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Improving Etch Characteristics of Oxides

IP.com Disclosure Number: IPCOM000095319D
Original Publication Date: 1965-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Krongelb, S: AUTHOR

Abstract

The techniques are for eliminating undercutting in thick oxide patterns. Thus, substantially vertical edges to patterns etched in the oxide are realized.

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Improving Etch Characteristics of Oxides

The techniques are for eliminating undercutting in thick oxide patterns. Thus, substantially vertical edges to patterns etched in the oxide are realized.

In etching very fine patterns, particularly on thick oxides, undercutting,
i.e.,lateral etching, degrades the patterns by creating sloping sides. This is because the portion of the oxide nearest the oxide surface is subject to lateral etching for a longer time than the lower regions of the oxide.

To achieve a more vertical edge to the pattern, the oxide is made with an etch rate which varies as a function of thickness. The etch rate is smallest near the top surface where the time for lateral etching is longest. The desired variable etch rate can be achieved in several ways.

For example, with pyrolytic SiO(2), the oxide can be aged in a moist atmosphere for a controlled length of time. Such aging results in a reduced etch rate and the depth to which the oxide is affected appears to depend on time. The deposition conditions can be varied during oxide formation. For example, phosphorous can be incorporated in gradually decreasing amounts as the oxide forms since layers con containing P have higher etch rates. The temperature of the system can be increased during the course of deposition, thus making use of the fact that the etch rate is lower when oxides are formed at higher temperature. The ethyl silicate concentration can be reduced during the course of deposition thus mak...