Dear all,

I am now doing bulk wet etching using TMAH and I need to etch into a
certain depth.  But I find the etch stop is indeed a tough job.  The
time etch stop is simple but not accurate, while SOI wafers are so
expensive which are not suitable for my research.  Can someone give an
idea to get an etch stop?  It should be practical and not very
expensive.  Since I need to etch through a silicon wafer, the etch
rate also matters.

Thanks ahead.

Xuefeng