Bulk micromachining of Ge for IR gratings

While silicon can be easily etched anisotropically using a KOH solution, the anisotropic etching of germanium is difficult to achieve. We describe experiments using different etchants and different masking layers. The best technological results are obtained using a solution of phosphoric acid and hydrogen peroxide . As a mask, a thin film of chromium is preferable. The slow-etching plane is the plane. At , the etch rate is . With this technology it is possible to fabricate V grooves and the other typical structures of anisotropic etching known from silicon technology. One possible application is the production of infrared optical devices in germanium.