Preparation method of diamond superlattice structure and diamond superlattice structure

Abstract

The invention provides a preparation method of a diamond superlattice structure and the diamond superlattice structure, and relates to the technical field of semiconductor material preparation. The method comprises the following steps: generating an intrinsic diamond layer on a monocrystal diamond substrate under a first reaction condition; wherein the first reaction condition is that hydrogen and a carbon source gas with a first concentration are introduced into a reaction chamber where the monocrystal diamond substrate is located, and microwave plasma excitation is carried out; under a first reaction condition, introducing a doping agent into the reaction chamber, and growing a doping layer on the intrinsic diamond layer; and stopping introducing the dopant, introducing an oxygen-containing gas into the reaction chamber under a first reaction condition, and / or generating a dopant adsorption layer on the doping layer so as to remove the residual dopant. According to the method, the residual dopant can be effectively removed, the steep change of the doping concentration on the nanoscale is realized, and the interface quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material preparation, and in particular to a preparation method of diamond superlattice structure and diamond superlattice structure. BACKGROUND

[0002] Single crystal diamond is known as the "ultimate semiconductor" due to its extremely high thermal conductivity, carrier mobility and breakdown field strength, and is an ideal material for preparing next-generation high-voltage, high-frequency and high-temperature power electronic devices. However, achieving stable and efficient doping is currently a technical challenge in this field. When using a dopant to dope single crystal diamond, the doping efficiency of the dopant in the diamond lattice is low and the activation energy is high, resulting in a too high resistivity of the prepared doped diamond, which is difficult to meet the application requirements of devices.

[0003] The superlattice structure can effectively improve the carrier mobility by modulating the doping and quantum confinement effect, and is an effective way to solve the poor conductivity of doped diamond. However, during the chemical vapor deposition (CVD) process, the residual dopant in the reaction chamber and pipeline has a strong "memory effect", which causes the residual phosphorus to continue to be doped when growing the intrinsic diamond layer, resulting in a blurred interface between the doped layer and the intrinsic diamond layer, a broadened carrier distribution, and an inability to form an ideal steep interface, which seriously degrades the electrical performance of the superlattice.

[0004] In related technologies, the method of prolonging the flushing time can be used to eliminate the memory effect, but the effect of removing the residual dopant is poor and cannot meet the interface control requirements of the superlattice structure. SUMMARY

[0005] The present application provides a preparation method of diamond superlattice structure and diamond superlattice structure to solve the problem that in related technologies, the method of prolonging the flushing time is used to eliminate the memory effect, but the effect of removing the residual dopant is poor and cannot meet the interface control requirements of the superlattice structure.

[0006] In a first aspect, the present application provides a preparation method of diamond superlattice structure, comprising: generating an intrinsic diamond layer on a single crystal diamond substrate under first reaction conditions; wherein the first reaction conditions are to introduce hydrogen and a first concentration of carbon source gas into a reaction chamber in which the single crystal diamond substrate is located, and to excite by microwave plasma; under the first reaction conditions, introducing a dopant into the reaction chamber to grow a doped layer on the intrinsic diamond layer; The doping agent is stopped from being introduced, an oxygen-containing gas is introduced into the reaction chamber under the first reaction condition, and / or an adsorption layer of the doping agent is formed on the doped layer to remove the residual doping agent.

[0007] In a possible implementation, the forming of the adsorption layer of the doping agent on the doped layer comprises: A carbon source gas with a second concentration is introduced into the reaction chamber, a carbon buffer layer is formed on the doped layer, and the carbon buffer layer is used as the adsorption layer of the doping agent, wherein the second concentration is higher than the first concentration.

[0008] In a possible implementation, the method further comprises: The microwave power for preparing the diamond superlattice structure is increased from the first power to the second power while the adsorption layer of the doping agent is formed on the doped layer.

[0009] In a possible implementation, the method further comprises: The doped layer is irradiated by a laser or a direct current bias is applied to the single crystal diamond substrate while the oxygen-containing gas is introduced into the reaction chamber in which the single crystal diamond is located.

[0010] In a possible implementation, before the intrinsic diamond layer is formed on the single crystal diamond substrate, the method further comprises: The single crystal diamond substrate is subjected to acid washing and hydrogen plasma treatment, and the treated single crystal diamond substrate is placed in the reaction chamber.

[0011] In a possible implementation, the doping agent is one of phosphine, nitrogen alkane and borane.

[0012] In a possible implementation, the oxygen-containing gas is introduced into the reaction chamber, comprising: The oxygen-containing gas with a target flow is introduced into the reaction chamber in a pulse mode within a first time period.

[0013] In a second aspect, an embodiment of the present application provides a diamond superlattice structure, which comprises, from bottom to top, a single crystal diamond substrate, an intrinsic diamond layer, a doped layer and an adsorption layer of a doping agent.

[0014] In a third aspect, an embodiment of the present application provides a semiconductor device, which comprises the diamond superlattice structure of the second aspect.

[0015] In a possible implementation, the semiconductor device comprises a PIN diode, a vertical field effect transistor and a Schottky barrier diode.

[0016] This invention provides a method for preparing a diamond superlattice structure and the diamond superlattice structure itself. The method includes: under first reaction conditions, generating an intrinsic diamond layer on a single-crystal diamond substrate, wherein the first reaction conditions involve introducing hydrogen gas and a carbon source gas of a first concentration into a reaction chamber containing the single-crystal diamond substrate, and exciting the mixture using microwave plasma. While maintaining the first reaction conditions, introducing a dopant into the reaction chamber to generate a doped layer on the intrinsic diamond layer. Then, stopping the dopant introduction, while maintaining the first reaction conditions, introducing oxygen-containing gas into the reaction chamber, and / or generating a dopant adsorption layer on the doped layer to remove residual dopant. The introduction of oxygen-containing gas into the reaction chamber utilizes the oxygen free radicals generated in the plasma to react with the residual dopant to generate volatile substances, which are then rapidly extracted. This effectively removes residual dopant adsorbed in the reaction chamber and on the sample surface, eliminating the "memory effect," achieving a steep change in doping concentration at the nanoscale, and improving interface quality. A dopant adsorption layer is formed on the doped layer. This adsorption layer adsorbs residual dopant, effectively removing it and achieving a steep change in doping concentration at the nanoscale, thus improving interface quality. Simultaneously, the high crystal quality and steep interface of the diamond superlattice structure result in superior electrical properties. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the implementation of a method for preparing a diamond superlattice structure according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a diamond superlattice structure provided in an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] To improve the electrical properties of diamond superlattice structures, residual dopants need to be removed during the preparation of diamond superlattices to increase the steepness of the interface between the doped layer and the intrinsic diamond layer.

[0020] In related technologies, extending the rinsing time can be used to remove residual dopants and eliminate the memory effect. However, this method is not very effective at removing residual dopants and cannot meet the interface control requirements.

[0021] Based on this, to improve the effectiveness of removing residual dopant and enhance the steepness of the interface between the doped layer and the intrinsic diamond layer, this application provides a method for preparing a diamond superlattice structure. During the preparation of the diamond superlattice structure, after the growth of the doped layer and before the intrinsic diamond layer, oxygen-containing gas is introduced to remove residual dopant. Specifically, oxygen free radicals generated by the oxygen-containing gas in the plasma react with the residual dopant to generate volatile substances that can be rapidly extracted. Therefore, it can effectively remove residual dopant adsorbed in the reaction chamber and on the sample surface, eliminating the "memory effect" and achieving a steep change in doping concentration at the nanoscale, thus improving interface quality. Alternatively, a dopant adsorption layer can be generated on the doped layer to adsorb residual dopant, which can also effectively remove residual dopant, achieving a steep change in doping concentration at the nanoscale and improving interface quality. Simultaneously, the high crystal quality and steep interface of the diamond superlattice structure result in superior electrical properties.

[0022] The aforementioned diamond superlattice structure can be applied to a variety of fields, including but not limited to high-power electronic devices, deep ultraviolet optoelectronic devices, and quantum computing.

[0023] In the field of high-power electronic devices, the ultra-high voltage resistance and thermal conductivity of diamond superlattice structure can be used to prepare high-efficiency and energy-saving circuit conversion chips, which can be applied to extreme scenarios such as new energy vehicles, power grids and aerospace.

[0024] In the field of deep ultraviolet optoelectronic devices, diamond superlattice structures can be used to manufacture highly sensitive solar-blind ultraviolet detectors and deep ultraviolet LEDs, which can be applied to sterilization, disinfection, and high-security ultraviolet communication.

[0025] In the field of quantum computing, the use of diamond superlattice structures to achieve precise positioning and efficient electronically controlled reading and writing of qubits paves the way for building large-scale, scalable diamond quantum processors.

[0026] Figure 1 This is a flowchart illustrating the implementation of a method for preparing a diamond superlattice structure according to an embodiment of the present invention. (Refer to...) Figure 1 As shown, the details are as follows: S101: Under the first reaction conditions, an intrinsic diamond layer is generated on a single-crystal diamond substrate; wherein, the first reaction conditions are to introduce hydrogen gas and a carbon source gas of a first concentration into the reaction chamber where the single-crystal diamond substrate is located, and to excite it by microwave plasma.

[0027] In one implementation scenario, before generating an intrinsic diamond layer on a single-crystal diamond substrate, the process further includes: acid washing and hydrogen plasma treatment of the single-crystal diamond substrate, and placing the treated single-crystal diamond substrate in a reaction chamber.

[0028] Acid washing and hydrogen plasma treatment are performed on the single-crystal diamond substrate to remove impurities on the surface of the single-crystal diamond substrate and optimize the surface structure of the single-crystal diamond substrate.

[0029] In one implementation scenario, a single-crystal diamond substrate can be placed in the reaction chamber of a microwave plasma chemical vapor deposition (MPCVD) device.

[0030] It should be noted that this embodiment does not limit the size and type of the single-crystal diamond substrate. For example, a 4×4×0.5 mm³ type Ib single-crystal diamond can be used as the substrate. Type Ib single-crystal diamond is usually prepared using the high-pressure high-temperature (HPHT) method.

[0031] Here, the carbon source gas can be methane (CH4), and its volume ratio with hydrogen can be 0.5% to 5%.

[0032] In some embodiments, when preparing the diamond superlattice structure, it is also necessary to control the reaction pressure, the temperature of the single-crystal diamond substrate, and the microwave power. In one implementation scenario, the controllable reaction pressure can be 150-220 mBar, the temperature of the single-crystal diamond substrate can be 800-950℃, and the microwave power can be 1.5-4 kW.

[0033] Optionally, the thickness of the intrinsic diamond layer can be 15-50 nm. For example, under the conditions of controlling the flow rate of hydrogen gas introduced into the reaction chamber to be 500 sccm, the flow rate of methane to be 15 sccm, the initial concentration to be 3%, the reaction pressure to be 200 mBar, the temperature of the single-crystal diamond substrate to be 880°C, and the microwave power to be 3 kW, an intrinsic diamond layer with a thickness of about 50 nm can be obtained by growing for 10 minutes.

[0034] S102: Under the condition of maintaining the first reaction, a dopant is introduced into the reaction chamber to grow a doped layer on the intrinsic diamond layer.

[0035] In some embodiments, the dopant is one of phosphine, aziran, or borane.

[0036] Specifically, when the dopant is phosphine (PH3) or aziran, the doped layer is an N-type doped layer; when the dopant is borane, the doped layer is a P-type doped layer.

[0037] In one implementation scenario, the input phosphine PH3 is a mixture of hydrogen or inert gas diluted in it, with a volume ratio of 500-2000 ppm to methane.

[0038] Here, using phosphine as a dopant as an example, the thickness of the resulting phosphorus-doped layer can be 2-25 nm. For instance, a PH3 / H2 mixture of 500 ppm can be introduced into the reaction chamber at a flow rate of 2 sccm, equivalent to a volume ratio of PH3 to methane (CH4) of approximately 1000 ppm. With other reaction conditions remaining constant, growth can be completed in 5 minutes, yielding a phosphorus-doped layer approximately 25 nm thick. These other reaction conditions include the gas introduced into the reaction chamber, the reaction pressure, the temperature of the single-crystal diamond substrate, and the microwave power.

[0039] S103: Stop the dopant supply, and while maintaining the first reaction conditions, introduce oxygen-containing gas into the reaction chamber, and / or generate a dopant adsorption layer on the doped layer to remove residual dopant.

[0040] In one implementation scenario, the dopant can be introduced into the reaction chamber after a preset time period, or the dopant can be introduced into the reaction chamber when the thickness of the doped layer reaches the required thickness.

[0041] In one implementation scenario, the oxygen-containing gas can be oxygen, specifically high-purity oxygen, to improve the efficiency of removing residual dopants.

[0042] Taking phosphine as an example of a dopant, the introduction of oxygen-containing gas into the reaction chamber utilizes the oxygen free radicals generated in the plasma to react with residual phosphorus to form volatile P2O5, which is then rapidly removed. This effectively removes residual phosphorus species adsorbed in the reaction chamber and on the sample surface, eliminating the "memory effect" and achieving a steep change in doping concentration at the nanoscale. Specifically, it can achieve an interface steepness better than 5 nm / decade, effectively improving the interface quality.

[0043] In one implementation scenario, oxygen-containing gas is introduced into the reaction chamber, including: during a first time period, a target flow rate of oxygen-containing gas is pulsedly introduced into the reaction chamber.

[0044] The target flow rate of oxygen-containing gas can be 10-100 sccm, and the pulse time can be 5-30 seconds. For example, the flow rate of high-purity oxygen that can be introduced into the reaction chamber is 30 sccm, and the pulse time is 15 seconds.

[0045] Here, by precisely controlling the flow rate and pulse time of oxygen-containing gas, the process of removing residual dopants using oxygen-containing gas achieves a low net etching rate of the diamond body in a hydrogen-rich plasma environment, without affecting the high crystal quality of the intrinsic diamond layer.

[0046] Meanwhile, the high crystal quality and steep interface of the diamond superlattice significantly improve the carrier mobility. The longitudinal resistivity of the diamond superlattice at room temperature is reduced by 1-2 orders of magnitude compared to the traditional uniform doped layer, resulting in superior electrical performance.

[0047] In another implementation scenario, oxygen-containing gas can be continuously introduced into the reaction chamber.

[0048] In some embodiments, while introducing oxygen-containing gas into the reaction chamber where the single-crystal diamond is located, the doped layer can be irradiated with a laser or a DC bias voltage can be applied to the single-crystal diamond substrate.

[0049] When irradiating the doped layer with a laser, a 150-250 nm ultraviolet laser can be used to promote the dissociation of residual dopants at the interface through photochemical effects. In one implementation scenario, the intensity of the ultraviolet laser can be 10-100 mJ / cm², which can be set according to actual needs.

[0050] When a DC bias is applied to a single-crystal diamond substrate, low-energy ion bombardment can be used to enhance the interface cleaning effect. The DC bias can range from -50V to -200V, and can be set according to actual needs. In addition, the MPCVD equipment needs to be equipped with a bias-enhanced nucleation (BEN) device in this case.

[0051] In some embodiments, generating a dopant adsorption layer on the doped layer includes: introducing a carbon source gas of a second concentration into a reaction chamber, generating a carbon buffer layer on the doped layer, and using the carbon buffer layer as the dopant adsorption layer, wherein the second concentration is higher than the first concentration.

[0052] The intrinsic diamond layer and the doped layer are the main structures of the diamond superlattice structure. The dopant adsorption layer is not a main structure of the diamond superlattice structure; its function is to actively capture or remove residual dopants at the interface.

[0053] The thickness of the dopant adsorption layer can be 1-5 nm, and this application does not impose a specific limit on it.

[0054] Here, the second concentration is higher than the first concentration. A higher concentration of carbon source gas is introduced into the reaction chamber, which increases the growth rate of the carbon buffer layer and enables it to adsorb residual dopants more quickly, thereby improving the removal efficiency of residual dopants.

[0055] In one possible implementation, while generating a dopant adsorption layer on the doped layer, the microwave power for preparing the diamond superlattice structure can be increased from a first power to a second power.

[0056] For example, during the process of growing the intrinsic diamond layer and the doped layer, the corresponding microwave power is 3kW. The microwave power can be increased from 3kW to 5kW in a short time to increase the growth rate of the carbon buffer layer, which can adsorb residual dopants more quickly, thereby improving the removal efficiency of residual dopants.

[0057] After the microwave power is maintained at 5 kW for a certain period, i.e., after the dopant adsorption layer has been grown, the microwave power can be reduced to 3 kW to continue growing the intrinsic diamond layer, completing one cycle of diamond superlattice structure fabrication. During the 5 kW microwave power period, the hydrogen gas and the initial concentration of carbon source gas remain constant. The duration of the 5 kW microwave power period can be set according to actual conditions, for example, it can be 15 seconds.

[0058] It should be noted that, since this application requires the preparation of a diamond superlattice structure, steps S101-S103 need to be repeated until the required number of diamond superlattice periods are formed. For example, steps S101-S103 can be repeated to obtain a diamond superlattice structure with 20 periods and a total thickness of approximately 1.5 μm.

[0059] In the process of preparing the diamond superlattice structure with the required number of cycles, the hydrogen gas and the first concentration of carbon source gas introduced into the reaction chamber must remain constant.

[0060] In one implementation scenario, the diamond superlattice structure prepared in this application is an asymmetric superlattice structure.

[0061] It should be noted that the flow rates of carbon source gas, hydrogen, and oxygen, the time for oxygen introduction, the reaction pressure, microwave power, the temperature range of the single-crystal diamond substrate, and the thickness of the intrinsic diamond layer, doped layer, and dopant adsorption layer provided in the embodiments of this application are all examples. Specific values ​​can be set according to actual needs, and this application does not limit them.

[0062] This application provides a method for preparing a diamond superlattice structure. Under first reaction conditions, an intrinsic diamond layer is generated on a single-crystal diamond substrate. The first reaction conditions involve introducing hydrogen gas and a carbon source gas of a first concentration into a reaction chamber containing the single-crystal diamond substrate, followed by microwave plasma excitation. While maintaining the first reaction conditions, a dopant is introduced into the reaction chamber to generate a doped layer on the intrinsic diamond layer. Then, the dopant introduction is stopped, and while maintaining the first reaction conditions, oxygen-containing gas is introduced into the reaction chamber, and / or a dopant adsorption layer is generated on the doped layer to remove residual dopant. The introduction of oxygen-containing gas into the reaction chamber utilizes the oxygen free radicals generated in the plasma to react with the residual dopant to generate volatile substances, which are then rapidly extracted. This effectively removes residual dopant adsorbed in the reaction chamber and on the sample surface, eliminating the "memory effect," achieving a steep change in dopant concentration at the nanoscale, and improving interface quality. A dopant adsorption layer is formed on the doped layer. This layer adsorbs residual dopant, effectively removing it and achieving a steep change in doping concentration at the nanoscale, thus improving interface quality. Simultaneously, the high crystal quality and steep interface of the diamond superlattice structure result in superior electrical properties. Furthermore, the diamond superlattice structure fabrication method of this application has high process compatibility, requiring no major modifications to existing MPCVD equipment; only the addition of a high-precision oxygen-containing gas flow controller is needed, facilitating industrial application.

[0063] Figure 2 This is a schematic diagram of a diamond superlattice structure provided in an embodiment of the present invention, for reference. Figure 2 As shown, the diamond superlattice structure 10 includes, from bottom to top: a single-crystal diamond substrate 101, an intrinsic diamond layer 102, a doped layer 103, and a dopant adsorption layer 104.

[0064] The above Figure 2 The structure shown is for only one cycle, which can be repeatedly generated to produce the intrinsic diamond layer 102, the doped layer 103 and the dopant adsorption layer 104 until the desired number of cycles is reached.

[0065] in addition, Figure 2 The relative positions of the single-crystal diamond substrate 101, the intrinsic diamond layer 102, the doped layer 103, and the dopant adsorption layer 104 are only specified, without limiting their thickness.

[0066] This application provides a semiconductor device including the diamond superlattice structure provided in the above embodiments.

[0067] In one implementation scenario, the semiconductor device includes a PIN diode, a vertical field-effect transistor, and a Schottky barrier diode.

[0068] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0069] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0070] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing a diamond superlattice structure, characterized in that, include: Under the first reaction conditions, an intrinsic diamond layer is generated on a single-crystal diamond substrate; wherein, the first reaction conditions are to introduce hydrogen gas and a carbon source gas of a first concentration into the reaction chamber where the single-crystal diamond substrate is located, and to excite it by microwave plasma. While maintaining the first reaction conditions, a dopant is introduced into the reaction chamber to grow a doped layer on the intrinsic diamond layer. Stop the flow of the dopant, and while maintaining the first reaction conditions, introduce oxygen-containing gas into the reaction chamber, and / or generate a dopant adsorption layer on the doped layer to remove residual dopant.

2. The method for preparing the diamond superlattice structure according to claim 1, characterized in that, The step of forming a dopant adsorption layer on the doped layer includes: A carbon source gas of a second concentration is introduced into the reaction chamber to generate a carbon buffer layer on the doped layer. The carbon buffer layer is used as the dopant adsorption layer, wherein the second concentration is higher than the first concentration.

3. The method for preparing the diamond superlattice structure according to claim 1 or 2, characterized in that, The method further includes: While generating a dopant adsorption layer on the doped layer, the microwave power for preparing the diamond superlattice structure is increased from a first power to a second power.

4. The method for preparing the diamond superlattice structure according to claim 1, characterized in that, The method further includes: While introducing oxygen-containing gas into the reaction chamber where the single-crystal diamond is located, the doped layer is irradiated with a laser or a DC bias voltage is applied to the single-crystal diamond substrate.

5. The method for preparing the diamond superlattice structure according to claim 1 or 2, characterized in that, Prior to generating an intrinsic diamond layer on a single-crystal diamond substrate, the method further includes: The single-crystal diamond substrate is subjected to acid washing and hydrogen plasma treatment, and the treated single-crystal diamond substrate is placed in the reaction chamber.

6. The method for preparing the diamond superlattice structure according to claim 1 or 2, characterized in that, The dopant is one of phosphine, aziran, or borane.

7. The method for preparing the diamond superlattice structure according to claim 1 or 2, characterized in that, The above includes: During the first time period, oxygen-containing gas at a target flow rate is pulsed into the reaction chamber.

8. A diamond superlattice structure, characterized in that, The diamond superlattice structure comprises, from bottom to top: a single-crystal diamond substrate, an intrinsic diamond layer, a doped layer, and a dopant adsorption layer.

9. A semiconductor device, characterized in that, Including the diamond superlattice structure as described in claim 8.

10. The semiconductor device according to claim 9, characterized in that, This includes PIN diodes, vertical field-effect transistors, and Schottky barrier diodes.

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