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Establishing End Point during Delineation Process

IP.com Disclosure Number: IPCOM000080158D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 57K

Publishing Venue

IBM

Related People

Hoekstra, JP: AUTHOR

Abstract

In order to properly delineate an insulating pattern by chemical etching, it is important to establish the moment when the total material desired to be removed by etching has been so removed. If the etch process is extended beyond this moment, there results an undercutting or lack of control of the pattern size.

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Establishing End Point during Delineation Process

In order to properly delineate an insulating pattern by chemical etching, it is important to establish the moment when the total material desired to be removed by etching has been so removed. If the etch process is extended beyond this moment, there results an undercutting or lack of control of the pattern size.

Heretofore, techniques which have been available for determining whether the precise amount of oxide has been chemically etched are the following:
A. Visual inspection with a microscope. This method relies upon

apparent color changes of the oxide as the oxide thins during the

etch process.
B. Depending upon the initial surface state of the surface upon

which etching is taken place, such as the

surface of a semiconductor, such surface is checked for a

change therein from a hydrophilic to a

hydrophobic state, or vice versa.
C. An electrical measurement upon the surface. A germanium or

silicon surface if a semiconductor surface

is involved. If oxide is present, no ohmic contact can be

made thereto. By repeatedly testing for the

achieving of such contact, the attaining

of the etch point can be determined.

It has been found that the three methods, viz., A, B and C outlined above, are unreliable, operator dependent and unable to be performed in situ. In particular, method C is dependent upon contact pressure, thereby making it difficult to interpret any results obtained thereby.

In the disclosure set forth herein, there is described a method for electrolytically determining in situ the end point in oxide etching. The method can be fully automated and, therefore, each substrate to be etched can be individually examined regardless of oxide thickness and other variations, such as temperature of the etching environment, etc., effecting the etch rate. The described method can electrically determine in situ when the oxide is removed. Problems which are confronted in the known methods, as described hereinabove, such as undercutting, overetching, lack of dimensional control, lifting of photoresist, effects of temperature changes in the etching process, and varying film thicknesses can be substantially minimized and in many situations completely eliminated. The availability of this end-point detection method enables automation, which has not been possible with known techniques.

Prior to considering the described method, it is to be realized that, heretofore, the information that has been required as necessary to determine the total etch time for removing an oxide on a substrate surface has been derived by the etching of a single substrate unit, i.e., a wafer, for example, and then examining the etched pattern with one of the three known methods as described hereinabove. The information derived from such examination is then employed

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as a criterion for etching a large batch of wafers. It is readily apparent that not only do the characteristics of wafers differ from each other,...