High pressure in situ HCl etching of Si1−xGex versus Si for advanced devices

We have studied the gaseous hydrochloric acid selective etching of SiGe versus silicon in a reduced pressure-chemical vapor deposition reactor. Non-classical metal oxide semiconductor field effect transistors (MOSFETs) architectures, such as silicon on nothing (SON) and multi-bridge channels (MBC) devices require high SiGe:Si etch selectivities in order to get rid of the sacrificial SiGe layers. We have probed the in situ HCl etching of Si and SiGe blanket layers of SiGe/Si stacks grown selectively in the Si windows of patterned wafers ('SON-like' substrates) and of SiGe/Si superlattices ('MBC-like' substrates) as a function of the reverse absolute temperature. A switch from high temperature, diffusion-limited/low temperature, Cl-desorption-limited etch regimes to a unique LT regime, together with a significant etch rate increase, has been evidenced when drastically increasing the HCl partial pressure. Very good selectivities (versus Si) have been obtained when laterally etching high Ge content Si1?xGex layers (typically ?30%). A preferential etch by HCl of the {1?0?0} crystallographic planes compared to the {1?1?0} ones has been noticed both for the lateral etch of the 'SON-like' patterns (preferential etch of the pattern corners) and for the 'MBC-like' patterns (fullsheet (0?0?1) etch rates ?10 times the {1?1?0} lateral etch rates). A slight etch rate difference between 'bottom-located' and 'top-located' Si1?xGex layers in Si/SiGe superlattices has also been highlighted. This etching technique is thus usable for the processing of SON or MBC devices provided that the selective {1?0?0}:{1?1?0} HCl etch reported here is taken into account.