Point-of-use ammonia purification for electronic component manufacture

• US 6,015,477 A
• Filed: 05/22/1998
• Issued: 01/18/2000
• Est. Priority Date: 01/07/1994
• 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:
  US09/083,184
• Time in Patent Office: 606 Days
• Field of Search: 203/13, 203/46, 423/484, 423/488, 202/158, 202/161, 202/172, 202/200, 95/226, 95/230, 437/250
• US Class Current: 203/13
• CPC Class Codes: C01B 7/0706 of hydrogen chloride
• CPC Class Codes: C01B 7/0712 by distillation
• CPC Class Codes: C01B 7/0731 by extraction
• CPC Class Codes: C01B 7/195 Separation; Purification
• CPC Class Codes: C01B 7/196 by distillation
• CPC Class Codes: C01B 7/198 by solid ion-exchangers
• CPC Class Codes: C01C 1/024 Purification
• CPC Class Codes: C01C 1/162 Ammonium fluoride
• CPC Class Codes: H01L 21/67023 for general liquid treatment, e.g. etching followed by cleaning
• CPC Class Codes: Y10S 203/17 Saline water conversion

Abstract

Highly purified ammonia for use in processes for the production of high-precision electronic components 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 scrubber whereby said ammonia gas is contacted with an aqueous solution of ammonia in deionized water; and

(c) recovering said ammonia gas emerging from said scrubber.

2. The method according to claim 1, further comprising purifying the ammonia gas in a distillation unit downstream from said scrubber.

3. The method according to claim 1, further comprising introducing the recovered ammonia gas into a chemical vapor deposition system.

4. The method according to claim 3, further comprising purifying the ammonia gas in a distillation unit downstream from said scrubber.

5. The method according to claim 4, further comprising dehydrating the ammonia gas emerging from said scrubber prior to said purification in said distillation unit.

6. The method according to claim 4, further comprising dissolving said ammonia gas emerging from said scrubber in purified water to form an aqueous solution.

7. The method according to claim 6, further comprising combining said aqueous solution with aqueous hydrogen peroxide.

8. The method according to claim 1, further comprising bubbling said ammonia gas emerging from said scrubber into an aqueous hydrogen peroxide solution.

9. The method according to claim 1, wherein the ammonia produced has less than 100 parts per trillion of any metallic impurity.

10. The method according to claim 1, further comprising directly applying the ammonia or an aqueous solution formed from the ammonia to a semiconductor substrate.