Paper EM-ThP8
Characterization of Plasma Etching Induced Interface States at Ti/p-SiGe Schottky Contacts

Thursday, October 18, 2007, 5:30 pm, Room 4C

SiGe/Si heterojunctions are particularly attractive in microelectronic and optoelectronic applications such as in heterojunction bipolar transistors, modudulated doped field effect transistors and infrared detectors. SiGe/Si heterostructures provide new possibilities to engineer the bandgap in a material compatible with mature Si technology and they are now widely used to release novel devices integrated with silicon-based circuits. Plasma etching is widely used in the semiconductor industry as it offers the capability of performing many processes in vacuum without exposing the semiconductor surface to the atmosphere. However, these plasma-etching techniques also result in lattice damage at and below the surface, which alters the electrical and optical properties of the etched semiconductor surface. We have used electrical measurements (DLTS) complemented by current-voltage (I-V) and capacitance-voltage (C-V) over a wide temperature range (100-300 K) at frequencies of 10-100KHz for assessment of the defects introduced in Si0.95Ge0.05 by argon plasma sputter etching. From DLTS, defect concentration depth profiling was extracted and revealed that the main defect introduced during argon plasma sputtering is located very close to the surface. I-V and C-V analysis shows that the electrical characteristics deviated from the ideal case and indicates the presence of lateral inhomogeneities of the barrier height, resulting from the plasma etching induced surface states at Ti/SiGe interface. From the low frequency and high frequency C-V plots, the interface states density and their energy distributions were extracted.