Novel porous silicon formation technology using internal current generation

A novel porous silicon formation technique that combines the advantages of thick layer anodization and electroless stain etch will be shown. A current generated by a galvanic element of silicon and a precious metal on the bac kside of a silicon wafer in a hydrofluoric acid (HF)/hydrogen peroxide (H2O 2)/ethanol electrolyte is utilised to generate porous silicon. In this case . the silicon operates as anode and the metal as cathode for current genera tion, This current is similar to the external current needed for anodizatio n. Besides the standard porous silicon etch solution HF (for electrochemica l silicon dissolution) and ethanol (to reduce surface tension), an oxidizin g agent, H2O2, is used to support the etch process and to generate a higher etch rate. Different kinds of metallization and etching solutions were inv estigated. This innovative technology enables to generate porous silicon layers of 10 mum without an external current. The porous structure achieved with this ne w technology is comparable with pores generated with anodization. (C) 2001 Elsevier Science B.V. All rights reserved.