On-site generation of ultra-high-purity buffered-hf and ammonium fluoride

Abstract

Provided is a novel method and system for preparing ultra-high-purity buffered-hydrofluoric acid or ammonium fluoride controlled concentration. The method comprises bubbling purified ammonia vapor into ultra-pure hydrofluoric acid. The inventive method and system can be used as an on-site subsystem in a semiconductor device fabrication facility for supplying the buffered-hydrofluoric acid and ammonium fluoride to points of use in the semiconductor device fabrication facility.

Description

[0001] The application is a continuation-in-part of copending application Ser. No. 08 / 674,130, filed on Jul. 1, 1996, which document is herein incorporated by reference, which application in turn claims the benefit of priority of U.S. Provisional Application Ser. No. 60 / 018,104, filed on Jul. 7, 1995. The present application also claims benefit of PCT / US96 / 10388, filed on Jun. 5, 1996, which documents are herein incorporated by reference.[0002] 1. Field of the Invention[0003] The present invention relates to a method and system for producing ultra-high-purity buffered-hydrofluoric acid (buffered-HF or BHF) or ultra-high-purity ammonium fluoride (NH.sub.4F). The invention has particular applicability in semiconductor fabrication for providing ultra-high-purity materials to a semiconductor manufacturing operation.[0004] 2. Description of the Related Art[0005] a. Contamination Control[0006] Contamination is generally an overwhelmingly important concern in integrated circuit (IC) manufa...

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Benefits of technology

0030] To meet the requirements of the semiconductor processing industry and to overcome the disadvantages of the related art, it is an object of the present invention to provide novel methods and systems for the preparation of ultra-high-purity buffered-hydrofluoric acid and ultra-high-purity ammonium fluoride in which the hydrofluoric acid and ammonium fluoride can

Problems solved by technology

The cost of a new IC wafer fabrication facility is typically more than one billion dollars ($1,000,000,000).

One important and basic source of contamination in semiconductor fabrication is impurities in the process chemicals.

Since the cleanup steps are performed so frequently in and are so critical to IC fabrication, contamination due to cleanup chemistry is very undesirable.

While plasma etching has many attractive capabilities, it is not adequate for use in cleanup processes.

There is simply no available chemistry with plasma etching to remove some of the most undesirable impurities, such as gold.

As a result, plasma etching will not remove such contaminants from the wafer surface.

Moreover, since the liquid cleanup steps are directly followed by high-temperature processes, contaminants on the wafer surface tend to be driven (i.e., diffused) into the wafer.

Wet processing has a major drawback insofar as ionic contamination is concerned.

However, many other species act as electrically active dopants, and are highly undesirable contaminants.

These contaminants can have deleterious effects on the IC devices, such as increased junction leakage at concentrations well below 10.sup.13 cm.sup.-3.

Moreover, some less desirable contaminants segregate into the silicon substrate.

Moreover,

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