Ultrasonic vibration used for improving interfacial adhesion strength between metal substrate and high-aspect-ratio thick SU-8 photoresist mould

Liqun Du; Ke Zhai; Xiaojun Li; Shuangjie Liu; Yousheng Tao

doi:10.1016/j.ultras.2020.106100

Ultrasonic vibration used for improving interfacial adhesion strength between metal substrate and high-aspect-ratio thick SU-8 photoresist mould

Ultrasonics. 2020 Apr:103:106100. doi: 10.1016/j.ultras.2020.106100. Epub 2020 Jan 31.

Authors

Liqun Du¹, Ke Zhai², Xiaojun Li², Shuangjie Liu³, Yousheng Tao²

Affiliations

¹ Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian 116024, China. Electronic address: duliqun@dlut.edu.cn.
² Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian 116024, China.
³ School of Equipment Engineering, Shenyang Ligong University, Shenyang 110016, China.

PMID: 32044567
DOI: 10.1016/j.ultras.2020.106100

Abstract

The fabrication of high-aspect-ratio metal micro device on metal substrate is largely limited by its poor interfacial adhesion strength between metal substrate and thick SU-8 photoresist mould. In this paper, ultrasonic treatment is introduced to improve the interfacial adhesion strength between metal substrate and a high-aspect-ratio inertial switch SU-8 mould. Firstly, a device for ultrasonic treatment was developed, ultrasonic vibration is applied to SU-8 film after post exposure baking in order to improve the interfacial adhesion strength. Compared with the traditional one, SU-8 photoresist mould treated by ultrasonic vibration can effectively improve the interfacial adhesion strength. After 90 min cavitation erosion test, SU-8 film treated by ultrasonic vibration remains 34.4% relative to nothing left of the SU-8 film without ultrasonic treatment. Besides, the mechanisms of ultrasonic treatment on improving interfacial adhesion strength are investigated. Finally, an inertial switch is successfully fabricated on metallic substrate with the ultrasonic treated SU-8 photoresist mould.

Keywords: High-aspect-ratio; Inertial switch; Interfacial adhesion strength; SU-8 photoresist mould; Ultrasonic treatment.