Dopant selective HF anodic etching of silicon-for the realization of low-doped monocrystalline silicon microstructures

The authors report on the use of the HF anodic etching technique to realize monocrystalline silicon microstructures. As it has been established that the rate of the silicon etching reactions is mainly governed by the availability of holes at the silicon surface which is in contact with the etching solution, the definition of the geometry of microstructures can be accomplished by methods which affect the hole concentration locally. It is demonstrated that the methods which exploit the sharp selectivity of HF anodic etching between p-Si and n-Si show good potential and can be used to manufacture suspended beams, making use of masked implantation of phosphorus for geometry definition. It is concluded that this technology offers new opportunities in the field of micromachining of silicon for micromechanical applications