JPS63116418A - Epitaxially growing method and system - Google Patents

Abstract

PURPOSE:To prevent the consumption of a compensating easily evaporating component material from decreasing and a grown layer from displacing in its composition by oxidizing it with oxidative gas plasma and reducing it with hydrogen gas plasma prior to an epitaxial growth. CONSTITUTION:A reaction tube 1 for performing an epitaxial growth, a gas introducing mechanism 2 connected to one end of the tube 1 for introducing oxidative gas and hydrogen gas to be able to switch, a pressure control mechanism 3 connected to the other one end of the tube 1 for holding the interior of the tube 1 at a predetermined vacuum degree, a pair of electrodes 4, 5 for holding part of the tube 1 from the exterior, and a high frequency power source 6 are provided. A growing substrate made of a CdTe single crystal plate and a base material made of Hg, Cd, Te are contained in a slider member 16, and Hg of easily evaporating component is contained in a retaining member 17. Then, an oxidation with oxidative plasma and a reduction with hydrogen plasma are executed. After reducing, an epitaxial growth is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an epitaxial growth method for orderly growing a crystal structure on a semiconductor single crystal, and an epitaxial growth apparatus used to carry out the method.

[Prior Art] Narrow energy gap semiconductors such as mercury cadmium telluride (HqCdTe) are known as materials for highly sensitive infrared detectors, and in order to manufacture these crystals over a large area and with good uniformity, it is generally necessary to Liquid phase or vapor phase epitaxial growth methods are used. For example, the liquid phase epitaxial growth method is basically carried out using an apparatus as shown in FIG. 3, as disclosed in Japanese Unexamined Patent Publication No. 58-138038. That is, a growth substrate 33 of cadmium telluride (CdTe) or the like is buried in a recess 32 provided in a support base 31, and liquid tanks 35 and 36 containing a base material 34 are placed on the support base 31. Slider part 3
7 is slidably arranged. These are further placed in a reaction tube 38 made of quartz and heated in an atmosphere of hydrogen gas supplied and discharged in the direction of the arrow in the figure. The slider member 31 sequentially slides to move the liquid tanks 35 and 36 onto the growth substrate 33 to perform melt-back cleaning and epitaxial growth. During this heating, if a component of the base material 34 or the growth substrate 33 that easily evaporates, for example mercury cadmium telluride, mercury is separately prepared and evaporated to balance the vapor pressure in the area where epitaxial growth is performed. control to maintain a uniform predetermined composition.

Normally, before starting this growth, the reaction tube 38, growth substrate 33, base material 34, etc. are thoroughly cleaned to remove organic matter, and then heated and maintained in a hydrogen gas atmosphere to remove the growth substrate 33, base material 34, etc. The base material 34 is reduced, but this is because organic components attached to the growth substrate 33 and base material 34, thin oxide layers formed on their surfaces, or adsorbed oxygen are mixed into the base material melt and the growth is reduced. This is to prevent impurities from being incorporated into the interface with the substrate 33 or into the epitaxially grown layer and deteriorating the crystal properties.

[Problems to be solved by the invention] However, contamination is caused by the chemicals and jigs themselves used to clean organic matter adhering to the surface, and also by the process of assembling them into the reaction tube after cleaning. A small amount of contaminants in the air will adhere to it.

Furthermore, the temperature at which the reduction treatment is carried out with hydrogen gas is necessarily limited to below the melting point of the base material, and it takes a long time to carry out sufficient treatment.On the other hand, even at such temperatures, the easily vaporized components are Because of the dissipation, it is necessary to prepare a large amount of easily evaporable component material for compensation. Further, in this case, it is very difficult to maintain vapor pressure equilibrium for a long time, and there is also the problem that the composition of the growing crystal tends to shift due to changes in the composition of the base material.

These problems arise not only in the open-tube liquid phase epitaxial growth method described above, but also in the closed-tube liquid phase epitaxial growth method in which the growth substrate and base material are sealed in a closed reaction tube. This is a common problem when it comes to growth methods.

The present invention was made in order to solve these problems, and it is possible to completely remove contamination caused by organic substances, reduce the consumption of easily evaporable component materials for compensation, and create an epitaxial structure that is less prone to compositional deviations. The purpose of the present invention is to provide a growth method and a growth device.

[Means for Solving the Problems] In the present invention, prior to performing epitaxial growth, the growth substrate and base material are first subjected to oxidation treatment in an oxidizing gas plasma atmosphere in a reaction tube in which the epitaxial growth is performed. , an epitaxial growth method characterized by subsequent reduction treatment in a hydrogen gas plasma atmosphere, a reaction tube for performing epitaxial growth, and a reaction tube connected to one end of the reaction tube to switch between an oxidizing gas, a hydrogen gas, and a replacement gas. a pressure control mechanism connected to another end of the reaction tube to keep the inside of the reaction tube at a predetermined degree of vacuum; and a pair of pressure control mechanisms that sandwich part or all of the reaction tube from the outside. This epitaxial growth apparatus is characterized in that it is equipped with electrodes and a power source that supplies high-frequency power to these electrodes to generate gas plasma within a reaction tube.

[Function] When an oxidizing gas such as oxygen gas or N20 gas or hydrogen gas is excited by plasma, each gas is ionized and becomes activated, greatly increasing its reactivity. Therefore,
By excitation of plasma while supplying these gases, organic substances are oxidized and decomposed in an oxidizing gas plasma atmosphere and are emitted as H20 and CO2.In addition, in a hydrogen gas plasma atmosphere, unlike conventional A sufficient reduction effect can be generated without heating and while the temperature is maintained at a low temperature, and oxide films and adsorbed oxygen on the surfaces of the growth substrate and base material can be removed. In particular, these can be performed with the growth substrate and base material placed in the reaction tube in which epitaxial growth is actually performed, so it is possible to proceed to epitaxial growth while maintaining ideal clean conditions. Furthermore, since all processes are carried out at low temperatures, the dissipation of easily evaporable components is negligible, and the consumption of compensating easily evaporable component materials is also short.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an epitaxial growth apparatus according to the present invention, and FIG.
This is a partial cross-sectional view taken along the line '. In each of these figures,
The epitaxial growth apparatus includes a reaction tube 1 for performing epitaxial growth, a gas introduction mechanism 2 connected to one end of the reaction tube 1 for introducing an oxidizing gas and a hydrogen gas in a switchable manner, and another part of the reaction tube 1. A pressure control mechanism 3 that is connected to one end and keeps the inside of the reaction tube 1 at a predetermined degree of vacuum, a pair of electrodes 4 and 5 that sandwich a part of the reaction tube 1 from the outside, and a high frequency It is roughly configured with a power source 6 that supplies electric power.

The gas introduction mechanism 2 includes a first gas supply source 7a that supplies oxygen gas as an oxidizing gas, a second gas supply source 7b that supplies hydrogen gas, and a third gas supply source that supplies nitrogen gas as a replacement gas. 7C, valves 8a, 8b and 8C for switching these gases, and flow rate controllers 9a, 9b and 9C for controlling the respective flow rates.

The pressure control mechanism 3 is connected to the reaction tube 1 via a trap 10, and includes a vacuum valve 11, a mechanical booster pump 12, and an oil rotary pump 13, and controls vacuum evacuation inside the reaction tube 1 and stable gas plasma. It is used to maintain the degree of vacuum created. Trap 10 is a mechanical
This prevents contamination due to backflow of oil vapor from the booster pump 12 and oil rotary pump 13, and traps Hg vapor in the hydrogen gas sent out during epitaxial growth. Further, a hydrogen combustion section 15 is connected to this trap 10 via a valve 14 in order to discharge and burn such hydrogen gas.

Inside the reaction tube 1, a slider member 16 containing a growth substrate 33 and a base material 34, and a receiver member 17 containing an easily evaporable component material are installed. As mentioned above, the electrodes 4 and 5 are arranged in a part of the outside of the reaction tube 1, and the main heater 18 and the sub-heater 19 are arranged in the other part.
is wrapped around it. The main heater 18 is for melting the base material 34 and performing epitaxial growth, and the sub-heater 19 is for controlling the vapor pressure of the easily evaporable component.

Next, the epitaxial growth method of the present invention using the above-mentioned growth apparatus will be explained by way of an example in which a mercury cadmium telluride crystal is epitaxially grown.

First, a growth substrate consisting of a Cd/e single crystal plate, Hc+,
A base material consisting of a single substance or a compound of Cd and Te is housed in a slider member 16, and HCI, which is an easily evaporable component, is housed in a receiver member 17.
The latter is placed at a position corresponding to the sub-heater 19. Next, oxidation treatment using oxidizing gas plasma, which is a feature of the present invention, and reduction treatment using hydrogen gas plasma are performed as described below.

First, the vacuum valve 11 of the pressure control mechanism 3 is fully opened, and the inside of the reaction tube 1 is evacuated by the oil rotary pump 13 and the mechanical booster pump 12, and then the first gas supply 2117
A constant flow of old oxygen gas is used as an oxidizing gas from reaction tube 1.
The inside of the reaction tube 1 is maintained at a predetermined degree of vacuum by controlling the vacuum valve 11. The degree of vacuum at this time is 1 to 10, which is a value that can form a stable oxygen gas plasma.
It is set to an appropriate range of about 0 Pa.

Subsequently, high frequency power is applied from the power source 6 to the electrodes 4 and 5 to generate oxygen gas plasma in the reaction tube 1 sandwiched between the electrodes 4 and 5. Then, activated oxygen is generated in this area, which oxidizes and decomposes organic matter adhering to the growth substrate, base material, inner wall of the reaction tube, etc., and the organic matter is discharged as a gas. The time for exposure to plasma depends on the high frequency power and the degree of organic contamination, but several hours is sufficient.

When the oxidation process is completed, the supply of oxygen gas is stopped, the inside of the reaction tube 1 is evacuated again, and a constant flow of hydrogen is supplied from the second gas supply source 7b by operating the valve 8b and the flow rate controller 9b. A gas is introduced into the reaction tube 1, and hydrogen gas plasma is generated in the same manner as in the case of oxygen gas. The activated hydrogen thus generated reduces, removes, and discharges the oxide film originally formed on the surface of the substrate or base material, the oxide film formed during the above-mentioned oxidation treatment, and the adsorbed oxygen. A few hours is also sufficient for this time.

After this reduction process, close the vacuum valve 11 of the pressure control mechanism 3,
The valve 14 to the hydrogen combustion section 15 is opened to switch the discharge of hydrogen gas, and the slider member 16 is moved to a position corresponding to the main heater 18 to start epitaxial growth. The epitaxial growth itself is carried out by controlling the temperature of the growth section using the main heater 18 and controlling the temperature of the member 17, that is, the vapor pressure of HQ, which is an easily evaporated component, using the sub-heater 19, in the same manner as in the known method. After epitaxial growth to a desired thickness is completed, the heating of both heaters 18 and 19 is stopped, and nitrogen gas is replaced from the third gas supply source 7C by operating the valve 8C and the flow rate controller 9C. The process is completed by stopping the supply of hydrogen gas.

The HqCdTe crystal epitaxially grown in this way is
The product is of good quality without deterioration of characteristics due to the contamination of organic matter or oxygen, that is, an increase in carrier concentration, and the consumption of HQ, which is an easily evaporable component, is reduced compared to the conventional method of reducing by heating in a hydrogen atmosphere. The amount was reduced by half, and the stability of the composition during epitaxial growth was also improved.

Although the explanation has been given here using an example of open-tube liquid phase epitaxial growth of HqCdTe, it goes without saying that the present invention can also be applied to the case of epitaxial growth of compound semiconductor crystals containing other easily evaporable components. In the case of closed tube liquid phase epitaxial growth, the entire reaction tube is sandwiched between electrodes.
After similarly performing plasma oxidation treatment and reduction treatment, both ends of the reaction tube may be sealed and epitaxial growth may be performed, and vapor phase epitaxial growth is also performed in exactly the same manner.

[Effects of the Invention] As explained above, according to the present invention, by performing oxidation treatment using oxidizing gas plasma and reduction treatment using hydrogen gas plasma prior to epitaxial growth,
An epitaxial growth method and its growth that can obtain high-quality crystals without contamination of organic matter or oxygen, and do not require heating, thereby reducing the consumption of compensating easily evaporable component materials and preventing composition shifts in the grown layer. equipment can be provided.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of one embodiment of the present invention, and Figure 2 is its A-
FIG. 3, a partial sectional view taken along line A', is a configuration diagram of a conventional example. 1.38...Reaction tube 2...Gas introduction mechanism 3...Pressure control mechanism 4,5...Electrode 6...
・Power supply 7...Gas supply source 10...
Trap 11... Vacuum valve 12... Booster pump 13... Oil rotary pump 14... Valve 15... Hydrogen combustion section 16, 37.
...Slider part 17...Base is member 18...Main heater 19...Sub-heater 31...Support stand 32...Recess 33...Growth substrate
34... Base material 35, 36... Liquid tank agent Chieko Tateno Figure 3

Claims (2)

[Claims] (1) Prior to performing epitaxial growth, the growth substrate and base material are first oxidized in an oxidizing gas plasma atmosphere and then reduced in a hydrogen gas plasma atmosphere in the reaction tube where the epitaxial growth is performed. An epitaxial growth method characterized by: (2) A reaction tube for epitaxial growth; a gas introduction mechanism connected to one end of the reaction tube for switchably introducing oxidizing gas, hydrogen gas, and replacement gas; It is equipped with a pressure control mechanism that is coupled to maintain a predetermined degree of vacuum inside the reaction tube, a pair of electrodes that sandwich part or all of the reaction tube from the outside, and a power source that supplies high-frequency power to these electrodes. , an epitaxial growth apparatus characterized by generating gas plasma in a reaction tube.