Low-resistance submicron CVD W interlevel via plugs on Al-Cu-Si

Abstract

The most critical issues of interfacial contact between CVD (chemical vapor deposition) W and Al-Cu-Si in submicron vias using SiH4 and H2 reduction of WF6 are addressed. The effect of process parameters of selective CVD W, especially when deposited by SiH4-based chemistry, on contact resistance to Al-Cu-Si is evaluated for the first time. It is observed that out of all process parameters the deposition temperature affects the contact resistance the most. As the deposition temperature increases, the contact resistance of the stack W/Al-Cu-Si decreases. Specific resistivities, as low as 3-5× 10-9Ωcm2, are realized at turret temperatures of 550°C. On the other hand, the contact resistances are relatively unaffected by partial pressures of SiH4 or WF6. As a result the growth rates which are dependent on partial pressures do not control the contact resistances. Phosphoric-chromic and buffered hydrofluoric acid cleanings combined with higher deposition temperatures yield relatively superior contact resistance compared to other cleaning techniques.