AVS 46th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM-WeP

Paper EM-WeP7
The Interfacial Reaction between Ti and (001)Si with an Interposed Mo Layer

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: S.-M. Chang, National Tsing Hua University, Taiwan, R.O.C.
Authors: S.-M. Chang, National Tsing Hua University, Taiwan, R.O.C.
L.-J. Chen, National Tsing Hua University, Taiwan, R.O.C.
Correspondent: Click to Email
Low resistivity TiSi@sub 2@ has been widely used in ultralarge scale integrated circuits because it possesses the low resistivity and compatibility with the SALICIDE processing. However, as the devices dimension shrinks to the deep submicron regime, it becomes increasingly more difficult to use thermal annealing to transform a structure from the high resistivity C49 phase to the low resistivity C54 phase due to insufficient nucleation sites of C54 phase at the C49 phase grain boundaries. Recently, a new and simple method for the reduction in the C54 transformation temperature was demonstrated. The formation temperature of the C54 TiSi@sub 2@ phase from the bilayer reaction of Ti on Si is lowered by about 100@super o@C by placing an interfacial layer of Mo between Ti and Si. However, the detailed mechanism is still not well understood. In the present study, high-resolution transmission electron microscopy (HRTEM) was utilized to study the interfacial reaction between Ti and Si with an interposed molybdenum layer. A thin amorphous TiSi@sub x@ layer was found to form and a thin Mo@sub 5@Si@sub 3@ layer was formed at the interface between the Si substrate and amorphous interlayer after 500@super o@C rapid thermal annealing (RTA) for 30 s. In addition, island formation was found to occur for Mo@sub 5@Si@sub 3@ after 535@super o@C RTA for 30 s. C49-TiSi@sub 2@ and Ti@sub 5@Si@sub 4@ phases were found to form simultaneously after 550@super o@C RTA for 30 s. The growth rate of amorphous TiSi@sub x@ layer was delayed with the presence of metallic interfacial layer. The formation temperature of the C49 TiSi@sub 2@ phase was also found to increase. The redistribution of Mo atoms, in the form of a ternary Ti-Mo-Si phase, after 550@super o@C RTA for 30 s, leads to the enhancement of the formation of C54-TiSi@sub 2@ by providing more heterogeneous sites needed for the transformation from C49- to C54-TiSi@sub 2@ phase.