ABSTRACT
Since the discovery of the interesting luminescent properties of microporous Si (Canham 1990; Lehmann and Gösele 1991), and controllable macropore etching under illumination in n-type silicon (Lehmann and Föll 1990), the development of porous Si systems has exponentially increased. In this regard, nowadays Si can be etched in a controlled manner, with lithiographically defined or undefined (random) patterns. Additionally, silicon can be electrochemically etched in various electrolytes, like HF-based solutions with fluorides (Hoffmann et al. 2000) and KOH-based (Mathwig et al. 2011) solutions. This chapter will deal with the basics of porosification, centering the discussion on the most common and successful etching system, the Si-HF system.
