equal to 0.1 is the third screened substrate.

[0014] In some exemplary embodiments, the lowest excitation wavelength in the deep ultraviolet band of the deep ultraviolet spectrometer used in step S3 can reach 177 nm.

[0015] In some exemplary embodiments, in step S4, the surface roughness Ra ≤ 1 nm.

[0016] (III) Beneficial effects

[0017] As can be seen from the above technical solutions, a method for screening diamond substrates provided by an embodiment of the present invention has at least the following beneficial effects:

[0018] By comprehensively evaluating substrate properties such as crystal quality, stress state, defect distribution, and surface quality, the problems of high defect transfer rate and unstable epitaxial layer quality caused by single parameter optimization in traditional screening technologies are solved, thereby improving the epitaxial crystal quality of CVD single crystal diamond, and it can be applied to the growth of diamond materials in high-end fields such as semiconductor diamond devices, quantum sensing, and optical windows. Description of the drawings

[0019] Through the following description of the embodiments of the present invention with reference to the drawings, the above content and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0020] Figure 1 Schematically shows a flowchart of a method for screening diamond substrates according to an embodiment of the present invention. Detailed implementation manners

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, numerous specific details are set forth in order to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0022] Figure 1 A schematic flow chart of a method for screening diamond substrates according to an embodiment of the present invention is schematically shown.

[0023] As Figure 1 shown, a method for screening diamond substrates according to an embodiment of the present invention includes steps S1 - S5. This screening method is designed according to the quality requirements of diamond substrates.

[0024] In step S1, crystal quality screening is performed on the diamond substrate, including measuring the rocking curve using an X-ray diffractometer. The screening conditions are as follows: if the substrate is a (100) crystal plane, the full width at half maximum (FWHM) of the (400) rocking curve ≤ 300 arcsec; if the substrate is a (111) crystal plane, the FWHM of the (111) rocking curve ≤ 200 arcsec; if the substrate is other crystal planes, the FWHM of the rocking curve ≤ 300 arcsec, to obtain a first screened substrate.

[0025] For example, when the growth crystal plane is the (100) crystal plane, the corresponding characteristic peak is the (400) characteristic peak, and the first preset FWHM is 300 arcsec; or when the growth crystal plane is the (111) crystal plane, the corresponding characteristic peak is the (111) characteristic peak, and the first preset FWHM is 200 arcsec; or when the growth crystal plane is other crystal planes other than the (100) and (111) crystal planes, the first preset FWHM is 300 arcsec.

[0026] Preferably, when measuring the (100) crystal plane, if the X-ray diffractometer uses the copper target Kα1 line, the used (400) characteristic peak is located at 2θ = 119.497°, and the full width at half maximum (FWHM) can be further preferably less than or equal to 250 arcsec; when measuring the (111) crystal plane, if the X-ray diffractometer uses the copper target Kα1 line, the used (111) characteristic peak is located at 2θ = 43.931°, and the full width at half maximum (FWHM) can be further preferably less than or equal to 150 arcsec.

[0027] In step S2, stress state screening is performed on the first screened substrate, including detecting the diamond characteristic peak through a Raman spectrometer, and limiting the full width at half maximum of the Raman peak ≤ 3.0 cm -1 , to obtain a second screened substrate.

[0028] In an embodiment of the invention, the typical characteristic peak of diamond in the Raman spectrum is located between 1332 - 1333 cm -1 ; and there are no relevant peaks of graphite inclusions or amorphous carbon phase near 1350 cm -1 and near 1580 cm -1 .

[0029] For example, by detecting the diamond characteristic peak with a Raman spectrometer, a substrate with a full width at half maximum (FWHM) of the Raman peak ≤ 3.0 cm -1 is screened.

[0030] In step S3, optical quality screening is performed on the second screened substrate, including using a deep ultraviolet photoluminescence spectrometer (excited at 177 nm) and a cathodoluminescence spectrometer to locate the free exciton emission peak (B1, 5.27 eV) and the dislocation-related defect peak (A band, 2.90 eV), determining the defect type and density in combination with a standard sample, and determining the defect distribution through spectral scanning imaging technology, and selecting a substrate that meets the preset optical quality to obtain a third screened substrate.

[0031] In an embodiment of the present invention, at least one free exciton recombination emission peak is detected near the diamond band edge at around 5.27 eV, which is called the B1 peak; the typical dislocation-related defect peak is located near 2.90 eV, and the width of this peak is relatively large, which is called the A band.

[0032] In an embodiment of the present invention, during the spectral measurement process, in order to obtain more obvious spectral peaks, the spectral test should be carried out under low temperature conditions (≤12 K). There should be no other impurity-related peaks with relatively high intensities in the entire spectral range (1.2 - 6.7 eV).

[0033] In an embodiment of the present invention, the deep ultraviolet photoluminescence spectrometer used in step S3 is an independently developed device (ZL 2011 1 0087894.9), and the lowest excitation wavelength in the deep ultraviolet band of the ultraviolet spectrometer can reach 177 nm.

[0034] In an embodiment of the present invention, the ratio of the intensity of the free exciton recombination emission peak to the intensity of the dislocation-related defect peak is used to judge the quality of the second screened substrate, and a strength ratio greater than or equal to 0.1 is preferred.

[0035] In step S4, surface quality screening is performed on the third screened substrate, including observing with an optical microscope with an objective lens of ≥50 times to determine that there are no visible defects; scanning an area of ≥5×5 μm 2 with an atomic force microscope, and limiting the surface roughness Ra ≤ 5 nm to obtain a fourth screened substrate.

[0036] In step S5, substrate tilt angle screening is performed on the fourth screened substrate, including measuring the substrate tilt angle using an X-ray single crystal orientator, screening substrates that meet a predetermined tilt angle to obtain target substrates, and completing the screening.

[0037] Example 1

[0038] Step 1: Randomly select 10 Ib-type HPHT diamond (100) substrates (size 3.5×3.5×1 mm 3 -5×5×1 mm 3 ).

[0039] Step 2: Use an X-ray diffractometer (model TD-3500) to measure the rocking curve of the (400) crystal plane characteristic peak, and screen samples with FWHM≤300 arcsec (6 samples pass), preferably samples with FWHM≤250 arcsec (4 samples pass).

[0040] Step 3: Perform Raman spectroscopy tests (Horiba LabRAM HR, 532 nm laser) on the 4 passed samples to detect the FWHM of the 1332 cm -1 characteristic peak. The results show that all 4 detected samples are low-stress substrates with FWHM≤3.0 cm -1 .

[0041] Step 4: Perform photoluminescence (PL) spectroscopy analysis (213 nm laser, DUVPL spectrometer) on the 4 passed samples to detect the intensity ratio of the B1 peak at 5.27 eV to the A band at 2.90 eV, and limit I(A band) / I(B1)≤0.1. A total of 2 samples pass; perform a PL scan on the substrate (step size 100 μm, area 3.5×3.5 mm 2 ), record the defect distribution, and if necessary, cut off the defect-dense part by laser cutting.

[0042] Step 5: Use an optical microscope (Olympus MX51) to observe the 2 passed substrates to confirm no visible scratches, protrusions, or pits; use an atomic force microscope (Dimension Edge) to scan the 5×5 μm 2 area, and the measured Ra values are 3.2 nm and 1.4 nm respectively, meeting the preset requirements. If necessary, the surface roughness can be further reduced by techniques such as mechanical polishing and reactive ion etching.

[0043] Step 6: Perform orientation tests (DX-100) on the growth surfaces of the 2 passed samples, and the measured tilt angles are 0.50° and 0.76° respectively, and it is determined that they meet the preset conditions (<1.00°).

[0044] Step 7: Perform CVD homoepitaxial growth on the 2 passed HPHT substrates, and the epitaxial layer reaches the expected result of high quality.

[0045] Those skilled in the art can understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A method for screening a diamond substrate, characterized in that: According to the quality requirements of the diamond substrate, a screening method for the diamond substrate is designed, and the method comprises: S1. Screening the crystal quality of the diamond substrate, including measuring the rocking curve using an X-ray diffractometer, wherein the screening conditions are: if the substrate is a (100) crystal plane, the half-width of the (400) rocking curve is ≤300 arcsec; if the substrate is a (111) crystal plane, the half-width of the (111) rocking curve is ≤200 arcsec; if the substrate is other crystal planes, the half-width of the rocking curve is ≤300 arcsec, and a first screened substrate is obtained; S2. Screening the stress state of the first screening substrate, including detecting diamond characteristic peaks by Raman spectrometer, and limiting the Raman peak half-height width ≤ 3.0 cm -1 , obtaining a second screening substrate; S3, performing optical quality screening on the second screening substrate, including using a deep ultraviolet photoluminescence spectrometer (177nm excitation) and a cathode fluorescence spectrometer to locate the free exciton luminescence peak (B1, 5.27eV) and the dislocation-related defect peak (A band, 2.90eV), combining with a standard sample to determine the defect type and density, and determining the defect distribution by spectral scanning imaging technology, selecting a substrate that meets the preset optical quality, and obtaining a third screening substrate; S4, performing surface quality screening on the third screening substrate, including observing with an optical microscope with a ≥50x objective lens to ensure that there are no visible defects; scanning with an atomic force microscope with a ≥5×5μm 2 region, limiting the roughness Ra≤5nm, to obtain a fourth screening substrate; and S5. Screening the fourth screening substrate for a substrate deflection angle, including using an X-ray single crystal orientation instrument to measure the substrate deflection angle, screening substrates that meet a predetermined deflection angle, obtaining a target substrate, and completing the screening.

2. The method according to claim 1, characterized in that In step S1, if the X-ray diffractometer uses a copper target Kα1 line, the (400) characteristic peak used when measuring the (100) crystal plane is located at 2θ=119.497°, and the screening condition is that the half-height width of the characteristic peak rocking curve is ≤150 arcsec.

3. The method according to claim 1, characterized in that In step S1, if the X-ray diffractometer uses a copper target Kα1 line, the (111) characteristic peak used to measure the (111) crystal plane is located at 2θ=43.931°, and the screening condition is that the half-height width of the characteristic peak rocking curve is ≤150 arcsec.

4. The method according to claim 1, characterized in that: In step S2, the typical characteristic peak of diamond is located at 1332-1333 cm -1 between; and At 1350cm -1 Position and 1580cm -1 There are no peaks related to graphite inclusions or amorphous carbon phase at this position.

5. The method according to claim 1, characterized in that In step S3, at least one free exciton recombination luminescence peak is detected near the diamond band edge at 5.27 eV, which is called B1 peak; The typical dislocation-related defect peak is located at 2.90 eV. Since the typical dislocation-related defect peak is relatively wide, it is called the A band.

6. The method according to claim 1, characterized in that In step S3, during the spectrum test, the test temperature is not greater than 12K to obtain a clear spectrum peak; and There are no other impurity-related peaks in the entire spectral range (1.2~6.7eV).

7. The method according to claim 1, characterized in that In step S3, the quality of the substrate is judged by using the ratio of the B1 peak intensity to the A band intensity, and substrates with an intensity ratio greater than or equal to 0.1 are selected as the third screening substrate.

8. The method according to claim 1, characterized in that The lowest excitation wavelength in the deep ultraviolet band of the deep ultraviolet spectrometer used in step S3 can reach 177 nm.

9. The method according to claim 1, characterized in that: In step S4, the surface roughness Ra≤1 nm.

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