Low-Temperature Parylene-Based Adhesive Bonding Technology for 150 and 200 mm Wafers for Fully Biocompatible and Highly Reliable Microsystems

Abstract

Wafer bonding is a crucial process for fabricating microsystems. Within this study, the polymer parylene was used to establish a low-temperature adhesive wafer bonding process for wafers of 150 and 200 mm diameters. The bonding process was investigated for silicon and glass wafers with different additional coatings including silicon dioxide, silicon nitride, aluminum, and parylene C. Important process parameters such as bonding temperature and time were also investigated and the parylene adhesive was analyzed in detail with respect to its dimensions and type. The performance of the parylene bonding was characterized in different aspects, including mechanical tests, cross-sectional scanning electron microscopy, infrared light transmission, and different hermeticity tests. The reliability of the parylene bonded compounds was also investigated with respect to constant loading, mechanical shocking, and thermal cycling. As a result, the parylene bonding is feasible with various materials and shows high tensile and shear strengths of up to 35 MPa and 80 MPa, respectively. Hermeticity was excellent, with a helium leakage rate lower than 10‒7 mbar∙l s−1. The parylene bonded compounds were proven to feature high reliability. Finally, application of the superior properties of the parylene bonding was demonstrated with respect to the fabrication of different three-dimensional structures.