[labnetwork] Need help with RIE process

[Bob Henderson]

Rick:

 

Holy lightning bolt you do seem to have a discharge problem. You didn't say
if the wafer has oxide on both sides but assuming it does I would suggest
stripping the oxide on the chuck side to avoid the charging problem you seem
to have. An electrostatic chuck works much better if you have a conductive
material or in this case a semiconductor material than a dielectric.
Assuming you also helium backside cooling with your E-chuck this should also
allow you to etch the oxide that is patterned without the need to run
multiple cycles. Depending on the RF power you might have to lower it a bit
to avoid reticulation of the photo resist. I also don't understand why you
are using 8 microns of resist as 1-2 microns should suffice assuming the
resist: oxide selectivity is around 3:1. If you care to share your process
recipe I might be able to help out some more. Bob Henderson

 

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of Morrison, Richard H., Jr.
Sent: Wednesday, March 04, 2015 5:08 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Need help with RIE process

 

Hi everyone,

 

I have a strange problem that I need some help with. We have an  Ulvac
NE-550 RIE system with an electrostatic chuck. The wafer is a double sided
polish with 1um of SiO2. One side has an AZ4620 resist pattern 8um thick to
etch the 1um of oxide. Because the process runs hot we break the etch into 9
different steps and move into the LL after every step. On the polished side
that is down on the ESC check we have craters on the surface that look like
a lightning strike or meteor strike, this is fairly deep several microns.

 

I have attached a photo of the damage. Have any of you seen anything like
this? I need to fix the issue because the side that is down ends up being
the frontside of the wafer and that is a killer defect. We think the oxide
is charging and when the lift pins come up (at ground potential) we get a
discharge.

 

Rick

 

 

Draper Laboratory

Principal  Member of the Technical Staff

Group Leader Microfabrication Operations

555 Technology Square

Cambridge Ma, 02139-3563

 

www.draper.com

rmorrison at draper.com

W 617-258-3420

C 508-930-3461

 

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