A Post-Complementary Metal Oxide Semiconductor Formation Process of High-Adhesiveness SU-8 Structures for Reliable Fabrication of Integrated Microelectromechanical System Sensors

摘要

In this study, a post CMOS reliable formation process for high-aspect-ratio SU-8 structures on integrated circuits is newly proposed. Enhancement of SU-8 adhesiveness is realized by forming a thin SU-8 layer (called an adhesive layer) over the surface of the circuit before the SU-8 structures are formed. Improvement of adhesion of thick SU-8 structures is very important to guaranty the reliability of MEMS microsensors. The negative effect of the adhesive SU-8 layer on the mechanical properties of silicon movable structures has been estimated and discussed with simple analytical formulae. Also, the effect of the adhesive layer on the silicon substrate has been demonstrated with test structure patterns. On the basis of the developed technique, a tactile sensor device has been successfully fabricated as an example of the application of this technique.