A technique to form a porous silicon layer with no backside contact by alternating current electrochemical process

We report here the formation of porous silicon under alternating current co nditions. Instead of applying the usual direct current electrochemical proc ess, an alternating current was applied with a given frequency and peak vol tage. The porous silicon layer properties are equivalent to the properties that would be achieved by the standard direct current formation technique ( i.e., same porosity level). The main advantages of this process are: (a) Th e alternating current formed porous silicon exhibits higher mechanical stab ility during the drying step than layers formed using the standard direct c urrent technique. (b) The alternating current process can be performed with out a deposited backside contact. These simplify the process and permit its integration with high temperature processing steps and clean furnaces of a modern very large sale-integrated technology. (C) 2000 American Institute of Physics. [S0003-6951(00)01028-7].