A device based on aluminum-doped diamond ohmic contact and a preparation method thereof

Abstract

This invention discloses a device based on aluminum-doped diamond ohmic contacts and its fabrication method. The method includes: selecting a single-crystal diamond substrate; growing a boron-doped diamond epitaxial layer on the single-crystal diamond substrate; fabricating an aluminum metal layer in two ohmic contact regions on the boron-doped diamond epitaxial layer; growing an aluminum oxide barrier layer on the aluminum metal layer and the boron-doped diamond epitaxial layer; performing rapid thermal annealing on the prepared sample to diffuse aluminum from the aluminum metal layer into the boron-doped diamond epitaxial layer directly below, forming an aluminum-doped diamond layer; removing the remaining aluminum metal layer and aluminum oxide barrier layer; and fabricating an ohmic electrode on the aluminum-doped diamond layer. The device fabricated by this invention has excellent ohmic contact, reduces contact resistivity and on-resistance, reduces Joule heat loss in current transmission, and significantly improves the efficiency and reliability of high-power, high-frequency devices. Furthermore, the fabrication process is simplified, has low cost, high repeatability, and high compatibility.

Description

Technical Field

[0001] This invention relates to the field of microelectronics technology, specifically to a device based on aluminum-doped diamond ohmic contacts and its fabrication method. Background Technology

[0002] Diamond, as the "ultimate semiconductor," possesses a series of outstanding physicochemical properties, making it a key material for overcoming technological bottlenecks. Its bandgap is as high as 5.45-5.5 eV, far exceeding that of silicon (1.12 eV), silicon carbide (3.26 eV), and gallium nitride (3.4 eV), naturally filtering visible light interference and giving it an inherent advantage in solar-blind ultraviolet detection; its thermal conductivity reaches 22 W / (cm²). K), which is 5 times that of copper, effectively solves the "self-heating effect" of devices; the breakdown field strength is as high as 10MV / cm, which can withstand higher voltages and reduce the risk of leakage; the carrier mobility is excellent (electrons: 4500cm² / (V)). s), Hole: 3800cm² / (V It ensures carrier transport efficiency under high-frequency operating conditions; at the same time, it also has the characteristics of high hardness, radiation resistance, and good chemical stability, and can adapt to extreme and harsh environments such as aerospace and nuclear industry.

[0003] However, due to the lack of key breakthroughs in efficient bulk doping technology, current research on ohmic contacts for diamond devices mainly focuses on field-effect transistors (FETs) that use surface-epitaxially heavily doped layers or surface hydrogen-terminated two-dimensional holes as conductive channels. Although these diamond FETs have shown great potential in power electronics applications, their overall performance still lags significantly behind that of mature gallium nitride-based high electron mobility transistors (HEMTs). High ohmic contact resistance is one of the core factors limiting performance improvement. The quality of the ohmic contact directly determines the frequency response characteristics and maximum output power capability of diamond microwave power devices: for high-frequency, small-size devices, the source-drain series resistance, primarily due to ohmic contact resistance, is the core bottleneck limiting frequency characteristic optimization; while for power devices, ohmic contact resistance not only affects the on-current and saturation voltage drop levels but also constrains further increases in maximum output power from both voltage carrying capacity and current transport perspectives.

[0004] Furthermore, the high-temperature annealing (above 500°C) or hydrogen plasma treatment using MPCVD (Microwave Plasma Chemical Vapor Deposition) required for forming high-quality ohmic contacts in mainstream diamond ohmic contact fabrication methods severely conflict with silicon-based device processes, significantly increasing the complexity and cost of diamond device fabrication. In the selection of ohmic contact electrodes for diamond p-type devices, traditional solutions heavily rely on gold (Au) as the electrode metal. However, this "gold dependence" is becoming a major obstacle to its large-scale application. Gold has a relatively low melting point (approximately 1064°C) and poor adhesion to certain dielectric materials. During subsequent high-temperature processes or long-term high-temperature operation of the device, gold electrodes may experience diffusion, spheroidization, or detachment, affecting long-term reliability. Moving towards "Au-free processes" has become an urgent improvement direction for the industry.

[0005] As diamond field-effect transistors (FETs), diodes, and other devices rapidly evolve towards higher frequencies, higher power outputs, and higher temperatures, the performance requirements for ohmic contacts are becoming increasingly stringent. In diamond FETs, low ohmic contact resistance can effectively reduce energy loss during current transmission, thereby significantly improving the transconductance characteristics and maximum operating current of the device. In power devices, ohmic resistance directly affects the device's saturation voltage and conduction current, suppressing the magnitude of the device's output power in terms of both voltage and current swing.

[0006] Traditional ohmic contact fabrication methods are no longer sufficient to meet the application requirements of such high-performance diamond devices. Therefore, it is urgent to achieve breakthrough improvements in ohmic contact performance through various technical approaches, such as optimized contact structure design, innovative contact material systems, and improved fabrication processes, so as to lay the foundation for a comprehensive improvement in the performance of diamond devices. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a device based on aluminum-doped diamond ohmic contacts and its fabrication method.

[0008] The technical problem to be solved by this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for fabricating a device based on an aluminum-doped diamond ohmic contact, comprising: Select the cleaned single-crystal diamond substrate; A boron-doped diamond epitaxial layer is grown on the cleaned single-crystal diamond substrate. Two spaced aluminum metal layers are fabricated on a boron-doped diamond epitaxial layer with two ohmic contact regions. An aluminum oxide barrier layer is grown on the two aluminum metal layers and the B-doped diamond epitaxial layer located between the two aluminum metal layers; The prepared sample is subjected to rapid thermal annealing. Under the blocking effect of the alumina barrier layer, the aluminum in the two aluminum metal layers diffuses into the B-doped diamond epitaxial layer located directly below the aluminum metal layer, forming two spaced aluminum-doped diamond layers. Remove any remaining aluminum metal layer and aluminum oxide barrier layer; Two ohmic electrodes made of aluminum material are fabricated on the two aluminum-doped diamond layers.

[0009] In one embodiment of the present invention, a cleaned single-crystal diamond substrate layer is selected, including: Select an undoped single-crystal diamond substrate; The single-crystal diamond substrate was sequentially cleaned with a strong acid mixture, acetone, ethanol, and deionized water to obtain the cleaned single-crystal diamond substrate.

[0010] In one embodiment of the present invention, growing a boron-doped diamond epitaxial layer on the cleaned single-crystal diamond substrate includes: A boron-doped diamond epitaxial layer was deposited on the cleaned single-crystal diamond substrate using chemical vapor deposition (CVD). The pressure was 140–160 mbar, the power was 4000–4200 W, the substrate surface temperature was 850–950 °C, the H2 flow rate was 300–400 sccm, the CH4 flow rate was 12–18 sccm, the BH3 flow rate was 1.0 sccm, and the deposition time was 20–30 min.

[0011] In one embodiment of the present invention, two spaced-apart aluminum metal layers are prepared on a boron-doped diamond epitaxial layer in two ohmic contact regions, including: The sample was coated with a resist, photolithographically ... In an argon atmosphere, the aluminum metal layer is magnetron sputtered on the B-doped diamond epitaxial layer in two ohmic contact regions and on the photoresist between the two ohmic contact regions using physical vapor deposition, wherein the argon flow rate is 80~100 sccm and the thickness of the aluminum metal layer is 50~100 nm. Remove the photoresist between the ohmic contact areas and the aluminum metal layer on top of the photoresist.

[0012] In one embodiment of the present invention, an alumina barrier layer is grown on the two aluminum metal layers and the boron-doped diamond epitaxial layer located between the two aluminum metal layers, comprising: In a vacuum atmosphere, an aluminum oxide barrier layer is deposited on two aluminum metal layers and a B-doped diamond epitaxial layer located between the two aluminum metal layers using atomic layer deposition (ALD) technology, wherein the temperature is 200-300 °C, the TMA pulse time is 0.2-0.5 s, and the deposition time is 100-120 min.

[0013] In one embodiment of the present invention, the prepared sample is subjected to rapid thermal annealing. Under the blocking effect of the alumina barrier layer, aluminum in the two aluminum metal layers diffuses into the boron-doped diamond epitaxial layer located directly below the aluminum metal layers, forming two spaced-apart aluminum-doped diamond layers, including: Rapid thermal annealing is performed using inert argon as a protective gas. Under the blocking effect of the alumina barrier layer, aluminum in the two aluminum metal layers diffuses into the boron-doped diamond epitaxial layer located directly below the aluminum metal layer to form two aluminum-doped diamond layers. The argon flow rate is 100~150 sccm, the temperature is 700~800℃, and the annealing time is 5~10 min.

[0014] In one embodiment of the present invention, removing the remaining aluminum metal layer and the aluminum oxide barrier layer includes: The residual aluminum metal layer and the aluminum oxide barrier layer are removed using a sodium hydroxide solution.

[0015] In one embodiment of the present invention, after fabricating two aluminum ohmic electrodes in the two aluminum-doped diamond layers, the method further includes: An alumina dielectric layer is prepared on the exposed portion of the B-doped diamond epitaxial layer; An aluminum gate electrode is fabricated on the alumina dielectric layer.

[0016] In one embodiment of the present invention, after fabricating two aluminum ohmic electrodes in the two aluminum-doped diamond layers, the method further includes: Schottky electrodes of aluminum material are fabricated on the exposed portion of the B-doped diamond epitaxial layer.

[0017] In a second aspect, the present invention also provides a device based on an aluminum-doped diamond ohmic contact, fabricated using any of the above-described methods, the device comprising: Single-crystal diamond substrate; A boron-doped diamond epitaxial layer is disposed on the single-crystal diamond substrate layer; Two aluminum-doped diamond layers are spaced apart on a boron-doped diamond epitaxial layer in the ohmic contact region, and the upper surface of the aluminum-doped diamond layer is at the same level as the upper surface of the boron-doped diamond epitaxial layer located between the two aluminum-doped diamond layers. Two ohmic electrodes made of aluminum are respectively disposed on two aluminum-doped diamond layers.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for fabricating a device based on an aluminum-doped diamond ohmic contact. The method first grows a boron-doped diamond epitaxial layer on a cleaned single-crystal diamond substrate. Then, two spaced-apart aluminum metal layers are fabricated on the boron-doped diamond epitaxial layer. An aluminum oxide barrier layer is then fabricated on the exposed boron-doped diamond epitaxial layer and the aluminum metal layers. Subsequently, under the barrier effect of the aluminum oxide barrier layer, rapid thermal annealing causes aluminum in the aluminum metal layer to diffuse into the boron-doped diamond epitaxial layer located directly below the aluminum metal layer. Thus, an aluminum-doped diamond layer is formed in the ohmic contact region through the diffusion of aluminum within the boron-doped diamond epitaxial layer. This invention utilizes low-melting-point aluminum metal in the boron-doped diamond contact layer. The aluminum-doped diamond layer formed by diffusion within the diamond epitaxial layer has a low activation energy, resulting in a device with extremely high carrier concentration and extremely low ohmic contact resistance at room temperature. This reduces contact resistivity and, consequently, conduction resistance, minimizing Joule heat loss during current transmission and significantly improving the efficiency and reliability of high-power, high-frequency devices. Furthermore, this invention effectively reduces contact resistance. Based on existing equipment, this invention achieves a high-conductivity ohmic contact device through a simple process, without relying on MPCVD equipment or precious metal gold electrodes. The fabrication process is simplified, cost-effective, highly repeatable, and also highly compatible.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for fabricating a device based on an aluminum-doped diamond ohmic contact provided by the present invention. Figures 2a-2f This is a schematic diagram illustrating the fabrication process of a device based on an aluminum-doped diamond ohmic contact provided by the present invention. Figure 3 This is a schematic diagram of the structure of a MOSFET device based on an aluminum-doped diamond ohmic contact provided by the present invention; Figure 4 This is a schematic diagram of the structure of a Schottky diode device based on an aluminum-doped diamond ohmic contact provided by the present invention; Figure 5 This is a schematic diagram of the contact Hall effect test results for doped diamond provided by the present invention. Figure 6This is a calculation diagram for Hall effect testing of doped diamond provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of a device based on an aluminum-doped diamond ohmic contact provided by the present invention.

[0021] In the picture: 1-Single crystal diamond substrate; 2-B-doped diamond epitaxial layer; 3-Aluminum metal layer; 4-Alumina barrier layer; 5-Aluminum-doped diamond layer; 6-Ohmic electrode; 7-Alumina dielectric layer; 8-Gate electrode; 9-Schottky electrode. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0023] Example 1 There are two main methods for fabricating ohmic contacts in p-type diamond devices. The first method uses MPCVD to form hydrogen terminals (CH bonds) on the diamond surface, inducing two-dimensional hole gas (2DHG) through surface electron transfer. This is then combined with a high work function metal to achieve a low-resistance contact. Typically, platinum or gold electrodes are used to form the ohmic contact with the hydrogen-terminated diamond. The second method uses MPCVD to epitaxially add a heavily doped layer to the diamond surface to increase carrier concentration, facilitating tunneling and achieving a low-resistance contact. Simultaneously, a Ti-based transition layer is combined, and high-temperature annealing causes Ti to react with diamond to form carbides such as TiC, effectively reducing the interfacial barrier. Finally, a highly conductive metal, Au, is used as the outer layer to improve overall conductivity and stability.

[0024] Existing methods for fabricating p-type diamond devices have problems such as high contact resistance, high processing difficulty, and high cost, which make it difficult to meet the needs of diamond device performance improvement and industrial application.

[0025] For hydrogen-terminated diamond, hydrogen is easily desorbed at high temperatures (>400 °C), leading to surface state changes and contact resistance degradation. Hydrogen-terminated diamond FETs typically use Au metal deposition to fabricate ohmic contacts, with a typical contact resistance of approximately 5 Ω·mm. While this value meets some basic research needs, it still represents a nearly one-order-of-magnitude difference compared to the ohmic contact resistances (typically ≤0.5 Ω·mm) achievable using mature semiconductor processes such as silicon and gallium nitride. For diamond with a high-concentration boron (B) doped layer epitaxially, combined with metallization, the contact resistance can be effectively reduced. However, high doping concentrations increase device leakage current, on-resistance, and power consumption. Furthermore, boron-doped diamond has a high carrier activation energy, with an activation rate of less than 0.1% at room temperature, resulting in poor conductivity.

[0026] In terms of process cost, both hydrogen-terminated diamond ohmic contacts and epitaxially heavily doped diamond ohmic contacts rely on microwave plasma chemical vapor deposition systems and require precious metal electrodes such as gold and platinum, as well as high-purity process gases. Furthermore, the poor adhesion between the Au electrode and the diamond surface leads to insufficient stability, resulting in reduced device reliability. Currently, this technology can only be applied to specialized fields where performance is extremely sensitive and cost is not a concern, and it cannot meet the basic requirements of economic efficiency, reliability, and consistency for large-scale commercial manufacturing.

[0027] The main problems this invention addresses are the difficulty in forming good ohmic contacts in traditional p-type diamond device fabrication processes, and the high complexity and cost of traditional ohmic contact fabrication due to its heavy reliance on MPCVD equipment and gold electrodes. Therefore, this invention provides a method for fabricating devices based on aluminum-doped diamond ohmic contacts. Please refer to [link to relevant documentation]. Figure 1 , Figures 2a-2f , Figure 1 This is a schematic flowchart illustrating a method for fabricating a device based on an aluminum-doped diamond ohmic contact provided by the present invention. Figures 2a-2f This is a schematic diagram illustrating the fabrication process of a device based on an aluminum-doped diamond ohmic contact provided by the present invention. The fabrication method of the device based on an aluminum-doped diamond ohmic contact provided by the present invention includes: Step 1, as follows Figure 2a As shown, the cleaned single-crystal diamond substrate layer 1 is selected.

[0028] Step 1.1: Select an undoped single-crystal diamond substrate layer 1.

[0029] Specifically, in this embodiment, an undoped single-crystal diamond substrate layer 1 is selected using CVD epitaxy. Specifically, it is (100) diamond with a quality that meets the growth requirements, and the substrate size is 5 mm × 5 mm × 0.5 mm.

[0030] Step 1.2: Clean the single crystal diamond substrate 1 sequentially with a strong acid mixture, acetone, ethanol, and deionized water to obtain the cleaned single crystal diamond substrate 1.

[0031] Specifically, the single-crystal diamond substrate 1 is cleaned in a strong acid mixture (H2SO4:HNO3) at a temperature below 200°C, and then sequentially cleaned in acetone, ethanol, and deionized water at room temperature to obtain the cleaned single-crystal diamond substrate 1.

[0032] Step 2, as follows Figure 2b As shown, a high-quality B-doped diamond epitaxial layer 2 is grown on the cleaned single-crystal diamond substrate 1 (i.e., the B-doped diamond epitaxial layer 2 is formed by doping B element into diamond).

[0033] Specifically, a boron-doped diamond epitaxial layer 2 was deposited on a cleaned single-crystal diamond substrate 1 using Microwave Plasma Chemical Vapor Deposition (MPCVD). The MPCVD equipment chamber pressure was 140-160 mbar, the power was 4000-4200 W, the substrate surface temperature was 850-950 ℃, the H2 flow rate was 300-400 sccm, the CH4 flow rate was 12-18 sccm, the BH3 flow rate was 1.0 sccm, and the deposition time was 20-30 min.

[0034] The microwave input frequency of the MPCVD equipment used in this embodiment is 2.45 GHz.

[0035] Step 3, as follows Figure 2c As shown, two spaced aluminum metal layers 3 are prepared on the B-doped diamond epitaxial layer 2 in the two ohmic contact regions.

[0036] Step 3.1: Coat the sample with photoresist, perform photolithography, and develop to expose two ohmic contact regions located on the B-doped diamond epitaxial layer 2.

[0037] In this embodiment, the photolithography process uses AZ6112 photoresist, and the photolithography machine used is SUSS MA / BA6.

[0038] Step 3.2: In an argon atmosphere, an aluminum metal layer 3 is magnetron sputtered onto the B-doped diamond epitaxial layer 2 in the two ohmic contact regions and onto the photoresist between the two ohmic contact regions using physical vapor deposition (PVD). The inert gas in the chamber during magnetron sputtering is argon, the argon flow rate is 80~100 sccm, the aluminum target purity is 99.9999%, and the sputtering time is 20 min.

[0039] Furthermore, the thickness of the aluminum metal layer 3 is 50~100 nm.

[0040] Step 3.3: Remove the photoresist between the ohmic contact areas and the aluminum metal layer on top of the photoresist.

[0041] Step 4, as follows Figure 2d As shown, an aluminum oxide barrier layer 4 is grown on two aluminum metal layers 3 and a B-doped diamond epitaxial layer 2 located between the two aluminum metal layers 3.

[0042] Specifically, in a vacuum atmosphere, an alumina barrier layer 4 is deposited on two aluminum metal layers 3 and a boron-doped diamond epitaxial layer 2 located between the two aluminum metal layers 3 using atomic layer deposition (ALD) technology.

[0043] In this embodiment, the gas atmosphere inside the cavity is a vacuum during atomic layer deposition, the temperature is 200~300 ℃, the TMA (Trimethylaluminum) pulse time is 0.2~0.5 s, and the deposition time is 100~120 min.

[0044] Because the deposited metal is aluminum, it will naturally oxidize into aluminum oxide in the air. Therefore, choosing aluminum oxide as the barrier layer will not introduce new substances that will affect doping. In addition, the melting point of aluminum oxide is much higher than that of aluminum, so it can act as a barrier for selective doping during high-temperature annealing. Furthermore, aluminum oxide is commonly used as a gate dielectric in semiconductor processes, so choosing aluminum oxide as the barrier layer is also compatible with mainstream processes.

[0045] Step 5, as follows Figure 2e As shown, the prepared sample is subjected to rapid thermal annealing (RTP). Under the blocking effect of the alumina barrier layer 4, the aluminum in the two aluminum metal layers 3 diffuses into the B-doped diamond epitaxial layer 2 located directly below the aluminum metal layer 3, forming two spaced aluminum-doped diamond layers 5.

[0046] Specifically, inert argon gas is used as a protective gas for rapid thermal annealing. Under the blocking effect of the alumina barrier layer 4, the aluminum in the two aluminum metal layers 3 diffuses into the B-doped diamond epitaxial layer 2 located directly below the aluminum metal layer 3 to form two aluminum-doped diamond layers 5.

[0047] In this embodiment, argon gas is used as the protective gas during rapid thermal annealing. The argon flow rate is 100-150 sccm, the temperature is 700-800 °C, and the annealing time is 5-10 min. Since the melting point of aluminum is 660 °C, the rapid thermal annealing temperature needs to be higher than this. However, excessively high temperatures can affect the quality of the diamond. This embodiment selects a temperature range of 700-800 °C, which is higher than the melting point of aluminum while ensuring the quality of the diamond.

[0048] Step 6, as follows Figure 2e As shown, the remaining aluminum metal layer 3 and aluminum oxide barrier layer 4 are removed.

[0049] Specifically, sodium hydroxide solution was used to remove the residual aluminum metal layer 3 and aluminum oxide barrier layer 4. The sample was placed in sodium hydroxide solution and left to stand for 10 minutes to complete the removal of aluminum metal layer 3 and aluminum oxide barrier layer 4.

[0050] Step 7, as follows Figure 2f As shown, two aluminum ohmic electrodes 6 are fabricated on two aluminum-doped diamond layers.

[0051] Specifically, two aluminum ohmic electrodes 6 were prepared on two aluminum-doped diamond layers using physical vapor deposition (PVD) and magnetron sputtering.

[0052] This invention proposes a device fabrication method based on aluminum-doped diamond ohmic contacts using single-crystal diamond substrates with different crystal orientations. The technical method employed in this invention utilizes a low-melting-point aluminum metal layer for thermal diffusion on the surface of a boron-doped diamond epitaxial layer, thereby forming an aluminum-doped diamond conductive layer (i.e., an aluminum-doped diamond layer). This aluminum-doped diamond conductive layer has a low activation energy, exhibits extremely high carrier concentration and extremely low ohmic contact resistance at room temperature, which is superior to the ohmic contacts of traditional p-type diamond devices. Furthermore, aluminum metal can be used instead of precious metals such as platinum and gold to fabricate electrodes, further reducing costs.

[0053] The preparation method of this invention is applicable to, but not limited to, different types of boron-doped diamond electronic devices. It has high practicality, simple process, and compatibility with current mainstream diamond device fabrication processes in boron-doped channel FET devices, as well as boron-doped conductive BJTs, PN junction diodes, and other devices. It can significantly improve the ohmic contact characteristics of diamond p-type devices.

[0054] Example 2 like Figure 3 As shown, this embodiment of the invention is based on the device prepared in Embodiment 1. This embodiment of the invention provides a method for preparing a MOSFET device. Based on steps 1 to 7 provided in Embodiment 1, this preparation method further includes: An alumina dielectric layer 7 is prepared on the exposed portion of the boron-doped diamond epitaxial layer 2, and an aluminum gate electrode 8 is prepared on the alumina dielectric layer 7 to complete the fabrication of the MOSFET device.

[0055] Example 3 like Figure 4 As shown, this embodiment of the invention is based on the device prepared in Embodiment 1. This embodiment of the invention provides a method for preparing a Schottky diode device. Based on steps 1 to 7 provided in Embodiment 1, this preparation method further includes: A Schottky electrode 9 made of aluminum material is fabricated on the exposed B-doped diamond epitaxial layer 2 to complete the fabrication of the Schottky diode device.

[0056] Example 4 This embodiment provides a specific method for fabricating a device based on an aluminum-doped diamond ohmic contact, based on the above embodiments. The fabrication method includes: S1: Select single-crystal diamond substrate layer 1.

[0057] Specifically, a 5 mm × 5 mm × 0.5 mm (100) single-crystal diamond substrate was selected. Before use, the substrate was subjected to X-ray diffraction (XRD) and atomic force microscopy (AFM) tests to ensure that the quality and surface roughness of the substrate met the requirements of MPCVD growth and subsequent device fabrication.

[0058] S2: Cleaning the single-crystal diamond substrate layer 1.

[0059] Specifically, the single-crystal diamond substrate is first cleaned in a strong acid mixture (H2SO4:HNO3) at 200 °C, and then ultrasonically cleaned with acetone, ethanol and water for 15 min respectively to ensure that no impurities are introduced into the single-crystal diamond substrate 1 during the growth process.

[0060] S3: A B-doped diamond epitaxial layer 2 is grown on the surface of a single-crystal diamond substrate 1.

[0061] Specifically, high-quality diamond single-crystal epitaxy was performed on a single-crystal diamond substrate 1 using an MPCVD equipment. The single-crystal diamond substrate 1 was placed in the MPCVD equipment, and the cavity pressure was evacuated to 0.001 mbar or below. H2 was introduced into the MPCVD equipment at a flow rate of 300 sccm. When the cavity pressure was increased to 15 mbar, the microwave source was turned on to ignite, raising the cavity pressure to 150 mbar with a power of 3200 W and a substrate surface temperature of 900 ℃. Before growth, the surface of the single-crystal diamond substrate 1 was etched with H plasma for 10 min. After the etching was completed, CH4 and BH3 were introduced to begin growth, with a CH4 flow rate of 18 sccm and a BH3 flow rate of 1 sccm. Growth was carried out for 30 min, resulting in a 600 nm thick B-doped diamond epitaxial layer 2.

[0062] S4: Photolithography and deposition of aluminum metal layer 3.

[0063] Specifically, the sample was coated with photoresist, photolithographically lithographically analyzed, and developed to expose two ohmic contact regions on the boron-doped diamond epitaxial layer 2. An aluminum metal layer 3 was then deposited on the boron-doped diamond epitaxial layer 2 in the ohmic contact regions using a magnetron sputtering system. Specifically, the sample was placed inside a chamber, and a vacuum of 1 × 10⁻⁶ was applied. -6 Below mbar, argon gas was introduced for ignition, and deposition began. The deposition time was 20 min, and the deposition thickness was 50 nm. After deposition, the photoresist and the aluminum metal layer on top of the photoresist were stripped by immersion in NMP (N-methylpyrrolidone) solution.

[0064] S5: Deposited alumina barrier layer 4.

[0065] Specifically, an alumina barrier layer 4 was deposited on two aluminum metal layers 3 and a B-doped diamond epitaxial layer 2 located between the two aluminum metal layers 3 using an atomic layer deposition apparatus. During deposition, the gas atmosphere inside the cavity was vacuum, the temperature was 250 ℃, the TMA pulse time was 0.2~0.5 s, the deposition time was 120 min, and the deposition thickness was 10 nm.

[0066] S6: Rapid annealing achieves aluminum-doped diamond layer 5.

[0067] Specifically, the samples were rapidly annealed using a rapid annealing furnace. Argon gas was used as the protective gas at a flow rate of 100 sccm, a temperature of 700℃, and an annealing time of 10 min. This allowed the aluminum in the aluminum metal layer 3 to diffuse onto the surface of the boron-doped diamond epitaxial layer 2, forming an aluminum-doped diamond layer 5. S7: Clean and remove residual aluminum metal layer 3 and aluminum oxide barrier layer 4 from the surface.

[0068] Specifically, using sodium hydroxide solution, the sample was placed in the sodium hydroxide solution and left to stand for 10 minutes to complete the removal of the upper aluminum metal layer 3 and the aluminum oxide barrier layer 4.

[0069] S8: Prepare an ohmic electrode; Specifically, the sample is coated with resist, photolithographically etched, and developed to expose the ohmic contact area. The sample is then placed in the chamber of a magnetron sputtering machine, and aluminum metal is deposited on two aluminum-doped diamond layers 5 to form ohmic electrodes 6. The vacuum is then evacuated to 1×10⁻⁶. -6 Below mbar, argon gas is introduced for ignition and deposition begins. The deposition time is 20 min, and the deposition thickness is 100 nm. After deposition, the sample is immersed in NMP solution for stripping.

[0070] S9: Complete the fabrication of subsequent device structures: For MOSFET devices, continue fabricating the alumina dielectric layer 7 and gate electrode 8, or for Schottky devices, continue fabricating the subsequent Schottky electrode 9.

[0071] like Figure 5 As shown, Figure 5 This is a schematic diagram of a contact Hall effect test result for doped diamond provided in an embodiment of the present invention. Figure 5 It can be seen that the sample has a low sheet resistance and a high surface carrier concentration. Calculations based on Hall effect measurements show that the aluminum-doped activation energy is extremely low, and surface carriers can be fully activated at room temperature. Figure 6 As shown, Figure 6 This is a calculation diagram of Hall effect testing of doped diamond provided by an embodiment of the present invention. The calculation results show that the aluminum doped layer has an extremely low activation energy of 8.2 meV.

[0072] Example 5 like Figure 7 As shown, based on the above embodiments, the present invention also provides a device based on an aluminum-doped diamond ohmic contact, which is fabricated using the preparation method provided in the above embodiments. The device includes: Single-crystal diamond substrate 1; B-doped diamond epitaxial layer 2 is disposed on single-crystal diamond substrate layer 1. Two aluminum-doped diamond layers 5 are disposed at intervals on the B-doped diamond epitaxial layer 2 in the ohmic contact region, and the upper surface of the aluminum-doped diamond layer 5 and the upper surface of the B-doped diamond epitaxial layer 2 located between the two aluminum-doped diamond layers 5 are on the same horizontal plane. Two aluminum ohmic electrodes 6 are respectively disposed on two aluminum-doped diamond layers 5.

[0073] In an optional embodiment, when the device is a MOSFET device, the MOSFET device further includes an alumina dielectric layer 7 disposed on a partially boron-doped diamond epitaxial layer 2 and an aluminum gate electrode 8 disposed on the alumina dielectric layer 7.

[0074] In another optional embodiment, when the device is a Schottky diode device, the Schottky diode device further includes a Schottky electrode 9 of aluminum material disposed on a portion of the B-doped diamond epitaxial layer 2.

[0075] This invention provides a specific device based on aluminum-doped diamond ohmic contacts and its fabrication method. The device structure, from bottom to top, consists of a single-crystal diamond substrate, a boron-doped diamond epitaxial layer, an aluminum-doped diamond layer, and an aluminum ohmic electrode. Using existing equipment, a simple process achieves ohmic contacts with excellent conductivity. It can be applied to boron-doped (p-type) channel MOSFETs, JFETs, and boron-doped conductive BJTs, PN junction diodes, Schottky diodes, and other diamond electronic devices. The device fabricated by this invention effectively reduces contact resistance, decreases Joule heat loss during current transmission, and significantly improves the efficiency and reliability of high-power, high-frequency devices. Moreover, compared to traditional hydrogen-terminated diamond ohmic contacts and heavily doped epitaxial diamond ohmic contacts, it eliminates the need for MPCVD equipment and precious metal electrodes, simplifying the fabrication process, reducing costs, and improving repeatability. This addresses the current pain points of complex diamond contact fabrication and difficult mass production, giving it better prospects in fields such as new energy inverters, aerospace extreme environment devices, and terahertz communication.

[0076] It should be noted that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention.

[0077] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0078] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings and the disclosure in carrying out the claimed invention. In the description of the invention, the word "comprising" does not exclude other components or steps, "a" or "an" does not exclude a plurality, and "a plurality" means two or more, unless otherwise explicitly specified. Furthermore, while different embodiments may describe certain measures, this does not mean that these measures cannot be combined to produce good results.

[0079] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0080] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a device based on an aluminum-doped diamond ohmic contact, characterized in that, include: Select the cleaned single-crystal diamond substrate; A boron-doped diamond epitaxial layer is grown on the cleaned single-crystal diamond substrate. Two spaced aluminum metal layers are fabricated on a boron-doped diamond epitaxial layer with two ohmic contact regions. An aluminum oxide barrier layer is grown on the two aluminum metal layers and the B-doped diamond epitaxial layer located between the two aluminum metal layers; The prepared sample is subjected to rapid thermal annealing. Under the blocking effect of the alumina barrier layer, the aluminum in the two aluminum metal layers diffuses into the B-doped diamond epitaxial layer located directly below the aluminum metal layer, forming two spaced aluminum-doped diamond layers. Remove any remaining aluminum metal layer and aluminum oxide barrier layer; Two ohmic electrodes made of aluminum material are fabricated on the two aluminum-doped diamond layers.

2. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, Select the cleaned single-crystal diamond substrate layer, including: Select an undoped single-crystal diamond substrate; The single-crystal diamond substrate was sequentially cleaned with a strong acid mixture, acetone, ethanol, and deionized water to obtain the cleaned single-crystal diamond substrate.

3. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, Growing a boron-doped diamond epitaxial layer on the cleaned single-crystal diamond substrate includes: A boron-doped diamond epitaxial layer was deposited on the cleaned single-crystal diamond substrate using chemical vapor deposition (CVD). The pressure was 140–160 mbar, the power was 4000–4200 W, the substrate surface temperature was 850–950 °C, the H2 flow rate was 300–400 sccm, the CH4 flow rate was 12–18 sccm, the BH3 flow rate was 1.0 sccm, and the deposition time was 20–30 min.

4. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, Two spaced aluminum metal layers are fabricated on a boron-doped diamond epitaxial layer in two ohmic contact regions, including: The sample was coated with a resist, photolithographically ... In an argon atmosphere, the aluminum metal layer is magnetron sputtered on the B-doped diamond epitaxial layer in two ohmic contact regions and on the photoresist between the two ohmic contact regions using physical vapor deposition technology, wherein the argon flow rate is 80~100 sccm and the thickness of the aluminum metal layer is 50~100 nm. Remove the photoresist between the ohmic contact areas and the aluminum metal layer on top of the photoresist.

5. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, An alumina barrier layer is grown on the two aluminum metal layers and the B-doped diamond epitaxial layer between the two aluminum metal layers, comprising: In a vacuum atmosphere, an aluminum oxide barrier layer is deposited on two aluminum metal layers and a B-doped diamond epitaxial layer located between the two aluminum metal layers using atomic layer deposition (ALD) technology, wherein the temperature is 200-300 °C, the TMA pulse time is 0.2-0.5 s, and the deposition time is 100-120 min.

6. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, The prepared sample is subjected to rapid thermal annealing. Under the blocking effect of the alumina barrier layer, aluminum in the two aluminum metal layers diffuses into the boron-doped diamond epitaxial layer located directly below the aluminum metal layers, forming two spaced-apart aluminum-doped diamond layers, including: Rapid thermal annealing is performed using inert argon as a protective gas. Under the blocking effect of the alumina barrier layer, aluminum in the two aluminum metal layers diffuses into the boron-doped diamond epitaxial layer located directly below the aluminum metal layer to form two aluminum-doped diamond layers. The argon flow rate is 100~150 sccm, the temperature is 700~800℃, and the annealing time is 5~10 min.

7. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, Removing the remaining aluminum metal layer and the aluminum oxide barrier layer includes: The residual aluminum metal layer and the aluminum oxide barrier layer are removed using a sodium hydroxide solution.

8. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, After fabricating two aluminum ohmic electrodes using the two aluminum-doped diamond layers, the process further includes: An alumina dielectric layer is prepared on the exposed portion of the B-doped diamond epitaxial layer; An aluminum gate electrode is fabricated on the alumina dielectric layer.

9. The method for fabricating a device based on an aluminum-doped diamond ohmic contact according to claim 1, characterized in that, After fabricating two aluminum ohmic electrodes using the two aluminum-doped diamond layers, the process further includes: Schottky electrodes of aluminum material are fabricated on the exposed portion of the B-doped diamond epitaxial layer.

10. A device based on an aluminum-doped diamond ohmic contact, characterized in that, The device is prepared using the preparation method according to any one of claims 1 to 9, and comprises: Single-crystal diamond substrate; A boron-doped diamond epitaxial layer is disposed on the single-crystal diamond substrate layer; Two aluminum-doped diamond layers are spaced apart on a boron-doped diamond epitaxial layer in the ohmic contact region, and the upper surface of the aluminum-doped diamond layer is at the same level as the upper surface of the boron-doped diamond epitaxial layer located between the two aluminum-doped diamond layers. Two ohmic electrodes made of aluminum are respectively disposed on two aluminum-doped diamond layers.

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