Patterned surfaces in p-type silicon by photodefined etching

We present a simple technique for photodefined etching of p-type silicon. The technique involves wet photoselective corrosion of silicon by an aqueous HF solution containing a strong oxidising agent bromine.. The etching process can be largely inhibited by light, allowing the shaping of photodefined 3-D structures on the surface of p-type silicon samples. These structures are not dependent on crystalline orientation, which is an important advantage in polycrystalline silicon texturing. The fundamentals behind the process, involving electrochemistry of semiconductors, are presented along with a discussion of the process parameters. The process was studied both in open circuit conditions, which have the advantage of requiring no electrical contacts, and with an imposed current, which should allow better etching contrast at any illuminated to dark area ratios. The results clearly demonstrate that it is possible to obtain effective etching inhibition in illuminated regions of the semiconductor, while high etch rates are retained in dark areas. q1999 Elsevier Science B.V. All rights reserved.