Two New Methods to Improve the Lithography Precision for SU-8 Photoresist on Glass Substrate

This paper introduces two novel approaches to effectively eliminate the influence of scattering light from the wafer chuck and enhance the lithography precision of SU-8 photoresist on glass substrate. The first method is based on the fact that Si wafer can partially reflect ultraviolet (UV) light, and the second one employs materials that have low optical transparency and can achieve complete absorption of the near-UV light penetrating through the SU-8 photoresist and the glass substrate. The SU-8 structures produced by these two methods have much better profiles than those fabricated by the conventional process, and the linewidth deviation is smaller than 1 μm. The two routines have advantages of simplicity and low cost, therefore are applicable to batch fabrication, and can significantly enhance the performance of microelectromechanical systems devices. These two methods were adopted to perform SU-8-based low-temperature bonding at wafer level and with high precision. The bonding shear strengths reach 2-26 MPa when the bonding temperature varied from 60°C to 1401°C.