Macro porous silicon formation for micromachining

This paper presents a new technique of micromachining using macro porous silicon. Macro porous silicon is made by electrochemical etching in hydrofluoric acid. The etch rate and the morphology of the etched surface as a function of etch parameters, (current density, applied voltage and HF concentration) are investigated. Optimization of these parameters makes it possible to fabricate a micromechanical structures such as 45 mu m deep, 3 mu m wide and 8 mu m pitch trenches. Furthermore the diameter of the pore is easy to control by adjusting the current density. During the pore formation an increase in the current density leads to an increase in the pore diameter. This does not effect the diameter of existing pores. This connection of the pores under the structure can be achieved. In this way, various kinds of single crystal silicon micromachined structures can be fabricated.