[mems-talk] Thick SiO2 etch

[Joe Lonjin]

CF4/CHF3 plasma in MERIE with backside He cooling.

Joe Lonjin
Penn State Nanofabrication Facility
190 MRI Building
230 Innovation Blvd
University Park, PA 16802
 
JJL13 at psu.edu 
(814) 865-9284
Fax (814) 865-7173
 

-----Original Message-----
From: Xiaoguang "Leo" Liu [mailto:liuxiaoguang at gmail.com] 
Sent: Thursday, April 19, 2007 6:42 PM
To: General MEMS discussion
Subject: [mems-talk] Thick SiO2 etch

Dear all

For one of my projects, I need to pattern thick thermal oxide of
1.5um. I used 49%HF:DI = 1:6 as the etchant and 20um AZ9260 as a mask
(the reason of using this thick resist is that I need to do a through
wafer Deep RIE after patterning the SiO2).

The etching of the oxide takes more than half an hour in the etchant.
My problem is that the photoresist can not stand the HF solution and
start to peel off (especially the smaller features) after about 20min.
HF also attacks the photoresist reducing the overall thickness of the
photoresist, which can impact my later DRIE process.

Could anybody illuminate me with a better method to etch the oxide
layer without destroying the photoresist?