MISFET device and preparation method thereof
The preparation of N-type diamond layers by boron-nitrogen co-doping using MPCVD technology solves the problem of insufficient performance of n-type diamond doping, improves the overall performance of MISFET devices, and is suitable for applications in high-voltage, high-power and high-temperature environments.
Patent Information
- Application Number
- CN202510901830.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-01
- Publication Date
- 2025-11-04
AI Technical Summary
In the existing technology, the n-type doping of diamond does not meet the requirements for practical application in terms of electron concentration and electron mobility, which limits its widespread application in high-performance electronic devices.
N-type diamond layers were prepared by boron-nitrogen co-doping using MPCVD technology. By controlling the growth temperature, pressure, microwave power, and gas ratio, the doping ratio of boron and nitrogen was optimized to form N-type diamond films with high electrical performance.
It significantly improves the electron concentration and mobility of N-type diamond, enhances the breakdown voltage, switching efficiency and heat dissipation performance of MISFET devices, and strengthens the stability and reliability of devices in high temperature and harsh environments.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of semiconductors, and particularly relates to a MISFET device and a preparation method thereof. BACKGROUND
[0002] With the advent of the 5G era, electronic devices are accelerating towards high power, multi-band, high efficiency, small size, high reliability and low cost. However, the traditional first-generation semiconductor material silicon (Si) and the second-generation semiconductor material gallium arsenide (GaAs) have been unable to meet the increasingly stringent requirements of modern high-performance electronic devices on material performance. In particular, silicon-based semiconductor devices have reached their theoretical limits in terms of breakdown voltage and carrier concentration, and cannot be further improved.
[0003] Diamond, as an ideal semiconductor material, has a wide band gap (5.47 eV), high carrier mobility (4500 ), high thermal conductivity (2200 W / mK) and excellent chemical stability, which can meet the needs of high-frequency, high-temperature, small-size, radiation-resistant, high-power and low-power loss electronic devices. Therefore, diamond is considered as the most excellent semiconductor material. The hole mobility of its intrinsic material is 8 times that of silicon, which is much higher than that of SiC and GaN materials by 10 to 50 times; and the thermal conductivity and carrier mobility of diamond are the highest in nature. In terms of breakdown field, the electric field strength of diamond is 30 times that of silicon, 3 to 4 times that of SiC, and even 10 times that of GaN, showing its excellent electronic performance.
[0004] Although the p-type doping technology of diamond has been relatively mature and can meet many application requirements, there are still great technical challenges in n-type doping. At present, the n-type doping of diamond has not yet reached the requirements of practical application in terms of performance indicators such as electron concentration and electron mobility, which limits the wide application of diamond in electronic devices. Therefore, it is particularly important to develop n-type diamond devices complementary to p-type diamond devices. In particular, the theoretical electron mobility of diamond needs to be significantly higher than its hole mobility (electron mobility: 4500 , hole mobility: 3800 ). Therefore, promoting the research and application of n-type diamond devices has important practical significance, which can provide stronger support for the next generation of high-performance electronic devices and promote their wide application in high-frequency, high-power and extreme environments. SUMMARY
[0005] Therefore, the application provides a boron-nitrogen co-doped N-channel diamond field effect tube and a preparation method thereof, aiming to prepare a high-electrical-performance N-channel diamond by using boron-nitrogen co-doping, so as to improve the performance of a metal-insulator-semiconductor field effect transistor (MISFET).
[0006] In a first aspect, the application provides a preparation method of a MISFET device, comprising: preparing a P-type substrate; etching the P-type substrate to form a source recess and a drain recess; preparing a boron-nitrogen co-doped N-type diamond layer in the source recess and the drain recess by using an MPCVD process; forming a gate dielectric layer on the surface of the P-type substrate; forming a source and a drain on the surface of the N-type diamond layer in the source recess and the drain recess, respectively; preparing a gate on the surface of the gate dielectric layer to form a MISFET device.
[0007] Optionally, the step of preparing a boron-nitrogen co-doped N-type diamond layer in the source recess and the drain recess by using an MPCVD process comprises: turning on a microwave power source, introducing a carbon source, a boron source, a nitrogen source and a growth gas into an MPCVD growth cavity under the condition that the growth temperature is 750-900°C and the growth pressure is 160-210 mbar, and epitaxially obtaining a boron-nitrogen co-doped N-type diamond layer; etching the boron-nitrogen co-doped N-type diamond layer, and retaining the N-type diamond layer in the source recess and the drain recess.
[0008] Optionally, the microwave power of the microwave power source is 3.7-6.0 kW.
[0009] Optionally, the concentration of the carbon source is 4-8%.
[0010] Optionally, the boron-nitrogen ratio is 1:1-1:4.
[0011] Optionally, the doping concentration of the boron-nitrogen co-doped N-type diamond layer is ~ .
[0012] Optionally, the preparation of the P-type substrate comprises: providing a growth substrate; pre-treating the growth substrate; epitaxially obtaining a P-type diamond substrate on the surface of the growth substrate by using an MPCVD process; removing the growth substrate.
[0013] Optionally, the P-type diamond substrate is epitaxially grown on the surface of the growth substrate by the MPCVD process, comprising: Under the condition of a growth temperature of 750-900℃ and a growth pressure of 160-190mbar, a microwave power of 3.7-6.0kW, a carbon source with a concentration of 4-8%, a boron source with a flow rate of 1-20sccm, and hydrogen with a flow rate of 200-550sccm are introduced into the MPCVD growth chamber to epitaxially grow a P-type diamond layer.
[0014] Optionally, the doping concentration of the P-type substrate is .
[0015] In a second aspect, the present application provides an MISFET device, comprising: a P-type substrate having a source recess and a drain recess; a boron-nitrogen co-doped N-type diamond layer formed in the source recess and the drain recess; a gate dielectric layer formed on the surface of the P-type substrate; a source formed on the surface of the boron-nitrogen co-doped N-type diamond layer in the source recess; a drain formed on the surface of the boron-nitrogen co-doped N-type diamond layer in the drain recess; a gate formed on the surface of the gate dielectric layer.
[0016] The technical method provided by the present application has the following beneficial effects: Firstly, the N-type diamond MISFET device is constructed, which fills the gap in the industry and provides the possibility of manufacturing diamond complementary devices in the industry, and the corresponding manufacturing method is provided. The improvement brought by using n-type diamond to make MOSFET and MISFET devices mainly lies in the following aspects: first, diamond has a wide band gap, which makes the device can withstand higher voltage without breakdown, thereby improving the voltage resistance of MISFET, suitable for high-voltage and high-power applications. Second, the low carrier mobility of diamond results in a significantly lower leakage current than traditional silicon materials, improving the switching efficiency and performance of the device, especially in high-temperature environments. Third, the extremely high thermal conductivity of diamond enables the MISFET device to dissipate heat more effectively, reducing performance degradation or failure due to overheating, and improving the stability and reliability of the device in high-power density and harsh environments. In summary, N-type diamond not only improves the voltage resistance of MISFET, reduces the leakage current, and enhances the heat dissipation capacity, making the device exhibit significant advantages in high-efficiency and high-reliability applications, significantly improving the comprehensive performance of MISFET.
[0017] Secondly, the electrical performance (electron concentration and electron mobility) of the N-type diamond can be improved by the boron-nitrogen co-doped N-type diamond prepared by the MPCVD process, so that the performance of the MISFET device can be further improved. BRIEF DESCRIPTION OF DRAWINGS
[0018] In order to more clearly illustrate the technical solutions of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0019] Figure 1 The flow chart of the MISFET device manufacturing method provided by an embodiment of the present application.
[0020] Figure 2 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0021] Figure 3 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0022] Figure 4 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0023] Figure 5 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0024] Figure 6 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0025] Figure 7 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0026] Figure 8 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0027] Figure 9 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0028] Figure 10 The structural schematic diagram in the MISFET device manufacturing process provided by an embodiment of the present application.
[0029] Figure 11A formation process of a boron-nitrogen co-doped and boron-oxygen co-doped N-type diamond structure provided by the present application can be compared with a diagram Figure 2 A structure schematic diagram in a MISFET device manufacturing process provided by an embodiment of the present application.
[0030] The reference signs are as follows: 11: P-type substrate; 111: source recess; 112: drain recess; 12: boron-nitrogen co-doped N-type diamond layer; 13: gate dielectric layer; 14: source; 15: drain; 16: back electrode; 17: gate. DETAILED DESCRIPTION
[0031] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.
[0032] Figure 1 A preparation method flowchart of a MISFET device provided by the present application. Referring to Figure 1 , comprising: S101, preparing a P-type substrate.
[0033] In an example, the step S101 comprises: Step 1, providing a growth substrate.
[0034] In an example, the growth substrate is a single crystal diamond substrate.
[0035] As an example, the size of the single crystal diamond substrate is 7mm×7mm×0.25mm, but is not limited thereto.
[0036] Step 2, pretreating the growth substrate.
[0037] In an example, the step 2 comprises: Surface treating the surface of the heterogeneous substrate, and the surface treating method is sequentially cleaning the substrate by a mixed solution of sulfuric acid and nitric acid, acetone, anhydrous ethanol, deionized water, and finally blowing dry with nitrogen.
[0038] The purpose of the surface treatment is to remove the contaminants on the surface of the substrate, and other surface treatment methods can be used as an alternative, which is not limited by the present application.
[0039] Step 3, epitaxially obtaining a P-type diamond substrate on the surface of the growth substrate by using an MPCVD process.
[0040] In an example, the step 3 comprises: The P-type diamond layer is epitaxially obtained by introducing a carbon source with a concentration of 4% to 8% into the MPCVD growth cavity, a boron source with a flow rate of 1 sccm to 20 sccm, and hydrogen with a flow rate of 200 sccm to 550 sccm under a microwave power of 3.7 kW to 6.0 kW, a growth temperature of 750°C to 900°C, and a growth pressure of 160 mbar to 190 mbar.
[0041] In an example, the P-type substrate has a doping concentration of .
[0042] For example, the P-type substrate has a doping concentration of .
[0043] Step 4, removing the growth substrate.
[0044] In an example, after the growth substrate is cut off, the P-type diamond substrate is polished on the side close to the growth substrate.
[0045] Referring to Figure 2 , a P-type substrate 11 is shown.
[0046] S102, etching the P-type substrate to form a source electrode recess and a drain electrode recess.
[0047] In an example, step S102 includes: First, a patterned photoresist layer is prepared on the surface of the P-type substrate.
[0048] The patterned photoresist layer is exposed to the source electrode recess preparation area and the drain electrode recess preparation area.
[0049] The photoresist layer can be prepared by photolithography technology, that is, by sequentially spin-coating photoresist on the surface of the P-type substrate, exposing the photoresist, and developing the photoresist to obtain the patterned photoresist layer.
[0050] Second, etching the side of the P-type substrate with the patterned photoresist layer to form a source electrode recess and a drain electrode recess.
[0051] The etching process includes reactive ion etching, sputter etching, and plasma etching.
[0052] Third, removing the patterned photoresist layer.
[0053] Referring to Figure 3 , a source electrode recess 111 and a drain electrode recess 112 are specifically shown.
[0054] S103, using an MPCVD process to prepare a boron-nitrogen co-doped N-type diamond layer in the source electrode recess and the drain electrode recess.
[0055] In an example, step S103 comprises: Step 1, turn on the microwave power source, and under the environment of a growth temperature of 750-900℃ and a growth pressure of 160-210mbar, introduce carbon source, boron source, nitrogen source and growth gas into the MPCVD growth cavity to epitaxially obtain a boron-nitrogen co-doped N-type diamond layer.
[0056] In an example, the microwave power of the microwave power source is 3.7-6.0kW.
[0057] In an example, the concentration of the carbon source is 4-8%.
[0058] In an example, the boron-nitrogen ratio is 1:1-1:4.
[0059] In an example, the doping concentration of the boron-nitrogen co-doped N-type diamond layer is ~ .
[0060] Referring to Figure 4 , a boron-nitrogen co-doped N-type diamond layer 12 is specifically shown.
[0061] Step 2, etch the boron-nitrogen co-doped N-type diamond layer to retain the N-type diamond layer in the source electrode groove and the drain electrode groove.
[0062] In an example, step 2 comprises: First, make a patterned photoresist layer on the surface of the boron-nitrogen co-doped N-type diamond layer.
[0063] The patterned photoresist layer protects the boron-nitrogen co-doped N-type diamond layer in the source electrode groove and the drain electrode groove.
[0064] Second, etch the boron-nitrogen co-doped N-type diamond layer.
[0065] The etching process comprises plasma etching.
[0066] Third, remove the patterned photoresist layer.
[0067] Referring to Figure 5 , a boron-nitrogen co-doped N-type diamond layer 12 after etching is specifically shown.
[0068] S104, form a gate dielectric layer on the surface of the P-type substrate.
[0069] First, make a gate dielectric layer.
[0070] In an example, the gate dielectric layer comprises an intrinsic diamond layer or an insulating material layer other than metal oxide.
[0071] As an example, the gate dielectric layer comprises an intrinsic diamond layer, which can be prepared by an MPCVD process.
[0072] In an example, the gate dielectric layer has a thickness of 40 nm to 200 nm.
[0073] Referring to Figure 6 , a gate dielectric layer 13 is specifically shown.
[0074] In a second step, the gate dielectric layer is etched.
[0075] In the etching of the gate dielectric layer, a reactive ion etching process is used.
[0076] Referring to Figure 7 , the gate dielectric layer 13 after etching is shown.
[0077] S105, a source and a drain are respectively formed on the surface of the N-type diamond layer in the source recess and the drain recess.
[0078] In an example, the source and the drain are sputtered by a magnetron sputtering method, and a back electrode is also sputtered on the side of the P-type substrate away from the source and the drain.
[0079] In an example, the material of the source, the drain and the back electrode comprises any one of Sc, Ti, Pt, Ti / Au alloy and Ti / Pt / Au alloy.
[0080] In an example, the source, the drain and the back electrode are ohmic contact electrodes.
[0081] Referring to Figure 8 , a source 14, a drain 15 and a back electrode 16 are specifically shown.
[0082] S106, a gate is made on the surface of the gate dielectric layer to form a MISFET device.
[0083] In an example, the gate is sputtered with a Schottky contact on the gate dielectric layer.
[0084] In an example, the gate comprises one of Ag, Au, Pt and Pd or a multi-layer alloy thereof.
[0085] After the gate is made, annealing treatment is performed to form the MISFET device.
[0086] Referring to Figure 9 , a MISFET device is specifically shown, which comprises: a P-type substrate 11 having a source recess 111 and a drain recess 112; a boron-nitrogen co-doped N-type diamond layer 12 formed in the source recess and the drain recess.
[0087] Gate dielectric layer 13, formed on the surface of the P-type substrate.
[0088] Source 14, formed on the surface of the boron-nitrogen co-doped N-type diamond layer in the source recess.
[0089] Drain 15, formed on the surface of the boron-nitrogen co-doped N-type diamond layer in the drain recess.
[0090] Back electrode 16, formed on the side of the P-type substrate away from the source and the drain.
[0091] Gate 17, formed on the surface of the gate dielectric layer 13.
[0092] Figure 10 The schematic diagram of the test results of the boron-nitrogen co-doped N-type diamond based on the MPCVD process provided in the present application. Referring to Figure 10 , Figure 10 The electron mobility and electron concentration of the N-type diamond prepared by boron-nitrogen co-doping and boron-oxygen co-doping are compared.
[0093] Among them, the electron mobility and electron concentration of the boron-nitrogen co-doped N-type diamond are much higher than those of the boron-oxygen co-doped N-type diamond.
[0094] Figure 11 The formation energy of the boron-nitrogen co-doped and boron-oxygen co-doped N-type diamond structure provided in the present application is compared, and the formation energy of the boron-nitrogen co-doped and boron-oxygen co-doped N-type diamond structure is further compared, Figure 11 The formation energy of the N-type diamond structure formed by different boron-nitrogen ratios and boron-oxygen ratios is represented.
[0095] It should be noted that the boron-nitrogen co-doped N-type diamond has the following advantages: 1. Boron and nitrogen can form stable boron-nitrogen covalent bonds, and the doping formation energy is significantly lower than single phosphorus doping or boron-oxygen co-doping. This is due to the fact that the boron-nitrogen covalent bond reduces the total energy of the system due to charge compensation, and the spatial matching of the boron-nitrogen covalent bond in the lattice is better, resulting in minimal lattice distortion. Therefore, it is easier to produce N-type doped diamond with high electrical performance by boron-nitrogen co-doping. By increasing the doping concentration to improve the electrical performance, the electrical performance will gradually reach the upper limit under the premise of not damaging the lattice. Due to the better spatial matching of the boron-nitrogen covalent bond in the diamond lattice, the upper limit of the electrical performance of the N-type diamond prepared by boron-nitrogen co-doping is higher, i.e. the electron concentration and electron mobility are higher.
[0096] 2、Boron provides holes, and nitrogen provides electrons, both of which form electrically neutral pairs, helping to adjust the local electric potential and suppress self-compensation behavior. Especially in diamond, boron-nitrogen co-doping can make the donor level shallower, improve ionization efficiency, and enhance n-type conductivity. For traditional phosphorus-doped N-type diamond, phosphorus is a typical N-type donor, but due to its deep energy level (about 0.6 eV) and large self-compensation effect (such as forming P-V pairs, etc.), it leads to low activation efficiency and limited carrier concentration. For example, compared with boron-oxygen co-doping in the prior art, boron and oxygen doping can form pairs, which can theoretically adjust the carrier concentration, but the overall ionization energy is not ideal due to the possible formation of deep level traps induced by oxygen, and the charge compensation behavior is unstable.
[0097] 3、Boron-nitrogen co-doping can introduce shallow donor levels without significantly reducing the band gap, optimizing the conduction band edge, and is beneficial to improving electron mobility and carrier concentration, and improving the overall electronic structure. The energy level introduced by traditional phosphorus doping is usually deep, which is not conducive to the generation of effective carriers, and may introduce impurity states affecting device performance. Boron-oxygen co-doping may introduce neutral defect states in the band gap, bringing electron recombination centers, which is not conducive to the improvement of conductivity.
[0098] 4、Boron and nitrogen co-doping can form bonds, whose bond length and bond energy are closer to bonds in the diamond crystal structure, the disturbance to the crystal structure after doping is minimal, the stability is best, and it is easy to industrialize and control. Compared with phosphorus doping, the atomic size difference of phosphorus is large, which easily causes local structure relaxation or even forms amorphous regions, and has poor stability. Compared with boron-oxygen co-doping, oxygen doping has strong chemical activity and is easy to form non-ideal bonding or oxygen vacancies, reducing the structural integrity.
[0099] In the process of preparing n-type boron-nitrogen co-doped diamond thin film by MPCVD, there are many difficult problems. Boron (B) and nitrogen (N) are introduced into the diamond lattice as co-doped elements to realize n-type conductivity through the mutual compensation of boron's deep donor level and nitrogen's deep acceptor level. However, the solubility of boron and nitrogen in diamond is extremely low, and they are easy to form B-N complex defects instead of being activated in the form of single doping atoms. The existence of multiple complex defects significantly reduces the generation efficiency of carriers (electrons), leading to insufficient n-type conductivity; in addition, the efficiency of boron (B) and nitrogen (N) doping into diamond is different, and how to accurately control the doping concentration ratio of boron and nitrogen is a key challenge to realize effective n-type doping; at the same time, the uniform distribution of impurity elements and the stability of the reaction environment also need to be considered, and the above factors will affect the crystal quality, conductivity and mechanical properties of the thin film. In addition, the optimization of equipment and the annealing process also affect the final performance of the thin film, therefore, accurate control of each link is the key to successfully preparing high-quality doped diamond thin film.
[0100] To address the challenges of doping n-type semiconductor diamond in existing technologies, which limits its effective application in high-performance electronic devices, particularly high-power devices, this invention proposes a boron-nitrogen co-doped high-performance n-type single-crystal diamond thin film based on MPCVD technology and its preparation method. The core of this method lies in achieving efficient co-doping of boron and nitrogen through precise control of process parameters during growth. In the MPCVD preparation process, high-purity... As a carbon source, As a carrier gas, and Used as boron and nitrogen sources respectively, with the gas ratio controlled as follows: : The boron-nitrogen concentration was set at 4-8%, ensuring a boron-nitrogen ratio between 1:1 and 1:4 to optimize the compensation effect between p-type holes (boron-substituted carbon atoms, donor level 0.37 eV) and n-type electrons (nitrogen-substituted carbon atoms, donor level 1.7 eV). The growth temperature was controlled in stages, maintaining a stable growth temperature of 750-900℃ by controlling microwave power and chamber pressure, with the temperature gradient controlled within ±10°C to avoid nitrogen desorption or boron diffusion. The microwave power was set at 3.7-6.0 kW, with initial low power reducing surface etching and subsequent power increases to enhance performance. , , Dissociation efficiency ( The decomposition rate increased from 20% to 50%. The reaction chamber pressure was maintained at 160-210 mbar, and the uniformity of the plasma spheres was adjusted to ensure the smoothness of the diamond growth surface. During growth, the spectral intensity of boron and nitrogen was monitored by in-situ optical emission spectroscopy (OES), and the flow rate was adjusted in real time. These control measures worked synergistically to enable efficient incorporation of boron and nitrogen into the lattice, reducing... Composite defects and lattice distortions ultimately result in electron mobilities of 10~1500. Carrier concentration ~ The present invention significantly enhances the application potential of N-type diamond thin films in high-power devices. Compared with existing technologies, the present invention overcomes the problems of low doping efficiency and poor uniformity through specific gas ratios, temperature segmentation, dynamic power adjustment, pressure bias design, and real-time monitoring, providing a feasible path for the research and development of n-type diamond-based electronic devices.
[0101] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for fabricating a MISFET device, characterized in that, include: Preparation of P-type substrates; The P-type substrate is etched to form source and drain trenches; Boron-nitrogen co-doped N-type diamond layers were fabricated in the source and drain trenches using MPCVD technology. A gate dielectric layer is formed on the surface of a P-type substrate; Source and drain electrodes are formed on the surface of the N-type diamond layer in the source and drain grooves, respectively. A gate is fabricated on the surface of the gate dielectric layer to form a MISFET device.
2. The method for fabricating a MISFET device according to claim 1, characterized in that, The steps for fabricating boron-nitrogen co-doped N-type diamond layers in source and drain trenches using MPCVD include: Turn on the microwave power supply, and in an environment with a growth temperature of 750℃~900℃ and a growth pressure of 160mbar~210mbar, introduce carbon source, boron source, nitrogen source and growth gas into the MPCVD growth chamber to obtain boron-nitrogen co-doped N-type diamond layer. The boron-nitrogen co-doped N-type diamond layer is etched to retain the N-type diamond layer located in the source and drain trenches.
3. The method for fabricating a MISFET device according to claim 2, characterized in that, The microwave power of the microwave power supply is 3.7kW~6.0kW.
4. The method for fabricating a MISFET device according to claim 2, characterized in that, The carbon source concentration is 4% to 8%.
5. The method for fabricating a MISFET device according to claim 2, characterized in that, The boron-nitrogen ratio is 1:1 to 1:
4.
6. The method for fabricating a MISFET device according to claim 1, characterized in that, The doping concentration of the boron-nitrogen co-doped N-type diamond layer is: ~ .
7. The method for fabricating a MISFET device according to any one of claims 1 to 6, characterized in that, The preparation of P-type substrates includes: Provide growth substrate; Pretreatment of the growth substrate; P-type diamond substrates were obtained by epitaxy on the surface of a growth substrate using MPCVD technology. Remove the growth substrate.
8. The method for fabricating a MISFET device according to claim 7, characterized in that, P-type diamond substrates are obtained by epitaxy on the surface of a growth substrate using MPCVD technology, including: In an environment with a growth temperature of 750℃~900℃ and a growth pressure of 160mbar~190mbar, a carbon source with a concentration of 4%~8%, a boron source with a flow rate of 1sccm~20sccm, and a hydrogen gas with a flow rate of 200sccm~550sccm are introduced into the MPCVD growth chamber with a microwave power of 3.7kW~6.0kW to obtain a P-type diamond layer.
9. The method for fabricating a MISFET device according to any one of claims 1 to 6, characterized in that, The doping concentration of the P-type substrate is ~ .
10. A MISFET device, characterized in that, include: A P-type substrate, wherein the P-type substrate has a source trench and a drain trench; A boron-nitrogen co-doped N-type diamond layer is formed in the source and drain trenches; A gate dielectric layer is formed on the surface of a P-type substrate; The source electrode is formed on the surface of a boron-nitrogen co-doped N-type diamond layer in the source electrode groove. The drain electrode is formed on the surface of the boron-nitrogen co-doped N-type diamond layer in the drain electrode groove; The gate is formed on the surface of the gate dielectric layer.