Two-step Al/Ti metallization to PtSi/Si structures

A two-step Al metallization procedure to prevent Al degradation of PtSi/Si Schottky barrier characteristics has been evaluated using Al3Ti as the kinetic barrier to the consumption of Ti. In the first step a thin Al layer is deposited on a Ti layer on PtSi/Si and is heated to the standard metallization process temperature of 450-500°C. The Al and Ti thicknesses are chosen so that the Al is consumed to form Al3Ti with Ti remaining between the aluminide and silicide. In the second step a thick layer of Al, compatible with interconnect requirements, is deposited and annealed at temperatures around 350°C. The formation rate of Al3Ti at this temperature is sufficiently low that consumption of Ti is minimal and the electrical characteristic of the PtSi/Si contact is preserved.