Diamond field effect transistor preparation method and diamond field effect transistor
By depositing a sacrificial layer on a diamond substrate and forming a conductive channel, and then covering and exposing the ends with a diamond epitaxial layer, the problem of hydrogen-terminated diamond devices being susceptible to external environmental influences is solved, thus achieving the stability of the conductive channel and the overall stability of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-04-07
AI Technical Summary
Existing hydrogen-terminated diamond devices are susceptible to external environmental influences and have poor stability.
A sacrificial layer is deposited and patterned on a diamond substrate to form a conductive channel. Then, a diamond epitaxial layer is deposited to completely cover the sacrificial layer, exposing its two ends to form source and drain electrodes. A conductive medium is formed by hydrogen plasma treatment to isolate the influence of the external environment.
It improves the stability of the conductive channel, ensures the connection between the source and drain electrodes, and enhances the overall stability of the device.
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Figure CN121815695A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of semiconductor technology, and more specifically, relates to a method for fabricating a diamond field-effect transistor and a diamond field-effect transistor. Background Technology
[0002] Buried trench devices made of silicon and silicon carbide are formed using impurity doping. Diamond doping involves artificially introducing specific impurity atoms into the diamond crystal structure to alter its inherent electrical properties, transforming it from an excellent insulator into a semiconductor or conductor. However, effective doping of diamond semiconductor materials still presents many challenges, and the impurity activation rate remains very low.
[0003] Hydrogen-terminated diamond two-dimensional cavitation technology liberates the ultimate semiconductor performance of diamond from its "bulk properties" to "surface properties" through the physical mechanism of surface transfer doping. However, the carbon-hydrogen bonds of hydrogen-terminated diamond are exposed on the outer surface of diamond, making them susceptible to the influence of the external environment, resulting in poor stability of the related devices. Summary of the Invention
[0004] The purpose of this application is to provide a method for fabricating a diamond field-effect transistor and a diamond field-effect transistor, aiming to solve the technical problems of existing hydrogen-terminated diamond devices being susceptible to external environmental influences and having poor stability.
[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: In a first aspect, a method for fabricating a diamond field-effect transistor is provided, comprising: A sacrificial layer is deposited on the top surface of a diamond substrate, and the sacrificial layer is patterned. A diamond epitaxial layer is deposited on the top surface of the diamond substrate; the diamond epitaxial layer completely covers the sacrificial layer, and the two ends of the sacrificial layer are exposed to the first end face and the second end face of the diamond epitaxial layer respectively, with the first end face and the second end face being disposed opposite to each other; A conductive channel is formed at the sacrificial layer; A source electrode is formed on the top surface of the diamond substrate, which abuts against the first end face, and the source electrode is connected to one end of the conductive channel. A drain electrode is formed on the top surface of the diamond substrate, which abuts against the second end face, and the drain electrode is connected to the other end of the conductive channel. A gate electrode is formed on the top surface of the diamond epitaxial layer.
[0006] Compared with the prior art, the diamond epitaxial layer of this application completely covers the sacrificial layer. After the conductive medium is deposited at the location of the sacrificial layer and a conductive channel is formed, the diamond epitaxial layer can achieve full coverage of the conductive channel, avoiding the exposure of the conductive channel. Therefore, it can isolate the influence of the external environment on the conductive channel and improve the conductivity stability of the conductive channel. Furthermore, the two ends of the sacrificial layer are exposed to the first end face and the second end face respectively. After the conductive channel is formed, the two ends of the conductive channel are exposed to the first end face and the second end face respectively, so that after the source electrode and the drain electrode are formed, the source electrode and the drain electrode can be connected through the conductive channel. Therefore, in this application, the conductive channel can be located within the diamond body, reducing external influences and ensuring that the source electrode and drain electrode are connected through the conductive channel, thus exhibiting good stability.
[0007] In conjunction with the first aspect, in one possible implementation, exposing the two ends of the sacrificial layer to the first and second end faces of the diamond epitaxial layer respectively includes: A source electrode region is etched on the diamond epitaxial layer, and the first end face is formed on the side of the diamond epitaxial layer that is in contact with the source electrode region, exposing one end of the sacrificial layer in the source electrode region. A drain electrode region is etched on the diamond epitaxial layer, and a second end face is formed on the side of the diamond epitaxial layer that is in contact with the drain electrode region, exposing the other end of the sacrificial layer in the drain electrode region.
[0008] Since the deposited diamond epitaxial layer needs to completely cover the sacrificial layer, the two ends of the sacrificial layer can be exposed by etching the source electrode region and the drain electrode region in order to connect the source electrode and the drain electrode.
[0009] In some embodiments, etching the source electrode region on the diamond epitaxial layer includes: A source window is photolithographically etched onto the diamond epitaxial layer, and a source electrode region is then formed at the source window using dry etching. The etching of the drain electrode region on the diamond epitaxial layer includes: A drain window is photolithographically etched on the diamond epitaxial layer, and a drain electrode region is formed at the drain window by dry etching.
[0010] By using photolithography to create source and drain windows, etching windows can be formed on the diamond epitaxial layer. This allows etching to proceed along the shape and size of the corresponding windows during the etching process, preventing misalignment and ensuring etching quality.
[0011] In conjunction with the first aspect, in one possible implementation, the sacrificial layer is made of a non-conductive material; The formation of the conductive channel at the sacrificial layer includes: The sacrificial layer is etched with an etchant and then deposited with a conductive medium after being treated with hydrogen plasma to form a conductive channel.
[0012] The conductive channel is formed by etching the sacrificial layer with an etchant and then depositing a conductive medium after treatment with hydrogen plasma. This process can eliminate impurities, ensure good conductivity of the conductive channel, and improve the overall conductivity of the device.
[0013] In some embodiments, the method of etching the sacrificial layer with an etchant and then depositing a conductive medium to form a conductive channel after hydrogen plasma treatment includes: The filling medium within the sacrificial layer is removed using a first etchant. A second etching solution is used to remove the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface, and to form conductive channel holes. The conductive channel holes are formed by treating them with hydrogen plasma to create conductive channel holes on the hydrogen terminal surface. The conductive medium is deposited within the conductive channel holes on the surface of the hydrogen terminal to form the conductive channel.
[0014] The first etchant is used to remove the precipitated sacrificial layer, and the second etchant is used to eliminate low-quality graphite at the heterogeneous interface. After hydrogen plasma treatment, hydrogen-terminated two-dimensional cavitation conductive channels are formed to ensure good conductivity of the conductive channels inside the diamond.
[0015] In some embodiments, the sacrificial layer is one or more metals such as titanium, aluminum, nickel, gold, platinum, and iridium, and the first etchant is aqua regia or a corresponding metal etchant. The sacrificial layer is SiO2, and the first etching solution is a buffer oxide etchant. The sacrificial layer is Al2O3, and the first corrosive solution is a hot phosphoric acid solution.
[0016] By selectively choosing different materials for the sacrificial layer and preparing a corresponding first etchant, the sacrificial layer of different materials can be removed in a targeted manner, thereby improving the targeting and adaptability of the first etchant.
[0017] In some embodiments, the second corrosive liquid is a mixture of concentrated sulfuric acid and nitric acid.
[0018] In some embodiments, after forming a conductive channel at the sacrificial layer, dry etching is used to remove the excess portion of the conductive medium deposited outside the conductive channel, and wet etching is used to etch the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface.
[0019] Excess conductive dielectric is removed by dry etching, and polycrystalline primary diamond is grown by wet etching. This eliminates the influence of conductive dielectric and primary diamond on the source and drain electrode regions, ensuring the integrity of the source and drain electrode formation.
[0020] The second etching solution is used to etch lower-quality diamonds, such as polycrystalline diamonds produced during growth. The mixture of concentrated sulfuric acid and nitric acid is a strong oxidizing acid solution, which has a better removal effect and helps to ensure the overall conductivity of the diamond.
[0021] In conjunction with the first aspect, in one possible implementation, the sacrificial layer is a P-type diamond layer, wherein the deposited P-type diamond layer forms the conductive channel.
[0022] P-type diamond has excellent electrical conductivity and can be directly used as a conductive channel. It can also further simplify the forming process of conductive channels, reduce operation steps, and improve work efficiency.
[0023] Secondly, this application also provides a diamond field-effect transistor, fabricated using the above-described diamond field-effect transistor fabrication method, wherein the diamond field-effect transistor comprises: A diamond substrate with conductive channels on its top surface; the diamond substrate is a high-resistivity layer. A diamond epitaxial layer is disposed on the top surface of the diamond substrate; the diamond epitaxial layer has a first end face and a second end face disposed opposite to each other; A source electrode and a drain electrode are disposed parallel to and spaced apart on the top surface of the diamond substrate; the source electrode abuts against the first end face, and the drain electrode abuts against the second end face; and The gate electrode is placed on top of the diamond epitaxial layer; The top surface of the conductive channel is fully covered by the diamond epitaxial layer; one end of the conductive channel is exposed to the first end face to connect with the source electrode; the other end of the conductive channel is exposed to the second end face to connect with the drain electrode.
[0024] The diamond field-effect transistor provided in this application, because it is prepared by the above-mentioned diamond field-effect transistor preparation method, has all the beneficial effects of the above-mentioned diamond field-effect transistor preparation method. It can embed the conductive channel inside the diamond, eliminate the influence of the external environment on the conductive channel, improve the conductivity stability of the conductive channel, and help improve the overall stability of the device. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 Schematic diagrams of the various stages of the diamond field-effect transistor fabrication method provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of a diamond field-effect transistor provided in an embodiment of this application.
[0027] In the figure: 1. Diamond substrate; 2. Sacrificial layer; 3. Diamond epitaxial layer; 31. First end face; 32. Second end face; 4. Conductive channel; 5. Source electrode region; 6. Drain electrode region; 7. Source electrode; 8. Drain electrode; 9. Gate electrode. Detailed Implementation
[0028] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.
[0029] It should be noted that when an element is referred to as being "set on" another element, it can be directly on or indirectly on that other element. It should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0030] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0031] It is important to understand that diamond currently has two structures: P-type doping and N-type doping. P-type doping is mainly boron doping and is a mature diamond doping technology with a high success rate. N-type doping still has a very low impurity activation rate. N-type doping is mainly phosphorus / nitrogen doping. The stable realization of high-quality N-type doping is the biggest bottleneck in realizing complete diamond electronic devices.
[0032] The carbon-hydrogen bonds of hydrogen-terminated diamond are exposed on the outer surface of the diamond. This can be understood as the conductive structure formed by hydrogen plasma treatment being exposed on the outer surface of the diamond. At this time, the exposed conductive structure is easily affected by the external environment, so the stability of the related devices formed is poor.
[0033] Please refer to the following: Figures 1 to 2 The method for fabricating a diamond field-effect transistor (DFPT) and the DFPT itself provided in this application are now described. The method for fabricating the DFPT includes the following steps: S100: Deposit sacrificial layer 2 on the top surface of diamond substrate 1 and pattern sacrificial layer 2; S200: Deposit a diamond epitaxial layer 3 on the top surface of the diamond substrate 1; make the diamond epitaxial layer 3 completely cover the sacrificial layer 2, and expose the two ends of the sacrificial layer 2 to the first end face 31 and the second end face 32 of the diamond epitaxial layer 3 respectively, with the first end face 31 and the second end face 32 being disposed opposite to each other. S300: A conductive channel 4 is formed at the sacrificial layer 2; S400: A source electrode 7 is formed on the top surface of the diamond substrate 1, which abuts against the first end face 31 and is connected to one end of the conductive channel 4. A drain electrode 8 is formed on the top surface of the diamond substrate 1, which abuts against the second end face 32 and is connected to the other end of the conductive channel 4. S500: A gate electrode 9 is formed on the top surface of the diamond epitaxial layer 3.
[0034] It is important to understand that the patterned sacrificial layer 2 is used to form the path of the conductive channel 4, and the size of the sacrificial layer 2 determines the size of the conductive channel 4. The conductive channel 4 is used to connect the source electrode 7 and the drain electrode 8. As a current channel with variable resistance that is precisely controlled by the gate voltage, the conductive channel 4 is not only the physical path through which current flows from the source to the drain, but also a "converter" and "amplifier" that converts the voltage control signal on the gate into a current output signal between the source and drain.
[0035] Preferably, the patterned sacrificial layer 2 extends along the direction from the first end face 31 to the second end face 32, so that the formed conductive channel 4 extends in a straight line, thereby reducing the resistance on the conductive channel 4. Optionally, the extension path of the conductive channel 4 can be designed according to actual needs, and the patterned sacrificial layer 2 is set accordingly. Specifically, the conductive channel 4 in the accompanying drawings of this application is only a schematic diagram of the quantity and direction, and the quantity and direction of the conductive channel 4 can be selectively set according to actual needs. Preferably, the formed conductive channel 4 is a plurality of conductive channels 4 arranged in parallel, which can achieve a larger output characteristic. And the strip or column size of the conductive channel 4 can be set according to actual needs.
[0036] Optionally, after the sacrificial layer 2 is deposited, the crystallinity of the sacrificial layer 2 can be improved by annealing.
[0037] Optionally, in S200, a 2μm thick diamond epitaxial layer 3 is deposited using an MPCVD device, and the diamond epitaxial layer 3 completely covers the sacrificial layer 2 to avoid exposing the sacrificial layer 2 to the external environment, thereby avoiding the exposure of the conductive channel 4.
[0038] Specifically, the diamond epitaxial layer 3 is selected from high-purity epitaxial layers or nitrogen-doped epitaxial layers, which are non-conductive or have poor conductivity. The thickness of the deposited diamond epitaxial layer 3 can be 10nm~200μm. The thickness of the deposited diamond epitaxial layer 3 will affect the capacitance of the gate electrode 9, thereby affecting the device performance. Specifically, if the deposition thickness increases, the gate capacitance decreases and the gate control deteriorates; if the thickness decreases, the gate capacitance increases and the gate control characteristics are enhanced, but the gate leakage current will increase. Therefore, the deposition thickness of the diamond epitaxial layer 3 can be selectively set according to actual needs. Preferably, the thickness of the diamond epitaxial layer 3 is 100nm.
[0039] It is important to understand that when the diamond epitaxial layer 3 completely covers the sacrificial layer 2, if the diamond epitaxial layer 3 directly covers both ends of the sacrificial layer 2, then the connection between the source electrode 7, the drain electrode 8 and the conductive channel 4 will not be possible.
[0040] Specifically, since the source electrode 7 abuts against the first end face 31 and one end of the sacrificial layer 2 is exposed to the first end face 31, the source electrode 7 can be easily connected to one end of the conductive channel 4; similarly, since the drain electrode 8 abuts against the second end face 32 and the other end of the sacrificial layer 2 is exposed to the second end face 32, the drain electrode 8 can be easily connected to the other end of the conductive channel 4.
[0041] Furthermore, the diamond substrate 1 can be nitrogen-doped N-type diamond.
[0042] It is important to understand that diamond materials have the characteristics of a large bandgap, a strong breakdown field, and high thermal conductivity. Therefore, transistors formed from diamond materials have significant advantages over similar devices made from silicon carbide and silicon, and can have higher breakdown voltage and current density.
[0043] Compared with the prior art, the diamond epitaxial layer 3 of this application completely covers the sacrificial layer 2. After depositing the conductive medium at the location of the sacrificial layer 2 and forming the conductive channel 4, the diamond epitaxial layer 3 can achieve full coverage of the conductive channel 4, avoiding the exposure of the conductive channel 4. Therefore, it can isolate the influence of the external environment on the conductive channel 4 and improve the conductivity stability of the conductive channel 4. Furthermore, the two ends of the sacrificial layer 2 are exposed to the first end face 31 and the second end face 32 respectively. After the conductive channel 4 is formed, the two ends of the conductive channel 4 are exposed to the first end face 31 and the second end face 32 respectively, so that after the source electrode 7 and the drain electrode 8 are formed, the source electrode 7 and the drain electrode 8 can be connected through the conductive channel 4. Therefore, in this application, the conductive channel 4 can be located within the diamond body, reducing external influences and ensuring the connection between the source electrode 7 and the drain electrode 8 and the conductive channel 4, thus exhibiting good stability.
[0044] Please see Figure 1 In some possible embodiments, in S200, the two ends of the sacrificial layer 2 are exposed to the first end face 31 and the second end face 32 of the diamond epitaxial layer 3, which may specifically include the following steps: etching a source electrode region 5 on the diamond epitaxial layer 3, forming a first end face 31 on the side of the diamond epitaxial layer 3 that is connected to the source electrode region 5, exposing one end of the sacrificial layer 2 in the source electrode region 5; etching a drain electrode region 6 on the diamond epitaxial layer 3, forming a second end face 32 on the side of the diamond epitaxial layer 3 that is connected to the drain electrode region 6, exposing the other end of the sacrificial layer 2 in the drain electrode region 6.
[0045] Specifically, when depositing the diamond epitaxial layer 3, the diamond epitaxial layer 3 directly covers both ends of the sacrificial layer 2. On the one hand, the sacrificial layer 2 is blocked by the diamond epitaxial layer 3, and the sacrificial layer 2 cannot be directly removed, and a conductive channel 4 is formed at the sacrificial layer 2. On the other hand, if the source electrode 7 or the drain electrode 8 is directly formed on the diamond substrate 1, the source electrode 7 and the drain electrode 8 cannot be connected through the conductive channel 4 at the sacrificial layer 2.
[0046] In this application, by removing part of the diamond epitaxial layer 3, a source electrode region 5 and a drain electrode region 6 are formed, so as to facilitate the formation of a source electrode 7 in the source electrode region 5 and a drain electrode 8 in the drain electrode region 6. Furthermore, in this application, the two ends of the sacrificial layer 2 are exposed in the source electrode region 5 and the drain electrode region 6 respectively. Therefore, after the source electrode 7 and the drain electrode 8 are formed, the conductive channel 4 can be connected to the source electrode 7 and the drain electrode 8.
[0047] It should be understood that the sacrificial layer 2 is a graphical structure that includes two connection ends. One connection end is exposed at the first end face 31 near the source electrode region 5 for connection with the source electrode 7, and the other connection end is exposed at the second end face 32 near the drain electrode region 6 for connection with the drain electrode 8.
[0048] Since the deposited diamond epitaxial layer 3 needs to completely cover the sacrificial layer 2, the two ends of the sacrificial layer 2 can be exposed by etching the source electrode region 5 and the drain electrode region 6 in order to connect the source electrode 7 and the drain electrode 8.
[0049] Please see Figure 1 In some embodiments, etching the source electrode region 5 on the diamond epitaxial layer 3 specifically includes the following steps: photolithographically etching a source window on the diamond epitaxial layer 3, and dry etching the source electrode region 5 at the source window.
[0050] The etching of the drain electrode region 6 on the diamond epitaxial layer 3 specifically includes the following steps: photolithographically etching a drain window on the diamond epitaxial layer 3, and then dry etching the drain electrode region 6 at the drain window.
[0051] By photolithographically creating source and drain windows, etching windows are formed on the diamond epitaxial layer 3, allowing etching to proceed along the shape and size of the corresponding windows during the etching process, thus avoiding deviations that could affect the etching quality.
[0052] Specifically, photoresist is coated on the diamond epitaxial layer 3, and the source and drain window patterns are defined by photolithography, i.e., the source window and drain window are formed; optionally, the dry etching method uses reactive ion etching, using oxygen-based or hydrogen-based plasma, to etch away the diamond epitaxial layer 3 to a certain depth at the source and drain windows to form the source electrode region 5 and the drain electrode region 6.
[0053] The source electrode region 5 and the drain electrode region 6 are used to create the step or groove region for subsequent fabrication of ohmic contacts. This step is not to fabricate the electrode itself, but to prepare an ideal interface region for the deposition and alloying of the electrode metal, which helps to reduce contact resistance and improve the overall device performance.
[0054] Specifically, when forming the source electrode 7 or the drain electrode 8, a layer of metal Au is evaporated by an electron beam, and after being peeled off, the source and drain ohmic contact electrodes are formed; when forming the gate electrode 9, a layer of metal Ti / Au is first evaporated by an electron beam, and after being peeled off, the gate electrode 9 is formed.
[0055] Optionally, when forming the source electrode 7 or the drain electrode 8, in addition to Au, one or more of Ti, Al, Pt, Ni, W, Pd, etc. can be selected; optionally, the formed source electrode 7 or drain electrode 8 can be formed into an ohmic contact with or without high-temperature annealing.
[0056] Optionally, the gate electrode 9 metal can be selected from one or more of the following: Ti, Al, Pt, Au, Ni, W, Pd, etc.
[0057] It should be understood that the diamond epitaxial layer 3 is used to form the gate dielectric, and the thickness of its deposition affects the performance of the gate electrode 9. Furthermore, before forming the gate electrode 9, a layer of gate dielectric can be deposited on the diamond epitaxial layer 3 to increase the thickness of the gate dielectric and reduce the risk of gate leakage.
[0058] Please see Figure 1 In some possible embodiments, the sacrificial layer 2 is a non-conductive material; forming a conductive channel 4 at the sacrificial layer 2 includes the following steps: etching the sacrificial layer 2 with an etchant and depositing a conductive medium after hydrogen plasma treatment to form the conductive channel 4.
[0059] The conductive channel 4, formed by etching the sacrificial layer 2 with an etchant and depositing a conductive medium after hydrogen plasma treatment, can eliminate impurities, ensure good conductivity of the conductive channel 4, and improve the overall conductivity of the device.
[0060] It should be understood that the non-conductive sacrificial layer 2 cannot achieve the function of conducting electricity. Therefore, before forming the conductive channel 4, the non-conductive sacrificial layer 2 needs to be removed in order to deposit the conductive medium.
[0061] The pre-deposited and patterned sacrificial layer 2 material is removed to create a cavity for the subsequent formation of conductive channel 4 or suspended structure; before depositing conductive medium, hydrogen plasma treatment can clean and modify the exposed cavity interior surface; the conductive medium completely fills or covers the previously formed cavity, thereby forming a conductive path with a specific shape surrounded by air or medium, namely conductive channel 4.
[0062] Please see Figure 1In some embodiments, the sacrificial layer 2 is etched with a first etchant and then a conductive medium is deposited after hydrogen plasma treatment to form a conductive channel 4. This can be understood as follows: the first etchant is used to remove the filling medium in the sacrificial layer 2; the second etchant is used to remove the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface and form a conductive channel hole; the conductive channel hole is treated with hydrogen plasma to form a conductive channel hole on the hydrogen terminal surface; and the conductive medium is deposited in the conductive channel hole on the hydrogen terminal surface to form a conductive channel 4.
[0063] The first etchant is used to remove the precipitated sacrificial layer 2, and the second etchant is used to eliminate low-quality graphite at the heterogeneous interface. After hydrogen plasma treatment, hydrogen-terminated two-dimensional cavitation conductive channels 4 are formed to ensure good conductivity of the conductive channels 4 inside the diamond.
[0064] Specifically, a first etchant with high selectivity for the sacrificial layer 2 material is used to completely remove the filling medium of the sacrificial layer 2 located in the patterned substrate groove, exposing the diamond growth structure. A second etchant or reactive ion etching process is used to selectively remove the diamond nucleation layer or defect layer with low electrical quality located at the heterojunction interface, and to form conductive channel holes with a pre-defined pattern in the high-quality epitaxial diamond layer.
[0065] In a hydrogen atmosphere, plasma is used to treat conductive channel holes to clean their surfaces and achieve hydrogen termination by forming CH bonds, thereby obtaining conductive channel holes with hydrogen-terminated surfaces that have surface conductivity. It should be understood that forming conductive channel holes with hydrogen-terminated surfaces can also be understood as hydrogen-terminating the surface of the hole wall of the conductive channel hole.
[0066] Optionally, atomic layer deposition (ALD) technology is used to conformally deposit a conductive medium in the conductive channel holes on the surface of the hydrogen terminal, ultimately forming a high-performance diamond-based conductive channel 4.
[0067] Specifically, the conductive medium can be selected by depositing a 2μm thick Al2O3 dielectric layer.
[0068] Optionally, the deposited conductive medium is one or a combination of Al2O3, HfO2, AlN, SiO2, and SiN.
[0069] Please see Figure 1 In some embodiments, the sacrificial layer 2 is one or more of the following metals: titanium, aluminum, nickel, gold, platinum, iridium, etc., and the first etching solution is aqua regia or a corresponding metal etching solution; the sacrificial layer 2 is SiO2, and the first etching solution is a buffer oxide etchant; the sacrificial layer 2 is Al2O3, and the first etching solution is a hot phosphoric acid solution.
[0070] By selectively choosing different materials for the sacrificial layer 2 and preparing corresponding first etchant solutions, the sacrificial layer 2 of different materials can be removed in a targeted manner, thereby improving the targeting and adaptability of the first etchant solution.
[0071] Aqua regia is the ultimate cleaning and etching agent in semiconductor processes, especially adept at treating precious metal contamination and providing ultra-clean surfaces. It is a highly oxidizing and corrosive mixed acid composed of concentrated nitric acid and concentrated hydrochloric acid in a specific volume ratio.
[0072] Buffer oxide etchants are usually aqueous buffer solutions of hydrofluoric acid and ammonium fluoride. HF reacts chemically with SiO2 to generate soluble hexafluorosilicic acid, which dissolves silicon dioxide. The addition of ammonium fluoride acts as a buffer, stabilizing the concentration of HF and making the corrosion rate more uniform and controllable.
[0073] Hot phosphoric acid solutions are typically phosphoric acid with a concentration of 85% or higher, and are used after heating to 150°C-180°C. High-temperature phosphoric acid reacts with Al₂O₃ to form soluble aluminum phosphate, thus achieving corrosion.
[0074] Please see Figure 1 In some embodiments, the second corrosive liquid is a mixture of concentrated sulfuric acid and nitric acid.
[0075] The second etching solution is used to etch lower-quality diamonds, such as polycrystalline diamonds produced during growth. The mixture of concentrated sulfuric acid and nitric acid is a strong oxidizing acid solution, which has a better removal effect and helps to ensure the overall conductivity of the diamond.
[0076] The second etching solution has high selectivity for the internal quality differences of diamond materials, and can selectively etch defects in the poor-quality parts to remove inferior ones and improve the performance of diamond devices.
[0077] Please see Figure 1 In some embodiments, after completing S300, dry etching is used to remove the excess portion of the conductive medium deposited outside the conductive channel 4, and wet etching is used to etch the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface.
[0078] Specifically, the excess portion of the conductive medium deposited outside the conductive channel 4 can be understood as the excess portion of the conductive medium deposited inside the source electrode region 5 or the drain electrode region 6.
[0079] It is important to understand that during the deposition of conductive medium to form conductive channel 4, the conductive medium not only fills the conductive channel hole where the original sacrificial layer 2 is located, but also disperses into the source electrode region 5 and the drain electrode region 6. Therefore, it is necessary to remove the conductive medium deposited in the source electrode region 5 and the drain electrode region 6, and low-quality crystals will be generated at the heterogeneous interface between the deposited conductive medium and the diamond substrate 1.
[0080] In this application, excess conductive medium is removed by dry etching, eliminating the conductive medium remaining in the source electrode region 5 or the drain electrode region 6; the influence of primary diamond such as polycrystalline diamond grown by wet etching is eliminated, completely exposing the source electrode region 5 and the drain electrode region 6 for making ohmic contacts, ensuring the cleanliness and integrity of the electrode regions, and ensuring the reliability of the formation of the source electrode 7 and the drain electrode 8.
[0081] Specifically, dry etching uses reactive ion etching, employing plasma to remove excess conductive dielectric. Wet etching uses a mixture of concentrated sulfuric acid and nitric acid as the etching solution. This mixture is a strong oxidizing acid solution, resulting in better removal and helping to maintain the overall conductivity of the diamond.
[0082] Please see Figure 1 In some possible embodiments, the sacrificial layer 2 is a P-type diamond layer, wherein the deposited P-type diamond layer forms a conductive channel 4.
[0083] P-type diamond has good electrical conductivity and can be directly used as a conductive channel 4 for conducting electricity. It can also further simplify the forming process of the conductive channel 4, reduce operation steps, and improve work efficiency.
[0084] In this embodiment, the method for fabricating a diamond field-effect transistor can be understood as comprising the following steps: S100: A P-type diamond layer is deposited on the top surface of the diamond substrate 1, and the P-type diamond layer is patterned. S200: Deposit a diamond epitaxial layer 3 on the top surface of the diamond substrate 1; make the diamond epitaxial layer 3 completely cover the P-type diamond layer, and expose the two ends of the P-type diamond layer to the first end face 31 and the second end face 32 of the diamond epitaxial layer 3 respectively, with the first end face 31 and the second end face 32 being disposed opposite to each other. S300: The patterned P-type diamond layer is the conductive channel 4; S400: A source electrode 7 is formed on the top surface of the diamond substrate 1, which abuts against the first end face 31 and is connected to one end of the conductive channel 4. A drain electrode 8 is formed on the top surface of the diamond substrate 1, which abuts against the second end face 32 and is connected to the other end of the conductive channel 4. S500: A gate electrode 9 is formed on the top surface of the diamond epitaxial layer 3.
[0085] Please see Figure 2Based on the same inventive concept, this application also provides a diamond field-effect transistor (DFET), fabricated using the aforementioned DFET fabrication method. The DFET includes a diamond substrate 1, a diamond epitaxial layer 3, a source electrode 7, a drain electrode 8, and a gate electrode 9. A conductive channel 4 is provided on the top surface of the diamond substrate 1. The diamond substrate 1 is a high-resistivity layer. The diamond epitaxial layer 3 is disposed on the top surface of the diamond substrate 1. The diamond epitaxial layer 3 has a first end face 31 and a second end face 32 disposed opposite to each other. The source electrode 7 and the drain electrode 8 are parallel and spaced apart on the top surface of the diamond substrate 1. The source electrode 7 abuts against the first end face 31, and the drain electrode 8 abuts against the second end face 32. The gate electrode 9 is placed on top of the diamond epitaxial layer 3. The top surface of the conductive channel 4 is fully covered by the diamond epitaxial layer 3. One end of the conductive channel 4 is exposed to the first end face 31 to connect with the source electrode 7. The other end of the conductive channel 4 is exposed to the second end face 32 to connect with the drain electrode 8.
[0086] It should be understood that the conductive channel 4 of the diamond field-effect transistor provided in this application is covered by the diamond epitaxial layer 3, and only the two ends of the conductive channel 4 are exposed at the first end face 31 and the second end face 32 of the diamond epitaxial layer 3. After the source electrode 7 and the drain electrode 8 are formed, the conductive channel 4 can be hidden to isolate the influence of the external environment.
[0087] The diamond field-effect transistor provided in this application, because it is prepared by the above-mentioned diamond field-effect transistor preparation method, has all the beneficial effects of the above-mentioned diamond field-effect transistor preparation method. The conductive channel 4 can be built into the diamond, eliminating the influence of the external environment on the conductive channel 4, improving the conductivity stability of the conductive channel 4, and helping to improve the overall stability of the device.
[0088] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for fabricating a diamond field-effect transistor, characterized in that, Includes the following steps: A sacrificial layer (2) is deposited on the top surface of a diamond substrate (1), and the sacrificial layer (2) is patterned. A diamond epitaxial layer (3) is deposited on the top surface of the diamond substrate (1) so that the diamond epitaxial layer (3) completely covers the sacrificial layer (2) and the two ends of the sacrificial layer (2) are exposed to the first end face (31) and the second end face (32) of the diamond epitaxial layer (3) respectively, with the first end face (31) and the second end face (32) being disposed opposite to each other; A conductive channel (4) is formed at the sacrificial layer (2); A source electrode (7) is formed on the top surface of the diamond substrate (1) and abuts against the first end face (31), and the source electrode (7) is connected to one end of the conductive channel (4). A drain electrode (8) is formed on the top surface of the diamond substrate (1) and abuts against the second end face (32), and the drain electrode (8) is connected to the other end of the conductive channel (4). A gate electrode (9) is formed on the top surface of the diamond epitaxial layer (3).
2. The method for fabricating a diamond field-effect transistor as described in claim 1, characterized in that, The method of exposing the two ends of the sacrificial layer (2) to the first end face (31) and the second end face (32) of the diamond epitaxial layer (3) includes: A source electrode region (5) is etched on the diamond epitaxial layer (3). The first end face (31) is formed on the side of the diamond epitaxial layer (3) that is connected to the source electrode region (5), exposing one end of the sacrificial layer (2) in the source electrode region (5). A drain electrode region (6) is etched on the diamond epitaxial layer (3). The side of the diamond epitaxial layer (3) that is connected to the drain electrode region (6) forms the second end face (32), exposing the other end of the sacrificial layer (2) in the drain electrode region (6).
3. The method for fabricating a diamond field-effect transistor as described in claim 2, characterized in that, The etching of the source electrode region (5) on the diamond epitaxial layer (3) includes: A source window is photolithographically etched on the diamond epitaxial layer (3), and a source electrode region (5) is formed at the source window by dry etching. The etching of the drain electrode region (6) on the diamond epitaxial layer (3) includes: A drain window is photolithographically formed on the diamond epitaxial layer (3), and a drain electrode region (6) is formed at the drain window by dry etching.
4. The method for fabricating a diamond field-effect transistor as described in claim 1, characterized in that, The sacrificial layer (2) is made of a non-conductive material; The formation of the conductive channel (4) at the sacrificial layer (2) includes: The sacrificial layer (2) is etched with an etchant and then a conductive medium is deposited after hydrogen plasma treatment to form a conductive channel (4).
5. The method for fabricating a diamond field-effect transistor as described in claim 4, characterized in that, The method of etching the sacrificial layer (2) with an etchant and then depositing a conductive medium to form a conductive channel (4) after hydrogen plasma treatment includes: The filling medium in the sacrificial layer (2) is removed using a first etchant; A second etching solution is used to remove the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface, and to form conductive channel holes. The conductive channel holes are formed by treating them with hydrogen plasma to create conductive channel holes on the hydrogen terminal surface. The conductive medium is deposited in the conductive channel holes on the surface of the hydrogen terminal to form the conductive channel (4).
6. The method for fabricating a diamond field-effect transistor as described in claim 5, characterized in that, The sacrificial layer (2) is one or more of the following metals: titanium, aluminum, nickel, gold, platinum, iridium, etc., and the first corrosion solution is aqua regia or a corresponding metal corrosion solution. The sacrificial layer (2) is SiO2, and the first etching solution is a buffer oxide etchant; The sacrificial layer (2) is Al2O3, and the first corrosive solution is a hot phosphoric acid solution.
7. The method for fabricating a diamond field-effect transistor as described in claim 5 or 6, characterized in that, The second corrosive solution is a mixture of concentrated sulfuric acid and nitric acid.
8. The method for fabricating a diamond field-effect transistor as described in claim 4, characterized in that, After forming a conductive channel (4) at the sacrificial layer (2), the excess portion of the conductive medium deposited outside the conductive channel (4) is removed by dry etching, and the low-quality primary diamond formed by the growth of diamond material at the heterogeneous interface is formed by wet etching.
9. The method for fabricating a diamond field-effect transistor as described in claim 1, characterized in that, The sacrificial layer (2) is a P-type diamond layer, wherein the deposited P-type diamond layer forms the conductive channel (4).
10. A diamond field-effect transistor, characterized in that, The diamond field-effect transistor is fabricated using the method described in any one of claims 1-9, wherein the diamond field-effect transistor comprises: A diamond substrate (1) has a conductive channel (4) on its top surface; the diamond substrate (1) is a high-resistivity layer; A diamond epitaxial layer (3) is disposed on the top surface of the diamond substrate (1); the diamond epitaxial layer (3) has a first end face (31) and a second end face (32) disposed opposite to each other; Source electrode (7) and drain electrode (8) are disposed parallel to each other and spaced apart on the top surface of the diamond substrate (1); the source electrode (7) abuts against the first end face (31), and the drain electrode (8) abuts against the second end face (32); and The gate electrode (9) is placed on top of the diamond epitaxial layer (3); The top surface of the conductive channel (4) is fully covered by the diamond epitaxial layer (3); one end of the conductive channel (4) is exposed to the first end face (31) to connect with the source electrode (7); the other end of the conductive channel (4) is exposed to the second end face (32) to connect with the drain electrode (8).