A diamond selective phase transformation method based on ion beam induction and its application

Abstract

The present invention discloses a diamond selective phase change method based on ion beam induction and its application, belonging to the field of semiconductor technology. The above method steps are: (1) preparing an ion beam blocking layer with a selective pattern on the surface of diamond, and then placing it in a high temperature environment of 400-1000 ° C, and irradiating it with an ion beam to make the exposed area of ​​diamond not covered and protected by the ion beam blocking layer undergo a structural phase change to form a diamond phase change area; (2) removing the ion beam blocking layer, leaving the diamond phase change area and the diamond non-phase change area, and realizing the selective phase change. The present invention can achieve stable low-resistance ohmic contact, avoid the problem of diamond doping activation, the temperature required for phase change is significantly lower than the ion implantation activation temperature and the doped diamond growth temperature, and the process is easy to control, the cost is low, and it has the potential for scale, which can provide an effective solution for breaking through the ohmic contact bottleneck of diamond electronic devices.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a diamond selective phase change method based on ion beam induction and an application thereof. Background Art

[0002] Diamond is known as the "ultimate semiconductor" for its ultra-wide bandgap, high mobility, and extremely high thermal conductivity, and has great application potential in power devices. However, its ultra-wide bandgap characteristics also lead to a high potential barrier when in contact with metals, making it difficult to form an effective ohmic contact. This problem has also become a bottleneck that must be overcome to realize the application of electronic devices.

[0003] For diamond, there are two traditional ohmic contact methods: ion implantation and secondary epitaxy. For the ion implantation scheme, a temperature of more than 1700°C is required to activate the injected boron ions, and the implantation process damages the diamond. For the secondary epitaxy scheme, a temperature of more than 850°C is required to epitaxially grow high-concentration boron-doped diamond, and it is difficult to achieve efficient activation. The strict epitaxial conditions also pose challenges to process compatibility. In addition to doped diamond, allotropes of diamond and other phases of carbon also have low contact barriers, but phase changes in diamond usually require high temperatures of more than 1200°C. Therefore, if a process method with lower temperature and better compatibility can be developed to promote efficient phase changes in diamond, a new ohmic contact scheme can be derived to help the excellent physical properties of diamond be fully utilized in electronic devices. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for ion beam induced diamond selective phase change which can circumvent the problem of difficulty in activating diamond doping, significantly reduce the temperature required for the process, improve process compatibility, and break through the bottleneck of diamond ohmic contact; another purpose of the present invention is to provide an application of the above method.

[0005] Technical solution: The diamond selective phase change method based on ion beam induction of the present invention comprises the following steps:

[0006] (1) preparing an ion beam blocking layer with a selected area pattern on the surface of the diamond, so that part of the diamond area is covered and the uncovered diamond area is exposed, and then placing it in a high temperature environment of 400-1000° C., through ion beam irradiation treatment, the exposed diamond area not covered and protected by the ion beam blocking layer undergoes a structural phase change to form a diamond phase change area, and the diamond area covered and protected by the ion beam blocking layer does not undergo a structural phase change;

[0007] (2) The ion beam blocking layer is removed, leaving the diamond phase change area and the diamond non-phase change area to achieve selective phase change.

[0008] Furthermore, in step (1), the material of the ion beam blocking layer includes one or more of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride, aluminum nitride, and boron nitride, and the thickness is 20nm-1000nm; the method for forming the selected area pattern includes one or more of wet etching, dry etching, and stripping; the ion beam blocking layer with a certain thickness can block the bombardment of the ion beam and avoid damage to the diamond lattice below; the ion beam blocking layer can be processed into the required selected area pattern through photolithography, wet etching / dry etching, or the ion beam blocking layer material is prepared according to the photoresist mask and stripped to achieve the required selected area pattern, for example, to achieve a selected area phase change only in the ohmic electrode area.

[0009] Furthermore, in step (1), the type of ion beam includes one or more of argon ion beam, hydrogen ion beam, and nitrogen ion beam. In the absence of ion beam irradiation, the diamond phase transition requires a temperature of more than 1200°C, and selective phase transition cannot be achieved. However, through ion beam irradiation induction, the temperature required for diamond phase transition can be significantly reduced, and the minimum temperature is only 400°C, which has great advantages over traditional diamond ion implantation activation (1700°C) and secondary epitaxy (850°C). Lower process temperatures can greatly improve compatibility and bring greater design space for the selection of diamond heterostructures and other processes.

[0010] Furthermore, in step (1), the depth of the diamond phase change region is 2nm-200nm. After the phase change to the diamond-like phase, the carrier concentration is significantly increased, and the extremely low resistivity (can reach below 0.05Ω·cm) can be significantly reduced, thereby obtaining a low ohmic contact resistance. As the treatment temperature increases and the time increases, the resistivity decreases slightly and the phase change depth increases significantly. Therefore, the phase change depth can be adjusted to a suitable range by temperature and time.

[0011] Furthermore, in step (1), the diamond surface has a surface terminal, and the surface terminal includes one or more of a hydrogen terminal, an oxygen terminal, a fluorine terminal, a silicon terminal, a nitrogen terminal, and a chlorine terminal. The method of the present invention is applicable to diamonds with different surface terminals and has strong scalability.

[0012] The method of the present invention has an easy-to-control process, an appropriate phase change depth, and a wide applicability to diamond conductive channel types and surface terminal states; based on an ion beam blocking layer with a selective pattern, a selective phase change can be achieved; based on the method, an ohmic contact electrode preparation method for a diamond conductive channel can be developed to achieve stable low-resistance ohmic contact.

[0013] The above-mentioned diamond selective phase change method based on ion beam induction is used in the preparation of ohmic contact electrodes based on diamond conductive channels.

[0014] Furthermore, the application method comprises the following steps:

[0015] (11) Preparing diamond phase change regions and diamond non-phase change regions on the diamond surface based on the above-mentioned ion beam-induced diamond selective phase change method;

[0016] (12) preparing a protective layer on the diamond phase change region;

[0017] (13) etching the non-phase-changed region of the diamond based on the protective layer, wherein the etching depth is less than the depth of the phase-changed region of the diamond, and preparing a diamond heterostructure having a conductive channel on the etched region;

[0018] (14) removing the protective layer and preparing a metal electrode on the diamond phase change region, wherein the metal electrode and the diamond phase change region together serve as an ohmic contact electrode of the diamond conductive channel region.

[0019] Alternatively, the method of application comprises the following steps:

[0020] (21) preparing a heterogeneous material on diamond, wherein the heterogeneous material and diamond form a heterostructure to obtain a diamond heterostructure having a conductive channel;

[0021] (22) Preparing a diamond phase change region and an ion beam blocking layer on a diamond heterostructure based on the above-mentioned ion beam-induced diamond selective phase change method;

[0022] (23) A metal electrode is prepared on the diamond phase change region, and the ion beam blocking layer is removed. The metal electrode and the diamond phase change region together become the ohmic contact electrode of the diamond conductive channel region.

[0023] Furthermore, the diamond heterostructure with a conductive channel is a heterostructure composed of one or more heterogeneous materials selected from silicon oxide, aluminum oxide, hafnium oxide, beryllium oxide, silicon nitride, aluminum nitride, and boron nitride and diamond. Since this method can achieve selective phase change and will not affect the conductive channel in the area covered by the ion beam blocking layer, it is suitable for diamond heterostructures with different conductive channels. The diamond surface can form different chemical bonds with the upper heterogeneous material to form a conductive channel, or it can have different surface terminals and heterogeneous materials to form a conductive channel, or it can have a thinner doped diamond layer to form a conductive channel.

[0024] Furthermore, the thickness of the heterogeneous material is 0.3-10 nm.

[0025] Furthermore, the metal electrode is one or more of titanium, gold, chromium, nickel, platinum, palladium, aluminum, and silver. 19 cm -3The contact barrier with the metal electrode is low, so the selection range of the metal electrode is also larger.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: (1) The ion beam-induced diamond selective phase change method proposed in the present invention avoids the high temperature required for diamond doping activation, and the process temperature required for inducing phase change is only 400°C at the lowest. Compared with the traditional diamond ion implantation activation (1700°C), secondary epitaxy (850°C), or phase change method (1200°C), the process temperature can be significantly reduced, the process compatibility is greatly improved, and a larger design space is provided for the selection of diamond heterostructures and other processes; (2) The ion beam-induced diamond selective phase change method proposed in the present invention can realize stable diamond low-resistance ohmic contact, the process is easy to control, the phase change depth is appropriate, and it has wide applicability to the diamond conductive channel type and surface terminal state; based on the ion beam blocking layer with a selective pattern, the selective phase change can be realized; and the hardware conditions required for the preparation method of the ohmic contact electrode are simple, and no high-energy consumption equipment such as ion implantation machine and microwave plasma chemical vapor deposition system is required; wafer-level preparation can be realized, and it has the potential for large-scale implementation. Therefore, the method of the present invention can provide an effective solution to the bottleneck of diamond ohmic contact. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the diamond selective phase transformation method based on ion beam induction in Example 1;

[0028] Figure 2 This is the Raman spectrum of the diamond phase transition region obtained in Example 1;

[0029] Figure 3 This is a flow chart of the first method for preparing a diamond conductive channel ohmic contact electrode based on ion beam induced diamond selective phase change of the present invention;

[0030] Figure 4 This is a flow chart of the second method for preparing a diamond conductive channel ohmic contact electrode based on ion beam induced diamond selective phase change of the present invention;

[0031] Figure 5 This is a graph showing the ohmic contact resistance of diamond obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the embodiments and drawings.

[0033] Example 1: Figure 1 As shown, the diamond selective phase change method based on ion beam induction provided in this embodiment includes the following steps:

[0034] S1, preparing an ion beam blocking layer silicon dioxide 21 with a selected area pattern on the surface of the diamond 10 with fluorine termination by BOE wet etching, so that part of the diamond area 11 is covered and the uncovered diamond area 12 is exposed;

[0035] S2. The diamond is placed in a high temperature environment of 700°C and irradiated with nitrogen ion beams to cause a structural phase change in the exposed diamond area not covered and protected by silicon dioxide, with a depth of about 10nm. The Raman spectrum is shown in the figure below: Figure 2 As shown in the figure, the Raman spectrum of the formed diamond phase transition area has changed significantly compared with diamond, and the new peak indicates the transition to the diamond-like phase. The diamond in the area protected by silicon dioxide has not undergone a structural phase transition.

[0036] S3, remove the ion beam blocking layer silicon dioxide 21, leaving the diamond phase change region 13 and the diamond non-phase change region 11, and realize the selective phase change. As a comparison, when the ambient temperature is only 300°C, it is not enough to cause the phase change; when the ambient temperature is 1300°C, the excessively high temperature inhibits the occurrence of the phase change process to a certain extent.

[0037] Example 2: Figure 3 As shown, the application of the ion beam induced diamond selective phase change method is to prepare the ohmic contact electrode of the boron nitride / diamond heterostructure conductive channel. The detailed steps are as follows:

[0038] S11, the surface terminal of the diamond 10 is originally an oxygen terminal, and a 100 nm hafnium oxide 21 having a selected area pattern is prepared on the surface of the diamond 10 by a stripping method according to a photoresist mask, so that part of the diamond area 11 is covered by hafnium oxide, and the diamond area 12 not covered by hafnium oxide is exposed;

[0039] S12, placing the diamond in a high temperature environment of 1000°C, and irradiating the diamond with an argon ion beam to cause a structural phase change in the exposed diamond region not covered and protected by hafnium oxide, thereby forming a diamond phase change region 13 with a depth of about 20 nm; the diamond in the region covered and protected by hafnium oxide does not undergo a structural phase change;

[0040] S13, removing the hafnium oxide 21 of the ion beam blocking layer, and preparing the aluminum oxide 41 of the protective layer in the diamond phase change region;

[0041] S14, etching the diamond non-phase-changed region to a depth of about 10 nm based on the protective layer of aluminum oxide, and preparing a boron nitride / diamond heterostructure 31 with an interface conductive channel in the region;

[0042] S15, removing the protective layer 41, and preparing metal electrodes chromium and gold 50 on the diamond phase change region 13, the chromium and gold electrodes 50 and the diamond phase change region 13 together form an ohmic contact electrode for the boron nitride / diamond heterostructure conductive channel.

[0043] For the boron nitride / diamond heterostructure, if a heterointerface conductive channel is prepared first, the electrode metal needs to pass through the boron nitride barrier layer to achieve contact with the conductive channel. Therefore, it is difficult to directly form a good ohmic contact in the conventional process sequence. The method of this embodiment provides a feasible solution to the ohmic contact problem.

[0044] Example 3: Figure 4 As shown, the application of the ion beam induced diamond selective phase change method is to prepare the ohmic contact electrode of the aluminum oxide / hydrogen terminal diamond heterostructure conductive channel. The detailed steps are as follows:

[0045] S21, preparing aluminum oxide with a thickness of 10 nm on the diamond 10 with hydrogen surface termination to realize an aluminum oxide / hydrogen-terminated diamond heterostructure 30 with a two-dimensional conductive channel;

[0046] S22, preparing an ion beam blocking layer of 100 nm silicon nitride 21 with a selected area pattern on the upper surface of the aluminum oxide / hydrogen terminal diamond heterostructure by dry etching silicon nitride with fluorine-based gas and wet etching aluminum oxide with aluminum etching solution, so that part of the diamond heterostructure area 31 is covered with silicon nitride, while the diamond in the uncovered area is exposed;

[0047] S23, placing the aluminum oxide / hydrogen-terminated diamond heterostructure in a high temperature environment of 400° C., and irradiating the diamond region not covered and protected by the ion beam blocking layer silicon nitride by hydrogen ion beam to cause a structural phase change in the diamond, thereby forming a diamond phase change region 13 with a depth of about 30 nm; the diamond in the region covered and protected by silicon nitride does not undergo a structural phase change, and the conductive channel is not affected;

[0048] S24, preparing metal electrodes titanium and gold 50 in the diamond phase change region, removing the ion beam blocking layer 21, and the titanium and gold electrodes and the diamond phase change region together become ohmic contact electrodes of the aluminum oxide / hydrogen terminal diamond heterostructure conductive channel.

[0049] The above ohmic contact electrode preparation method requires simple hardware conditions and does not require high-energy consumption equipment such as ion implanters and microwave plasma chemical vapor deposition systems; it can achieve wafer-level preparation and has the potential for large-scale implementation. Figure 5 As shown in the figure, the ohmic contact performance achieved based on this method is excellent, with a contact resistance of only 0.3Ω·mm, which is much lower than the conventional contact resistance of 1Ω·mm. Therefore, it can provide an effective solution to the bottleneck of diamond ohmic contact and lay a solid foundation for the development of high-performance power devices.

[0050] Based on the method of this embodiment, the preparation of ohmic contact electrodes based on selective phase change is achieved using only a 400°C environment; at the same time, because the aluminum oxide / hydrogen-terminated diamond heterostructure interface has not undergone other processes, the interface quality is excellent, providing a high-speed channel for carrier transport.

[0051] In summary, the ion beam-induced diamond selective phase change method of the present invention avoids the high temperature required for diamond doping activation, greatly improves process compatibility, and brings greater design space for the selection of diamond heterostructures and other processes. The ion beam-induced diamond selective phase change method based on the present invention can achieve stable diamond low-resistance ohmic contact, the process is easy to control, the phase change depth is appropriate, and it has wide applicability for diamond conductive channel types and surface terminal states; and the hardware conditions required for the ohmic contact electrode preparation method are simple, and no high-energy consumption equipment such as ion implanters and microwave plasma chemical vapor deposition systems are required; wafer-level preparation can be achieved, and it has the potential for large-scale implementation. Therefore, it can provide an effective solution to the bottleneck of diamond ohmic contact and lay a solid foundation for the development of high-performance power devices, etc.

[0052] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A diamond selective phase change method based on ion beam induction, characterized in that: The following steps are involved: (1) preparing an ion beam blocking layer with a selected area pattern on the surface of the diamond, so that part of the diamond area is covered and the uncovered diamond area is exposed, and then placing it in a high temperature environment of 400-1000° C., through ion beam irradiation treatment, the exposed diamond area not covered and protected by the ion beam blocking layer undergoes a structural phase change to form a diamond phase change area, and the diamond area covered and protected by the ion beam blocking layer does not undergo a structural phase change; (2) The ion beam blocking layer is removed, leaving the diamond phase change area and the diamond non-phase change area to achieve selective phase change.

2. The method for diamond selective phase change based on ion beam induction according to claim 1, characterized in that: In step (1), the material of the ion beam blocking layer includes one or more of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride, aluminum nitride, and boron nitride, and the thickness is 20nm-1000nm; the method for forming the selected area pattern includes one or more of wet etching, dry etching, and stripping.

3. The method for diamond selective phase change based on ion beam induction according to claim 1, characterized in that: In step (1), the type of the ion beam includes one or more of an argon ion beam, a hydrogen ion beam, and a nitrogen ion beam.

4. The method for selective phase change of diamond based on ion beam induction according to claim 1, characterized in that: In step (1), the depth of the diamond phase change region is between 2nm and 200nm.

5. The method for selective phase change of diamond based on ion beam induction according to claim 1, characterized in that: In step (1), the diamond surface has surface terminations, and the surface terminations include one or more of hydrogen terminations, oxygen terminations, fluorine terminations, silicon terminations, nitrogen terminations, and chlorine terminations.

6. An application of the diamond selective phase change method based on ion beam induction according to claim 1 in preparing an ohmic contact electrode of a diamond heterostructure conductive channel.

7. The use according to claim 6, characterized in that: The method of application comprises the following steps: (11) Preparing a diamond phase change region and a diamond non-phase change region on a diamond surface based on the method of claim 1; (12) preparing a protective layer on the diamond phase change region; (13) etching the non-phase-changed region of the diamond based on the protective layer, wherein the etching depth is less than the depth of the phase-changed region of the diamond, and preparing a diamond heterostructure having a conductive channel on the etched region; (14) removing the protective layer and preparing a metal electrode on the diamond phase change region, wherein the metal electrode and the diamond phase change region together serve as an ohmic contact electrode of the conductive channel of the diamond heterostructure.

8. The use according to claim 6, characterized in that: The method of application comprises the following steps: (21) preparing a heterogeneous material on diamond, wherein the heterogeneous material and diamond form a heterostructure to obtain a diamond heterostructure having a conductive channel; (22) Preparing a diamond phase change region and an ion beam blocking layer on a diamond heterostructure based on the method of claim 1; (23) A metal electrode is prepared on the diamond phase change region, and the ion beam blocking layer is removed. The metal electrode and the diamond phase change region together become the ohmic contact electrodes of the diamond heterostructure conductive channel.

9. The use according to any one of claims 7-8, characterized in that: The diamond heterostructure with a conductive channel is a heterostructure composed of diamond and one or more heterogeneous materials selected from silicon oxide, aluminum oxide, hafnium oxide, beryllium oxide, silicon nitride, aluminum nitride, and boron nitride.

10. The use according to any one of claims 7-8, characterized in that: The metal electrode is one or more of titanium, gold, chromium, nickel, platinum, palladium, aluminum, and silver.

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