Effect of Glass Materials on Joints in Anodic Bonding of Glass to Silicon

Borosilicate glass is often used as a material during the anodic bonding process because the thermal expansion coefficient of glass is very close to that of silicon. However, in recent years, a new chemical composition of glass was developed as a joinable glass at lower bonding temperature. To ensure the reliability of anodic bonding joints of the new glass to silicon, it is necessary to clarify the influence of bonding conditions and the comparison of performance of anodic bonding joints of new glass and borosilicate glasses. In this study, the effect of the bonding conditions on the tensile strength and thickness of the reaction layer and bonding charge density of anodic bonding joint of three glasses (TEMPAX, PYREX, SW-YY) to silicon was comparatively investigated. The main results obtained are as follows. The anodic bonding joints using SW-YY was bonded at a lower bonding temperature than TEMPAX and PYREX. Under the same bonding conditions, thickness of the reaction layer on joints of SW-YY to silicon was the thickest of all. Independent of glasses, the increase in the bonding charge density resulted in stabilized tensile strength and the fracture modes changed to glass fractures. Thus, measuring the bonding charge density during the anodic bonding process helped to clarify the effects of the bonding conditions on the anodic bonding joints of glass to silicon.