Subject: Re: Anyone know of a good anisotropic Si etch recipe?
From: Mary Tang <>
Date: Mon, 17 Sep 2012 09:35:53 -0700

Hi Katie and pquest users --

Is this a persistent problem?  Looking at Coral history, it looks like 
high/spiky reflected power was reported from 7/17-7/23, but it was 
thought to be resolved:  "Recentered microwave tuning potentiometer.  
Ran various recipes including the user's recipe with no problems.  
Microwave tuning was very stable."

If this is not the case, please do let us know -- and please do note 
this on Coral, as this informs everyone of the issues and provides us 
with info needed to resolve.  If you could also please let us know which 
recipe you are running when you observe problems, it would help a lot as 



(Katie - which recipe are you using and what materials are on your 

On 9/14/2012 10:08 PM, Katie Chang wrote:
> Hello PQuesters,
> I was wondering if anyone might know of any good recipes for anisotropic
> etching of Si. We're currently using a Cl2/O2 recipe that has given us good
> results when it works, but that causes pquest to have a weird problem*
> about 50% of the time. We're hoping that some experienced pquest users
> might have another recipe that pquest might handle better.
> Would anyone have any recommendations?
> --Katie
> **More information on the weird problem*
> *
> *
> The weird pquest problem we're getting is that some days when I run the
> recipe, the reflected microwave power will spike up to about 50 and refuse
> to be turned down by any tuning of the knobs. Increasing the target power
> to try to compensate just increases the reflected the power by the same
> amount. For some reason, running an oxygen clean and then immediately
> trying to run our Cl2/O2 again will sometimes fix the problem...for about 2
> minutes.
> We are etching SOI pieces attached to a dummy with carbon tape. However
> once this problem starts, it persists even if we take our sample out and
> put in a blank dummy wafer.
> When we try to etch our sample under these conditions, we've found that the
> Si comes out very rough and any metal that we put down as a mask gets
> sputtered away very quickly. We aren't sure why.
> Anyone ever see this problem before?

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
Paul G. Allen Room 136, Mail Code 4070
Stanford, CA  94305