ELECTROCHEMICAL ETCHING OF POROUS SILICON SACRIFICIAL LAYERS FOR MICROMACHINING APPLICATIONS

Using porous silicon (PS) as a thick sacrificial layer, free-standing structures at a large distance from the bulk can be obtained. The very high specific surface of PS makes its removal using dilute alkaline s olutions possible. In this work different technological conditions, su ch as adding ethanol or ultrasonic stirring, are studied in order to o ptimize the removal of PS using a one-step process with 0.1% KOH solut ion. Finally, cathodic polarization of the sample during the removal p rocess is proposed as a method to enhance and improve the etching of P S whilst avoiding possible oxide formation. This electrochemical etchi ng of a PS sacrificial layer allows good quality free-standing polysil icon structures featuring a smooth substrate to be obtained.