Low temperature selective growth of Ga-doped and Ga–B co-doped germanium source/drain for PMOS devices

Abstract

The peculiarities and physical properties of gallium-doped (Ge:Ga) and gallium and boron co-doped germanium (Ge:Ga:B) epilayers grown at low temperature (320°C) by chemical vapor deposition are investigated and benchmarked against their boron-doped (Ge:B) counterpart. Ge:Ga films with resistivities < 0.3 mohm.cm are demonstrated, outperforming Ge:B prepared with a similar method. A selective Ge:Ga growth process based on a cyclic deposition and etch routine is developed and applied to fin structures. Full process selectivity towards nitride and oxide surfaces is demonstrated. Ga incorporation is however reduced, compared to non-selective growth, resulting in a degradation of the electrical performance. Ti / Ge:Ga(:B) contacts are finally evaluated, with the aim of providing new solutions for advanced Ge-based devices.