Improved Metal Gate Process by Simultaneous Gate-Oxide Nitridation during W/WNx Gate Formation

The improvement of gate dielectric reliability by simultaneous gate dielectric nitridation during W/WN x gate sputtering deposition was investigated. The time-to-breakdown (t bd) of the W/WN x gate metal-oxide-semiconductor (MOS) capacitor was improved compared to that of the W gate by increasing the N2 flow ratio (R N) during the reactive sputtering deposition of the WN x gate with an N2–Ar gas mixture. The surface nitridation of the gate dielectric of the W/WN x gate MOS capacitor was confirmed to occur simultaneously with the reactive sputtering deposition of the WN x layer. The improvement of the gate dielectric reliability was achieved by the nitridation, which terminated the dangling bonds formed in the gate dielectric surface during the metal gate sputtering process. Other characteristics of the W/WN x gate electrode were also demonstrated. The W/WN x gate provides low resistivity, a near-mid-gap work function and a good gate etch profile.