A method for treating silicon carbide surfaces

Abstract

This invention provides a method for treating the surface of silicon carbide, comprising growing an oxide layer on the surface of a silicon carbide substrate; depositing a doped layer on the oxide layer surface using an atomic layer deposition apparatus; and vacuum annealing the silicon carbide substrate containing the doped layer and oxide layer at a set vacuum level using an annealing furnace. This significantly reduces the interface state density between silicon carbide and the oxide layer, thereby improving the inversion channel electron mobility of silicon carbide power devices and avoiding any impact on the performance of the silicon carbide power devices. This invention uses an annealing furnace to perform high-temperature annealing on the silicon carbide substrate containing the doped layer and oxide layer, avoiding the introduction of new impurities during the annealing process, reducing defects in the oxide layer, improving the quality of the oxide layer, and simultaneously allowing precise control of the junction depth of phosphorus atom diffusion through temperature and time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a method for treating the surface of silicon carbide. Background Technology

[0002] In recent years, according to domestic statistical data analysis of power devices, the market size of high-voltage silicon carbide power devices has increased significantly year by year. The main market applications of silicon carbide devices include photovoltaics, power supplies, uninterruptible power supplies, electric / hybrid vehicles, wind power generation, rail transit, motor drives, and charging piles. With its wide bandgap and high critical breakdown field strength, silicon carbide materials are expected to gradually replace silicon devices in power electronic devices to improve the working efficiency of existing power electronic equipment. In short, the continuous progress of silicon carbide power electronic devices will promote the development of the power electronics technology field.

[0003] Silicon carbide (SiC) possesses unparalleled advantages over traditional silicon and bromide in terms of bandgap, maximum electric field strength, doping concentration, and thermal conductivity, making it particularly suitable for high-voltage, high-frequency, high-power, high-irradiation, and certain wavelength optoelectronic detection technologies. Therefore, silicon carbide materials have garnered widespread attention from researchers in power microwave and optoelectronic devices.

[0004] In the fabrication of silicon carbide power devices, high-temperature oxidation is one of the core processes that determines the performance of silicon carbide power devices. Compared with other wide bandgap semiconductors such as argon nitride, silicon carbide has its own advantages. Silicon carbide generates an oxide film through thermal oxidation without introducing other impurity elements, making it easy to be compatible with silicon power device fabrication processes.

[0005] Currently, the treatment of silicon carbide involves growing an oxide layer and then annealing the silicon carbide containing the oxide layer in a nitrogen atmosphere. The interface state density between silicon carbide and the oxide layer is high, resulting in low electron mobility in the inversion channel of silicon carbide power devices, which seriously affects the performance of silicon carbide power devices. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology in terms of high interface state density between silicon carbide and oxide layer, the present invention provides a method for treating silicon carbide surface, comprising:

[0007] An oxide layer is grown on the surface of a silicon carbide substrate;

[0008] A doped layer is deposited on the surface of the oxide layer;

[0009] The silicon carbide substrate containing the doped layer and oxide layer is vacuum annealed at a set vacuum level.

[0010] The process of growing an oxide layer on the surface of a silicon carbide substrate includes:

[0011] The silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. One or more of O2, NO and N2O are introduced at a flow rate of 1SLM-10SLM.

[0012] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 1min-5h. Then, the introduction of one or more of O2, NO and N2O is stopped to obtain the oxide layer.

[0013] The process of growing an oxide layer on the surface of a silicon carbide substrate includes:

[0014] The silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. H2 and O2 are introduced at a flow rate of 1SLM-10SLM.

[0015] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 1min-5h. Then, the introduction of H2 and O2 is stopped to obtain the oxide layer.

[0016] The process of growing an oxide layer on the surface of a silicon carbide substrate includes:

[0017] The silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. One or more of O2, NO and N2O are introduced at a flow rate of 1SLM-10SLM.

[0018] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min, maintained for 1min-5h, and one or more of O2, NO and N2O are stopped.

[0019] Maintain the internal temperature of the oxidation furnace, and introduce H2 and O2 at a flow rate of 1 SLM-10 SLM for 1 min-5 h, then stop introducing H2 and O2 to obtain an oxide layer.

[0020] The deposition of a doped layer on the surface of the oxide layer includes:

[0021] A silicon carbide substrate containing an oxide layer is placed in an atomic layer deposition apparatus, and the atomic layer deposition apparatus is evacuated.

[0022] The atomic layer deposition equipment is heated to a preset temperature;

[0023] A doped layer is deposited on the surface of the oxide layer using a P-doped source, a silicon-doped source, and an oxygen source in sequence.

[0024] The vacuum annealing of the silicon carbide substrate containing the doped layer and oxide layer at a preset vacuum level includes:

[0025] A silicon carbide substrate containing a doped layer and an oxide layer is placed in an annealing furnace, and the annealing furnace is evacuated to a set vacuum level.

[0026] The internal temperature of the annealing furnace is raised to 900℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 30min-2h.

[0027] The internal temperature of the annealing furnace is reduced to room temperature at a cooling rate of 10℃ / min-200℃ / min.

[0028] The oxide layer has a thickness of 2nm-30nm.

[0029] The preset temperature is 200-500℃;

[0030] The thickness of the doped layer is 2nm-30nm;

[0031] The exposure time of the P-doped source, silicon source and oxygen source in the atomic layer deposition equipment is 100ms-3s;

[0032] The P-doping source is a group P hydride or a group halide oxide;

[0033] The silicon doping source is a silicon-containing alkyl compound, a silicon-containing hydride, or a silicon-containing halide.

[0034] The oxygen source is water vapor or oxygen.

[0035] The set vacuum level is 10. -6 torr-10 -9 torr.

[0036] Before growing an oxide layer on the surface of a silicon carbide substrate using dry oxidation and / or wet oxidation processes, the process includes:

[0037] The silicon carbide substrate was cleaned using the RCA standard.

[0038] The silicon carbide substrate is an N-type silicon carbide substrate or a P-type silicon carbide substrate;

[0039] The silicon carbide substrate has an ion doping concentration of 1×10⁻⁶. 13 ~10 21 cm -3 Its thickness ranges from 0.1 μm to 500 μm.

[0040] The technical solution provided by this invention has the following beneficial effects:

[0041] In the silicon carbide surface treatment method provided by the present invention, an oxide layer is grown on the surface of a silicon carbide substrate; a doped layer is deposited on the surface of the oxide layer; and the silicon carbide substrate containing the doped layer and the oxide layer is vacuum annealed according to a set vacuum degree, which greatly reduces the interface state density between silicon carbide and the oxide layer.

[0042] The technical solution provided by this invention performs high-temperature annealing on silicon carbide substrates containing doped and oxide layers, reducing the introduction of impurities at the interface between the silicon carbide substrate and the oxide layer, avoiding the introduction of new impurities during the annealing process, reducing defects in the oxide layer, improving the quality of the oxide layer, and at the same time, the junction depth of phosphorus atom diffusion can be precisely controlled by temperature and time.

[0043] This invention introduces phosphorus doping when depositing a doped layer on the surface of an oxide layer using an atomic layer deposition device. After high-temperature annealing, phosphorus atoms form more stable chemical bonds in the oxide layer, which can effectively eliminate the band gap caused by dangling bonds at the silicon carbide / silicon dioxide interface.

[0044] The technical solution provided by this invention can obtain an interface structure with controllable junction depth, and ultimately obtain a high-quality low-density interface.

[0045] This invention can improve the inversion channel electron mobility of silicon carbide power devices and avoid affecting the performance of silicon carbide power devices. Attached Figure Description

[0046] Figure 1 This is a flowchart of the silicon carbide surface treatment method in an embodiment of the present invention. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings.

[0048] This invention provides a method for treating the surface of silicon carbide, the specific flowchart of which is shown below. Figure 1 As shown, the specific process is as follows:

[0049] S101: An oxide layer is grown on the surface of a silicon carbide substrate;

[0050] S102: Deposit a doped layer on the surface of the oxide layer;

[0051] S103: Vacuum annealing is performed on a silicon carbide substrate containing doped and oxide layers at a set vacuum level.

[0052] The silicon carbide substrate to be processed is either an N-type or P-type silicon carbide substrate; the silicon carbide substrate is 4H-SiC or 6H-SiC; the ion doping concentration of the silicon carbide substrate is 1×10⁻⁶. 13 ~1021 cm -3 Its thickness ranges from 0.1 μm to 500 μm. In this embodiment of the invention, a silicon carbide substrate with a thickness of 350 μm is selected.

[0053] Before growing an oxide layer on the surface of a silicon carbide substrate, the following steps are included:

[0054] The silicon carbide substrate was cleaned using the RCA standard, and the specific process is as follows:

[0055] (1) Prepare hydrofluoric acid solution (HF:H2O = 1:10);

[0056] (2) Clean and dry the sample holder for later use;

[0057] (3) Place the above silicon carbide sample on the support and arrange them in order;

[0058] (4) Prepare solution #3 (sulfuric acid: H2O2 = 3:1), add the sulfuric acid last, and boil water in another container at the same time;

[0059] (5) Boil in solution #3 for 15 minutes, heat to 250°C, lift the rack and let it cool for a while;

[0060] (6) Place the bracket in hot water and rinse it;

[0061] (7) Prepare solution #1 (ammonia:H2O2:H2O = 1:1:5-1:1:7). Pour the first two into hot water and heat to 75-85℃.

[0062] Time 10-20 min (using complexation to remove heavy metal impurities), remove the sample holder, put it into solution #1, 15 min, take it out and put it in hot water to rinse;

[0063] (8) Prepare solution #2 (HCl:H2O2:H2O=1:1:5) by pouring the first two into hot water;

[0064] (9) Remove the silicon wafer, immerse it in liquid #2 for 15 minutes, then remove it and place it in hot water to rinse it.

[0065] (10) Remove the oxide layer on the surface of the silicon carbide sample by applying 1% hydrofluoric acid for 5 to 120 seconds.

[0066] (11) Rinse with deionized water for 20 minutes. The surface after ultrasonic treatment has hydroxyl groups.

[0067] An oxide layer can be grown on the surface of a silicon carbide substrate using dry oxidation, wet oxidation, or a combination of both, as detailed below:

[0068] 1. Growing an oxide layer on a silicon carbide substrate using a dry oxidation process, including:

[0069] A silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. One or more of O2, NO and N2O are introduced at a flow rate of 1SLM-10SLM. In this embodiment of the invention, a heating rate of 20℃ / min is selected to raise the internal temperature of the oxidation furnace to 1000℃, and the introduced gas is N2O.

[0070] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 1min-5h. Then, the introduction of one or more of O2, NO and N2O is stopped to obtain an oxide layer. In this embodiment of the invention, the internal temperature of the oxidation furnace is increased to 1300℃ at a heating rate of 50℃ / min, and the thickness of the oxide layer obtained is 20nm.

[0071] 2. Growing an oxide layer on the surface of a silicon carbide substrate using a wet oxidation process, including:

[0072] The silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. H2 and O2 are introduced at a flow rate of 1SLM-10SLM.

[0073] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 1min-5h. Then, the introduction of H2 and O2 is stopped to obtain the oxide layer.

[0074] 3. Growing oxide layers on silicon carbide substrates using dry oxidation and wet oxidation processes, including:

[0075] A silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. One or more of O2, NO and N2O are introduced at a flow rate of 1SLM-10SLM. In this embodiment of the invention, a heating rate of 20℃ / min is selected to raise the internal temperature of the oxidation furnace to 1000℃, and the introduced gas is N2O.

[0076] The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min, maintained for 1min-5h, and one or more of O2, NO and N2O are stopped.

[0077] Maintain the internal temperature of the oxidation furnace (i.e., keep the internal temperature of the oxidation furnace at 1200℃-1500℃), and introduce H2 and O2 at a flow rate of 1SLM-10SLM for 1min-5h. Then stop introducing H2 and O2 to obtain an oxide layer. In this embodiment of the invention, the internal temperature of the oxidation furnace is raised to 1300℃ at a heating rate of 50℃ / min, and the thickness of the oxide layer obtained is 20nm.

[0078] A doped layer is deposited on the surface of the oxide layer, including:

[0079] A silicon carbide substrate containing an oxide layer is placed in an atomic layer deposition apparatus, and the apparatus is evacuated. In this embodiment of the invention, the vacuum level of the atomic layer deposition apparatus is 10. -5 torr;

[0080] Heat the atomic layer deposition equipment to a preset temperature;

[0081] A doped layer is deposited on the surface of the oxide layer using a P-doped source, a silicon-doped source, and an oxygen source in sequence.

[0082] The preset temperature is 200-500℃, and the preset temperature in this embodiment of the invention is 300℃.

[0083] Vacuum annealing of a silicon carbide substrate containing doped and oxide layers at a preset vacuum level includes:

[0084] A silicon carbide substrate containing doped and oxide layers is placed in an annealing furnace, and the furnace is evacuated to a set vacuum level of 10. -6 torr-10 -9 torr;

[0085] The internal temperature of the annealing furnace is raised to 900℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 30min-2h; in this embodiment of the invention, the internal temperature of the annealing furnace is raised to 1200℃ at a heating rate of 20℃ / min and maintained for 60min.

[0086] The internal temperature of the annealing furnace is reduced to room temperature at a cooling rate of 10℃ / min-200℃ / min. In this embodiment of the invention, the cooling rate is 10℃ / min. Thus, a low-density silicon carbide substrate with an interface state between the silicon carbide and the oxide layer is obtained.

[0087] The thickness of the doped layer is 2nm-30nm, and the thickness of the doped layer obtained in this embodiment of the invention is 20nm.

[0088] The exposure time of the P-doped source, silicon source, and oxygen source in the atomic layer deposition equipment is 100ms-3s;

[0089] The P-doping source is a group P hydride (such as PH3) or a halide oxide (such as P0CL3).

[0090] The silicon doping source is a silicon-containing alkyl compound, a silicon-containing hydride, or a silicon-containing halide;

[0091] The oxygen source is water vapor or oxygen.

[0092] The silicon carbide substrate and oxide layer treated by the silicon carbide surface treatment method provided in this embodiment of the invention have low interface state density and high oxide layer quality, and can improve the inversion channel electron mobility of silicon carbide power devices, thus avoiding any impact on the performance of silicon carbide power devices.

[0093] For ease of description, the various parts of the device described above are divided into modules or units according to their functions. Of course, in implementing this application, the functions of each module or unit can be implemented in one or more software or hardware components.

[0094] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0095] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0096] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0097] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention by referring to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the present invention pending approval.

Claims

1. A method for treating the surface of silicon carbide, characterized in that, include: An oxide layer is grown on the surface of a silicon carbide substrate; A doped layer is deposited on the surface of the oxide layer; The silicon carbide substrate containing the doped layer and oxide layer is vacuum annealed at a set vacuum level. The process of growing an oxide layer on the surface of a silicon carbide substrate includes: The silicon carbide substrate is placed in an oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900℃-1200℃ at a heating rate of 10℃ / min-200℃ / min. One or more of O2, NO and N2O are introduced at a flow rate of 1SLM-10SLM. The internal temperature of the oxidation furnace is increased to 1200℃-1500℃ at a heating rate of 10℃ / min-200℃ / min, maintained for 1min-5h, and one or more of O2, NO and N2O are stopped. Maintain the internal temperature of the oxidation furnace, and introduce H2 and O2 at a flow rate of 1 SLM-10 SLM for 1 min-5 h, then stop introducing H2 and O2 to obtain an oxide layer; The deposition of a doped layer on the surface of the oxide layer includes: A silicon carbide substrate containing an oxide layer is placed in an atomic layer deposition apparatus, and the atomic layer deposition apparatus is evacuated. The atomic layer deposition equipment is heated to a preset temperature; A doped layer is deposited on the surface of the oxide layer using a P-doped source, a silicon-doped source, and an oxygen source in sequence; The vacuum annealing of the silicon carbide substrate containing the doped layer and oxide layer at a preset vacuum level includes: A silicon carbide substrate containing a doped layer and an oxide layer is placed in an annealing furnace, and the annealing furnace is evacuated to a set vacuum level. The internal temperature of the annealing furnace is raised to 900℃-1500℃ at a heating rate of 10℃ / min-200℃ / min and maintained for 30min-2h. The internal temperature of the annealing furnace is reduced to room temperature at a cooling rate of 10℃ / min-200℃ / min; The set vacuum level is 10. -6 torr-10 -9 torr.

2. The method for treating the surface of silicon carbide according to claim 1, characterized in that, The oxide layer has a thickness of 2nm-30nm.

3. The method for treating the surface of silicon carbide according to claim 1, characterized in that, The preset temperature is 200-500℃; The thickness of the doped layer is 2nm-30nm; The exposure time of the P-doped source, silicon source and oxygen source in the atomic layer deposition equipment is 100ms-3s; The P-doping source is a group P hydride or a group halide oxide; The silicon doping source is a silicon-containing alkyl compound, a silicon-containing hydride, or a silicon-containing halide. The oxygen source is water vapor or oxygen.

4. The method for treating the surface of silicon carbide according to claim 1, characterized in that, Before growing an oxide layer on the surface of a silicon carbide substrate using dry oxidation and / or wet oxidation processes, the process includes: The silicon carbide substrate was cleaned using the RCA standard.

5. The method for treating the surface of silicon carbide according to claim 1, characterized in that, The silicon carbide substrate is an N-type silicon carbide substrate or a P-type silicon carbide substrate; The silicon carbide substrate has an ion doping concentration of 1×10⁻⁶. 13 ~10 21 cm -3 Its thickness ranges from 0.1 μm to 500 μm.

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