Applications - Backside Metals (BSM)
A backside metal (BSM) is commonly used in standard bipolar and high performance power and discrete devices. The BSM stack requires excellent adhesion and a low stress on the silicon. High intrinsic stress in thin films can cause adhesion problems and compromise long-term reliability.

A typical BSM process sequence starts with deposition of an adhesion layer(s). The adhesion layer(s) is used to promote the bonding of the underlying semiconductor surfaces. A clean and oxide free surfaces is critical to promote inter-atomic bonding to form low thermal-impedance layer and often times good ohmic contact. Subsequently, barrier layer or wetting layer is deposited to promote effective wetting and good bonding with solder. The layer also needs to have low thermal conductance and stress to satisfy mechanical reliability requirements. Subsequently, an oxidation-resistance layer is deposited to seal the surface from environmental impact.