Fast chemical thinning of germanium wafers for optoelectronic applications

Chemical thinning of germanium wafers was carried out in H3PO4:HNO3:HF aqueous solutions, in which etch rates and surface morphology was adjusted through changes in etchant dilution and viscosity. Pitless and smooth surfaces (RMS = 0.42 nm) were obtained at industrially acceptable rates via a diffusion-controlled mechanism. Etchant-resistant wax enabled reversible bonding to a polypropylene substrate, emerging as a potential route for industrial production of thinned germanium optoelectronics.