Formation of Reliable Al-Si/Si Contacts by Chemical Oxidation of the Contact Area

As feature sizes become smaller than 2 μm, and also contact sizes cross this limit, the resistance and reliability of AlSi to Si contacts are limited by silicon recrystallization from the AlSi into the contacts. This problem, often referred to as Si Solid Phase Epitaxy, Si-SPE, can be both a yield limiter and a reliability hazard. This can be prevented by applying a simple chemical oxidation just prior to the metallization. Such a cheap, simple, reliable and reproducible step completely inhibits preferential Si recrystallization in contacts to Si by modification of the surface. Contact resistances can be kept in the range of diffusion sheet resistances, with a very small spread, and VLSI device yield and performance can be made more reproducible and reliable.