CN105441902B - A kind of preparation method of epitaxial silicon carbide graphene composite film - Google Patents

Abstract

The present invention relates to technical field of semiconductors, especially a kind of preparation method of epitaxial growth carborundum graphite alkene laminated film, it comprises the following steps：Pretreated substrate is placed in chemical vapor deposition chamber body, controls the vapor deposition chamber Absolute truth reciprocal of duty cycle to be higher than 10^‑4Pa, 2~10 microns of silicon carbide epitaxial layers are grown in the substrate surface at 1500~1600 DEG C；The temperature of the chemical vapor deposition chamber body is controlled to be reduced to 1000 DEG C; 1600 DEG C are heated to from 1000 DEG C to the chemical vapor deposition chamber body under protective atmosphere; make the silicon carbide epitaxial layers STRUCTURE DECOMPOSITION and restructuring, obtain graphene composite bed on the substrate.This method can be not entirely dependent on expensive monocrystal SiC base material, but use high temperature chemical vapor deposition apparatus, realize the continuous growth of silicon carbide epitaxy layer graphene.

Description

A kind of preparation method of epitaxial silicon carbide-graphene composite film

technical field

The invention belongs to the technical field of semiconductor thin film materials, and relates to a preparation method of a novel semiconductor thin film material, specifically, a method for continuously epitaxially growing large-area and uniform graphene on a silicon carbide epitaxial layer.

Background technique

Graphene is a carbon material that is tightly packed into a two-dimensional honeycomb structure by a single layer of carbon atoms. It has excellent mechanical, thermal, optical, electrical and chemical properties due to its unique crystal and electronic band structure. High carrier mobility, super large specific surface area, perfect quantum tunneling effect, half-integer quantum Hall effect, etc. After the first discovery of graphene by A.K.Geim and K.S. Novoselov of the University of Manchester in 2004, graphene quickly became an international frontier and hotspot in the current research fields of materials, physics, chemistry, semiconductors, microelectronics, biology, and new energy. Silicon carbide has a layered structure, and its basic constituent unit is a silicon-carbon biatomic layer composed of silicon atoms and carbon atoms. In the process of making silicon carbide wafers, since the cutter cannot be completely fine, it cannot be completely cleaved along the direction of the weaker Si-C bond between layers, but has an included angle with the cleavage plane. , so that after the cleavage operation, the silicon carbide is stepped in a certain direction. It is also because of this that it is possible to grow high-quality graphene on its steps.

There are many methods for preparing graphene, such as mechanical exfoliation, liquid phase or gas phase dissociation, redox method, tailoring nanotube method, chemical vapor deposition method, single crystal metal epitaxy and SiC epitaxial growth method, etc. The SiC epitaxial growth method is to heat SiC to a certain temperature under a certain vacuum, so that the silicon atoms evaporate, and the remaining carbon atoms are restructured to form graphene. Since the substrate SiC on which graphene is grown in this way is semi-insulating, the grown samples do not need to perform cumbersome work such as substrate corrosion and sample migration, and can directly perform electrical tests. In this way, the influence of defects, doping and other factors introduced in the transfer process is reduced. This also makes epitaxial growth of graphene on SiC substrate one of the most effective ways to realize the application of graphene in the field of microelectronics.

At present, SiC epitaxial growth of graphene is based on single crystal SiC substrate. The SiC material obtained by the traditional single crystal preparation method has many defects, and it is difficult to control the thickness and doping, which often fails to meet the requirements of manufacturing devices. However, high-quality single crystal SiC substrates are also expensive. In addition, before the epitaxial growth of graphene, it is necessary to perform a hydrogen etching step on the substrate, because silicon carbide will have many scratches on the surface after the chemical mechanical polishing (CMP) process, and the quality of the graphite prepared directly by it is relatively low. Poor, but the shape and quality of samples grown on uniform steps will be much better. Hydrogen etching is a recognized feasible solution to remove scratches and other defects on the sample surface. However, improper hydrogen etching will cause lattice defects on the surface of the SiC substrate, and will cause the deposition of silicon compounds, which will excessively reduce the enrichment of silicon on the SiC surface and affect the epitaxial growth of graphene.

Contents of the invention

In order to solve the above problems, the invention provides a kind of preparation method of epitaxial silicon carbide-graphene composite film, it comprises the steps:

Step 1: Place the pretreated substrate in a chemical vapor deposition (CVD) chamber, control the absolute vacuum of the chemical vapor deposition chamber to be higher than 10 ^-4 Pa, and grow on the surface of the substrate at 1500-1600°C 2-10 micron silicon carbide epitaxial layer;

Step 2: Control the temperature of the chemical vapor deposition chamber to drop to 1000°C, and heat the chemical vapor deposition chamber from 1000°C to 1600°C under a protective atmosphere to decompose and recombine the structure of the silicon carbide epitaxial layer , obtaining a graphene composite layer on the substrate.

Wherein, the substrate is SiC.

Wherein, before the first step, it also includes: growing a buffer layer with a thickness of 10-100 nm on the substrate by molecular beam epitaxy.

Wherein, the substrate is GaN or Al ₂ O ₃ ; the buffer layer is AlN.

Wherein, in the second step, the temperature of the chemical vapor deposition chamber is controlled to be 1300-1600° C. under a protective atmosphere.

Wherein, in the step 2, the heating of the chemical vapor deposition chamber adopts a stepwise temperature rise, and the specific operation is as follows:

Controlling the temperature of the chemical vapor deposition chamber to rise to 1100° C. and maintaining it for 10 minutes;

Controlling the temperature of the chemical vapor deposition chamber to rise to 1200° C. and maintaining it for 10 minutes;

The temperature of the chemical vapor deposition chamber is controlled to rise to a range of 1300-1600° C. and maintained for 30-50 minutes.

Further, in the step 2, the heating of the chemical vapor deposition chamber adopts a stepwise temperature increase, and a more preferred specific operation is:

Controlling the temperature of the chemical vapor deposition chamber to rise to 1100° C. and maintaining it for 10 minutes;

Controlling the temperature of the chemical vapor deposition chamber to rise to 1200° C. and maintaining it for 10 minutes;

The temperature of the chemical vapor deposition chamber is controlled to rise to a range of 1450-1600° C. and maintained for 30-50 minutes.

Beneficial effects of the present invention:

(1) The epitaxial growth of graphene film does not completely depend on the expensive single crystal silicon carbide substrate, but the preparation of graphene heterogeneous composite film is carried out directly after the growth of silicon carbide epitaxial layer, and it can also be grown on other heterogeneous substrates to further reduce costs.

(2) The silicon carbide epitaxial layer obtained by chemical vapor deposition is often of high quality, and can guarantee a faster growth rate and doping control, which is very suitable for the growth of high-quality silicon carbide epitaxial layer-graphene composite film, and also SiC-graphene heterogeneous films with different doping types can be obtained.

(3) The method of the present invention omits the complicated steps of etching the substrate surface with hydrogen and then making up for the enrichment of silicon on the surface, and obtains a high-quality few-layer graphene composite layer.

Description of drawings

Fig. 1a is an atomic force microscope (AFM) surface two-dimensional topography test chart of the silicon carbide epitaxial layer of the present invention; Fig. 1b is an AFM three-dimensional topography test chart.

Fig. 2 is an X-ray photoelectron spectrum analysis diagram of the epitaxial silicon carbide-graphene composite thin film of the present invention.

Fig. 3a is a Raman spectrum diagram of the epitaxial silicon carbide-graphene composite film of the present invention; Fig. 3b is a Raman spectral scanning imaging diagram of the epitaxial silicon carbide-graphene composite film of the present invention.

Detailed ways

Below, the present invention will be described in detail in combination with specific embodiments.

Example 1:

The substrate of the epitaxial silicon carbide-graphene composite film provided in this example is 4H-SiC with the silicon facing up, and the specific implementation steps are as follows:

Step 1: firstly, the substrate is cleaned and pretreated by a standard RCA cleaning method (a wet chemical cleaning method) to eliminate surface oxides and other impurity particles.

Then place the pretreated substrate in an induction-heated high-temperature chemical vapor deposition reaction (Chemical Vapor Deposition, CVD for short) chamber, and first evacuate to make the absolute vacuum degree higher than 10 ⁻⁴ Pa. Continuously feed H ₂ with a flow rate of 7 slm, and use H ₂ to etch to remove surface oxides and surface scratches. At the same time, the heating chamber gradually increases the temperature of the chamber from room temperature to 1600°C. Hold at 1600 °C for 10 min as a pre-growth phase.

Then keep the above temperature and pressure, feed SiH ₄ and C ₃ H ₈ , the flow rates are respectively 9 sccm and 2 sccm to grow the silicon carbide epitaxial layer. After reacting for 60 minutes, the temperature of the chemical vapor deposition chamber was lowered to 1000° C., and at the same time, Ar was introduced at a flow rate of 1 slm for protection. At this time, a SiC epitaxial layer with a thickness of 2-10 microns was formed on the surface of the substrate. The surface morphology quality of the silicon carbide epitaxial layer was characterized by an atomic force microscope, as shown in Figure 1. Among them, it can be seen from Figure 1a that after the growth of the silicon carbide epitaxial layer, the surface morphology of SiC begins to become orderly, forming regular step stripes, which is more conducive to the growth of graphene. It can be seen from Figure 1b that the step fluctuation of SiC is around 10nm. Through the analysis of AFM software, the root mean square roughness of SiC surface is 2.4nm. Compared with hydrogen etched SiC surface, the effect is better.

Step 2: Continuously feed Ar with a flow rate of 1slm in the chemical vapor deposition chamber for protection, and adjust the pressure to maintain at 5Torr (with an atmospheric pressure equivalent to 760 mmHg pressure as a reference standard, 1Torr is 1/760 mmHg Atmospheric pressure), and then the chemical vapor deposition chamber is heated stepwise from 1000°C to 1300-1550°C. The specific operation is: first raise the temperature of the chamber from 1000°C to 1100°C and stabilize it for 10 minutes; then raise the temperature of the chamber from 1100°C to 1200°C and keep it for 10 minutes; then raise the temperature of the chamber from 1200°C to 1550°C and hold for 30 minutes. Among them, Fig. 3a is the Raman spectrum of graphene directly heteroepitaxially grown after epitaxial growth of 4H-SiC. The data have been normalized and the growth temperatures are 1300°C, 1450°C and 1550°C respectively. It can be seen that at 1300°C, there are no obvious G peaks and 2D peaks in the Raman spectrum, indicating that there is no graphene formed on the substrate. When the temperature rises to about 1450℃, there is obvious formation of graphene, showing that the G peak (1587cm ^-1 ) and 2D (2695cm ^-1 ) peaks appear simultaneously. The strong D peak (1344cm ^-1 ) indicates that there are impurities or defects in the graphene lattice structure. As the temperature further increased to 1550 °C, the G peak and 2D peak signals of graphene became more obvious, indicating that it was less and less affected by the SiC substrate. The fainter D peak indicates fewer impurities and defects. Figure 3b is a Raman 2D peak scanning image of epitaxially grown graphene at 1550°C, with a range of 25 μm × 25 μm and a step of 0.5 μm × 0.5 μm. It can be seen that the color of the large area in the scanning image is relatively consistent, indicating that the number of graphene layers is relatively uniform, and the large number of boundaries in the middle indicates that the single crystal area of SiC epitaxial graphene is small. Therefore, in the stepwise heating process, the temperature of the last heating operation is preferably controlled above 1450°C; and, the higher the temperature, the smaller the impurities and lattice defects of graphene, and the higher the quality of graphene.

After a stepwise heating process, the silicon carbide epitaxial layer undergoes a series of reconstructions, and finally cools down naturally under the protection of Ar to obtain a stable graphene composite layer formed on the surface of the substrate. When the temperature of the cavity is lowered to 1000°C, Close the Ar input; when the temperature of the cavity is lowered to room temperature, Ar is introduced into the cavity to restore the atmospheric pressure, and the cavity is opened to take out the epitaxial silicon carbide-graphene composite film product obtained in this embodiment.

Adopt X-ray photoelectron spectroscopy to verify the formation of the graphene composite layer (see Figure 2), the specific operation is: the relationship diagram and curve A of the C (1s) of the graphene composite layer sample and the binding energy and curve A are fitted to obtain B, C,D peaks. D peak (283.5eV) is from SiC substrate peak. The C peak (284.5eV) at the high binding energy is close to the C-sp2 bond position of graphite, so the C peak is a component of graphene, which further verifies that graphene can be obtained by this experimental method. The binding energy position of the B peak (284.9eV) is very close to the position of the diamond C-sp3 bond, which may be the carbon atom in the buffer layer.

Raman spectroscopy is used to verify that the epitaxial silicon carbide-graphene composite film obtained in this embodiment has good crystal quality, and the number of layers of the graphene composite layer is controlled below 4 layers, and has good uniformity (see Figure 3).

Example 2:

The substrate of the epitaxial silicon carbide-graphene heterogeneous film provided in this example is Al ₂ O ₃ , and the specific implementation steps are as follows:

Step 1: firstly, the substrate is cleaned and pretreated by a standard RCA cleaning method to eliminate surface oxides and other impurity particles.

The pretreated substrate was placed in molecular beam epitaxy (MBE) to grow a layer of AlN film with a thickness of 10 nm as a buffer layer. Then the substrate with the buffer layer grown is placed in an induction-heated high-temperature CVD furnace, and first vacuumed so that the absolute vacuum degree is higher than 10 ⁻⁴ Pa. Continuously inject 9 slm of H ₂ , and use H ₂ to etch to remove surface oxides and surface scratches. The chamber temperature was gradually increased from room temperature to 1600 °C, and kept at 1600 °C for 10 minutes as a pre-growth stage.

Then SiH ₄ and C ₃ H ₈ were introduced, and the flow rates were 10sccm and 3sccm respectively to grow the silicon carbide epitaxial layer. After reacting for 60 minutes, the temperature of the chemical vapor deposition chamber was lowered to 1000° C., and at the same time, Ar was introduced at a flow rate of 1 slm for protection. At this time, a SiC epitaxial layer with a thickness of 2-10 microns was formed on the surface of the substrate.

Step 2: Continuously inject Ar at a flow rate of 2 slm into the chemical vapor deposition chamber for protection, adjust the pressure to keep it at 10 Torr, and then raise the temperature of the chemical vapor deposition chamber stepwise from 1000°C to 1500°C. The specific operation is: first raise the temperature of the chamber from 1000°C to 1100°C and stabilize it for 10 minutes; then raise the temperature of the chamber from 1100°C to 1200°C and keep it for 10 minutes; then raise the temperature of the chamber from 1200°C to 1500°C and hold for 40 minutes. After a stepwise heating process, the silicon carbide epitaxial layer undergoes a series of reconstructions, and finally cools down naturally under the protection of Ar to obtain a stable graphene composite layer formed on the surface of the substrate. When the temperature of the cavity is lowered to 1000°C, Close the Ar input; when the temperature of the cavity is lowered to room temperature, Ar is introduced into the cavity to restore the atmospheric pressure, and the cavity is opened to take out the epitaxial silicon carbide-graphene heterogeneous film product obtained in this embodiment.

Atomic force microscopy was used to characterize the surface morphology quality of epitaxial silicon carbide, and X-ray photoelectron spectroscopy and Raman spectroscopy were used to verify the formation of graphene and its crystal quality, layer number and uniformity.

The object of the present invention is to provide a method for continuously growing silicon carbide epitaxial-graphene composite (heterogeneous) thin films. This method does not completely rely on the expensive single crystal SiC substrate material, but uses self-developed induction heating high-temperature CVD equipment to realize the continuous growth of silicon carbide epitaxial layer-graphene. The quality of the SiC epitaxial layer obtained by the CVD method is often high, and can ensure a faster growth rate and doping control, which is very suitable for the growth of high-quality silicon carbide epitaxial layer-graphene heterogeneous composite film. In addition, this method omits the step of etching the surface of the substrate with hydrogen and then making up for the enrichment of silicon on the surface, and obtains high-quality few-layer graphene.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone with knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the scope of the claims of the present invention.

Claims (5)

1. a kind of preparation method of epitaxial silicon carbide-graphene composite film, it comprises the following steps：

Step 1：Pretreated substrate is placed in chemical vapor deposition chamber body, controls the chemical vapor deposition chamber body Absolute truth reciprocal of duty cycle is more than 10^-4Pa, 2~10 microns of silicon carbide epitaxial layers are grown in the substrate surface at 1500~1600 DEG C；

Step 2：The temperature of the chemical vapor deposition chamber body is controlled to be reduced to 1000 DEG C, to the chemistry under protective atmosphere Vapor deposition chamber takes staged heat temperature raising, makes the silicon carbide epitaxial layers STRUCTURE DECOMPOSITION and restructuring, on the substrate Obtain graphene composite bed；

The concrete operations of the staged heat temperature raising are：

Control the chemical vapor deposition chamber temperature to be increased to 1100 DEG C, and kept for 10 minutes；

Control the chemical vapor deposition chamber temperature to be increased to 1200 DEG C, and kept for 10 minutes；

The chemical vapor deposition chamber temperature rise is controlled up to 1300~1600 DEG C of scopes, and is kept for 30~50 minutes.

2. preparation method according to claim 1, it is characterised in that the substrate is SiC.

3. preparation method according to claim 1, it is characterised in that also include before the step 1：

Grow the thick cushions of 10~100nm on the substrate using molecular beam epitaxy.

4. preparation method according to claim 3, it is characterised in that the substrate is GaN or Al₂O₃；The cushion is AlN。

5. preparation method according to claim 1, it is characterised in that to the chemical vapor deposition chamber in the step 2 The heating of body takes staged to heat up, and concrete operations are：

Control the chemical vapor deposition chamber temperature to be increased to 1100 DEG C, and kept for 10 minutes；

Control the chemical vapor deposition chamber temperature to be increased to 1200 DEG C, and kept for 10 minutes；

The chemical vapor deposition chamber temperature rise is controlled up to 1450~1600 DEG C of scopes, and is kept for 30~50 minutes.