You can use black wax Apiezon.

Rick


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Xiaoyong Liu
Sent: Thursday, January 07, 2010 3:08 PM
To: [email protected]
Subject: [mems-talk] protecting layer/material during KOH Si etching
forSiN membrane formation

Hi All,

      I am in a processing of making SiN membrane by using KOH chemical
etching on SiN(~50nm) coated Si wafers. There are some patterns on one
side of wafer, and I want them intact during KOH etching. The total
etching time will be about 5-6 hours.  I am wondering if there is any
material/film I can put on to protect that side of wafer, and can be
readily removed afterwards.

Thanks a lot

Xiaoyong