CN114232089B - Periodic Modulation Method of Diamond Nucleation Density on Silicon Carbide Substrate - Google Patents

Abstract

The application provides a periodic modulation method of nucleation density of diamond on a silicon carbide substrate, which is used for preparing grooves on a carbon surface or a silicon surface of the silicon carbide substrate. And placing the silicon carbide substrate with the grooves in a growth cavity of a CVD device, introducing reaction gas and auxiliary gas to grow diamond particles, and finally, after growing for a preset time, taking the silicon carbide substrate out of the growth cavity, and observing the morphology and nucleation density of the diamond particles at the bottom, the side wall and the outside of the grooves. Based on the difference of the nucleation densities of the diamond particles at different positions of the groove when the diamond particles are contacted with plasmas in the growth process, the periodic modulation of the nucleation densities of the diamond particles on the silicon carbide substrate is realized.

Description

Periodic Modulation Method of Diamond Nucleation Density on Silicon Carbide Substrate

technical field

The present application relates to the technical field of chemical vapor deposition of diamond films, in particular to a method for periodically modulating the nucleation density of diamond on a silicon carbide substrate.

Background technique

Diamond possesses excellent optical, electrical, mechanical and thermal properties, and thus has great application potential. In particular, thin diamond films are ideal semiconductor materials due to their wide bandgap, optical transparency, and exceptionally high thermal conductivity. It has good application prospects in high-tech fields such as high-density integrated circuit packaging materials, protective coatings, and electrochemical electrodes. In recent years, the growth of diamond thin films by microwave plasma chemical vapor deposition (MPCVD) has received increasing attention, because even polycrystalline diamond has great advantages over most existing crystals. In particular, the highest acoustic velocity and thermal conductivity driven by high carrier mobility and unique optical properties make diamond films ideal for many emerging device applications, such as ultra-high frequency acoustic filters, power electronics, integrated optical circuits, and quantum transducer etc.

The substrates used for diamond film growth include silicon (Si), molybdenum (Mo), silicon carbide (SiC) and the like. Since the lattice parameters and structure of diamond-related substrate materials are important considerations in determining good film growth, all substrate materials do not respond equally in achieving good film adhesion. The lattice matching of diamond and β-SiC is good, and the lattice mismatch rate is about 18.2% (the lattice mismatch rate of diamond and Si is 52%). Therefore, when SiC is used as the substrate, it is easier to nucleate. In addition, the SiC material has a small thermal expansion coefficient and a high thermal conductivity. These characteristics are very similar to diamond, which makes the adhesion of the diamond film on the SiC substrate better. Combining the properties of the two materials has great application potential. Since there are many problems in the nucleation of diamond polycrystals, many studies have shown that there is a close relationship between its thermal conductivity and grain size. In order to modulate the thermal conductivity of diamond polycrystals, it is necessary to particles are modulated.

Contents of the invention

In order to solve the above problems, an embodiment of the present application provides a method for periodically modulating the nucleation density of diamond on a silicon carbide substrate.

The method for periodically modulating the nucleation density of diamond on a silicon carbide substrate provided in the embodiment of the present application mainly includes the following steps:

Prepare grooves on the carbon or silicon surface of the silicon carbide substrate;

placing the silicon carbide substrate in a growth chamber of a CVD device;

The reaction gas and auxiliary gas are introduced to grow the diamond particles, and after the growth reaches a preset time, the silicon carbide substrate is taken out of the growth chamber.

The method for periodically modulating the nucleation density of diamond on a silicon carbide substrate provided in the embodiment of the present application is to prepare grooves on the carbon or silicon surface of the silicon carbide substrate, and then prepare the silicon carbide substrate with the grooves placed in the growth chamber of the CVD equipment, fed with reaction gas and auxiliary gas to grow diamond particles, and finally, after growing for a preset time, the silicon carbide substrate was taken out of the growth chamber, and the concave Morphology and nucleation density of diamond particles at the bottom, sidewalls, and exterior of the groove. Based on the fact that during the growth process of diamond particles, different positions in the groove are exposed to different plasmas, which makes the nucleation density of diamond particles at different positions in the groove different, and then realizes the periodicity of the nucleation density of diamond particles on the silicon carbide substrate. modulation.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings without paying creative labor.

FIG. 1 is a schematic flow diagram of a method for periodically modulating the nucleation density of diamond on a silicon carbide substrate provided in an embodiment of the present application;

Fig. 2 provides the schematic diagram of diamond nucleation on SiC substrate for the implementation of the present application;

Figure 3a is an SEM image of diamond particles deposited at the bottom of the SiC substrate groove at a methane concentration of 1 sccm and a nucleation time of 10 min;

Figure 3b is an SEM image of diamond particles deposited at the bottom of the SiC substrate groove at a methane concentration of 3 sccm and a nucleation time of 10 min

Figure 3c is an SEM image of diamond particles deposited at the bottom of the SiC substrate groove at a methane concentration of 6 sccm and a nucleation time of 10 min;

Figure 3d is an SEM image of diamond particles deposited at the bottom of the SiC substrate groove at a methane concentration of 9 sccm and a nucleation time of 10 min;

Figure 3e is an SEM image of diamond particles deposited at the bottom of the SiC substrate groove at a methane concentration of 12 sccm and a nucleation time of 10 min;

Figure 4a is an SEM image of diamond particles deposited at the SiC substrate groove under the conditions of a CH flow rate of ₆ sccm and a growth time of 1 h;

Figure 4b is an SEM image of the diamond particles deposited at the bottom of the groove in Figure 4a;

Figure 4c is the first SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a;

Figure 4d is the second SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a;

Figure 4e is the first SEM image of diamond particles deposited outside the grooves in Figure 4a;

Figure 4f is a second SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a;

Figure 5 is the Raman spectrum of diamond nucleated at the SiC substrate groove under the conditions of CH4 flow rate of 6 sccm and growth time of 1 h.

Detailed ways

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with aspects of the invention as recited in the appended claims.

This embodiment utilizes microwave plasma chemical vapor deposition (Microwave Plasma Chemical VaporDeposition, MPCVD) method to carry out diamond thin film deposition, what adopted is the ARDIS-300MPCVD equipment that Russian Optosystems Company produces to describe the principle, also can adopt CVD (chemical Vapor deposition, Chemical Vapor Deposition) equipment, this embodiment does not specifically limit.

The method provided by this embodiment will be described in detail below with reference to the accompanying drawings. Figure 1 is a schematic diagram of the basic flow of the method for periodically modulating the nucleation density of diamond on a silicon carbide substrate provided in this embodiment. The method mainly includes the following steps:

S101: Prepare grooves on the carbon surface or the silicon surface of the silicon carbide substrate.

Specifically, the grooves can be made on the C surface or the Si surface of the silicon carbide substrate by laser cutting or cutting with a saw blade. The grooves can be arranged uniformly or non-uniformly, and the grooves can be alternately arranged. The arrangement can also be a non-alternative arrangement. In terms of size, the width of the grooves can be 100-500 μm, and the depth of the grooves can be 50-300 μm, but not within this numerical range. In order to better observe the nucleation conditions at different positions of the groove, preferably, the cross-sectional shape of the groove is set to be a square, specifically, it may be a rectangle or a square structure.

S102: Place the silicon carbide substrate in a growth chamber of a CVD device.

After the groove is made, the surface of the silicon carbide substrate can be cleaned with hydrofluoric acid, acetone, absolute ethanol and deionized water in order to remove the debris generated when the groove is made. Of course, it is not limited to this cleaning Way.

S103: The reaction gas and the auxiliary gas are introduced to grow the diamond particles, and after the growth reaches a preset time, the silicon carbide substrate is taken out of the growth chamber.

After the silicon carbide substrate is placed in the growth chamber of the MPCVD equipment, H ₂ and CH ₄ are introduced as reaction gases, and Ar, O ₂ and/or N ₂ are used as auxiliary gases to grow diamond particles. Among them, the present embodiment The auxiliary gas plays the role of adjusting the size of diamond particles and the quality of nucleation.

In this embodiment, the microwave power used is 2000-8000W, and the temperature of the silicon carbide substrate measured by a double-interference infrared radiant pyrometer is 800-1100°C. The pyrometer is measured through a 2mm slit. The deposition process uses H ₂ and CH ₄ at a pressure of about 150 Torr. The flow rate of H ₂ is about 50-600 sccm, and the flow rate of CH ₄ is 1-40 sccm.

In order to better observe the diamond nucleation process, this embodiment uses multiple silicon carbide substrates to grow diamond particles at different CH ₄ flow rates and different growth times. Concretely, the flow velocity of setting H ₂ is the first preset value, different _CH flow velocities are respectively set to carry out the growth of diamond particles, and the growth time is the first preset time, for example, the flow velocity of H ₂ can be set as 150 Arbitrary value in ~ 300sccm, the flow velocity of CH is respectively 1sccm, 3sccm, 6sccm, 9sccm and 12sccm to carry out the growth of diamond particles, and the growth time is 5 _~ 15min; the flow velocity of setting H ₂ is the first preset value, and the Set the flow rate of CH ₄ as the second preset value to grow the diamond particles, and the growth time is the second preset time. Wherein, the second preset time is greater than the first preset time; the second preset value of the CH ₄ flow rate is any value of the selected CH ₄ flow rate when the growth time is equal to the first preset time. For example, set the flow rate of _H2 to be any value in 150-300 sccm, the flow rate of _CH4 to be any value in 1 sccm, 3 sccm, 6 sccm, 9 sccm and 12 sccm, and the growth time to be 0.5-1.5 h.

FIG. 2 is a schematic diagram of diamond nucleation on a SiC substrate provided for the implementation of the present application. As shown in Figure 2, based on the fact that during the growth of diamond particles, there are differences in exposure to plasma at different positions in the groove. Among them, the plasma at the bottom of the groove is the least exposed and the nucleation density of diamond particles is the lowest, and the outside of the groove is exposed to plasma. The most plasma is received and the nucleation density of diamond particles is the highest, so that the difference in the nucleation density of diamond particles in different positions of the groove can realize the modulation of diamond particles in different positions of the groove, that is, the diamond particles can be formed on the silicon carbide substrate. Nuclei density is periodically modulated.

Based on the above method, the observation method of the nucleation process will be further introduced in combination with examples below. In this embodiment, grooves are prepared on the C surface of the silicon carbide substrate by saw blade method, the groove interval is 1 mm, the depth of the groove is 110 μm, and the width is 200 μm. After cleaning, the sample is placed in MPCVD. Using a microwave power of 4000W, the substrate temperature was measured at 900°C with a double-interference infrared bolometer. The substrate temperature was measured by a double-interference infrared bolometer with an emissivity of 0.1 through a 2mm slit. The deposition process was carried out at 150 Torr. Do it under pressure. The flow rate of H ₂ was 150 sccm, the flow rate of CH ₄ was 1 sccm, 3 sccm, 6 sccm, 9 sccm and 12 sccm, and the growth time was 10 min; another sample was grown for 1 h, the flow rate of CH ₄ was 6 sccm, and other conditions remained unchanged.

The sample was taken out for observation. In this embodiment, a scanning electron microscope (SEM) was used to observe the morphology of the diamond particles. Figures 3a, 3b, 3c, 3d and 3e are SEM images of diamond particles deposited at the bottom of SiC substrate grooves at methane concentrations of 1 sccm, 3 sccm, 6 sccm, 9 sccm and 12 sccm, and nucleation time of 10 min, respectively. As shown in Figures 3a-3e, as the methane concentration increases, the number of spherical particles gradually increases.

Figure 4a is the SEM image of the diamond particles deposited in the groove of the SiC substrate under the condition that the flow rate of CH ₄ is 6 sccm and the growth time is 1 h. It can be seen that the particle distribution in the groove is dense. Fig. 4b is an SEM image of diamond particles deposited at the bottom of the groove in Fig. 4a, that is, an enlarged view of area A in Fig. 4a, and the grain size in the middle region is greater than 5 μm.

Figure 4c is the first SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a, and Figure 4d is the second SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a, that is, the enlarged view of the B area in Figure 4a, It can be seen that the crystal grains near the side wall of the groove are hemispherical, the crystal plane is gradually smooth, and the grain gradually forms a flat square plane from a sphere, and there are many small square planes on the grain surface. Figure 4e is the first SEM image of the diamond particles deposited outside the groove in Figure 4a, that is, the enlarged view of area C in Figure 4a, it can be seen that the diamond grains near the groove are obviously in the shape of single crystal diamond, and the crystal planes are mostly square and triangle. There is a bonding layer between the crystal grains and the substrate; Figure 4f is the second SEM image of the diamond particles deposited on the sidewall of the groove in Figure 4a, the diamond particles on the sidewall of the groove are in the shape of an angular octahedron, showing a flat Square (100) faces and rough hexagonal (111) faces.

Figure 5 is the Raman spectrum of diamond nucleated at the SiC substrate groove under the conditions of CH4 flow rate of 6 sccm and growth time of 1 h. In this embodiment, three positions at the bottom of the groove, at the side wall of the groove and outside the groove were respectively measured. ①, ② and ③ represent the Raman shift positions of zero-stress diamond, graphite and trans-polyacetylene. According to the Raman results in Figure 5, the spherical particles in the groove are graphite, the side walls of the groove are diamond particles, and the diamond phase outside the groove is more obvious.

Each embodiment in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. Other embodiments of the present application will be readily apparent to those skilled in the art from consideration of the specification and practice of the disclosure of this application. This application is intended to cover any modification, use or adaptation of the application, these modifications, uses or adaptations follow the general principles of the application and include common knowledge or conventional technical means in the technical field not disclosed in the application . The specification and examples are to be considered exemplary only, with a true scope and spirit of the application indicated by the following claims.

It should be understood that the present application is not limited to the precise constructions which have been described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (8)

1. A method for periodic modulation of diamond nucleation density on a silicon carbide substrate, characterized in that the method comprises: Prepare grooves on the carbon or silicon surface of the silicon carbide substrate; placing the silicon carbide substrate in a growth chamber of a CVD device; The reaction gas and auxiliary gas are introduced to grow the diamond particles, and after the growth reaches a preset time, the silicon carbide substrate is taken out of the growth chamber. 2. The method according to claim 1, characterized in that, the method for preparing grooves on the carbon surface or the silicon surface of the silicon carbide substrate comprises: Grooves are prepared on the carbon or silicon surface of the silicon carbide substrate by laser cutting or saw blade cutting. 3. The method according to claim 1, characterized in that, the cross-section of the groove is a square structure. 4. The method according to claim 3, characterized in that, the groove has a width of 100-500 μm and a depth of 50-300 μm. 5. The method according to claim 1, wherein the reaction gas and the auxiliary gas are introduced to grow the diamond particles, and after the growth reaches a preset time, the silicon carbide substrate is taken out from the growth chamber, include: Set the flow rate of _H2 as the first preset value, set different _CH4 flow rates respectively to grow the diamond particles, and the growth time is the first preset time; Set the flow rate of _H2 as the first preset value, set the _CH4 flow rate as the second preset value for the growth of diamond particles, and the growth time as the second preset time; Wherein, the second preset time is greater than the first preset time; the second preset value of the CH ₄ flow rate is any one of the selected CH ₄ flow rates when the growth time is the first preset time. value. 6. method according to claim 5, it is characterized in that, setting _H The flow velocity is the first preset value, different CH _flow velocity is set respectively The growth of diamond particles is carried out, and the growth time is the first preset time ,include: Set the flow rate of _H2 to any value from 150 to 300 sccm, and the flow rate of _CH4 to 1 sccm, 3 sccm, 6 sccm, 9 sccm and 12 sccm respectively to grow diamond particles, and the growth time is 5 to 15 min . 7. according to the described method of claim 5 or 6, it is characterized in that, setting _H The flow velocity is the first preset value, setting CH _The flow velocity carries out the growth of diamond particles as the second preset value, and the growth time is Second preset time, including: Set the flow rate of _H2 to any value in 150-300 sccm, and the flow rate of _CH4 to any value in 4-8 sccm to grow diamond particles, and the growth time is 0.5-1.5 h. 8. method according to claim 1, is characterized in that, feeds reaction gas and auxiliary gas and carries out the growth of diamond particle, comprises: The microwave power used is 3500-4000 W, and the temperature of the silicon carbide substrate measured by a double-interference infrared bolometer is 850-950 °C, wherein the substrate temperature is measured by a double-interference infrared bolometer with an emissivity of 0.1 Measured through a 2mm slit; The reaction gas includes H ₂ and CH _{4 ,} the flow rate of H ₂ is 100-400 sccm, and the flow rate of CH ₄ is 1-20 sccm.