Si/SiGe growth by low-energy plasma-enhanced chemical vapor deposition

Nowadays, microelectronic industry targets (in term of down-scaling and throughput) require some severe reduction of the SiGe epitaxial growth temperature or/and increase of the growth rate. A possible alternative to meet these requirements is low-energy plasma-enhanced chemical vapor deposition (LEPECVD). We have studied the deposition kinetics of silicon, silicon-germanium and germanium using LEPECVD. This new deposition technique offers promising advantages compared to thermally activated CVD such as low deposition temperature and high growth rate. Different regimes are observed depending on the growth temperature. High temperatures can be associated to a mix between thermally and plasma-activated deposition, whereas only plasma-assisted deposition occurs at low temperatures. Crystalline quality of the layers was checked through the mean of photoluminescence, which revealed no defects. A high growth rate (100 nm min−1) that can be achieved very easily with LEPECVD allows to grow quickly very thick layers. We have used this technique to grow step-graded thick SiGe layers which are almost fully relaxed. Those virtual substrates exhibited the well-known cross-hatch pattern, with RMS roughness from 2 to 10 nm for pure Ge layers.