Wetting of silicon single crystal by silver and tin, and their interfaces

Abstract

A study of wetting of silicon single crystals and electrode metals was undertaken to investigate the wetting mechanisms and to clarify the interfaces between the silicon wafer and silver and tin. The experiments were performed using a high-temperature surface tension measuring equipment in vacuum and 5% H₂/Ar atmospheres (10⁵ Pa). The contact angles were measured by taking photographs through a telescope during the wetting experiment. Silicon was wetted by silver with a contact angle of 42°, whereas it was not wetted by tin in vacuum and in the 5% H₂/Ar atmosphere. However, heat treatment of silicon in vacuum or 5% H₂/Ar atmosphere prior to the wetting experiment reduced the contact angles compared to the cases with no heat treatment. The bonding interfaces between silicon and silver are also discussed.