Novel lithography process for extreme deep trench by using laminated negative dry film resist

Abstract

For the fabrication of MEMS(micro electro mechanical system) devices such as HAR(high-aspect-ratio) microstructures with an extreme deep trench, a novel lithography method was newly developed in this study. In the case of the deep trench, the liquid photoresist is not or very thinly coated at edge parts of the trench boundary. And, if a very thick resist coated, it is nearly impossible to develop the photoresist in the deep trench. To solve these problems, it is capped by laminating negative DFR(dry film resist) film on the cavity opening of the deep trench. Then positive photoresist is conventionally coated and patterned by the same photomask for the deep trench. To apply electric signals from outside to inside of the trench, aluminum on sidewall and bottom of the deep trench was successfully patterned by newly developed lithography method.