Overview

Semiconductor-metal interfaces play a crucial role in modem electronic and optoelectronic devices. SiGe and related group-IV alloys have shown a great potential for next generation devices and circuits for VLSI/ULSI applications. Though Al and Al-Si have been successfully used in Si devices, they are not the best choices for contacts to group-IV alloy films. For applications of poly-SiGe as gate material, the interaction of the SiGe alloys with noble/refractory metals should also be investigated for low resistance contacts and as metal-semiconductor diodes.

The choice of metals for ohmic contacts for strained layers should satisfy several requirements. First, the composition of the unreacted alloys must remain unchanged after contact reactions. Second, a single compound, not a mixture of compounds (e.g., silicides and germanides), should be in contact with the alloy mm. Third, the consumption of the alloy film during reaction must be small since the thicknesses of the strained layers are limited by the critical thickness. In table 9.1 important material properties of commonly used metals for microelectronic device fabrication using Si and Ge are presented.