RU2482229C1 - METHOD FOR PRODUCTION OF EPITAXIAL FILMS OF (SiC)1-x(AlN)x SOLID SOLUTION - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: epitaxial films of (SiC)_1-x(AlN)_x solid solution where the x is more than 0 but less than 1, are produced by way of sedimenting a solid solution onto a monocrystal SiC-6H substrate at a temperature of 1000°C by way of magnetron ion plasma sputtering performed in an atmosphere of argon and nitrogen from a composite target representing a polycrystal silicon carbide disc the rear surface whereof is coated with a layer of chemically pure aluminium. Concentration of Si, C, Al atoms in sedimented films is regulated by way of measuring the area of the aluminium layer on the target surface while nitrogen concentration is regulated by way of changing the ratio of nitrogen pressure to overall pressure inside the sputtering chamber.

EFFECT: production technology simplification, produced films perfection and possibility to produce films of aide-zone solid solution within the whole compositions interval.

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Description

The invention relates to the field of technology for producing multicomponent semiconductor materials, and more specifically to a technology for producing single-crystal epitaxial films of wide-gap solid solution of silicon carbide with aluminum nitride (SiC) _1-x (AlN) _x .

The invention can most effectively be used:

1. In the electronics industry to obtain a semiconductor material - solid solution (SiC) _1-x (AlN) _x to create solid-state power and optoelectronic devices on its basis.

2. To obtain buffer layers (SiC) _1-x (AlN) _x when growing crystals of aluminum nitride (AlN) or gallium nitride (GaN) on substrates of silicon carbide (SiC).

It is known that to obtain bulk single crystals and epitaxial films of a solid solution (SiC) _1-x (AlN) _x , the method of sublimation epitaxy is used (patent SU 1297523, January 21, 1994). The essence of this method is that sublimation is carried out from sources, which are used as a mixture of SiC and AlN powders or specs with different AlN contents. Single substrates SiC are used as substrates. The vapor vapor source is transferred to the substrate due to the temperature gradient between the source and the substrate.

The main disadvantages of the sublimation method for producing (SiC) _1-x (AlN) _x are:

1. The high temperature of sublimation of the source and deposition on the substrate (2000-2400 ° C).

2. Poor reproducibility of the composition and perfection of epitaxial films.

3. The inability to control and control the thickness of the growing layers.

4. The inability to obtain multilayer structures with sharp heteroboundaries due to cross diffusion in the boundary region between the layers at high deposition temperatures.

It is also known that to obtain solid solutions of (SiC) _1-x (AlN) _x , the method of magnetron ion-plasma sputtering from two sources (Tungasmita S. et al. Growth of epitaxial (SiC) _x (AlN) _x-1 thin films on 6H-SiC by ion-assisted dual magnetron sputter deposition. Proceedings of the international Conference on Silicon Carbide and Related Materials. 2001. Materials Science Forum., V.386-393, n.2, 2002, p.1481-1484) .

This method involves the deposition of a thin film of (SiC) _1-x (AlN) _x solid solution on a 6H-SiC substrate at a temperature of 1000 ° C by simultaneous direct-current ion-plasma magnetron sputtering of two targets (from polycrystalline SiC and pure Al) to nitrogen environment. The composition of the deposited films is controlled by varying the discharge currents and nitrogen pressure.

The main disadvantage of this method is that two magnetron systems are used for independent sputtering of two targets, which complicates the design of the process unit and increases energy costs.

Another disadvantage is that magnetron sputtering from two independent sources does not provide homogeneous mixing of the sprayed materials in a wide range of concentrations.

Another way to obtain epitaxial films of the solid solution (SiC) _1-x (AlN) _x is a method of producing epitaxial films of the solid solution (SiC) _1-x (AlN) _x , where the component x is greater than zero, but less than one, containing the deposition of solid on a single-crystal substrate SiC-6H at a temperature of 1000 ° C by ion-plasma magnetron sputtering of a target of a polycrystalline solid solution (SiC) _1-x (AlN) _x with alternating current with a frequency of 13.56 MHz (patent RU 2333300, September 10, 2008) .

The essence of this method is to apply a high frequency alternating electric field to the gas discharge gap, in which, during one half-cycle (when the target is at a negative potential), a high-resistance (dielectric) target is sprayed and a positive charge accumulates on it, and after another half-time (when the target is under positive potential) highly mobile plasma electrons arrive at the target in a larger quantity than ions during the negative half-period. Electrons not only neutralize the positive charge that arises on the target during ion bombardment, but also creates a negative bias potential relative to the plasma on it, which accelerates positively charged ions that carry out the bombardment, which provides conditions for the sputtering of a high-resistance target.

The disadvantages of this method are:

1. The difficulty of matching the high-frequency generator with the reactive load of the target.

2. The instability of the discharge associated with the variability of the reactance of the target.

3. The speed of sputtering with alternating current is half that of direct current, since the sputtering of the target occurs in one half-cycle of alternating current.

Of the known methods for producing epitaxial layers of a silicon carbide solid solution with aluminum nitride, the closest in technical essence is the method of producing epitaxial layers of a SiC-AlN solid solution on 6H-SiC substrates by magnetron ion-plasma sputtering from a single target of a polycrystalline SiC-AlN solid solution (RU patent 2260636, September 20, 2005).

This method involves the deposition on a single crystal substrate of 6H-SiC films of a solid solution (SiC) _1-x (AlN) _x at a temperature of 1000 ° C by ion-plasma magnetron sputtering of a target of a direct current polycrystalline SiC-AlN solid solution made by hot pressing a mixture of powders SiC and AlN. The composition of the epitaxial layers is controlled by a change in the composition of the target.

A significant disadvantage of this method is that the polycrystalline target of the SiC-AlN solid solution has a large specific resistance, depending on the composition. Due to the high resistance of the target, sputtering them with direct current becomes problematic. In practice, obtaining films of a (SiC) _1-x (AlN) _x solid solution with an x content of more than 60 percent by spraying a polycrystalline target of a direct current SiC-AlN solid solution fails.

The objective of the present invention is to develop a new method for producing epitaxial layers of a solid solution (SiC) _1-x (AlN) _x .

The technical result consists in simplifying the production technology, in improving, the perfection of the resulting films and the possibility of obtaining films of solid solution (SiC) _1-x (AlN) _x in the entire range of compositions.

The technical result is achieved by sputtering a composite target. The composite target is a polycrystalline silicon carbide disk with a diameter of 6 cm and a thickness of 0.4 cm, made of silicon carbide powder by pressing and then sintering in argon at a temperature of 2100 K. A certain part of the sprayed surface of the disk is coated with a layer of chemically pure aluminum deposited by thermal evaporation through a mask in high vacuum. The use of a composite target allows one to strictly dose the composition of atomized atoms, and therefore, the concentration of Si, C, Al atoms in the deposited film (SiC) _1-x (AlN) _x by changing the area of the aluminum layer on the target surface. The concentration of nitrogen atoms in the synthesized films is regulated by changing the ratio of nitrogen pressure to the total pressure in the spray chamber.

A method of producing epitaxial films of a solid solution of silicon carbide with aluminum nitride (SiC) _1-x (AlN) _x , where component x is greater than zero but less than unity, containing the deposition of a solid solution on a single-crystal SiC-6H substrate at a temperature of 1000 ° C magnetron-ion plasma spraying, characterized in that the spraying is carried out in an atmosphere of argon and nitrogen from a composite target, which is a disk of polycrystalline silicon carbide, a predetermined part of the surface of which is coated with a layer of chemically pure aluminum, while ntsentratsiyu Si atoms, C, Al in the deposited films is controlled by changing the area of the aluminum layer on the target surface, and the concentration of nitrogen - nitrogen pressure change ratio to the total pressure in a spray chamber.

Concrete example

The method for producing epitaxial films of a solid solution (SiC) _1-x (AlN) _x consists of the following operations performed in sequence:

1. Loading the working camera:

a) preparing a substrate, which is a plate of single crystal 6H-SiC orientation (0001). (Etching in KOH at 500 ° C for 10 minutes, boiling in distilled water 2 times, washing in deionized water).

b) Installing the substrate in a graphite heater.

c) Installation of a composite target (with a ratio of the aluminum layer area to the total target area of 0.25) on a magnetron.

2. Pumping air from the working chamber with a 2-stage vacuum system up to 10 ^-6 mm Hg

3. Turning on the power of the substrate heater and bringing the temperature of the substrate to 1000 ° C.

4. Turning on the electronic gas inlet system, setting the Ar pressure in the working chamber from 0.3 · 10 ^-3 to 0.8 · 10 ^-3 mm Hg. and nitrogen pressure 25 percent of argon pressure.

5. Turning on the power of the magnetron and obtaining a discharge current with a density of 5-25 mA / cm ² .

6. 5 minutes after the start of the sputtering process, the targets open the shutter and deposit on the substrate for 0.5-3 hours.

7. Upon reaching the desired thickness of the epitaxial layer, the magnetron power is turned off, and the substrate with the epitaxial film is cooled to room temperature for 30 minutes.

Figure 1 shows the structural diagram of the magnetron sputtering system for epitaxy of films (SiC) _1-x (AlN) _x , where 1 is the installation plate, 2 is insulation, 3 is the cathode input, 4 is the grounded shield, 5 is the magnetic circuit, 6 is ring magnets (based on NeFeB magnets), 7 - composite SiC target with A1, 8 - magnetic field lines, 9 - sprayed material flow, 10 - shutter, 11 - SiC substrate, 12 - graphite heater for the substrate.

Figure 2 presents x-rays from the epitaxial film (SiC) _1-x (AlN) _x and the SiC substrate, which demonstrate the single-crystal phase of the obtained film.

2 also shows reference data of a PDF-4 file cabinet (cards No. 04-010-5698 for 6H-S1C substrate and No. 00-025-1133 for 2H-AlN).

Figure 3 presents the image of the cleavage of the epitaxial film (SiC) _1-x (AlN) _x on the substrate, obtained using atomic transmission microscopy. The above measurement results show the possibility of obtaining the proposed method of films of solid solution (SiC) _1-x (AlN) _x .

Thus, we have developed a new method that allows one to obtain epitaxial films of (SiC) _1-x (AlN) _x solid solution over the entire range of changes in the chemical composition.

The main advantages of our proposed method:

1. Improving the efficiency of sputtering and stability of the plasma discharge due to the low resistivity of the composite target used.

2. The possibility of changing the composition of the obtained films of solid solution (SiC) _1-x (AlN) _x in a wide range by changing the part of the target area coated with aluminum, as well as changing the ratio of nitrogen pressure to the total pressure in the spray chamber.

Claims (1)

A method of producing epitaxial films of a solid solution of silicon carbide with aluminum nitride (SiC) _1-x (AlN) _x , where component x is greater than zero but less than unity, containing the deposition of a solid solution on a single-crystal SiC-6H substrate at a temperature of 1000 ° C magnetron-ion plasma spraying, characterized in that the spraying is carried out in an atmosphere of argon and nitrogen from a composite target, which is a disk of polycrystalline silicon carbide, a predetermined part of the surface of which is covered with a layer of chemically pure aluminum, while the concentration of Si, C, Al atoms in the deposited films is controlled by changing the area of the aluminum layer on the target surface, and the nitrogen concentration by changing the ratio of nitrogen pressure to the total pressure in the spray chamber.

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