Wet clean study on cobalt silicide and contact processes

Cobalt silicide has been used in ULSI process from 180nm to 90nm node and beyond. As a conventional self-aligned silicide process procedure [1], cobalt is firstly deposited on cleaned silicon surface, then annealed (450~600° C) to produce Co
₂
Si or CoSi with resistivity around 100~150Ω cm. A Hydrochloric and Hydrogen Peroxide Mixture (HPM) was used to strip the unreacted cobalt film from dielectric layer, e.g. SiO
₂
or SiN of gate spacer and salicide block). The following wet clean and second anneal (750~900°C are to prevent metal contamination and to transfer silicide as low resistivity CoSi
₂
(14-20 Ω cm), respectively. Furthermore, ILD gap fill, CMP and contact-hole etch processes are implemented for contact formation.