need some more information i.e. what should be the value of electrical supply and how long we need to do the etching to make a good PSi??

I used to make PSi in Madrid Spain (in 1996). We had to deposit Aluminum on the back of the wafer using a Thermal evaporator, then we would send the wafer to be cut in perfect circles (expensive and time consuming!).. One of the Doctoral students there created a nice teflon PSi cell that we'd fill with HF solutions and lower a teflon cylinder in it for etch) the teflon cylinder had a window at the bottom showing only a portion of the circular piece of silicon. It was fun (and dangerous :).. But I think your method makes it much easier and cheaper! Thank you for sharing!