JPH0732138B2 - Vapor phase growth method of phosphorus-containing compound semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to chemical vapor deposition of a phosphorus-containing compound semiconductor, particularly metalorganic chemical vapor deposition (hereinafter referred to as MOCVD).
The present invention relates to a vapor phase growth method of a compound semiconductor containing phosphorus, which is formed on a substrate by means of.

[Conventional technology]

The vapor phase growth of this kind of phosphorus-containing compound semiconductor is performed, for example, by the following method. Indium phosphide (hereinafter InP
When a thin film of () is vapor-deposited, a gas of trimethylindium (hereinafter referred to as TMI) that is a source of indium or a gas of triethylindium (TEI) and phosphine (hereinafter referred to as PH ₃ ) that is a source of phosphorus are described. ) And indium and phosphorus in an amount of 1: 1 to bond with each other, and these gases are diluted several tens of times (for example, 30 times) with hydrogen gas as a carrier gas, and the diluted gas is mixed. After that, it is supplied to the reaction chamber. Then, InP is crystal-grown in the reaction chamber on the substrate kept at a high temperature (for example, 600 ° C. to 700 ° C.) suitable for film formation by the heating means. When the film formation is completed, the substrate is cooled to almost room temperature, and then the substrate is taken out of the reaction chamber.

[Problems to be Solved by the Invention]

The problems in the conventional vapor phase growth method of the compound semiconductor containing phosphorus of this kind are as follows.

Although InP is deposited on the substrate by the above method, InP is thermally decomposed when it contacts a high temperature portion in the reaction chamber other than the substrate, and a single phosphorus is deposited in the reaction chamber or a portion such as a waste gas pipe. To deposit.

When the substrate is taken out of the reaction chamber in such a state,
The reaction chamber or waste gas piping is exposed to air. Then, there is a problem in that the phosphorus precipitate is combined with oxygen in the air and burns rapidly depending on the deposition state and amount, and in some cases, explosively burns, resulting in a very dangerous state.

Conventionally, in order to solve this problem, a well-known load lock mechanism including a pre-chamber, a sluice valve, a vacuum pump, etc., is provided between the reaction chamber and the atmosphere, and air is allowed to enter the reaction chamber and the exhaust gas system piping. A method has been adopted in which the substrate is taken out without causing it. In this case, the above-mentioned problem can be avoided for the time being, but it is impossible to remove the phosphorus that has precipitated in the reaction chamber or the portion of the waste gas system such as pipes, and it is necessary to disassemble or clean it regularly. The need arises. As a result, during the disassembly and cleaning, the above-mentioned danger becomes a problem again.

Further, as disclosed in JP-A-62-42516,
There is one that prevents burning and explosion of the phosphorus deposit by coating the phosphorus deposit with the deposit of arsenic or an arsenic compound. However, in that case, not only the structure of the apparatus becomes complicated because precipitates of arsenic or arsenic compound are generated, but also highly toxic arsenic or arsenic compound has to be intentionally deposited, which is safe for workers. There was a big problem in keeping.

An object of the present invention is to provide a vapor phase growth method for a phosphorus-containing compound semiconductor that does not cause rapid or explosive burning of phosphorus precipitates and that can ensure worker safety. To provide.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, a compound semiconductor containing phosphorus is formed on a substrate in a reaction chamber,
Oxygen gas diluted to a concentration less than the oxygen gas concentration in air by an inert gas is supplied into the reaction chamber so as to slowly oxidize the phosphorus-containing precipitate generated in the reaction chamber during film formation. I decided to.

[Action]

When the above method is adopted, it is the same as the conventional method that the phosphorus precipitated in the reaction chamber or the pipe of the waste gas system is oxidized and generates heat when exposed to the diluted oxygen gas. Since the gas concentration is set lower than the oxygen gas concentration in air (20.968% by volume), the oxidation reaction becomes slow and the calorific value per unit time becomes small. Therefore, phosphorus pentoxide (hereinafter referred to as P ₂ O ₅ ) is an oxide that does not pose a safety problem even if the precipitate of phosphorus is exposed to air without the risk of explosion when exposed to air in the conventional method. Can be converted to.

〔Example〕

FIG. 1 shows a gas system diagram of a MOCVD apparatus which is an embodiment to which the vapor phase growth method of a compound semiconductor containing phosphorus of the present invention is applied. First, this gas system will be described.

A pipe 1 for supplying PH ₃ diluted with hydrogen gas as a carrier gas and a pipe 2 for supplying TMI diluted with hydrogen gas are connected via valves 3 and 4, respectively, and both gases are connected. After being mixed, they are supplied into the reaction chamber 5. The reaction chamber 5 includes a substrate mounting table (not shown), a substrate, and heating means for the substrate.

The gas supplied from the nitrogen gas pipe 6 and the oxygen gas pipe 7 is further supplied to the reaction chamber 5 by a mass flow controller.
Valve 1 after being mixed by a certain ratio, measured by 8,9
Supplied via 0.

Waste gas from the reaction chamber 5 is a valve 11, a filter 12, a variable conductance valve for adjusting the reaction pressure in the reaction chamber 5.
After passing through 13, it is sent to a waste gas treatment device 15 by a vacuum pump 14, where it is rendered harmless and then released into the atmosphere.

An example of the vapor phase growth method for a phosphorus-containing compound semiconductor of the present invention in an apparatus having such a gas system will be described below.

During film formation, valves 3 and 4 are opened and valve 10 is closed,
PH ₃ and TMI diluted with hydrogen gas are supplied into the reaction chamber 5 to form a film on the substrate. At this time, unreacted gas and PH
₃ , hydrogen gas supplied as a carrier gas for TMI is treated and discharged through a valve 11, a filter 12, a variable conductance valve 13, a vacuum pump 14, and a waste gas region device 15. At this time, as described above, phosphorus is in the form of a film in the piping and each device located in the reaction chamber 5 and downstream thereof.
Precipitates in the form of fine powder or flakes.

When the film formation is completed, the substrate is cooled. At this time, the heating by the heating means (not shown) in the reaction chamber 5 is usually stopped, and the valve (not shown) located upstream of the valves 3 and 4 is also used. The supply of PH ₃ and TMI is stopped by closing, and only hydrogen gas, which is a carrier gas, is supplied to the reaction chamber 5 at a flow rate almost the same as that during film formation.

After the cooling is completed and the temperature of the reaction chamber 5 and the substrate inside the chamber have reached almost room temperature, the valves 3 and 4 are closed to stop the supply of hydrogen gas and at the same time the valve 10 is opened, and the volume ratio of nitrogen gas is set to, for example, Oxygen gas diluted to a concentration of 5% is supplied into the reaction chamber. By this operation, phosphorus deposited in the reaction chamber and the pipes and equipment located downstream thereof is
It is slowly oxidized without any reaction such as sudden heat generation, and is converted into P ₂ O ₅ which is a substance that is safe even when it comes into contact with air. The oxygen gas concentration should be appropriately set depending on the deposition state and amount of phosphorus deposits, and it is considered that about 1% to 5% by volume is appropriate. If the concentration is too high, it becomes impossible to perform slow oxidation, and if the concentration is too low, the takt time becomes too long, which is not preferable. In principle, it is impossible for the mild oxidation to deteriorate the quality of the thin film on the substrate or increase the contamination.

In this embodiment, the nitrogen gas supplied from the nitrogen gas pipe and the oxygen gas supplied from the oxygen gas pipe are mixed via the mass flow controller so that the oxygen gas has a predetermined concentration. However, a gas in which an inert gas having a predetermined oxygen concentration and an oxygen gas are mixed may be filled in a cylinder in advance, and the gas may be supplied to the reaction chamber from the cylinder. In addition, in the present embodiment, the target substance to be slowly oxidized is a precipitate of simple substance of phosphorus, but it is obvious that a substance such as a phosphorus compound which is likely to cause rapid combustion is also targeted. Further, the inert gas that dilutes the oxygen gas is not limited to nitrogen gas. Further, the compound semiconductor containing phosphorus formed on the substrate is not limited to InP.

〔The invention's effect〕

As described above, according to the present invention, after depositing a phosphorus-containing compound semiconductor on a substrate in a reaction chamber, the phosphorus-containing precipitate generated in the reaction chamber during film formation is slowly oxidized. As described above, since oxygen gas diluted to a concentration lower than the oxygen gas concentration in air by an inert gas in volume ratio is supplied to the reaction chamber, phosphorus that is unavoidably deposited during film formation is exposed to air. Even safe to convert to P ₂ O ₅ . Therefore, it is possible to eliminate the possibility that the precipitate will explode when it comes into contact with air, and it is possible to reliably maintain the safety during the process and maintenance.

[Brief description of drawings]

FIG. 1 is a gas system diagram of an MOCVD apparatus which is an embodiment to which the vapor phase growth method for a compound semiconductor containing phosphorus of the present invention is applied. 5: Reaction chamber, 6: Nitrogen gas pipe, 7: Oxygen gas pipe, 8, 9: Mass flow controller, 10: Valve.

Claims (1)

[Claims] 1. After forming a phosphorus-containing compound semiconductor on a substrate in a reaction chamber, a phosphorous-containing compound semiconductor is formed in the reaction chamber so as to slowly oxidize the phosphorus-containing precipitate formed in the reaction chamber. A vapor phase growth method for a compound semiconductor containing phosphorus, characterized in that oxygen gas diluted to a concentration less than oxygen gas concentration in air by an active gas is supplied.