A method to form Si recess for Ge selective epitaxial growth using dry etch

Waveguide coupled Ge photodetector (Ge-PD) is a key component of optical communications and interconnections. Because waveguide coupled Ge-PD requests waveguide and Ge to be at the same height, Ge must grow in selected silicon recess. Thus, obtaining a smooth silicon recess of accurate depth is key to high quality Ge epitaxial growth. The method generally used is wet TMAH etching, but it is difficult to control silicon recess depth and profile using this method. A new dry etching method that can easily control the etching depth, sidewall profile and surface smoothness of silicon has been developed.