Effect Of Ultrasonic Treatment On Adhesion Between SU-8Photoresist And Metal Substrate

SU-8photoresist is a negative, epoxy-type, near UV photoresist and is commonly used in micro electro mechanical systems (MEMS) and other thick resist application fields. However, poor adhesion strength between SU-8photoresist and metal substrate makes it difficult to bind, even contributes to the lithography failure. This significantly restricts the improvement of image resolution and depth-to-width ratio. At present, the researches on the adhesion strength between SU-8photoresist and metal substrate mostly focus on the improvement and the optimization of the process parameters or the design of the mask, or chemical modification.In this paper, ultrasonic treatment technology is adopted for the enhancement of the adhesion property between SU-8photoresist and metal substrate and the effect of ultrasonic input power on interface adhesion strength is investigated. The advantage of the ultrasonic treatment method is that it can effectively decrease the experiment amounts, and then reduce time and cost.The effect mechanism of ultrasonic treatment technology on adhesion between SU-8photoresist and metal substrate is discussed. The analysis result shows that the internal stress in SU-8photoresist layer is the main factor of reducing the adhesion strength between SU-8photoresist and metal substrate. Ultrasonic treatment technology can decrease the internal stress by reducing the defects cross-linked network in SU-8photoresist; therefore, adhesion strength between SU-8photoresist and metal substrate is improved.In ultrasonic treatment experiments, the effect of ultrasonic treatment on adhesion between SU-8photoresist and metal substrate is investigated. The adhesion property between photoresist layer and substrate in different ultrasonic input power is analyzed and the interface adhesion strengths are quantitatively measured by scratch test. The experimental results show that ultrasonic treatment technology can effectively enhance the adhesion strength between SU-8photoresist and metal substrate and the adhesion strength increases with the input power.