Hello, Ananth Krishnan

Two methods can be used to thin the backside of SOI wafer.

1 You can make a special model to fix your wafer. Make sure that the
chemical ethant could not reach the the active layer.

2 You can deposit/grow a protective layer (metal, oxide silicon nitride and
so on) on the front side of SOI wafer. In my experience, I deposit Ti/Au on
the SOI wafer and etch the back side in TMAH (80C, 25%, 25 hours, about
490um). Finally, Au and Ti are removed by I2&KI2 and H2O2. It works well.



2009/4/1 Ananth Krishnan 

> Hello,
>
> Is there a way to chemically etch and thin down <100> oriented silicon
> handle layer of a SOI wafer from 700 microns to 200 microns without
> affecting the top silicon? I tried polishing, but our machine is not flat
> leading to thinning down on side much more than other even after very good
> alignment with respect to center of polishing lap. I need to cleave the
> sample after thinning down.