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Browse Prior Art Database

Self-Developing Resists for Direct-Viewing Alignment

IP.com Disclosure Number: IPCOM000042235D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Chao, VW: AUTHOR [+5]

Abstract

This article relates generally to photoresist and more particularly to self-developing resists which produce a relief image when exposed to photon, ion or electron beams of appropriate energy. The self-developing material described in this article produces a relief image during exposure to a photon, electron or ion beam of a suitable energy. After exposure, a wafer coated with such a self-developing material can readily be examined with a microscope illuminated with light in a non-exposing spectrum. Using this approach, there is no longer any necessity for using wet chemicals on the mask aligner. In addition to single layer usage on test wafers, the self-developing resist can be coated on a conventional resist on device wafers, so that alignment calibration, for example, can be done on a wafer-to-wafer basis.

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Self-Developing Resists for Direct-Viewing Alignment

This article relates generally to photoresist and more particularly to self- developing resists which produce a relief image when exposed to photon, ion or electron beams of appropriate energy. The self-developing material described in this article produces a relief image during exposure to a photon, electron or ion beam of a suitable energy. After exposure, a wafer coated with such a self- developing material can readily be examined with a microscope illuminated with light in a non-exposing spectrum. Using this approach, there is no longer any necessity for using wet chemicals on the mask aligner. In addition to single layer usage on test wafers, the self-developing resist can be coated on a conventional resist on device wafers, so that alignment calibration, for example, can be done on a wafer-to-wafer basis. For polychromatic imaging systems such as a reflective lens system or a proximity printer, the top layer should be opaque in the spectral region to which the bottom layer will be exposed. The top layer is first exposed for self-development. The wafer is then examined for alignment accuracy and may be moved to a correctly aligned position according to the reading. The top layer is now removed with a blanket exposure without affecting the bottom layer consisting of a conventional resist. The wafer is then exposed as usual to obtain a correctly aligned image. As an example, a self-developing resist sensitive to wavelengths above 260 nm can be used in conjunction with polymethyl methacrylate (PMMA) as the bottom layer. PMMA, being sensitive to wavelengths below 260 nm, remains completely unaffected during exposure, examination, and removal of the top layer. When a refractive projection aligner is used, the exposure wavelength is limited to only one or two lines. A triple layer structure is used to facilitate wafer-to-wafer alignment calibration on device wafers. The top and middle...