CN117116747A - A kind of pretreatment method of silicon carbide wafer and silicon carbide wafer - Google Patents

Abstract

This application provides a pretreatment method for silicon carbide wafers and silicon carbide wafers, including the steps of: using cleaning liquid to clean and dry the polished silicon carbide wafer; and performing gas plasma treatment on the dried silicon carbide wafer. ; Carry out lightly doped phosphorus ion implantation on the silicon carbide wafer after plasma treatment; perform annealing treatment on the silicon carbide wafer after phosphorus ion implantation to obtain a pretreated silicon carbide wafer. Through plasma treatment, traps on the surface state and interface can be reduced, and the dual effects of physical cleaning and chemical cleaning can be achieved. Surface impurities can be removed without damaging the deep structure of the substrate. At the same time, the SiC can be further improved through the phosphorus ion implantation process. Surface flatness improves the surface characteristics of SiC wafers and improves the quality of SiC wafers, thereby reducing the impact of state density on subsequent device performance.

Description

A kind of pretreatment method of silicon carbide wafer and silicon carbide wafer

Technical field

The present application relates to the field of semiconductor manufacturing, in particular to a pretreatment method for silicon carbide wafers and silicon carbide wafers.

Background technique

Power devices are the core of power electronics technology and play a vital role in the development of power electronics technology toward high frequency and high power density. Silicon carbide (SiC) material has the characteristics of wide bandgap, high thermal conductivity, high breakdown voltage and high saturation electron drift velocity. It is an important material for preparing high-temperature and high-power power electronic devices. In addition, SiC has a unique advantage that high-quality silicon dioxide (SiO ₂ ) compound semiconductors can be obtained directly through thermal oxidation. Therefore, SiO ₂ obtained after thermal oxidation of SiC is often used as a material for metal oxide semiconductor devices (MOS). Gate dielectric, as well as SiC surface passivation, play an important role in the industrial application of power devices.

In practical applications, there are many defects such as surface traps and dangling bonds at the SiC interface, resulting in a large interface state density, which will lead to problems such as low channel mobility of SiC-based devices. At present, high-quality MOS interface treatment of SiC materials mainly relies on the nitridation annealing (POA) process after oxidation, which still limits the improvement of channel mobility.

Contents of the invention

In view of the above problems, the present application is proposed to provide a pretreatment method for silicon carbide wafers and silicon carbide wafers that overcome the problems or at least partially solve the problems, including:

A pretreatment method for silicon carbide wafers, including the steps:

Gas plasma treatment of silicon carbide wafers;

Perform lightly doped phosphorus ion implantation on the plasma-treated silicon carbide wafer;

The silicon carbide wafer after phosphorus ion implantation is annealed to obtain a pre-treated target silicon carbide wafer.

Further, before the step of performing gas plasma treatment on the silicon carbide wafer, it also includes:

Polishing silicon carbide wafers;

Use hydrofluoric acid solution to clean the polished silicon carbide wafer, and the cleaning time is 10-90 seconds;

The cleaned silicon carbide wafer is dried in an environment of 80-120°C for 10-30 minutes.

Further, the hydrofluoric acid solution is a solution in which the volume ratio of hydrofluoric acid to water is 1:10.

Further, the step of performing gas plasma treatment on the silicon carbide wafer includes:

Place the dried silicon carbide wafer in a reaction chamber with Ar and NH ₃ mixed plasma;

The reaction chamber is heated so that the internal temperature of the reaction chamber is 200-600°C and maintained for 30-300 seconds.

Further, the volume ratio of Ar to NH ₃ is 10-20:1.

Furthermore, it also includes:

Stop heating the reaction chamber;

Ar gas was introduced into the reaction chamber, and the silicon carbide wafer was cooled to room temperature in the Ar gas environment.

Further, the step of implanting lightly doped phosphorus ions into the plasma-treated silicon carbide wafer includes:

Under conditions of 800-1400°C, lightly doped phosphorus ions are implanted into the plasma-treated silicon carbide wafer, the implantation depth is 0.01-0.1μm, and the implantation concentration is 10 ¹³ -10 ¹⁴ ions/cm ³ .

Furthermore, it also includes:

The silicon carbide wafer after phosphorus ion implantation is placed in an Ar environment.

Further, the step of annealing the silicon carbide wafer after phosphorus ion implantation to obtain a pretreated silicon carbide wafer includes:

The silicon carbide wafer after phosphorus ion implantation is annealed at an annealing temperature of 1000-1600°C and a treatment time of 10-30 minutes to obtain a pre-treated silicon carbide wafer.

A silicon carbide wafer, the silicon carbide wafer is obtained by processing the pretreatment method described in any one of the above.

This application has the following advantages:

In the embodiments of the present application, compared with the silicon carbide interface in the prior art, there are many defects such as surface traps and dangling bonds, which lead to problems such as low channel mobility of silicon carbide-based devices. The present application provides a method for silicon carbide The solution for pre-treatment of gas treatment and ion implantation is as follows: perform gas plasma treatment on silicon carbide wafers; perform lightly doped phosphorus ion implantation on the silicon carbide wafer after plasma treatment; The silicon carbide wafer is annealed to obtain a pre-treated target silicon carbide wafer. The gas plasma treatment process solves the problem of silicon carbide surface defects, and through the injection of lightly doped phosphorus ions, the structural defects of the substrate itself are further eliminated and the flatness of the silicon carbide surface is improved.

Description of drawings

In order to explain the technical solution of the present application more clearly, the drawings needed to be used in the description of the present application will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application and are not useful in this field. Ordinary technicians can obtain other drawings based on these drawings without exerting creative labor;

Figure 1 is a step flow chart of a silicon carbide wafer pretreatment method provided by an embodiment of the present application;

FIG. 2 is a process flow chart of a silicon carbide wafer pretreatment method provided by an embodiment of the present application.

Detailed ways

In order to make the purpose, features and advantages of the present application more obvious and understandable, the present application will be described in further detail below in conjunction with the accompanying drawings and specific implementation modes. Obviously, the described embodiments are part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

By analyzing the existing technology, the inventor found that the existing technology mainly relies on the nitriding annealing process after oxidation for the interface treatment of silicon carbide materials. Annealing in a NO or N ₂ O atmosphere will lead to nitrogen aggregation and holes at the interface. Trapping effect, but while eliminating C atoms at the interface, NO or N ₂ O introduces O at the interface for further oxidation, forming a very fast interface state at the edge, which will also limit the improvement of channel mobility.

Referring to Figure 1 , a method for preprocessing silicon carbide wafers provided by an embodiment of the present application is shown;

The methods include:

S110. Perform gas plasma treatment on the silicon carbide wafer;

S120. Perform lightly doped phosphorus ion implantation on the silicon carbide wafer after plasma treatment;

S130. Perform annealing treatment on the silicon carbide wafer after phosphorus ion implantation to obtain a pre-processed target silicon carbide wafer.

In the embodiments of the present application, compared with the silicon carbide interface in the prior art, there are many defects such as surface traps and dangling bonds, which lead to problems such as low channel mobility of silicon carbide-based devices. The present application provides a method for silicon carbide The solution for pre-treatment of gas treatment and ion implantation is as follows: perform gas plasma treatment on silicon carbide wafers; perform lightly doped phosphorus ion implantation on the silicon carbide wafer after plasma treatment; The silicon carbide wafer is annealed to obtain a pre-treated target silicon carbide wafer. The gas plasma treatment process solves the problem of silicon carbide surface defects, and through the injection of lightly doped phosphorus ions, the structural defects of the substrate itself are further eliminated and the flatness of the silicon carbide surface is improved.

Below, a method for preprocessing silicon carbide wafers in this exemplary embodiment will be further described.

As described in step S110, the silicon carbide wafer is subjected to gas plasma treatment.

In an embodiment of the present invention, the specific process of "performing gas plasma treatment on the silicon carbide wafer" in step S110 can be further explained in conjunction with the following description.

As described in the following steps, the silicon carbide wafer is placed in a reaction chamber with Ar and NH ₃ mixed plasma;

As described in the following steps, the reaction chamber is heated so that the internal temperature of the reaction chamber is 200-600°C and maintained for 30-300 seconds.

It should be noted that the principle of plasma cleaning treatment is that in a vacuum state, a very high frequency alternating electric field is formed by the electrodes in the vacuum chamber, and the reactive gases in the chamber form plasma under the action of the alternating electric field. Under the dual effects of the chemical reaction of active plasma and repeated physical bombardment, the objects being cleaned in the cavity turn volatile residues, impurities, dust, oxides, etc. on the surface into ions or gaseous substances. These ions or gases are evacuated by the vacuum. Remove the discharge cavity from the bottom and peel off the surface of the object to be cleaned, thereby achieving the purpose of cleaning.

In the process of cleaning substrate impurities and surface oxides through plasma, pure hydrogen has the highest efficiency, but there are problems with discharge stability and safety. At the same time, the cost of _H2 is high, which is not conducive to large-scale industrial application. Through this designed solution, the use of Ar/NH ₃ mixed plasma treatment can effectively complete surface cleaning of impurities, remove oxides and improve surface lattice distribution problems. Through Ar atmosphere annealing, the substrate surface stress can be further eliminated and suppressed The natural oxidation of the surface optimizes the surface lattice distribution and improves the surface flatness of the substrate.

Under non-high-temperature conditions, plasma treatment only affects the nanoscale surface of the material and does not change the original characteristics of the material. It is a pretreatment method suitable for silicon carbide gate oxidation. Due to the strong repulsion between internal H atoms in NH ₃ in plasma gas, compared with H ₂ , the bond energy is reduced and it is more likely to break. During low-temperature plasma treatment, active ions such as N, N ⁺ , Nm (metastable state), N ^* and N ₂ can be formed. When they come into contact with the material surface, they can form free radicals or unsaturated radical reactions, thus Combines with impurity ions on the silicon carbide surface. Through plasma surface treatment, surface defects can be reduced and the SiC wafer surface can be smoothed.

The volume ratio of Ar to NH ₃ is 10-20:1.

As described in the following steps, stop heating the reaction chamber;

As described in the following steps, Ar gas is introduced into the reaction chamber, and the silicon carbide wafer is cooled to room temperature in an Ar gas environment.

It should be noted that Ar gas is used for protection to prevent the high temperature of the silicon carbide wafer from reacting with the surrounding environment during cooling and affecting the quality of the silicon carbide wafer.

Before step S120 of performing gas plasma treatment on the silicon carbide wafer, it also includes:

Polishing silicon carbide wafers;

Use hydrofluoric acid solution to clean the polished silicon carbide wafer, and the cleaning time is 10-90 seconds;

The cleaned silicon carbide wafer is dried in an environment of 80-120°C for 10-30 minutes.

It should be noted that there will be many C and O pollutants and surface adsorbates on the surface of the silicon carbide substrate, which will affect the interface. Therefore, before plasma pretreatment, the impurities and natural oxide layer on the surface of the silicon carbide substrate need to be removed first. To remove particulate impurities attached to the surface of the SiC wafer, the cleaning solution selected is a mixed solution of hydrofluoric acid (HF) and deionized water (H ₂ 0). The volume ratio of HF and H ₂ 0 is 1:10. The time is 10~90 s. There will be many surface adsorbents on the surface of silicon carbide. When the silicon carbide wafer is in contact with the air, a natural oxide film will also be formed. Therefore, the silicon carbide wafer needs to be cleaned to remove particulate pollutants and particles attached to the surface. Natural oxide film.

As described in step S120, lightly doped phosphorus ions are implanted into the silicon carbide wafer after plasma treatment.

It should be noted that the light doping process is to add conductive elements into the semiconductor, which is divided into light doping, medium doping and heavy doping according to different adding proportions.

In an embodiment of the present invention, the specific process of "performing lightly doped phosphorus ion implantation on the silicon carbide wafer after plasma treatment" in step S120 can be further explained in conjunction with the following description.

As described in the following steps, perform lightly doped phosphorus ion implantation on the plasma-treated silicon carbide wafer at 800-1400°C, with a depth of 0.01-0.1μm and a concentration of 10 ¹³ -10 ¹⁴ ions/cm ³ ;

It should be noted that through lightly doped P ion implantation, the structural defects of the substrate itself can be further eliminated and the SiC surface flatness can be improved.

As described in the following steps, the silicon carbide wafer after phosphorus ion implantation is placed in an Ar environment.

After the ion implantation process, the silicon carbide wafer is annealed, which needs to be processed in an Ar environment.

As described in step S130, the silicon carbide wafer after phosphorus ion implantation is annealed to obtain a pre-processed target silicon carbide wafer.

In an embodiment of the present invention, the specific process of "annealing the silicon carbide wafer after phosphorus ion implantation to obtain a pre-processed target silicon carbide wafer" in step S130 can be further explained in conjunction with the following description.

As described in the following steps, the silicon carbide wafer after phosphorus ion implantation is annealed, the annealing temperature is 1000-1600°C, and the processing time is 10-30 minutes.

In a specific implementation, refer to FIG. 2 , which is a process flow chart of a pretreatment method before gate oxide to improve surface defects of silicon carbide wafers. The specific steps are to clean the polished SiC wafer, and clean the SiC wafer with a low degree of oxidation in HF solution for 30 s to remove the natural oxide film attached to the surface of the SiC wafer. The cleaned wafer was then placed in a drying oven at 100°C and dried for 10 minutes. The dried wafer is then placed in a 400°C reaction chamber, and surface Ar and NH ₃ mixed plasma treatment is performed for 2 minutes to activate surface activity. The wafer after surface plasma treatment was implanted with low-energy lightly doped P ions. The implantation concentration was 1.2×10 ¹³ ions/cm ³ , the implantation depth was 0.04 μm, and the implantation temperature was 850°C. Finally, the wafer was placed in an inert gas Ar atmosphere and annealed on a 1050°C hot stage for 20 minutes. Surface analysis tests were conducted on annealed and untreated silicon carbide wafers to compare surface flatness and impurity particle distribution. The results show that the surface height distribution of the SiC wafer after surface plasma treatment and Ar annealing is flatter, surface impurities are reduced, surface flatness is improved, and the performance of the silicon carbide wafer is also improved.

Although preferred embodiments of the embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once the basic inventive concepts are understood. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

Finally, it should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or any such actual relationship or sequence between operations. Furthermore, the terms "comprises," "comprises," or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or end device that includes a list of elements includes not only those elements, but also elements not expressly listed or other elements inherent to such process, method, article or terminal equipment. Without further limitation, an element defined by the statement "comprises a..." does not exclude the presence of additional identical elements in a process, method, article or terminal device including the stated element.

The above is a detailed introduction to a silicon carbide wafer pretreatment method provided by this application. Specific examples are used in this article to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand this application. The application method and its core idea; at the same time, for those of ordinary skill in the field, there will be changes in the specific implementation and application scope based on the ideas of this application. In summary, the contents of this specification should not be understood as a limitation on this application.

Claims (10)

1. A pretreatment method for silicon carbide wafers, characterized in that it includes the steps: Gas plasma treatment of silicon carbide wafers; Perform lightly doped phosphorus ion implantation on the plasma-treated silicon carbide wafer; The silicon carbide wafer after phosphorus ion implantation is annealed to obtain a pre-treated target silicon carbide wafer. 2. The pretreatment method according to claim 1, characterized in that, before the step of performing gas plasma treatment on the silicon carbide wafer, it also includes: Polishing silicon carbide wafers; Use hydrofluoric acid solution to clean the polished silicon carbide wafer, and the cleaning time is 10-90 seconds; The cleaned silicon carbide wafer is dried in an environment of 80-120°C for 10-30 minutes. 3. The pretreatment method according to claim 2, wherein the hydrofluoric acid solution is a solution in which the volume ratio of hydrofluoric acid to water is 1:10. 4. The pretreatment method according to claim 1, characterized in that the step of performing gas plasma treatment on the silicon carbide wafer includes: Place the silicon carbide wafer in a reaction chamber with Ar and NH ₃ mixed plasma; The reaction chamber is heated so that the internal temperature of the reaction chamber is 200-600°C and maintained for 30-300 seconds. 5. The pretreatment method according to claim 4, characterized in that the volume ratio of Ar to _NH is 10-20:1. 6. The pretreatment method according to claim 4, further comprising: Stop heating the reaction chamber; Ar is introduced into the reaction chamber, and the silicon carbide wafer is cooled to room temperature in an Ar environment. 7. The pretreatment method according to claim 1, wherein the step of implanting lightly doped phosphorus ions into the plasma-treated silicon carbide wafer includes: Under conditions of 800-1400°C, lightly doped phosphorus ions are implanted into the plasma-treated silicon carbide wafer, the implantation depth is 0.01-0.1μm, and the implantation concentration is 10 ¹³ -10 ¹⁴ ions/cm ³ . 8. The pretreatment method according to claim 7, further comprising: The silicon carbide wafer after phosphorus ion implantation is placed in an Ar environment. 9. The pretreatment method according to claim 1, wherein the step of annealing the silicon carbide wafer after phosphorus ion implantation to obtain a pretreated silicon carbide wafer includes: The silicon carbide wafer after phosphorus ion implantation is annealed at an annealing temperature of 1000-1600°C and a treatment time of 10-30 minutes to obtain a pre-treated silicon carbide wafer. 10. A silicon carbide wafer, characterized in that the silicon carbide wafer is processed by the pretreatment method according to any one of claims 1 to 9.