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

The most critical issues of interfacial contact between CVD (chemical vapor deposition) W and Al-Cu-Si in submicron vias using SiH ₄ 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^-9 Ωcm ², 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