Disconnection of NiSi shared contact and its correction using NH3 soak treatment in Ti/TiN barrier metallization

During Ti/TiN barrier metallization of a shared contact in SRAM, an NH₃ soak treatment selectively deoxidized silicon oxide on NiSi at the gate shoulder, improving the resistance of the contact. This deoxidizing NH₃ soak treatment drastically reduced the drawbacks of conventional NH₃ plasma treatment: plasma-induced damage of gate oxide and excessive nitridation of Ti/TiN. Although NH₃ gas does not kinetically deoxidize silicon oxide, it does selectively deoxidize silicon oxide on the NiSi. We think that this is because the NiSi surface promotes the deoxidization of silicon oxide by NH₃.