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Proceedings Paper

Thick resist alignment technology for MEMS and advanced packaging
Author(s): Chad Brubaker; Bernhard Wieder; Paul Lindner
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Paper Abstract

The number of lithographic applications that require ultra-thick layers of resist (>50 um) is rapidly increasing. One field in which this requirement is growing is in the field of MEMS (Micro-Electro-Mechanical-Systems) and MOEMS (Micro-Optical-Electro-Mechanical-Systems). A second is in the realm of wafer-level, advanced chip scale packaging1. For both of these fields, ultra-thick, as well as high aspect ratio, photolithography is an absolute requirement for device processing. The process optimization required to obtain high aspect ratio structures in these ultra-thick photoresist films is extremely challenging. Alignment accuracy is a critical factor in this process. Because of the thick films involved, the alignment keys between mask and wafer could be separated by more than a hundred microns. Standard microscope and objectives have limited depth of focus. Once resist thickness and separation gap exceeds the depth of focus, alignment accuracy suffers from image quality between substrate and mask. Various special microscope options have been developed for alignment of very thick resist. However, most of these processes suffered from one failing or another. This paper addresses a new method to perform true large gap alignment for these applications. True large gap alignment systems overcome these limitations by using identical focal planes for mask and wafer alignment key. Both alignment keys are focused clearly with resist thickness and separation gap of up to 500 um. This paper will present detailed experimental results of alignment accuracy obtained at different thicknesses of photoresist in a contact/proximity production aligner system.

Paper Details

Date Published: 16 June 2003
PDF: 7 pages
Proc. SPIE 5037, Emerging Lithographic Technologies VII, (16 June 2003); doi: 10.1117/12.484736
Show Author Affiliations
Chad Brubaker, EV Group US Inc. (United States)
Bernhard Wieder, EV Group US Inc. (United States)
Paul Lindner, EV Group Inc. (Austria)

Published in SPIE Proceedings Vol. 5037:
Emerging Lithographic Technologies VII
Roxann L. Engelstad, Editor(s)

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