JP5032040B2 - Method for producing hydrogen selenide - Google Patents

Description

  The present invention relates to a method for producing high-purity hydrogen selenide, particularly hydrogen sulfide as an impurity, and hydrogen selenide with a very small residual amount of moisture.

  Hydrogen selenide has recently attracted particular attention as an important material as a dopant gas for silicon semiconductors, as a raw material gas for compound semiconductors such as ZnSe, and also as a raw material for CIS solar cells. In applications, high purity products with particularly low impurity concentration are desired.

As a method for producing hydrogen selenide, several production methods are known. Gaseous hydrogen selenide is obtained by directly hydrogenating a raw material such as metal selenium or selenium oxide by contacting hydrogen at a temperature of 500 to 700 ° C. There is a method.
In this direct method, once generated gaseous hydrogen selenide is cooled and liquefied or solidified, and the resulting liquefied product or ambient gas around the solidified product is removed by exhaust to remove hydrogen and other selenides. Gas components accompanying hydrogen gas are removed, and purification is performed by increasing the purity of hydrogen selenide.

However, in such a manufacturing method, impurities such as moisture and hydrogen sulfide cannot be sufficiently removed even after purification.
Impurity hydrogen sulfide is derived from sulfur entrained in metal selenium, selenium oxide, etc. as raw materials, and since selenium and sulfur are homologous elements, sulfur is adequately purified in the metal selenium purification process. This is because about several tens of ppm remain without being completely removed.

  In addition, the moisture is brought along with the air when the raw material is charged into the reactor, and the water adsorbed on the inner wall surface of the reactor is accompanied by gaseous hydrogen selenide.

In hydrogen selenide used in the production of semiconductors, such moisture and hydrogen sulfide are impurities that should be avoided as much as possible. However, methods for removing these impurities are not known.
Regarding the production method and purification method of hydrogen selenide, there are the following known documents.
Japanese Examined Patent Publication No. 62-12164 Japanese Patent No. 2640517

  Accordingly, an object of the present invention is to obtain a method for producing hydrogen selenide having a high purity and particularly a small amount of moisture and hydrogen sulfide.

To solve this problem,
The invention according to claim 1 evacuates the reaction system under heating while contacting the metal selenium or the selenium compound with high-purity hydrogen having a purity of 99.99% by volume or more at a temperature of 100 to 400 ° C. Sometimes called a process.)
The gaseous hydrogen selenide obtained by contacting with high-purity hydrogen at a temperature of 500 to 700 ° C. is further liquefied or solidified, and the liquefied product or the ambient gas around the solidified product is evacuated. By vaporizing the solidified material,
This is a method for producing hydrogen selenide, characterized in that high-purity gaseous hydrogen selenide having a hydrogen sulfide content of less than 1 ppm is obtained (hereinafter sometimes referred to as this step).

  In the present invention, in the preliminary process, low-boiling components such as sulfur contained in the raw material are discharged out of the system as they are or as hydrides. At the heating temperature of this preliminary step, selenium in the raw material does not react with hydrogen and does not become hydrogen selenide. Further, moisture adsorbed in the reaction system is also desorbed and discharged out of the system. Thereby, a raw material will be refine | purified with high purity.

In this step, the refined raw material reacts with hydrogen to form hydrogen selenide, and this hydrogen selenide thus has a high purity with little impurities such as moisture and hydrogen sulfide.
Further, the gaseous hydrogen selenide obtained in this step is further liquefied or solidified, and after evacuating the ambient gas around the liquefied product or solidified product, the liquefied product or solidified product is vaporized to obtain a high-purity gas. If the hydrogen selenide is obtained, gas components such as hydrogen gas contained in the ambient gas around the liquefied or solidified product are also removed, thereby further improving the purity.

FIG. 1 shows an example of a production apparatus used in the method for producing hydrogen selenide according to the present invention. Reference numeral 1 in the drawing denotes a reaction furnace.
The reactor 1 contains metal selenium and a selenium compound as raw materials therein and can be heated to 700 ° C.

A pipe 2 is connected to the reaction furnace 1, and high purity hydrogen from a high purity hydrogen supply source (not shown) is sent into the reaction furnace 1 through a valve 3.
In addition, a tube 4 is connected to the reaction furnace 1, and a reaction product gas is discharged from the reaction furnace 1 from the tube 4. The pipe 4 is branched in the middle of the pipe 4 and connected to a pipe 5. The pipe 5 is connected to an exhaust device (not shown) via a valve 6 so that the reaction product gas can be discharged out of the system.

Further, the pipe 4 is connected to the trap part 8 via the valve 7, and the reaction product gas from the reaction furnace 1 is sent to the trap part 8.
The trap unit 8 includes a trap body and a heat medium tank that is provided on the outer periphery of the trap body and cools or heats the trap body, and cools and liquefies or solidifies the reaction product gas introduced into the trap body from the pipe 4. Alternatively, this liquefied product or solidified product is vaporized.

  In addition, a pipe 9 is connected to the trap body of the trap portion 8, the pipe 9 is branched in the middle of the trap section 8, and a pipe 10 is connected. The pipe 10 is connected to an exhaust device (not shown) via a valve 11, The gas in the gas phase of the trap body can be discharged out of the system. Further, gas from the trap body is led out from the pipe 9 through the valve 12 as product gas.

Next, a method for producing hydrogen selenide using this production apparatus will be described.
(Preliminary process)
The reactor 1 is filled with metal selenium and selenium compounds as raw materials. The metal selenium is in powder form or in bulk form, and the selenium compound may be in powder form solid or liquid. As the selenium compound, selenium oxide, selenate, selenite and the like are used. As the raw material, one having as high purity as possible is used, and one having a total impurity residual amount of less than 0.1 wt% is preferable.

Next, high purity hydrogen is supplied from the tube 2 into the reaction furnace 1. As the high-purity hydrogen, those having a purity of 99.99% by volume or more and a dew point of −70 ° C. or less are used. Thereafter, the temperature in the reactor 1 is set to 400 ° C. or less, preferably 100 to 400 ° C., the high pressure hydrogen is kept flowing under normal pressure, and the product gas is discharged out of the system through the pipes 4 and 5 and the valve 6. .
In this temperature range, selenium and hydrogen in the raw material do not react, and low-boiling impurities such as moisture, sulfur, carbon, oxygen, and halogen contained in the raw material become gaseous and enter the gas phase. Transition.

  The gaseous impurities transferred to the gas phase are discharged out of the system as they are, or react with hydrogen and discharged out of the system as hydrides. For example, sulfur in the raw material reacts with hydrogen and is discharged as hydrogen sulfide. Further, the moisture adsorbed on the inner wall surface of the reactor 1 is heated, desorbed and discharged out of the system.

Although the heating time of the reaction furnace 1 depends on the filling amount of the raw material, it is 1 to 10 hours, and the flow rate of the high purity hydrogen is 1 to 10 L / min at 0 ° C. at atmospheric pressure .
By this preliminary process, impurities having a low boiling point in the raw material are removed, and the raw material is in a purified state.

(This process)
After the preliminary process is completed, high-purity hydrogen is introduced at a temperature in the reaction furnace 1 of 500 to 700 ° C. and a pressure of normal pressure. At this temperature, selenium in the raw material reacts with hydrogen to form hydrogen selenide. At this time, the valve 6 is closed, the valve 7 is opened, and the generated gas (hydrogen selenide gas) generated in the reaction furnace 1 is sent to the trap unit 8.

  In the trap unit 8, the heat medium tank is filled with a cooling medium such as liquefied nitrogen, the trap body is cooled below the liquefaction temperature or solidification temperature of hydrogen selenide, and the generated gas from the reactor 1 is cooled in the trap body. The hydrogen selenide contained therein is once collected in the trap body as a liquid or solid.

In the gas phase in the trap body, a gas component having a very low boiling point such as hydrogen contained in the generated gas is present. This gas component passes through the pipes 9 and 10 and the valve 11 to the outside of the system. To be discharged.
The heating time of the reaction furnace 1 in this step is 1 to 10 hours although it depends on the amount of raw material charged.

  When the supply of the product gas from the reaction furnace 1 is finished, the valves 7 and 11 are closed, the valve 12 is opened, and the temperature of the trap body of the trap section 8 is set to the vaporization temperature of hydrogen selenide or higher and trapped in the trap body. Vaporized liquid or solid hydrogen selenide is vaporized. In order to set the temperature of the trap body of the trap unit 8 to be equal to or higher than the vaporization temperature of hydrogen selenide, there are a method of filling the heat medium tank with water at room temperature and a method of flowing air at room temperature.

  Thereby, hydrogen selenide vaporized from the trap body of the trap unit 8 is led out as a product gas through the pipe 9 and the valve 12.

  In such a production method, low-boiling impurities contained in the raw material are removed from the raw material in the preliminary process, and moisture adsorbed on the inner wall surface of the reactor 1 is also desorbed and discharged out of the system. The For this reason, at the time when the preliminary process is completed, the raw material is purified to an extremely high purity.

  Therefore, in this step, the hydrogen selenide produced by the reaction of selenium and hydrogen in the raw material contains almost no impurities. Further, since the generated hydrogen selenide is once liquefied or solidified in the trap body of the trap unit 8 and the atmospheric gas such as gaseous hydrogen in the trap body is exhausted, the hydrogen selenide is vaporized to produce the product gas. In this case, the atmospheric gas is not mixed into the product hydrogen selenide gas.

  For this reason, according to the production method of the present invention, as is clear from the specific examples described later, the hydrogen sulfide and moisture contained in the product hydrogen selenide gas can be reduced to less than 1 ppm.

Specific examples are shown below.
(Comparative example)
The apparatus shown in FIG. 1 was used. After filling the reactor 1 with high purity metal selenium (purity: 99.999 wt%), the trap body of the trap unit 8 is cooled to −196 ° C., and the reactor 1 is heated to 600 ° C. at normal pressure. Hydrogen was allowed to flow for 4 hours, and the generated gas was solidified in the subsequent trap section 8. Only the vapor phase of the trap part was evacuated while the generated gas was solidified. Thereafter, analysis of impurities in the product gas which had been vaporized again was performed by gas chromatography.
Table 1 shows the results of impurity analysis.

Example 1
The apparatus shown in FIG. 1 was used.
Preliminary process: High purity metal selenium (purity: 99.999 wt%) was charged into the reactor 1, and hydrogen gas was allowed to flow for 4 hours while heating the reactor 1 at 350 ° C. at normal pressure and 250 ° C., etc. .
This step: Hydrogen was circulated for 4 hours in a state where the reactor 1 was heated to 600 ° C., and the generated gas was solidified in the trap portion 8 cooled to −196 ° C. in the subsequent stage. Only the vapor phase of the trap portion 8 was evacuated while the generated gas was solidified. Thereafter, analysis of impurities in the product gas which had been vaporized again was performed by gas chromatography.
The impurity analysis results are shown in Table 2.

  It was confirmed that high-purity hydrogen selenide having a low impurity concentration can be obtained as compared with a comparative example in which no preliminary process was performed.

(Example 2)
The apparatus shown in FIG. 1 was used.
Preliminary process: High purity metal selenium (purity: 99.999 wt%) is charged into the reactor 1, and high purity hydrogen gas is allowed to flow for 4 hours while heating the reactor to 350 ° C at normal pressure and piping to 250 ° C. It was. Thereafter, the heating was stopped, and the mixture was left overnight with high purity hydrogen gas sealed.
This step: The next day, the subsequent trap portion was cooled to -196 ° C, and high purity hydrogen was circulated for 4 hours in a state where the reactor was heated to 600 ° C, and the generated gas was solidified in the trap portion. Only the gas phase of the trap part was evacuated while the generated gas was solidified. After that, impurities in the vaporized product gas were analyzed again.
Table 3 shows the results of impurity analysis.

  It was confirmed that high-purity hydrogen selenide having a low impurity concentration can be obtained as compared with a comparative example in which no preliminary process was performed.

It is a schematic block diagram which shows an example of the manufacturing apparatus used for the manufacturing method of this invention.

Explanation of symbols

1 ... Reactor, 8 ... Trap part

Claims (1)

After contacting the metal selenium or selenium compound with high-purity hydrogen having a purity of 99.99% by volume or more at a temperature of 100 to 400 ° C. , the reaction system was evacuated under heating,
The gaseous hydrogen selenide obtained by contacting with high-purity hydrogen at a temperature of 500 to 700 ° C. is further liquefied or solidified, and the liquefied product or the ambient gas around the solidified product is evacuated. By vaporizing the solidified material,
A process for producing hydrogen selenide, characterized by obtaining high-purity gaseous hydrogen selenide having a hydrogen sulfide content of less than 1 ppm .

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