JPS59152297A - Gas-phase crystal growth system - Google Patents

Abstract

PURPOSE:The whole of piping system is surrounded with an air-tight vessel and the vessel is filled with a high-purity gas inside so that only the high-purity gas is mixed in the pipings, even if there should be leaks in the piping system, thus preventing the contamination of the starting gases in the pipings with impurities. CONSTITUTION:The piping system for feeding the starting gases to the gas- phase crystal growth chamber is composed of inlets of starting gases 1, filteres 2, pressure controllers 3, flow rate controller 4, switching valves 5, joints 6 and the outlets of starting gases 8 and piping connecting them 7. The whole of the piping system is placed in the air-tight vessel 10. The vessel 10 is provided with the inlets and outlets of the starting gases as well as the inlet 11 and outlet 12, each of which is provided with a valve 13 and 14, on the wall. Thus, the vessel is filled with high-purity gas 15 and only high-purity gas is mixed in the starting gases, even if the piping system should have leaks, without contamination with impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vapor phase growth apparatus, and particularly to a vapor phase growth apparatus that prevents contamination of source gas and maintains high purity.

In vapor phase growth, it is well known that trace amounts of impurities in the source gas sent to the reaction region have a significant effect on the grown layer. Therefore, in order to perform high-quality vapor phase growth with good reproducibility, it is necessary to sufficiently reduce the amount of impurities mixed into the source gas. There are many types of substances that become impurities and their causes of contamination, but one of the major causes of contamination is the mixture that exists in component piping included in equipment that adjusts, mixes, and switches the flow rate of raw gas. There are minute leaks in the devices and parts for switching, the joints and piping that connect them, and impurities in the atmosphere can enter through these leaks. In this case, oxygen and water vapor have particularly important effects on vapor phase growth.

GaAs and Ga are typical ■-■ group compound semiconductors.
Taking the vapor phase growth of A'tAs as an example, it is known that even if the concentration of oxygen or water vapor contained in the reaction region is only about 0,000 ppm, the carrier concentration of the grown layer changes greatly. In addition, the photo-resistance of the GaAtAs growth layer
The luminescence intensity (which indicates the optical quality of the grown layer) is significantly weakened. Therefore, the concentration of oxygen or water vapor contained in the reaction region needs to be at least 0.1 pI)m or less, preferably o, otppm or less.

On the other hand, in the equipment actually used for vapor phase growth, many parts are used to adjust, mix, and switch the flow rate of source gases, and the number of joints that connect these parts is also large. It becomes very large.

Even if sufficient care is taken to prevent leakage from each individual component, some degree of leakage is unavoidable with actually available components. In particular, in vapor phase growth, a large number of various parts such as pressure regulators, lid adjustment devices, switching valves, etc. are used, and the raw material gas also contains corrosive gases. For this reason, it is not possible to design a device with the priority of eliminating leakage, as in the case of so-called ultra-high-performance devices. The leakage value varies depending on the parts, but is 10""
atrn.cc/sec, and this value is about 10-'atrn m cc/sec for parts for ultra-high vacuum equipment.
It is about 100 times smaller than sec. l Q” atm@c
The amount of leakage c/sec is a small enough value for one location, but since the number of parts and joints used in an actual device ranges from several hundred to more than 1,000, the total amount of leakage is ephemeral. After all, the amount of oxygen or water vapor mixed in from the atmosphere contained in the gas sent to the reaction region is reduced to 0.1 p.
There was a drawback that it was extremely difficult to make the value less than I)m.

An object of the present invention is to provide a vapor phase growth apparatus that eliminates the above-mentioned drawbacks, prevents contamination of impurities from the atmosphere during feeding of raw material gas to a vapor phase growth chamber, and maintains purity.

According to the present invention, devices and parts such as a flow rate adjustment device, a pressure adjustment device, a switching valve, a mixer, a joint, etc., for adjusting the flow rate and pressure of various raw material gases sent to the vapor growth chamber, switching gases, and mixing the gases. and an airtight container that has piping that connects the device and parts, and an inlet and an outlet for raw gas, and that houses the device and the component piping and connects it to the inlet and outlet;
A vapor phase growth apparatus characterized in that the airtight container is filled with a high purity gas is obtained.

Next, embodiments of the present invention will be described using the drawings.

The figure is a piping system diagram of one embodiment of the present invention.

The piping system for sending source gas to the vapor phase growth chamber includes a source gas inlet 1, a filter 2, a pressure regulator 3, and a flow rate regulator 4.
, gas switching valve 5, joint 6, source gas outlet 8. etc. are connected by piping 7. The entire piping system is housed in an airtight container 10.

An inlet 1 and an outlet 8 for raw material gas are attached to the wall of the airtight container 10 . Further, in order to fill the airtight container 10 with high purity gas, an inlet 11 and an outlet 12 for the high purity waste 15 are provided on the wall of the container 10 via valves 13 and 14.

If the entire piping system is surrounded by an airtight container and filled with high-purity gas in this way, even if there is a leak in the piping system, it will be high-purity gas and not impurities that will get mixed into the source gas. The raw material gas is kept at high purity without being dyed.

An example of measuring the amount of impurities mixed in in the above embodiment will be explained.

High-purity hydrogen with an oxygen concentration of o, oappm was flowed as the raw material gas 5- in a piping system having 10 flow regulating devices and approximately 1000 piping connection points.

First, the inside of the airtight container 10 is filled with normal atmosphere, the above-mentioned hydrogen is introduced from the raw material gas inlet 1, and the raw material gas outlet 8
When the oxygen concentration in hydrogen was measured, it was found to have increased by 0.4 ppmK. This increase is the original oxygen concentration of 0.03 f)I)
This is a more than 10-fold increase over m, indicating that there are considerable leakages in the piping system through which oxygen from the atmosphere can enter.

Next, after filling the inside of the airtight container 10 with dry high-purity nitrogen gas, hydrogen with an oxygen concentration of 0.03 ppm was flowed and measurement at the outlet 8 revealed that the oxygen concentration was o, oappm.
No oxygen contamination from the atmosphere was observed.

As mentioned above, eliminating leaks in individual parts and joints between parts is extremely difficult and nearly impossible.

However, as in the present invention, by simply surrounding the entire piping system with an airtight container and making the atmosphere around the piping system a high-purity gas, contamination with impurities and people can be prevented.

As in the present invention, it is extremely easy to house the entire piping system in an airtight container and fill it with high-purity gas. Since the airtight container also leaks, the oxygen and water vapor concentrations in the airtight container differ between the inlet 11 and the outlet 12. Therefore, compared to the entire piping system housed inside the book, the number of connections is far fewer, and there are fewer leaks as well, so the mixing of oxygen and water vapor into the high-purity gas can be kept to 0.1% or less. is easy, and therefore the amount of oxygen and water vapor mixed into the raw material gas is completely negligible.

As explained in detail above, according to the present invention, by adding a simple device, it is possible to prevent contamination of impurities from the atmosphere during feeding of the raw material gas to the vapor growth chamber, and maintain the purity of the raw material dregs. Since a vapor phase growth apparatus can be obtained, the effect is great.

[Brief explanation of drawings]

The figure is a piping system diagram of one embodiment of the present invention. 1... Raw material gas inlet, 2... Filter, 3... Pressure regulator, 4... Flow rate regulator, 5... Waste switching valve, 6...
Joint, 7... Piping, 8... Raw gas outlet, 10... Airtight container, 11... High purity gas inlet, 12... ...High purity gas outlet,
13.14... Valve, 15... High purity gas.

Claims (1)

[Claims] Devices and parts such as flow rate adjustment devices, pressure adjustment devices, switching valves, mixers, joints, etc. for adjusting the flow rate and pressure of various raw material gases sent to the vapor growth chamber, gas switching, and mixing, and the devices and parts described above. an airtight container that has an inlet and an outlet for raw material gas, houses the equipment and component piping, and is connected to the inlet and outlet; and a high-purity container filled in the airtight container. A vapor phase growth apparatus characterized by containing a gas.