CN111681943A - A kind of treatment method of silicon carbide surface - Google Patents

Abstract

The invention provides a method for treating the surface of silicon carbide. An oxide layer is grown on the surface of a silicon carbide substrate; a doping layer is deposited on the surface of the oxide layer by atomic layer deposition equipment; The layered silicon carbide substrate is vacuum annealed according to the set vacuum degree, which greatly reduces the interface state density between the silicon carbide and the oxide layer, thereby improving the inversion channel electron mobility of the silicon carbide power device, and avoiding the impact of the silicon carbide on the silicon carbide. The performance of the power device is affected. In the present invention, an annealing furnace is used to anneal the silicon carbide substrate containing the doped layer and the oxide layer at high temperature, so as to avoid the introduction of new impurities during the annealing process, reduce defects in the oxide layer, and improve the quality of the oxide layer. The junction depth for the diffusion of phosphorus atoms can be precisely controlled by temperature and time.

Description

A kind of treatment method of silicon carbide surface

technical field

The invention relates to the technical field of semiconductors, in particular to a method for treating the surface of silicon carbide.

Background technique

In recent years, according to the 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 drive and charging piles, etc., silicon carbide materials are expected to gradually replace silicon devices in power electronic devices due to their wide band gap and high critical breakdown field strength, so as to improve the working efficiency of existing power electronic equipment. , the continuous progress of silicon carbide power electronic devices will play a revolutionary role in the development of power electronics technology.

Silicon carbide (SiC) has the incomparable advantages of traditional silicon and arsenic in terms of band gap, maximum field strength, doping concentration and thermal conductivity, especially suitable for high voltage, high frequency, high power, high radiation and certain Some wavelengths of photodetection technology. Therefore, silicon carbide materials have received extensive attention from researchers in power microwave and optoelectronic devices.

Among them, in the preparation process of silicon carbide power devices, the high-temperature oxidation process is one of the core processes that determine the performance of silicon carbide power devices. Compared with other wide-bandgap semiconductors such as nitride, silicon carbide has its own advantages. The thermal oxidation process generates an oxide film without introducing other impurity elements, which makes silicon carbide easy to be compatible with the silicon power device fabrication process.

At present, the treatment of silicon carbide is to grow an oxide layer, and then use a nitrogen atmosphere to anneal the silicon carbide containing the oxide layer. The interface state density between the silicon carbide and the oxide layer is high, resulting in the inversion channel of the silicon carbide power device. The low electron mobility seriously affects the performance of SiC power devices.

SUMMARY OF THE INVENTION

In order to overcome the deficiency of the high interface state density between the silicon carbide and the oxide layer in the above-mentioned prior art, the present invention provides a method for treating the surface of silicon carbide, comprising:

grow oxide layer on the surface of silicon carbide substrate;

depositing a doped layer on the surface of the oxide layer;

Vacuum annealing is performed on the silicon carbide substrate containing the doped layer and the oxide layer according to the set vacuum degree.

The growing oxide layer on the surface of the silicon carbide substrate includes:

The silicon carbide substrate is put into the oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900 ° C-1200 ° C at a heating rate of 10 ° C/min-200 ° C/min, and O is fed at a flow rate of 1SLM-10SLM. _2. One or more of NO and N ₂ O;

The internal temperature of the oxidation furnace was raised to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and then one of O ₂ , NO and N ₂ O was stopped. A variety of oxide layers are obtained.

The growing oxide layer on the surface of the silicon carbide substrate includes:

Put the silicon carbide substrate into the oxidation furnace, and increase the internal temperature of the oxidation furnace to 900 °C-1200 °C at a heating rate of 10 °C/min-200 °C/min, and pass H at a flow rate of 1SLM-10SLM. ₂ and O ₂ ;

The internal temperature of the oxidation furnace was increased to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and then H ₂ and O ₂ were stopped to obtain an oxide layer.

The growing oxide layer on the surface of the silicon carbide substrate includes:

The silicon carbide substrate is put into the oxidation furnace, and the internal temperature of the oxidation furnace is increased to 900 ° C-1200 ° C at a heating rate of 10 ° C/min-200 ° C/min, and O is fed at a flow rate of 1SLM-10SLM. _2. One or more of NO and N ₂ O;

The internal temperature of the oxidation furnace is increased to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and one or more of O ₂ , NO and N ₂ O are stopped. kind;

The internal temperature of the oxidation furnace was maintained, and H ₂ and O ₂ were fed in at a flow rate of 1SLM-10SLM for 1min-5h, and then the feeding of H ₂ and O ₂ was stopped to obtain an oxide layer.

The depositing a doped layer on the surface of the oxide layer includes:

Putting the silicon carbide substrate containing the oxide layer into the atomic layer deposition equipment, and evacuating the atomic layer deposition equipment;

heating the atomic layer deposition apparatus to a preset temperature;

A doping layer is deposited on the surface of the oxide layer by using a P doping source, a silicon doping source and an oxygen source in sequence.

The vacuum annealing of the silicon carbide substrate containing the doped layer and the oxide layer according to a preset vacuum degree includes:

Putting the silicon carbide substrate containing the doped layer and the oxide layer into an annealing furnace, and evacuating the annealing furnace to a set vacuum degree;

Raise the internal temperature of the annealing furnace to 900°C-1500°C at a heating rate of 10°C/min-200°C/min, and maintain for 30min-2h;

The internal temperature of the annealing furnace was lowered to room temperature at a cooling rate of 10°C/min-200°C/min.

The thickness of the oxide layer is 2nm-30nm.

The preset temperature is 200-500°C;

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

The exposure time of the P doping source, the silicon source and the oxygen source in the atomic layer deposition equipment is all 100ms-3s;

The P doping source is a P group hydride or halogen 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.

The set vacuum degree is 10 ^-6 torr-10 ^-9 torr.

Before growing an oxide layer on the surface of the silicon carbide substrate by a dry oxidation process and/or a wet oxidation process, the steps include:

The silicon carbide substrates were cleaned using RCA standards.

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

The ion doping concentration of the silicon carbide substrate is 1×10 ¹³ to 10 ²¹ cm ⁻³ , and the thickness thereof is 0.1 μm to 500 μm.

The technical scheme provided by the invention has the following beneficial effects:

In the method for treating the surface of silicon carbide provided by the present invention, an oxide layer is grown on the surface of a silicon carbide substrate; a doping layer is deposited on the surface of the oxide layer; Vacuum annealing at a constant vacuum degree greatly reduces the interface state density between the silicon carbide and the oxide layer;

The technical solution provided by the present invention is to perform high temperature annealing on the silicon carbide substrate containing the doped layer and the oxide layer, thereby 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, and reducing the amount of impurities in the oxide layer. Defects, improve 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;

The invention introduces phosphorus element doping when depositing a doped layer on the surface of the oxide layer by atomic layer deposition equipment. After high temperature annealing, phosphorus atoms are used to form more stable chemical bonds in the oxide layer, which can effectively eliminate silicon carbide/silicon dioxide. The energy gap band brought by the interface dangling bond;

The technical solution provided by the present invention can obtain an interface structure with a controllable junction depth, and finally obtain a high-quality low-density interface;

The invention can improve the inversion channel electron mobility of the silicon carbide power device, and avoid affecting the performance of the silicon carbide power device.

Description of drawings

FIG. 1 is a flow chart of a method for processing a silicon carbide surface in an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

An embodiment of the present invention provides a method for processing a silicon carbide surface. The specific flowchart is shown in FIG. 1 , and the specific process is as follows:

S101: growing an oxide layer on the surface of the silicon carbide substrate;

S102: deposit a doped layer on the surface of the oxide layer;

S103 : vacuum annealing the silicon carbide substrate containing the doped layer and the oxide layer according to the set vacuum degree.

The silicon carbide substrate to be processed is an N-type silicon carbide substrate or a 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 ¹³ ～ 10 ²¹ cm ^-3 , and its thickness is 0.1 μm to 500 μm. In the embodiment of the present invention, a silicon carbide substrate with a thickness of 350 μm is selected.

By growing an oxide layer on the surface of a silicon carbide substrate, including:

The RCA standard is used to clean the silicon carbide substrate. The specific process is as follows:

(1) prepare hydrofluoric acid solution (HF:H2O=1:10);

(2) The sample holder is cleaned and dried for use;

(3) Take the above-mentioned silicon carbide samples and place them on the support, and place them in order;

(4) Match with 3# liquid (sulfuric acid: H2O2=3:1), add sulfuric acid at the end, and boil water in another container at the same time;

(5) Boil and wash with 3# solution, heat to 250℃ for 15min, lift the support and cool for a while;

(6) Put the bracket into hot water and flush it;

(7) Prepare 1# solution (ammonia: H2O2: H2O=1:1:5-1:1:7), pour the first two into hot water, heat at 75-85°C,

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

(8) Prepare 2# solution (HCl:H2O2:H2O=1:1:5) and pour the first two into hot water;

(9) Take out the silicon wafer, put it into the 2# solution, take it out and put it in hot water for 15 minutes, and rinse it with water;

(10) 1% hydrofluoric acid for 5 to 120 s to remove the oxide layer on the surface of the silicon carbide sample;

(11) Rinse with deionized water for 20 minutes, and the surface after ultrasonic treatment has hydroxyl groups.

The oxide layer can be grown on the surface of the silicon carbide substrate by a dry oxidation process or a wet oxidation process, or by a combination of the dry oxidation process and the wet oxidation process, as follows:

1. An oxide layer is grown on the surface of a silicon carbide substrate by a dry oxidation process, including:

Put the silicon carbide substrate into the oxidation furnace, and increase the internal temperature of the oxidation furnace to 900 °C-1200 °C at a heating rate of 10 °C/min-200 °C/min, and pass O ₂ , One or more of NO and N ₂ O; in the embodiment of the present invention, a heating rate of 20° C./min is selected to raise the internal temperature of the oxidation furnace to 1000° C., and the gas introduced is N ₂ O;

The internal temperature of the oxidation furnace was raised to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and then one of O ₂ , NO and N ₂ O was stopped. Various methods were used to obtain an oxide layer. In the embodiment of the present invention, the internal temperature of the oxidation furnace was raised to 1300° C. at a heating rate of 50° C./min, and the thickness of the obtained oxide layer was 20 nm.

2. An oxide layer is grown on the surface of a silicon carbide substrate by a wet oxidation process, including:

The silicon carbide substrate was put into the oxidation furnace, and the internal temperature of the oxidation furnace was increased to 900 °C-1200 °C at a heating rate of 10 °C/min- ₂₀₀ °C/min, and H and O ₂ ;

The internal temperature of the oxidation furnace was increased to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and then H ₂ and O ₂ were stopped to obtain an oxide layer.

3. The oxide layer is grown on the surface of the silicon carbide substrate through the dry oxidation process and the wet oxidation process, including:

Put the silicon carbide substrate into the oxidation furnace, and increase the internal temperature of the oxidation furnace to 900 °C-1200 °C at a heating rate of 10 °C/min-200 °C/min, and pass O ₂ , One or more of NO and N ₂ O; in the embodiment of the present invention, a heating rate of 20° C./min is selected to raise the internal temperature of the oxidation furnace to 1000° C., and the gas introduced is N ₂ O;

The internal temperature of the oxidation furnace is increased to 1200°C-1500°C at a heating rate of 10°C/min-200°C/min, maintained for 1min-5h, and one or more of O ₂ , NO and N ₂ O are stopped. kind;

Maintain the internal temperature of the oxidation furnace (that is, keep the internal temperature of the oxidation furnace at 1200°C-1500°C), feed H ₂ and O ₂ at a flow rate of 1SLM-10SLM, maintain for 1min-5h, and then stop feeding H ₂ and O ₂ to obtain For the oxide layer, in the embodiment of the present invention, the internal temperature of the oxidation furnace is raised to 1300° C. at a heating rate of 50° C./min, and the thickness of the obtained oxide layer is 20 nm.

Deposit a doped layer on the surface of the oxide layer, including:

Put the silicon carbide substrate containing the oxide layer into the atomic layer deposition equipment, and vacuumize the atomic layer deposition equipment. In the embodiment of the present invention, the vacuum degree of the atomic layer deposition equipment is 10 ^-5 torr;

heating the atomic layer deposition equipment to a preset temperature;

A doping layer is deposited on the surface of the oxide layer by using a P doping source, a silicon doping source and an oxygen source in sequence.

The preset temperature is 200-500°C, and the preset temperature in the embodiment of the present invention is 300°C.

Vacuum annealing the silicon carbide substrate containing the doped layer and the oxide layer according to the preset vacuum degree, including:

Put the silicon carbide substrate containing the doped layer and the oxide layer into the annealing furnace, and evacuating the annealing furnace to the set vacuum degree, and the set vacuum degree is 10 ^-6 torr-10 ^-9 torr;

The internal temperature of the annealing furnace is raised to 900°C-1500°C at a heating rate of 10°C/min-200°C/min, and maintained for 30min-2h; The internal temperature was raised to 1200°C and maintained for 60min;

The internal temperature of the annealing furnace is lowered to room temperature at a cooling rate of 10°C/min-200°C/min. In the embodiment of the present invention, the cooling rate is 10°C/min. So far, the low-density silicon carbide and the oxide layer are obtained. Interface state silicon carbide substrate.

The thickness of the doped layer is 2 nm-30 nm, and the thickness of the doped layer obtained in the embodiment of the present invention is 20 nm.

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

P doping source is P group hydride (such as PH3) or halogen oxide (such as POCL3);

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

The source of oxygen is water vapor or oxygen.

The interface state density between the silicon carbide substrate and the oxide layer treated by the method for treating the silicon carbide surface provided by the embodiment of the present invention is low, the quality of the oxide layer is high, and the inversion channel electron migration of the silicon carbide power device can be improved. rate, to avoid affecting the performance of silicon carbide power devices.

For the convenience of description, each part of the device described above is divided into various modules or units by function and described respectively. Of course, when implementing the present application, the functions of each module or unit may be implemented in one or more software or hardware.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may 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.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

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 of ordinary skill in the art can still modify or equivalently replace the specific embodiments of the present invention with reference to the above embodiments. Any modifications or equivalent replacements that depart from the spirit and scope of the present invention fall within the protection scope of the present invention for which the application is pending.

Claims (11)

1. A method of treating a silicon carbide surface, comprising:

growing an oxide layer on the surface of the silicon carbide substrate;

depositing a doping layer on the surface of the oxidation layer;

and carrying out vacuum annealing on the silicon carbide substrate containing the doping layer and the oxidation layer according to a set vacuum degree.

2. The method according to claim 1, wherein the growing an oxide layer on the surface of the silicon carbide substrate comprises:

putting the silicon carbide substrate into an oxidation furnace, raising the internal temperature of the oxidation furnace to 900-1200 ℃ at a heating rate of 10-200 ℃/min, and introducing O at a flow rate of 1-10 SLM₂NO and N₂One or more of O;

raising the internal temperature of the oxidation furnace to 1200-1500 ℃ at a heating rate of 10-200 ℃/min, maintaining for 1-5 h, and stopping introducing O₂NO and N₂O, to obtain an oxide layer.

3. The method according to claim 1, wherein the growing an oxide layer on the surface of the silicon carbide substrate comprises:

putting the silicon carbide substrate into an oxidation furnace, and raising the internal temperature of the oxidation furnace by 10-200 ℃/minThe temperature rate is increased to 900-1200 ℃, and H is introduced at the flow rate of 1SLM-10SLM₂And O₂；

Raising the internal temperature of the oxidation furnace to 1200-1500 ℃ at a heating rate of 10-200 ℃/min, maintaining for 1-5H, and stopping introducing H₂And O₂And obtaining an oxide layer.

4. The method according to claim 1, wherein the growing an oxide layer on the surface of the silicon carbide substrate comprises:

putting the silicon carbide substrate into an oxidation furnace, raising the internal temperature of the oxidation furnace to 900-1200 ℃ at a heating rate of 10-200 ℃/min, and introducing O at a flow rate of 1-10 SLM₂NO and N₂One or more of O;

raising the internal temperature of the oxidation furnace to 1200-1500 ℃ at a heating rate of 10-200 ℃/min, maintaining for 1-5 h, and stopping introducing O₂NO and N₂One or more of O;

maintaining the internal temperature of the oxidation furnace, and introducing H at the flow rate of 1SLM-10SLM₂And O₂Maintaining for 1min-5H, and stopping introducing H₂And O₂And obtaining an oxide layer.

5. The method for treating silicon carbide surface according to claim 1 wherein said depositing a doped layer on the surface of said oxide layer comprises:

putting a silicon carbide substrate containing an oxide layer into the atomic layer deposition equipment, and vacuumizing the atomic layer deposition equipment;

heating the atomic layer deposition equipment to a preset temperature;

and depositing a doping layer on the surface of the oxide layer by sequentially adopting a P doping source, a silicon doping source and an oxygen source.

6. The method for processing the silicon carbide surface according to claim 1, wherein the step of performing vacuum annealing on the silicon carbide substrate containing the doped layer and the oxidized layer according to a preset vacuum degree comprises the following steps:

putting the silicon carbide substrate containing the doped layer and the oxide layer into an annealing furnace, and vacuumizing the annealing furnace to a set vacuum degree;

raising the internal temperature of the annealing furnace to 900-1500 ℃ at a temperature raising rate of 10-200 ℃/min, and maintaining for 30-2 h;

and reducing the internal temperature of the annealing furnace to room temperature at a cooling rate of 10-200 ℃/min.

7. The method of treating a silicon carbide surface according to any of claims 2 to 4 wherein the oxide layer has a thickness of 2nm to 30 nm.

8. The method as recited in claim 5, wherein the predetermined temperature is 200-500 ℃;

the thickness of the doped layer is 2nm-30 nm;

the exposure time of the P doping source, the silicon source and the oxygen source in the atomic layer deposition equipment is 100ms-3 s;

the P doping source is a P-group hydride or a halogen-group 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.

9. The method of treating a silicon carbide surface according to claim 1 or 6 wherein the set vacuum is 10^-6torr-10^-9torr。

10. The method for processing the silicon carbide surface according to claim 1, wherein the step of growing the oxide layer on the surface of the silicon carbide substrate by a dry oxidation process and/or a wet oxidation process comprises the following steps:

and cleaning the silicon carbide substrate by adopting RCA standard.

11. The method for treating the surface of silicon carbide according to claim 1, wherein the silicon carbide substrate is an N-type silicon carbide substrate or a P-type silicon carbide substrate;

the ion doping concentration of the silicon carbide substrate is 1 × 10¹³～10²¹cm^-3The thickness of the film is 0.1-500 mu m.

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