First you have to determine the etch depth of the junction. You can determine
the theoretical value or use FIB method and staining to determine the actual
junction depth. Using a low power silicon etch rie process somewhere around
50 watts rf power you can then determine the silicon etch rate of your rie
process. Try to etch at least two minutes then use a Dektac or other surface
profilometer to determine the etch depth/time to give you an average etch
rate in silicon. Determine percentage of depth beyond you junction you are
trying to achieve and you are there. Good Luck

Bob Henderson
Process Integration,LLC