[mems-talk] Releasing of the nitride suspended structure

[yun wang]

Hi:

I had the same problem before when I was trying to get a double fixed Cu beam deposited on silicon substrate. The sacrificed layer was PR. There are two causes of the sticking. One is the residual stress within the deposited layer which causes the deformation of the structure, especially when you are using bi-layer structure. The second is the releasing process. You may want to avoid using DI water because the surface tension of water may drive the two structures together during drying. What we did was putting the wafer in alcohol  after solving the sacrificed layer. And then we put the container into a vaporizing chamber in room temperature to vaporize all the alcohol, leaving the suspended structure released. Hope this process can be helpful to your problem.
 
Yun Wang
Advanced Micro-Nano-Devices Lab
Department of Systems Design Engineering
University of Waterloo, ON, CA
Email:y83wang at engmail.uwaterloo.ca

----- Original Message ----
From: deepak agrawal <deepakiitm at gmail.com>
To: mems-talk at memsnet.org
Sent: Wednesday, January 10, 2007 12:47:16 PM
Subject: [mems-talk] Releasing of the nitride suspended structure

Can i use the dry etching to etch the Aluminum so that there will be no
chance of stiction. Is there anyone has the knowledge about dry etching
recipe of Aluminum.

<<Hi all,
I am trying to release the nitride suspended structure. In that structure I
have 1.2um thick sacrificial layer of Aluminum on a silicon substrate over
which 0.2um thin structural layer of silicon nitride deposited by PECVD
process. At the top, combined layer of chrome and gold are using to get the
top electrode. The top electrode and nitride pattern are etched by wet and
RI etching respectively.
For releasing, ortho phosphoric etchant is using to etch the Aluminum from
the active area. The sample is placed in the etchant at 60c temperature for
17 minutes followed by 10 minutes in DI water and 10 minutes in oven at
120c. I am not getting the released structure. The full pattern is sticking
with the surface of silicon. Is there any change in the process that i can
do to get the released device.>>