Improvements to bit line contact processing in trench DRAM

Ionized physical vapor deposition of titanium and titanium nitride contact metal was investigated to assess whether adding extra nitrogen into the chamber reduced contact current leakage and whether lowering the RF bias power would reduce ion bombardment. The results of multiple analyses confirm that plasma deposition with extra nitrogen can suppress the accumulation of Ti atoms and, therefore, the formation of TiSi _x, and that lowering the RF power can reduce the ratio of resputtering and decrease the thickness of the Ti layer. The two techniques can be effectively implemented in bit line contact processing to reduce current leakage while improving product performance and reliability.