Chemical vapour etching of silicon and porous silicon: silicon solar cells and micromachining applications

In this work, we used HNO3/HF Vapour Etching (VE) of silicon (Si) wafers for the formation of different porous structures. Depending on the volume ratio of the HNO3/HF acid mixture, we can obtain Porous Silicon (PS) layers or a (NH4)(2)SiF6 like powder phase. These two kind of porous structures may be used in silicon solar cells and in micromachining applications. The VE technique allows producing thick porous layers (> 100 mu m) in short times. Simple masking films enable to selectively groove Si wafers, leading to the formation of holes and channels of different sizes suitable for their application in micromachining. The various grooving profiles were investigated by Scanning electron microscopy (SEM). (c) 2005 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim.