Novel Photolithography Yield-Enhancement Technique: Megasonic-Enhanced Development

Abstract

MEMS-specific processes required to adapt standard IC manufacturing technologies in order to accommodate its custom requirements. Photolithography is one of the standard techniques which had to adapt particularly to the use of thick resists needed for high aspect ratio features fabrication. In order to work with resist thickness varying between few tens and up to few hundreds of micrometers the standard process flow had to be changed to multiple-layers coating, customized (and very long) baking times, special exposure techniques and development. This paper introduces a megasonic-enhanced method used for developing resists. In case of MEMS applications this method brings not only a major yield improvement (better quality features) but also a major decrease of process time.

Megasonic Enhanced Photo Resist Removal Using Unique Solvent Free Phase-Fluids on an Advanced Single Wafer Resist Processing System

“…The initial application of megasonic enhanced processing was targeted to particulate removal as the ability of the cavitation to move micro and nano particles to the macro stream and away from the substrate surface was critical to cleaning performance. Later applications of proximity Megasonics to photo resist and high aspect ratio processes in single wafer configurations added both uniformity and accelerated process times (increased throughput) (5). The rapid exchange of fluid below the conventional boundary layer accelerated the conventional etch/solvent/develop processes by eliminated the diffusion layer leading to much shorter process times and process fluid usage.…”

Unique Applications of Megasonic Energy to MEMS Single Substrate Wet Processes

“…The main wet process in microlithography consists of development of the exposed pattern, sometimes in very thick PR. (1) Other wet steps are used for surface cleaning as well as for the eventual removal or stripping of the PR used for interim masking (e.g. in lift-off processes).…”