I can think of two reasons:
(1) wafers tend to be bowed so they will not lie flat against the steel
chuck
(2) if you have trenches etched on the backside of the wafer, you will not
have good thermal contact

Shivalik

----- Original Message -----
From: "Yuzhu Li" 
To: 
Sent: Sunday, September 19, 2004 11:09 AM
Subject: [mems-talk] Why He backside cooling?


> Hi, I have a naive question about plasma etcher: it is very importan to
> cool the wafer during etching, then why not put wafer on the stainless
steel
> subtrate directly, why use He gas cooling? since steel have much higher
> thermal conductivity than He gas.
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