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Removal of Mobile Sodium from Silicon Dioxide

IP.com Disclosure Number: IPCOM000072868D
Original Publication Date: 1970-Oct-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Barile, CA: AUTHOR [+2]

Abstract

The profile of Na/+/ distribution in thermally oxidized silicon shows a buildup of Na/+/ at both the Si-SiO(2) interface and air-SiO(2) interface. By using a sequence of etching and annealing steps, the concentration of mobile sodium is decreased at the interfaces.

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Removal of Mobile Sodium from Silicon Dioxide

The profile of Na/+/ distribution in thermally oxidized silicon shows a buildup of Na/+/ at both the Si-SiO(2) interface and air-SiO(2) interface. By using a sequence of etching and annealing steps, the concentration of mobile sodium is decreased at the interfaces.

Much of the electrically mobile sodium is found at the air-SiO(2) surface. This mobile Na+ is removed by etching away about 200 angstroms of SiO(2). The Na+ remaining in the SiO(2) is redistributed by annealing in an inert gas at a high temperature (e.g. 500 degrees C). By re-etching the SiO(2) surface, the total mobile Na+ in the SiO(2) is further reduced.

This etch-anneal-etch cycle may be modified and used with sputtered or pyrolytic SiO(2). To obtain an initial Na+ distribution as described above, an anneal step may be needed first. The resulting treatments involves an anneal- etch-anneal-etch cycle.

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