[mems-talk] RIE Question

[bobhendu at aol.com]

Joe:

Those conditions should have produced a much deeper etch than that so there must be something wrong with your etch tool. What was the reflected power indicator during etch. If it was less than 10 watts then it should have etched properly. If not you might get the results you described. Might not be a bad idea to run at a higher pressure say around 100 mtorr as SF6 being electronegative can be hard to tune to under certain conditions. Bob Henderson


-----Original Message-----
From: Joseph Grogan <jgrogan at seas.upenn.edu>
To: General MEMS discussion <mems-talk at memsnet.org>
Sent: Thu, 30 Aug 2007 12:58 pm
Subject: [mems-talk] RIE Question

Hi All,

We have a very old Plasmalab RIE in our facility that I tried using to etch a Si wafer patterned with 1813 resist. I used the following parameters:

02 flow rate: 5 sccm
SF6 flow rate: 20 sccm
pressure: 20 mT
power: 150 W
time: 1 hr

I had hoped to get a depth in the neighborhood of 60um or more with these settings (based on literature such as Williams' etch rates paper). Unfortunately, I only got around 4.5 um deep, and that was only in the center 2" of my 4" wafer. The outer 2" of my wafer was coated in an odd white chalky film that smudged off a little if I wiped it.?

Does anyone have a guess as to what my problem is??