Browse Prior Art Database

Removal of Colloidal Silicon From Hydrofluoric Acid

IP.com Disclosure Number: IPCOM000040454D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Fury, MA: AUTHOR

Abstract

This technique allows chemical removal of colloidal SiF6-- from HF, which colloids can impair semiconductor manufacturability by obstructing open Si contacts. A significant concern in the use of wet chemical processing in semiconductor manufacturing is the removal of particulates and chemical contaminants from the process solutions. In particular, colloidal fluorosilicic acid (H2SiF6) in hydrofluoric acid (HF) becomes critical as device geometries reach 1 micron and below. HF is typically used to remove SiO2 and expose bare Si contact areas for subsequent processing. The exposed Si is very chemically active and will adsorb the charged colloidal species. Removal of the colloids by rinsing is very difficult, and subsequent chemical removal may be required, although such is undesirable in most hot process precleaning schemes.

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Removal of Colloidal Silicon From Hydrofluoric Acid

This technique allows chemical removal of colloidal SiF6-- from HF, which colloids can impair semiconductor manufacturability by obstructing open Si contacts. A significant concern in the use of wet chemical processing in semiconductor manufacturing is the removal of particulates and chemical contaminants from the process solutions.

In particular, colloidal fluorosilicic acid (H2SiF6) in hydrofluoric acid (HF) becomes critical as device geometries reach 1 micron and below. HF is typically used to remove SiO2 and expose bare Si contact areas for subsequent processing. The exposed Si is very chemically active and will adsorb the charged colloidal species. Removal of the colloids by rinsing is very difficult, and subsequent chemical removal may be required, although such is undesirable in most hot process precleaning schemes. Removal of the SiF6-- by filtration is impossible due to: 1.the small size (1.10 nm) of the colloids, 2. lack of available ultrafilters (to 1 nm), which

are chemically compatible with HF, and

3. the gel nature of the colloids which allows them

to squeeze through filters if a significant pressure

drop develops. The method here provides a novel alternative to filtration for removing SiF6-- from HF in semiconductor processing.

It is known (see U.S. Patent 4,125,594) that weak anion exchange resins can remove SiF6-- very effectively from solutions of up to 10% by weight HF, (concentrated HF is 49%). The applications in the reference are significantly different from those disclosed here. As an example, one embodiment might be the incorporation of an inert containment housing in an HF filtration f...