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Method of Switching Fields During Wafer Exposure

IP.com Disclosure Number: IPCOM000080986D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Moritz, H: AUTHOR [+2]

Abstract

With the projection exposure method the fields are smaller than a wafer. For applying a continuous structure to a full wafer, the fields have to be switched. This has the disadvantage that the quality of the switching of the fields becomes visible, only after the photoresist on the wafer has been developed. In order to reduce the switching tolerances, the table movement must be as accurate as possible. In addition, the image scale during projection has to be strictly adhered to.

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Method of Switching Fields During Wafer Exposure

With the projection exposure method the fields are smaller than a wafer. For applying a continuous structure to a full wafer, the fields have to be switched. This has the disadvantage that the quality of the switching of the fields becomes visible, only after the photoresist on the wafer has been developed. In order to reduce the switching tolerances, the table movement must be as accurate as possible. In addition, the image scale during projection has to be strictly adhered to.

The method employed consists in making the structure exposed in a field visible, and in optimally adjusting the neighboring fields by direct optical control. This leads to inconsistencies in the table movement and the image scale being compensated, to critical field boundaries being adapted at the expense of noncritical ones, and to trapezoidal image errors being considered.

The method is based on the effect that exposed resist differs from unexposed resist, this difference being made optically visible. 1st Possibility.

The unexposed resist absorbs light of such wavelengths which expose the resist more intensively than the exposed resist. If the intensities used are low, the exposed structure becomes visible without fully exposing the resist. The adjusting time is a function of the exposure intensity. 2nd Possibility.

The refractive index and/or the thickness of the unexposed resist is other than that of the exposed resist. This effect is m...