Low-damage method for improving dielectric adhesion of hydrogen-terminated diamond transistors

Abstract

The application provides a low-damage preparation method for improving hydrogen-terminated diamond transistor medium adhesion, and belongs to the technical field of semiconductor devices, and comprises the following steps: forming a hydrogen-terminated diamond surface conductive channel by hydrogen plasma treatment or growing a diamond epitaxial layer on a diamond substrate; coating a layer of coupling agent on the hydrogen-terminated diamond surface, drying and high-temperature annealing to form a medium layer; photoetching an active region pattern window, removing the medium layer by using dry etching or wet etching, and realizing device isolation; photoetching a source electrode region and a drain electrode region, depositing a source metal and a drain metal, and stripping to form a source-drain ohmic contact; depositing a medium as a gate passivation layer; photoetching a gate root topography, etching or corroding the upper medium layer; photoetching a gate window, depositing a gate metal, and stripping to form a gate electrode; depositing a passivation layer; and photoetching an electrode pattern and etching and corroding the electrode. The application can realize low-damage preparation of hydrogen-terminated diamond transistor medium adhesion.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors. Background Technology

[0002] The development of satellite communications, power electronics, and other systems has placed higher demands on semiconductor power devices. Diamond materials possess a large bandgap, high breakdown electric field, high thermal conductivity, and high electron and hole mobility, which can reduce the need for heat dissipation equipment and lighten the overall weight of the device, offering significant advantages in both radio frequency and power electronics applications. However, due to the low activation rate of n-type doped carriers and the low mobility of p-type doped carriers in diamond, current diamond devices are primarily based on two-dimensional hole gases formed by hydrogen termination.

[0003] Two-dimensional cavitation gas on the surface of hydrogen-terminated diamond opens a window for diamond device fabrication, serving as a conductive channel. However, the two-dimensional cavitation gas formed in hydrogen-terminated diamond is located on or near the diamond surface, and its conductivity is affected by the external environment. Dielectric passivation is an essential process for almost all semiconductor devices. However, the carbon dangling bonds on the surface of hydrogen-terminated diamond are mostly passivated by hydrogen, resulting in the dielectric deposition on the surface of hydrogen-terminated diamond only forming van der Waals forces, leading to poor adhesion and stability. Based on this, this invention provides a low-damage fabrication method to improve the dielectric adhesion of hydrogen-terminated diamond transistors. Summary of the Invention

[0004] Based on this, embodiments of the present invention provide a low-damage preparation method for improving the dielectric adhesion of hydrogen-terminated diamond transistors, which can protect the hydrogen terminal from damage and has good dielectric adhesion.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors, the method comprising:

[0006] Step 1: Hydrogen-terminated conductive channels are formed on the diamond substrate by hydrogen plasma treatment or by growing a diamond epitaxial layer.

[0007] Step 2: Apply a coupling agent to the surface of the hydrogen-terminated diamond, dry and anneal at high temperature to form a dielectric layer;

[0008] Step 3: Photolithographically create the active area pattern window, remove the dielectric layer using dry etching or wet etching, and then treat with oxygen plasma or ozone to achieve device isolation.

[0009] Step 4: Photolithography is used to create the source electrode region and the drain electrode region. Source and drain metals are deposited, and the metals are stripped off. Source and drain ohmic contacts are formed with or without annealing.

[0010] Step 5: Deposit the medium as the gate passivation medium layer;

[0011] Step 6: Photolithographically create the gate root morphology and etch or corrode the upper dielectric layer;

[0012] Step 7: Photolithographically create the gate window, deposit gate metal, and peel off to form the gate electrode;

[0013] Step 8: Deposit a passivation dielectric layer;

[0014] Step 9: Photolithographically pattern the electrode, use dry etching or wet etching techniques to etch the electrode, and thicken the electrode to facilitate subsequent bonding and wire lead-out, thus producing a hydrogen-terminated diamond transistor.

[0015] Alternatively, based on step four, proceed directly to step seven to form a straight grid.

[0016] In one feasible approach, in step one, the growth temperature is 550-650℃ and the growth time is 8-10 min, to epitaxially grow a layer of hydrogen-terminated diamond.

[0017] In one feasible manner, in step two, the coupling agent applied is a diluted tetramethoxysilane or tetraethoxysilane.

[0018] In one feasible approach, the source-drain ohmic contact in step four is prepared using one or more of Al, Si, Ti, Pt, Au, and Ir, with or without high-temperature alloy annealing.

[0019] In one feasible approach, in step four, annealing is performed in an annealing furnace at 450-550°C for 25-35 minutes to form a source-drain ohmic contact.

[0020] In one feasible approach, the gate passivation layer in step five comprises any one of Al2O3, SiNx, SiO2, TiO2, MoO3, and AlN, with a thickness of 5 nm to 500 nm.

[0021] In one feasible approach, the gate morphology in step six fills the gate slots and overflows them to form a T-shaped gate structure.

[0022] In one feasible approach, the gate metal in step seven is prepared using a metal thin film deposition technique. The gate metal is one or a combination of two or more of aluminum, titanium, nickel, platinum, and gold, and has a thickness between 2 nm and 50 μm.

[0023] In one feasible approach, in step seven, a gate window is photolithographically etched, an 80-120 nm gate metal Al is deposited by electron beam evaporation, and then the gate electrode is stripped away to form the gate electrode.

[0024] In one feasible approach, the passivation layer material in step eight is any one of SiNx, Al2O3, SiO2, TiO2, MoO3, and AlN; and the thickness is between 5 nm and 20 μm.

[0025] The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors provided by this invention has the following advantages compared with the prior art: On the one hand, using a diamond substrate, hydrogen-terminated diamond surface conductive channels are formed on the epitaxial layer of the diamond substrate surface through hydrogen plasma treatment or hydrogen annealing, etching, high-temperature annealing, and other techniques. Then, a coupling agent can be used to bond with the hydrogen-terminated diamond, thereby achieving excellent adhesion. On the other hand, after device passivation, the problem of contamination of the hydrogen-terminated diamond surface during device fabrication is avoided. Moreover, the device channel can be well isolated from the outside world, thereby improving the stability of the device and ultimately achieving low-damage fabrication of hydrogen-terminated diamond transistors with good dielectric adhesion. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the intermediate product prepared in step one of the embodiments of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of the intermediate product prepared in step two of this invention.

[0028] Figure 3 This is a schematic diagram of the structure of the intermediate product prepared in step four of this embodiment of the invention;

[0029] Figure 4 This is a schematic diagram of the structure of the intermediate products prepared in steps five to seven according to an embodiment of the present invention;

[0030] Figure 5 A schematic diagram of the final hydrogen-terminated diamond transistor prepared according to an embodiment of the present invention;

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Diamond substrate; 2. Hydrogen-terminated diamond surface conductive channel; 3. First passivation layer; 4. Source / drain ohmic contact; 5. Second passivation layer; 6. Gate metal; 7. Third passivation layer. Detailed Implementation

[0033] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0034] Please refer to the following: Figures 1 to 5The present invention will now describe a low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors includes the following steps:

[0035] Step 1: On a high-quality diamond substrate 1, hydrogen plasma treatment or growth of a high-quality diamond epitaxial layer of a certain thickness is performed to form a hydrogen-terminated diamond surface conductive channel 2. (See [link]). Figure 1 ;

[0036] Step two: Coat the surface of the hydrogen-terminated diamond with a diluted coupling agent, dry it, and anneal it at high temperature to form a dielectric layer, which is the first passivation layer 3. See [link to previous steps]. Figure 2 ;

[0037] Step 3: Photolithographically create the active area pattern window, remove the dielectric layer using dry etching or wet etching, and treat with oxygen plasma or ozone to achieve device isolation;

[0038] Step four: Photolithography is used to create the source and drain electrode regions. Source metal S and drain metal D are deposited. The regions are then stripped, and with or without annealing, source-drain ohmic contacts 4 are formed. (See attached diagram) Figure 3 ;

[0039] Step 5: The deposited medium serves as the gate passivation medium layer, which is the second passivation layer 5;

[0040] Step 6: Photolithographically create the gate root morphology and etch or corrode the upper dielectric layer;

[0041] Step 7: Photolithographically create the gate window, deposit gate metal 6, and lift off to form the gate electrode G. (See below) Figure 4 ;

[0042] Step 8: Deposit a passivation dielectric layer, which is the third passivation layer 7;

[0043] Step nine: Photolithography is used to create the electrode pattern. Dry or wet etching techniques are then used to etch the electrodes, and the electrodes are thickened to facilitate subsequent bonding and wire lead-out, thus fabricating a hydrogen-terminated diamond transistor. See [link to documentation]. Figure 5 .

[0044] Since the fabrication of hydrogen-terminated diamond devices inevitably involves processes such as coating, baking, and plasma treatment, these processes can contaminate or affect the conductive channels on the surface of the hydrogen-terminated diamond. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors provided by this invention offers the following advantages compared to existing technologies: Firstly, by using a diamond substrate, hydrogen-terminated diamond conductive channels are formed on the surface of the diamond substrate through hydrogen plasma treatment or hydrogen annealing, etching, and high-temperature annealing. Then, a coupling agent can be used to bond with the hydrogen-terminated diamond, achieving excellent adhesion. Secondly, after device passivation, the contamination of the hydrogen-terminated diamond surface during fabrication is avoided. Furthermore, the device channels are effectively isolated from the external environment, thereby improving device stability and ultimately achieving low-damage fabrication of hydrogen-terminated diamond transistors with excellent dielectric adhesion.

[0045] This invention provides a low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors. This method achieves high adhesion and low-damage dielectric fabrication of hydrogen-terminated diamond transistors, enabling applications not only in radio frequency (RF) devices but also in power electronic devices. Specifically, by designing different field plate structures, gate-source-gate-drain distances, dielectric thicknesses, and metal thicknesses, different frequencies and voltage ratings of RF and power electronic devices can be achieved as needed. Due to the wide bandgap, high breakdown field strength, and high heat dissipation of diamond material, compared to gallium nitride (GaN) devices, diamond devices can handle higher power densities with smaller heat dissipation equipment, thereby reducing the overall mass of the semiconductor device.

[0046] Furthermore, in step one, the growth temperature is 550-650℃, the growth time is 8-10 min, and a layer of hydrogen-terminated diamond is epitaxially grown.

[0047] Furthermore, in step two, the coupling agent applied is diluted tetramethoxysilane or tetraethoxysilane. The coupling agent can be applied by spin coating or vacuum spraying.

[0048] Furthermore, the source-drain ohmic contact in step four is prepared using one or more of Al, Si, Ti, Pt, Au, and Ir, with or without high-temperature alloy annealing.

[0049] Furthermore, in step four, the annealing temperature in the annealing furnace is 450-550℃, and the annealing time is 25-35 minutes to form a source-drain ohmic contact.

[0050] Furthermore, the gate passivation layer in step five includes, but is not limited to, any one of Al2O3, SiNx, SiO2, TiO2, MoO3, and AlN, with a thickness of 5nm to 500nm.

[0051] Furthermore, in step six, the gate morphology fills the gate trench and overflows the gate trench to form a T-shaped gate structure, which results in a larger size and can effectively improve the breakdown voltage of the device.

[0052] Furthermore, steps five and six can also be omitted. Step four skips steps five and six and proceeds directly to step seven, thereby forming a straight grid.

[0053] Furthermore, the preparation of the gate metal in step seven includes, but is not limited to, the use of electron beam evaporation technology, or ALD technology or other metal thin film deposition technology. The gate metal is one or a combination of two or more of aluminum, titanium, nickel, platinum and gold, with a thickness between 2 nm and 50 μm.

[0054] Furthermore, in step seven, the gate window is photolithographically etched, and 80-120nm gate metal Al is deposited by electron beam evaporation and then stripped to form the gate electrode.

[0055] Furthermore, the passivation layer in step eight is prepared using, but is not limited to, CVD technology. The passivation layer material can be SiNx, and the passivation layer material can be any one of SiNx, Al2O3, SiO2, TiO2, MoO3, and AlN. The thickness is between 5 nm and 20 μm.

[0056] The specific fabrication process for hydrogen-terminated diamond transistors is as follows:

[0057] Example 1:

[0058] (1) A flat single-crystal diamond substrate is given a layer of hydrogen-terminated diamond by MPCVD equipment, and a microwave power supply is turned on to generate hydrogen plasma. The temperature is set to 600℃ and the growth time is 10 min. A layer of hydrogen-terminated diamond is epitaxially formed on the surface, and the surface is combined with the gas adsorbed in the air to form a two-dimensional cavitation gas in the surface conductive channel.

[0059] (2) Spin-coat a diluted coupling agent, such as tetramethoxysilane diluted with ethanol, onto the surface of hydrogen-terminated diamond, dry it on a hot plate, and anneal it under vacuum at high temperature to form a SiO2 dielectric layer.

[0060] (3) Photolithography active area pattern window, dry etching to remove dielectric layer, oxygen plasma treatment for 5 min to achieve device isolation, acetone, alcohol, deionized water treatment to remove photoresist.

[0061] (4) Photolithography is used to create the source and drain regions. BOE is used to etch SiO2 into the source and drain regions. Electron beam evaporation stage is used to evaporate metal Ti / Au with thicknesses of 30 / 200nm respectively. After peeling, metal electrodes are formed. After alloy annealing at 500℃ for 30min in an annealing furnace, ohmic contacts are formed.

[0062] (5) LPCVD deposition of 200nm thick SiN dielectric as passivation layer;

[0063] (6) Electron beam lithography is used to etch the gate root morphology, and dry etching is used to selectively etch the upper dielectric layer; acetone, alcohol and deionized water are used to remove the photoresist.

[0064] (7) Photolithography is used to form the gate window, and a 100nm thick gate metal Al is deposited by electron beam evaporation and then peeled off to form the gate electrode;

[0065] (8) A 500 nm thick SiO2 passivation layer was deposited by PECVD;

[0066] (9) Photolithography is used to create electrode patterns, dry etching is used to create electrodes, and the electrodes are thickened to facilitate subsequent bonding and wire lead-out, thereby achieving low-damage and high-adhesion hydrogen-terminated diamond transistor fabrication.

[0067] Example 2: Adjusting process parameters. In step one, the growth temperature is 620℃ and the growth time is 9min to epitaxially grow a layer of hydrogen-terminated diamond. In step four, the annealing temperature in the annealing furnace is 450℃ and the annealing time is 25min to form source-drain ohmic contacts.

[0068] The terminology is explained as follows:

[0069] BOE etching is a commonly used surface etching method, primarily used for etching silica (SiO2). BOE is an abbreviation for Buffered Oxide Etchant, a strongly acidic solution typically composed of a mixture of hydrofluoric acid (HF) and ammonium oxide (NH4F).

[0070] ALD (Atomic Layer Deposition) is a method that deposits materials onto a substrate surface layer by layer in the form of single-atom films. ALD is similar to conventional chemical deposition. However, in ALD, the chemical reaction of the new atomic layer is directly related to the previous layer, ensuring that only one atomic layer is deposited per reaction.

[0071] There are many methods for depositing thin films, including physical and chemical vapor deposition (PVD), molecular beam epitaxy (MBE), spin coating or spray coating, and electroplating. However, physical and chemical vapor deposition (PVD) is the most commonly used.

[0072] CVD: Chemical vapor deposition (CVD) includes low-pressure CVD (LPCVD), atmospheric pressure CVD (APCVD), plasma-enhanced CVD (PECVD), and metal-organic CVD (MOCVD). In recent years, a novel thin film deposition technology, atomic layer deposition (ALD), has attracted widespread attention.

[0073] Hydrogen plasma treatment is a technique that utilizes the unique physical and chemical properties of hydrogen in a plasma state. This technique involves transforming hydrogen gas into a plasma state under specific conditions (such as high temperature, high pressure, or an electric field), thereby obtaining highly reactive hydrogen atoms and ions. Hydrogen plasma treatment has a wide range of applications, including but not limited to material surface treatment, hydrogen extraction and storage, and sample processing in chemical analysis.

[0074] Oxygen plasma treatment technology is a novel surface treatment technology widely used in high-tech fields such as electronics, semiconductors, medical devices, and aerospace, as well as in industrial manufacturing. The generation principle of oxygen plasma is based on plasma physics; it involves ionizing oxygen molecules through an electric field to form an oxygen plasma gas. This gas can be guided under controlled conditions onto the surface of objects requiring surface treatment.

[0075] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors, characterized in that, The method includes: Step 1: A hydrogen-terminated diamond surface conductive channel (2) is formed on a diamond substrate (1) by hydrogen plasma treatment or by growing a diamond epitaxial layer. Step 2: A coupling agent is applied to the surface of the hydrogen-terminated diamond, dried and annealed at high temperature to form a dielectric layer (3); Step 3: Photolithographically create the active area pattern window, remove the dielectric layer using dry etching or wet etching, and then treat with oxygen plasma or ozone to achieve device isolation. Step 4: Photolithography is used to create the source electrode region and the drain electrode region, and the source metal and drain metal are deposited. The metal is then stripped and, with or without annealing, source-drain ohmic contacts are formed (4). Step 5: Deposit the medium as a gate passivation layer (5); Step 6: Photolithographically create the gate root morphology and etch or corrode the upper dielectric layer; Step 7: Photolithographically create the gate window, deposit gate metal (6), and peel off to form the gate electrode; Step 8, deposit a passivation layer (7); Step 9: Photolithographically pattern the electrode, use dry etching or wet etching techniques to etch the electrode, and thicken the electrode to facilitate subsequent bonding and wire lead-out, thus producing a hydrogen-terminated diamond transistor. Alternatively, based on step four, proceed directly to step seven to form a straight grid.

2. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step one, the growth temperature is 550-650℃, the growth time is 8-10 min, and a layer of hydrogen-terminated diamond is epitaxially grown.

3. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step two, the coupling agent applied is diluted tetramethoxysilane or tetraethoxysilane.

4. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step four, the source-drain ohmic contacts are prepared using one or more of Al, Si, Ti, Pt, Au, and Ir, with or without high-temperature alloy annealing.

5. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step four, the sample is annealed in an annealing furnace at 450-550℃ for 25-35 minutes to form a source-drain ohmic contact.

6. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, The gate passivation layer in step five includes any one of Al2O3, SiNx, SiO2, TiO2, MoO3, and AlN, with a thickness of 5nm to 500nm.

7. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step six, the grid morphology fills the grid groove and overflows the grid groove to form a T-shaped grid structure.

8. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, The gate metal in step seven is prepared using metal thin film deposition technology. The gate metal is one or a combination of two or more of aluminum, titanium, nickel, platinum, and gold, and its thickness is between 2 nm and 50 μm.

9. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, In step seven, the gate window is photolithographically etched, and 80-120nm gate metal Al is deposited by electron beam evaporation and then stripped to form the gate electrode.

10. The low-damage fabrication method for improving the dielectric adhesion of hydrogen-terminated diamond transistors as described in claim 1, characterized in that, The passivation layer material in step eight is any one of SiNx, Al2O3, SiO2, TiO2, MoO3, and AlN; the thickness is between 5 nm and 20 μm.

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