Hi all
          I am making some grating layers on <110> oriented silicon. I had to
etch 30 um down to the silicon wafer to form vertical walls of 5 um width. the
openig was also 5um. for that i aligned the features along the (111) flat. I was
trying to etch the exposed silicon using 20 % wt KOH solution at 76 degrees and
i used 85% KOH salt. after few minutes of etching it produced a black
precipitate over the etched portion and stopped the further etching. i was also
tried with 30% KOH solution at 75 degrees. that time also the precipitate was
formed and further etching was stopped. does anyone know about it and any
suggestion regarding this will be highly appreciated. thanks i advance.

 renil