Characteristics of a poly-silicon contact plug technology

Summary form only given. Polysilicon plug technology takes advantage of the desirable properties of LPCVD polysilicon (i.e. conformal step coverage, smooth texture, good etchability) to planarize submicron contacts. In addition, sputtered and CVD barrier metal layers are utilized to ensure good ohmic contact and maintain a low-resistance plug. It is shown that the polysilicon plugs completely fill the contact holes and provide a nearly planar surface for the sputtered aluminum. In addition, the RIS+CVD TiN barrier is highly conformal for all observed contact sizes. The specific contact resistance to n⁺ and p ⁺ doped silicon was found to be less than 5×100^-7 Ω-cm². To titanium silicide, the contact resistance dropped to below 2×10^-8 Ω-cm² . The composite resistivity of the polysilicon plug plus CVD and RIS TiN barrier was less than 5×100^-4 Ω-cm² . Shallow junction, contact-intensive diode structures exhibited good breakdown voltages and leakage current below 5 nA/cm². These results demonstrate a reproducible contact plug technology suitable for advanced MLM CMOS circuits