Study of low resistance contact structure using composition-modulated interface layer for 0.1-μm generation ULSI

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In this project, in order to realize reducing the parasitic resistance such as the contact resistivity at the metal/Si contact and the ultra shallow junction at source/drain regions, we aimed to the establishment of the applicable contact structure for sub-0.1 μm ULSI devices. We have clarified the relationship between the solid phase reactions and the electrical properties at the Ti/SiGe(C)/Si contact structure.(1) The reaction products change from Ti5Ge_6, to C49-TiSi_2, C54-Ti(Si_<1_y>Ge_y)_2 with an increase in annealing temperature. The transformation temperature to C54-Ti(Si_<1-y>Ge_y)_2 in this structure is higher than that in the Ti/SiGe/Si structure. The Ti(SiGe)_2/Ge-rich SiGe/Si structure with the composition-modulated interface of Ge can be formed with annealing the Ti/Ge/Si structure.(2) The Schottky barrier height estimated from the I-V measurement of the Ti/p-SiGe/p-Si structure decreases with the increase in the Ge composition. This structure is expected to be effective to reduce the contact resistivity.(3) In the Ti/SiGeC/Si sample with the low Ge composition, C49-Ti(SiGe)_2 is formed after the 550℃-annealing and the transformation to C54-phase occurs after 750℃ RTA. On the other hand, in the case of the high Ge composition, Ti_6Ge_5 is formed at 550℃, C49-Ti(SiGe)_2 is formed with RTA at 650〜700℃, and the transformation to the C54-phase completes at 750℃. Almost Ge in the SiGe layer can be mixed in the C54-phase by using the RTA method.(4) In the Ti/SiGeC/Si sample with the high Ge composition, while the Ti_6Ge_5 is formed with the conformal layer-structure, -grains of C49- and C54-phase agglomerate and the discontinuous film is formed. The reason why that occurs is the inhomogenization of the Ge composition in the reaction layer with the formation of the Ti_6Ge_5. On the other hand, in the sample with the low Ge composition, the conformal and flat layer of C49- and C54-phase can be formed.