JPS6138384A - Method of recovering argon gas for atmosphere - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for regenerating a single crystal into an integral shape during the production of a silicon semiconductor single crystal.

(Prior Art) Conventionally, the reality is that the argon gas used as an atmospheric gas during the manufacturing process as described above has been naturally released into the atmosphere without being recovered. Focusing on this uneconomical issue, we removed some of the impurities from the exhausted recovered argon through a filter and adsorbent, and then used N in the purification process.
Attempts have been proposed to remove m,01 and reuse argon of up to 69 purity.

(Problems to be Solved by the Invention) However, since the above-mentioned prior art employs a titanium getter system for removing Nm, it is difficult to reactivate the titanium used for removing Nl. However, the uneconomical nature of not being able to do so still remained, and improvements were desired. (Means for Solving the Problem) In view of the above, the present invention employs low-temperature dropless purification and uses recovered argon gas immediately before purification to vaporize (high purity) liquid argon, which is the source of the atmospheric gas. Economic efficiency has been further improved by utilizing the cold energy of liquid nitrogen, and if necessary, the cold energy of inexpensive liquid nitrogen.

According to the present invention, the purified argon can be widely used as other atmospheric gases even though it does not become the highly purified argon gas of SIXNA.

That is, the present invention uses a filter to remove dust in the exhausted recovered gas using high-purity argon gas as an inert atmosphere.
Next, some impurities are removed by pressure adsorption and/or thermal adsorption, followed by liquefaction with liquid argon and/or liquid nitrogen, and finally low-temperature dropless purification to recover high-purity argon in liquid or gas form. The present invention relates to a method for recovering argon gas for atmospheric use.

(Function) The argon gas used as an inert atmosphere during the production of silicon semiconductor single crystals contains 8 iog, oil, and moisture.

CO2, Ohiro, Nz are included as impurities,
The purity is on the order of 97, of which 8 io! and oil are first removed by a filter and then the HI3, cow is removed by known pressure swing adsorption and/or heat swing adsorption. But ox,
The recovered argon gas, which still contains Ns, is liquefied before being subjected to the next low-temperature distillation. If the cold energy of argon alone is still insufficient, it can be supplemented with the cold energy of liquid nitrogen.

Conversely, it is also possible to liquefy using only the cold heat of liquid nitrogen. The cold energy of the liquid argon and/or nitrogen is obtained by vaporizing the liquid argon and/or nitrogen through the vaporizer of the recovered argon gas liquefier. The liquefied recovered argon is then subjected to low-temperature distillation and has the lowest boiling point, N-weight (B, P-19
5,8℃) first, followed by Ar (B, P-185,
7b), then 0! (B, P - 183°C), and the purity of argon reaches five nines.

A flowchart showing the implementation of the above recovery method is shown in FIG. It can be easily understood that each of the above-mentioned processes is indicated by a letter in each block of the flowchart. The vaporizer used between the high-purity liquid argon and the Si semiconductor manufacturing equipment is a normal vaporizer that collects the vaporized high-purity argon gas and a portion of the high-purity liquid argon as described above. High-purity argon gas vaporized through a vaporizer (not shown) of an argon gas liquefier is combined with the argon gas and sent to the Si semiconductor manufacturing equipment. Since the recovered liquid argon has a purity of the five-nine order, it cannot be used as is for Si semiconductor devices that require six-nine-order purity, but is instead applied to other atmospheres. Further, the recovered liquid argon may be appropriately vaporized and stored as recovered gaseous argon.

(Effects of the Invention) As described above, the present invention liquefies recovered argon gas that has been crudely purified by filtering and adsorption, and then liquefies the recovered argon gas by low-temperature distillation. , 0. This method obtains five-nine-order recovered liquid argon or gaseous argon by fractionating the respective amounts of recovered argon, so although the final purity is lower than that of the conventional purification method using a titanium getter, it is economically advantageous to recover argon. It becomes possible to regenerate the gas, and in this case, if the above liquefaction is carried out using the cold heat of vaporizing liquid argon or liquid nitrogen, it will be noteworthy in terms of cost. This invention played a role in recycling.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for implementing the invention. one or more one

Claims (1)

[Claims] 1. Using a filter to remove dust in the exhausted recovered gas using high-purity argon gas as an inert atmosphere, and then removing some of the impurities by pressure adsorption and/or thermal adsorption,
A method for recovering atmospheric argon gas, which comprises subsequently liquefying it with liquid argon and/or liquid nitrogen, and finally recovering high-purity argon in liquid or gaseous form through low-temperature distillation purification.