On-site ammonia purification for semiconductor manufacture

• US 6,001,223 A
• Filed: 03/10/1998
• Issued: 12/14/1999
• Est. Priority Date: 07/07/1995
• Status: Expired due to Fees

• Current Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Original Assignee: Air Liquide America LP (Mitsubishi Chemical Group Corp.)
• Inventors: Hoffman, Joe G., Clark, R. Scot
• Primary Examiner(s): BHAT, NINA NMN
• Application Number:
  US09/037,522
• Time in Patent Office: 644 Days
• Field of Search: 203/12, 203/40, 203/42, 423/237, 423/238, 423/352, 202/161, 202/172, 202/200, 95/232, 95/226
• US Class Current: 203/12
• CPC Class Codes: C01C 1/024 Purification

Abstract

Highly purified ammonia for use in semiconductor manufacturing is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Claims

1. A method for the preparation of ultra-high-purity ammonia, said method comprising:

(a) drawing ammonia gas from a vapor space above liquid ammonia in an ammonia-containing reservoir;

(b) passing said ammonia gas through a unit whereby said ammonia gas is contacted with an aqueous solution of ammonia in deionized water, thereby purifying said ammonia gas; and

(c) recovering said purified ammonia gas emerging from said unit.

2. A method in accordance with claim 1, further comprising dissolving said ammonia gas emerging from said scrubber in purified water.

3. A method in accordance with claim 1, further comprising passing said ammonia gas through a distillation column for further purification.

4. A method in accordance with claim 1, further comprising the additional step of:

(b'"'"') passing said purified ammonia gas from said unit through a distillation column for further purification, and dissolving said ammonia gas emerging from said distillation column in purified water.

5. A method in accordance with claim 4, in which steps (b) and (b'"'"') are conducted at a temperature ranging from about 15°

to about 35°

C.

6. A method in accordance with claim 4, in which steps (b) and (b'"'"') are conducted at a temperature ranging from about 15°

to about 35°

C. and at a pressure of from about atmospheric pressure to about 30 psi above atmospheric pressure.

7. A method in accordance with claim 1, in which step (b) is conducted at a temperature ranging from about 10°

to about 50°

C.

8. A method in accordance with claim 7, in which step (b) is conducted at a temperature ranging from about 15°

to about 35°

C.

9. A method in accordance with claim 1, in which step (b) is conducted at a temperature ranging from about 15°

to about 35°

C. and at a pressure of from about atmospheric pressure to about 30 psi above atmospheric pressure.