CN114232089A

CN114232089A - Method for Periodic Modulation of Diamond Nucleation Density on Silicon Carbide Substrate

Info

Publication number: CN114232089A
Application number: CN202111326033.1A
Authority: CN
Inventors: 彭燕; 胡秀飞; 王希玮; 徐现刚
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2021-11-10
Filing date: 2021-11-10
Publication date: 2022-03-25
Anticipated expiration: 2041-11-10
Also published as: CN114232089B

Abstract

The application provides a method for periodically modulating nucleation density of diamond on a silicon carbide substrate, which is characterized in that grooves are prepared on a carbon surface or a silicon surface of the silicon carbide substrate. Placing the silicon carbide substrate with the groove in a growth cavity of CVD equipment, introducing reaction gas and auxiliary gas to grow diamond particles, finally taking the silicon carbide substrate out of the growth cavity after the silicon carbide substrate grows for a preset time, and observing the bottom and the side wall of the groove and the appearance and nucleation density of the diamond particles outside the groove. Based on the difference that the different positions of the groove are contacted with plasma in the growth process of the diamond particles, the nucleation density of the diamond particles at different positions of the groove is different, and further the nucleation density of the diamond particles on the silicon carbide substrate is periodically modulated.

Description

Method for periodically modulating nucleation density of diamond on silicon carbide substrate

Technical Field

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

Background

Diamond has excellent optical, electrical, mechanical and thermal properties and thus has great application potential. In particular, diamond films have the characteristics of wide band gaps, optical transparency and exceptionally high thermal conductivity, and are ideal semiconductor materials. Has good application prospect in high-tech fields such as high-density integrated circuit packaging materials, protective coatings, electrochemical electrodes and the like. In recent years, research on growing diamond films using a Microwave Plasma Chemical Vapor Deposition (MPCVD) method has received increasing attention because even polycrystalline diamond has a greater advantage than most existing crystals. Particularly, the highest acoustic wave velocity and thermal conductivity driven by high carrier mobility and unique optical characteristics make the diamond film an ideal material for many emerging device applications, such as ultrahigh frequency acoustic filters, power electronics, integrated optical circuits, quantum transducers and the like.

Substrates for diamond film growth are silicon (Si), molybdenum (Mo), silicon carbide (SiC), and the like. Since the lattice parameters and structure of the substrate materials associated with diamond are important considerations in determining good film growth, the response of all substrate materials in achieving good film adhesion is not the same. Diamond is lattice matched to beta SiC with a lattice mismatch of about 18.2% (diamond to Si lattice mismatch of 52%). Therefore, when SiC is used as a substrate, nucleation is easier. In addition, the SiC material has small thermal expansion coefficient and high thermal conductivity coefficient, and the characteristics are very similar to those of diamond, so that the adhesion of the diamond film on the SiC substrate is better. Combines the properties of the two materials and has great application potential. Since there are many problems with the nucleation of diamond polycrystals at present, many studies have shown that there is a close relationship between the thermal conductivity and the grain size, and in order to modulate the thermal conductivity of diamond polycrystals, it is necessary to modulate the grains of diamond polycrystals.

Disclosure of Invention

In order to solve the problems, the embodiment of the 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 the diamond on the silicon carbide substrate mainly comprises the following steps:

preparing a groove on a carbon surface or a silicon surface of the silicon carbide substrate;

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

and introducing reaction gas and auxiliary gas to grow the diamond particles, and taking the silicon carbide substrate out of the growth cavity after the diamond particles grow for a preset time.

According to the method for periodically modulating the nucleation density of the diamond on the silicon carbide substrate, the groove is formed in the carbon surface or the silicon surface of the silicon carbide substrate, then the silicon carbide substrate with the groove is placed in the growth cavity of the CVD equipment, the reaction gas and the auxiliary gas are introduced to grow the diamond particles, and finally the silicon carbide substrate is taken out from the growth cavity after the growth is carried out for the preset time, and the bottom, the side wall and the appearance and the nucleation density of the diamond particles outside the groove are observed. Based on the difference that the different positions of the groove are contacted with plasma in the growth process of the diamond particles, the nucleation density of the diamond particles at different positions of the groove is different, and further the nucleation density of the diamond particles on the silicon carbide substrate is periodically modulated.

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 embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

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

FIG. 2 is a schematic diagram of the present application as it is implemented to provide nucleation of diamond on a SiC substrate;

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

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

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

FIG. 3d is an SEM image of diamond particles deposited on the bottom of a groove in a SiC substrate with a methane concentration of 9sccm and a nucleation time of 10 min;

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

FIG. 4a is CH₄SEM images of diamond particles deposited at the groove of the SiC substrate under the conditions that the flow rate is 6sccm and the growth time is 1 h;

FIG. 4b is an SEM image of diamond particles deposited on the bottom of the grooves in FIG. 4 a;

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

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

FIG. 4e is a first SEM image of diamond particles deposited outside the grooves of FIG. 4 a;

FIG. 4f is a second SEM image of diamond particles deposited on the sidewalls of the recess in FIG. 4 a;

FIG. 5 is a Raman spectrum of diamond nucleated at a groove of a SiC substrate at a CH4 flow rate of 6sccm for a growth time of 1 h.

Detailed Description

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, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

In the present embodiment, the Deposition of the diamond film is performed by Microwave Plasma Chemical Vapor Deposition (MPCVD), which adopts the principle of ARDIS-300MPCVD manufactured by russian optisystems, and the CVD (Chemical Vapor Deposition) equipment can be used in the specific implementation process, which is not limited in particular.

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

s101: and preparing a groove on the carbon surface or the silicon surface of the silicon carbide substrate.

Specifically, the grooves can be formed on the C surface or the Si surface of the silicon carbide substrate by using a laser cutting or saw cutting method, the grooves can be uniformly or non-uniformly arranged, the grooves can be alternately or non-alternately arranged, the width of the groove can be 100-500 μm, and the depth of the groove can be 50-300 μm, but not within the numerical range. In order to better observe the nucleation condition of different positions of the groove, the cross section of the groove is preferably square, and particularly, the cross section can be rectangular or square.

S102: and placing the silicon carbide substrate in a growth chamber of the CVD equipment.

After the groove is formed, the surface of the silicon carbide substrate may be cleaned by sequentially using hydrofluoric acid, acetone, absolute ethyl alcohol and deionized water to remove debris generated during the groove formation, which is not limited to the cleaning method.

S103: and introducing reaction gas and auxiliary gas to grow the diamond particles, and taking the silicon carbide substrate out of the growth cavity after the diamond particles grow for a preset time.

After the silicon carbide substrate is placed in a growth chamber of an MPCVD device, H is introduced₂、CH₄As reaction gas、Ar、O₂And/or N₂And the like as an auxiliary gas to perform the growth of the diamond particles, wherein the auxiliary gas in the embodiment plays a role in adjusting the size, nucleation quality and the like of the diamond particles.

In the embodiment, the used microwave power is 2000-8000W, the temperature of the silicon carbide substrate is 800-₂And CH₄At a pressure of about 150Torr, H₂The flow rate of (C) is about 50to 600sccm, CH₄The flow rate of (2) is 1 to 40 sccm.

To better observe the diamond nucleation process, the present example utilized multiple silicon carbide substrates, each at a different CH₄The growth of the diamond particles was carried out at flow rates and different growth times. Specifically, set H₂The flow rate of (1) is a first preset value, and different CH are respectively set₄The diamond particles are grown at a flow rate for a first predetermined time, for example, H can be set₂The flow rate of (C) is any value of 150to 300sccm, CH₄The flow rates of the diamond particles are respectively 1sccm, 3sccm, 6sccm, 9sccm and 12sccm, and the growth time is 5-15 min; set H₂Is a first preset value, and CH is set₄And the flow rate is a second preset value, the growth of the diamond particles is carried out, and the growth time is a second preset time. The second preset time is longer than the first preset time; CH (CH)₄The second preset value of the flow rate is the selected CH when the preset time is the first preset time₄Any value in the flow rate. For example, set H₂The flow rate of (C) is any value of 150to 300sccm, CH₄The flow rate is 1sccm, 3sccm, 6sccm, 9sccm or 12sccm, and the growth time is 0.5-1.5 h.

Fig. 2 is a schematic diagram of the present application as it is implemented to provide nucleation of diamond on a SiC substrate. As shown in fig. 2, based on the difference that the plasma is contacted at different positions of the groove in the growth process of the diamond particles, wherein the plasma contacted at the bottom of the groove is the least and then the nucleation density of the diamond particles is the lowest, and the plasma contacted at the outside of the groove is the most and then the nucleation density of the diamond particles is the largest, the difference of the nucleation densities of the diamond particles at different positions of the groove further realizes the modulation of the diamond particles at different positions of the groove, that is, the diamond particles realize the periodic modulation of the nucleation density on the silicon carbide substrate.

Based on the above method, the observation method of the nucleation process will be further described below with reference to examples. In this embodiment, grooves are formed on the C-side of a silicon carbide substrate by a dicing saw method, the intervals between the grooves are 1mm, the depth of the grooves is 110 μm, and the width of the grooves is 200 μm, and after cleaning, a sample is placed on MPCVD. The substrate temperature was measured at 900 ℃ using a double interference infrared bolometer with a microwave power of 4000W, measured by a 2mm slit dual interference infrared bolometer with an emissivity of 0.1, and the deposition process was carried out at a pressure of 150 Torr. H₂At a flow rate of 150sccm, CH₄The flow rate of the silicon nitride is 1sccm, 3sccm, 6sccm, 9sccm and 12sccm, and the growth time is 10 min; another sample was grown for 1h, CH₄The flow rate of (3) was 6sccm, and other conditions were unchanged.

The sample was taken out and observed, and the morphology of the diamond particles was observed by a Scanning Electron Microscope (SEM) in this example. SEM images of diamond particles deposited on the bottom of the SiC substrate grooves at methane concentrations of 1sccm, 3sccm, 6sccm, 9sccm, and 12sccm, nucleation times of 10min, as shown in FIGS. 3a, 3b, 3c, 3d, and 3e, respectively. As shown in fig. 3a to 3e, the spherical particles gradually increase with increasing methane concentration.

FIG. 4a is CH₄Under the conditions that the flow rate is 6sccm and the growth time is 1h, the SEM image of the diamond particles deposited at the groove of the SiC substrate can show that the particles in the groove are densely distributed. Fig. 4b is an SEM image of the diamond particles deposited on the bottom of the grooves in fig. 4a, i.e. an enlarged view of area a in fig. 4a, with a grain size greater than 5 μm in the middle area.

Fig. 4c is a first SEM image of the diamond particles deposited on the side wall of the groove in fig. 4a, and fig. 4d is a second SEM image of the diamond particles deposited on the side wall of the groove in fig. 4a, which is an enlarged view of the area B in fig. 4a, it can be seen that grains near the side wall of the groove have a hemispherical shape, crystal planes are gradually smoothed, and the particles gradually form a flat square plane from the sphere, and the surface of the particles has many fine square planes. Fig. 4e is a first SEM image of the diamond particles deposited outside the grooves in fig. 4a, i.e. an enlarged view of the region C in fig. 4a, and it can be seen that the diamond grains located near the notches apparently have a single crystal diamond shape with mostly square and triangular facets. A bonding layer is arranged between the crystal grain and the substrate; fig. 4f is a second SEM image of diamond particles deposited on the groove sidewalls of fig. 4a, the diamond particles on the groove sidewalls assuming an angular octahedral shape with flat square (100) faces and rough hexagonal (111) faces.

FIG. 5 is a Raman spectrum of diamond nucleated at a groove of a SiC substrate at a CH4 flow rate of 6sccm for a growth time of 1 h. In the embodiment, the bottom of the groove, the side wall of the groove and the outer position of the groove are respectively measured, and the Raman displacement positions of the zero-stress diamond, the graphite and the trans-polyacetylene are shown. Raman results from fig. 5 show that the spherical particles in the grooves are graphite, the side walls of the grooves are diamond particles, and the granular diamond phase outside the grooves is more distinct.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that 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

1. a method for periodic modulation of nucleation density of diamond on silicon carbide substrate, is characterized in that, described method comprises:

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

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

The growth of diamond particles is carried out by feeding reactive gas and auxiliary gas, and after the growth reaches a preset time, the silicon carbide substrate is taken out from the growth chamber.

2. The method according to claim 1, wherein the method for preparing the groove on the carbon surface or the silicon surface of the silicon carbide substrate comprises:

The grooves are prepared on the carbon surface or silicon surface of the silicon carbide substrate by means of laser cutting or saw blade cutting.

3. The method according to claim 1, wherein the cross section of the groove is a square structure.

4 . The method according to claim 3 , wherein the groove has a width of 100-500 μm and a depth of 50-300 μm. 5 .

5. The method according to claim 1, wherein the growth of diamond particles is carried out by feeding a reactive gas and an auxiliary gas, and after the growth reaches a preset time, the silicon carbide substrate is taken out from the growth chamber, include:

Setting the flow rate of H ₂ as the first preset value, setting different CH ₄ flow rates respectively to carry out the growth of diamond particles, and the growth time is the first preset time;

Setting the flow rate of H ₂ as the first preset value, setting the flow rate of CH ₄ as the second preset value to carry out 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. The method according to claim ₅ , wherein the flow rate of H is set to be the first preset value, different _CH flow rates are respectively set to carry out the growth of diamond particles, and the growth time is the first preset time ,include:

Set the flow rate of H ₂ to any value in 150-300 sccm, and the flow rate of CH ₄ to be 1 sccm, 3 sccm, 6 sccm, 9 sccm and 12 sccm, respectively, for the growth of diamond particles, and the growth time is 5-15 min.

7. The method according to claim ₅ or 6, wherein the flow rate of H is set to be the first preset value, and the flow rate of _CH is set to be the second preset value to carry out the growth of diamond particles, and the growth time is The second preset time, including:

Set the flow rate of H ₂ to be any value in 150-300 sccm, and the flow rate of CH ₄ to be any value in 4-8 sccm, respectively, to carry out the growth of diamond particles, and the growth time is 0.5-1.5 h.

8. method according to claim 1, is characterized in that, feeding reaction gas and auxiliary gas to carry out the growth of diamond particle, comprising:

The microwave power used is 3500-4000W, and the temperature of the silicon carbide substrate is measured by a double-interference infrared bolometer pyrometer to be 850-950°C, wherein the substrate temperature is passed by a double-interference infrared bolometer with an emissivity of 0.1. Measured with a 2mm slit;

The reaction gas includes H ₂ and CH ₄ , the flow rate of H ₂ is about 100-400 sccm, and the flow rate of CH ₄ is 1-20 sccm.