KR19990035452A - Meteorological growth method and apparatus - Google Patents

Abstract

The gas phase growth method and apparatus according to the present invention relates to a gas phase growth method and apparatus for injecting a plurality of gases toward a substrate to grow single crystals on the substrate by chemical reaction of the gases. This method and apparatus allows the rate of movement of each atom separated from the gases by the chemical reaction to be controlled by an electric field.

Description

Meteorological growth method and apparatus

The present invention relates to a gas phase growth method and apparatus.

Single crystal growth methods include various methods such as gas phase, liquid phase, solid phase, and melting. Factors for selecting such a single crystal growth method include the inherent characteristics of the single crystal to be grown, the possibility of expansion of the growth area, the quality of the grown single crystal, the possibility of mass production, and the use of the grown single crystal.

The vapor phase growth method may be referred to as a method of crystallizing a gaseous substance to form a single crystal. This method is excellent in the quality of grown crystals and can obtain single crystals of various forms, such as thin films, large crystals, and needles. In particular, the method is effectively used in the growth of semiconductor single crystals of group II-VI and III-V.

Vapor growth methods are roughly classified into CVD (chemical vapor deposition) and PVD (physical vapor deposition). CVD is a growth method that allows some or all of a raw material to be moved to a crystal growth region in a separated state by a chemical reaction. PVD is a growth method that allows the constituent atoms of the crystal to physically move into the crystal growth region. Recently, the methods that have been spotlighted in the field of thin film growth include MOCVD (Metal Organic Chemical Vapor Deposition), a kind of CVD, and Molecular Beam Deposition (MBE), a kind of PVD. Other vapor growth methods include Hydride or Halide Vapor Phase Epitaxy (HVPE) and Sublimation Vapor Phase Epitaxy (SVPE). Such vapor growth methods are particularly effective for manufacturing gallium nitride (GaN) wafers.

Gallium nitride is a wide bandgap semiconductor having a band gap energy of 3.39 eV (electron volt), and is a material suitable for application to short wavelength light emitting devices and high temperature electronic devices. In order to grow high quality gallium nitride by the liquid phase growth method, a high temperature of about 1,500 [° C.] is required. At this time, since the vapor pressure of nitrogen is increased at high temperature to about 15,000 atm, a reactor capable of withstanding this is required. In addition, the expansion of the growth area is difficult (currently 80 mm ² is the limit), the device application is limited, and the mass production is difficult. Therefore, a vapor phase growth method is adopted to grow gallium nitride single crystals.

1 is a side cross-sectional view of an HVPE vapor phase growth apparatus to which a conventional gallium nitride growth method is applied. Referring to the drawings, a conventional HVPE vapor phase growth apparatus is provided with a quartz tube 11 as a cylindrical reactor, a substrate support 12 and crystal tubes 111 and 112 for injection as concentric cylinders. The frame correction tube 11 is provided with an injection section and a discharge section of nitrogen gas (N ₂ ), ammonia gas (NH ₃ ), and gallium chloride gas (GaCl). Here, nitrogen gas (N ₂ ) is injected for the smooth flow of ammonia gas (NH ₃ ) and gallium chloride gas (GaCl). The frame crystal tube 11 is installed inside a heating furnace (not shown) to maintain a growth temperature of about 1,100 [° C.]. Ammonia gas (NH ₃ ) is present in the first injection tube (111), gallium chloride gas (GaCl) is in the second injection tube (112), and an outer wall and frame crystal tube (11) of the first injection tube (111). Nitrogen gas (N ₂ ) is injected between the inner walls of the panel. Injection quartz tubes 111 and 112 are spaced apart from the substrate support 22. The substrate support 12 is installed in the frame crystal tube 11 so that the substrate 13 is supported toward the injection portion, and supports the substrate 13 and performs heat transfer. A sapphire or silicon carbide (SiC) substrate is used as the substrate 13 to be seated on the substrate support 12. The growth of gallium nitride crystals formed on the surface of the substrate 13 is performed according to the following formula (1).

GaCl + NH _3- > GaN + HCl + 2H ₂

Except for the elements attached to the surface of the substrate 13 and the inner wall of the frame correction tube 11, the remaining elements are discharged.

According to the conventional vapor phase growth method and apparatus as described above, the composition of the gallium nitride single crystal formed on the substrate 13 does not match the stoichiometric composition. This is because the moving speeds of the injected gases do not coincide and there is a difference in the vapor pressure of the crystalline atoms. For example, since the moving speeds of ammonia gas (NH ₃ ) and gallium chloride gas (GaCl) do not coincide, the amount of atoms transferred on the substrate 13 per unit time is not uniform. In addition, since the nitrogen vapor pressure at high temperature is high, the amount of gallium (Ga) atoms is actually higher. As a result, a large amount of crystal defects are generated due to the lack of nitrogen atoms, and the grown gallium nitride has the properties of the n-type semiconductor.

In order to reduce such composition variation, a method of relatively increasing the amount of ammonia gas (NH ₃ ) has been used. For example, a molar ratio of ammonia gas (NH ₃ ) to gallium chloride gas (GaCl) is 50: 1 to 1,000: 1 to inject. However, even in such a method, it is difficult to control the amount of gas with respect to the composition variation, and thus the composition of the grown gallium chloride cannot be stoichiometrically approached.

It is an object of the present invention to provide a vapor phase growth method and apparatus which can easily control the composition of a single crystal to be grown.

1 is a side cross-sectional view of an HVPE vapor phase growth apparatus to which a conventional gallium nitride growth method is applied.

2 is a side cross-sectional view of an HVPE vapor phase growth apparatus to which a gallium nitride growth method according to the present invention is applied.

<Explanation of symbols for main parts of the drawings>

11, 21 ... frame crystal tube, 12, 22 ... substrate support,

13, 23 ... substrate, 111, 211 ... first infusion lens,

112, 212 ... second infusion tube, 24 ... DC power supply,

25 ... electrode network.

The vapor phase growth method of the present invention for achieving the above object relates to a vapor phase growth method for growing a single crystal on the substrate by a chemical reaction of the gases by injecting a plurality of gases toward the substrate. The method is such that the rate of movement of each atom separated from the gases by the chemical reaction is controlled by an electric field.

The gas phase growth apparatus of the present invention for achieving the above another object is related to a gas phase growth apparatus which injects a plurality of gases toward a substrate and grows a single crystal on the substrate by chemical reaction of the gases. The apparatus includes an electric field generator for controlling the moving speed of each atom separated from the gases by the chemical reaction.

According to the gas phase growth method and apparatus of the present invention, since the moving speed of the crystal components to be grown is relatively controlled by the electric field, the composition of the single crystal to be grown can be easily and precisely controlled.

Hereinafter, preferred embodiments of the present invention will be described in detail.

2 is a side cross-sectional view of the HVPE vapor phase growth apparatus to which the gallium nitride growth method according to the present invention is applied. Referring to the drawings, the HVPE vapor phase growth apparatus according to the present invention includes a frame crystal tube 21 as a cylindrical reactor, a substrate support 22, crystal tubes 211 and 212 for injection as concentric cylinders and electric field generators 24 and 25. ) Is provided. The electric field generators 24 and 25 include a DC power supply 24 and an electrode network 25. The frame correction tube 11 is provided with an injection section and a discharge section of nitrogen gas (N ₂ ), ammonia gas (NH ₃ ), and gallium chloride gas (GaCl). Here, nitrogen gas (N ₂ ) is injected for the smooth flow of ammonia gas (NH ₃ ) and gallium chloride gas (GaCl). This frame crystal tube 21 is provided inside a heating furnace (not shown) and is controlled by the growth temperature. Ammonia gas (NH ₃ ) is present in the first injection tube (211), gallium chloride gas (GaCl) is in the second injection tube (212), and the outer wall and frame crystal tube (11) of the first injection tube (211). Nitrogen gas (N ₂ ) is injected between the inner walls of the panel. Injection crystal tubes 211 and 212 are spaced apart from the substrate support 22. The substrate support 22 made of graphite is provided in the frame crystal tube 21 so that the substrate 23 is supported toward the injection portion, and performs the functions of supporting the substrate 23 and heat transfer. It is also electrically connected to the anode of the DC power supply 24, and acts as the anode of the electric field. The electrode network 25 made of graphite is provided on the outlet side of the injection quartz tubes 211 and 212 to act as a cathode of the electric field.

The process of growing gallium nitride using the above vapor phase growth apparatus is described below.

First, the sapphire substrate 23 is seated on the substrate support 12. Next, the temperature of the furnace is 1,100 [° C.] to thermally clean the frame quartz tube 21, the injection quartz tubes 211 and 212, and the sapphire substrate 23. Next, ammonia gas (NH ₃ ) is injected to nitrate the surface of the sapphire substrate 23. Next, after lowering the temperature of the heating furnace to 600 [° C.], nitrogen gas (N ₂ ), ammonia gas (NH ₃ ), and gallium chloride gas (GaCl) were injected to form a gallium nitride buffer layer on the sapphire substrate 23. Å] to form a thickness. Next, the temperature of the heating furnace is set to 1,050 [° C], and the grown gallium nitride buffer layer is thermally washed. Nitrogen gas (N ₂ ), ammonia gas (NH ₃ ) and gallium chloride gas (GaCl) are injected to form a gallium nitride single crystal on the sapphire substrate 23. μ Grow at a speed of m / hr. Ie 20 per hour μ Grow to a thickness of m.

In the growth stage of the gallium nitride single crystal, an electric field is formed by connecting the negative electrode of the DC power supply 24 to the electrode network 25 and the positive electrode to the substrate support 22. The voltage of the DC power supply 24 can be adjusted here, so that an electric field of 1 to 100 [V / cm] can be formed. The strength of this electric field must be properly adjusted according to the size of the frame correction tube 21 and the flow rate of the gases to be injected. When the electric field is formed in this way, the following phenomenon occurs.

Gallium atoms (Ga) and nitrogen atoms (N) in gallium nitride (GaN) have charges of different polarities, so gallium atoms (Ga) are decelerated and nitrogen atoms (N) are accelerated. Accordingly, since a larger amount of nitrogen atoms (N) and a smaller amount of gallium atoms (Ga) reach the surface of the sapphire substrate 23, the composition variation due to the difference in vapor pressure can be reduced. In addition, by appropriately adjusting the direction and intensity of the electric field by the simulation (simulation) and experiment, it is possible to minimize the composition deviation according to the speed variation of the gases. For example, an optimum electric field strength for compositional variation may be obtained using a personal computer (PC), and the output voltage of the DC power supply 24 may be controlled accordingly. Therefore, the composition ratio of the grown crystal can be matched stoichiometrically, and the composition ratio can be easily and precisely varied.

As described above, according to the gas phase growth method and apparatus according to the present invention, it is possible to easily and precisely control the composition of the single crystal to be grown, thereby increasing the quality, reliability and productivity of the grown crystal.

The present invention is not limited to the above embodiments, and modifications and improvements are possible at the level of those skilled in the art.

Claims (10)

In the vapor phase growth method of injecting a plurality of gases toward the substrate, to grow a single crystal on the substrate by a chemical reaction of the gases, The movement speed of each atom separated from the gases by the chemical reaction, A vapor phase growth method characterized by being controlled by an electric field. The method of claim 1, wherein the electric field, And a direct current voltage applied to the mixed region of the gases. In the vapor phase growth apparatus for injecting a plurality of gases toward the substrate to grow a single crystal on the substrate by a chemical reaction of the gases, And a field generating unit for controlling a moving speed of each atom separated from the gases by the chemical reaction. The method of claim 3, wherein the electric field generating unit, And a direct current power source applied to the mixed region of the gases. The method of claim 4, wherein A cylindrical reactor provided with an inlet and an outlet of the gases; And And a substrate support installed in the cylindrical reactor so that the substrate is supported toward the injection portion. The method of claim 5, wherein the injection portion, And a concentric cylinder through which each gas passes. The method of claim 6, wherein the ends of the concentric cylinders, And an electrode network of the DC power supply is provided. The method of claim 7, wherein the electrode network, A vapor phase growth apparatus comprising a graphite component. The method of claim 5, wherein the substrate support, Vapor phase growth apparatus characterized in that connected to one electrode of the DC power supply. The method of claim 5, wherein the substrate support, A vapor phase growth apparatus comprising a graphite component.