[labnetwork] Plasma etch of chalcogenides

[Matt Moneck]

Hi Tzu-Min,

 

I suggest finding an alternative machine for this material if at all possible.  In addition, there are safety concerns with this material and a number of other chalcogenides (see more below).  

 

We have an STS Multiplex DRIE running the Bosch process, and we have set strict protocols (similar to yours) regarding the materials that can go into the system.  That being said, there have been a few occasions where we have deviated from those protocols and regretted it.  In some instances, those deviations have led to too much polymer formation and drops in etch rate along with changes in etch profile.  These deviations were fairly easy to recover from but did lead to some down time.  In other instances, the recovery was not as easy.  There was one instance where metal masks (metals that did not easily form volatile compounds with fluorine) were used in the tool.  Ultimately, this led to resputtering of material onto the chamber sidewalls and changes in our Si etch process.  Extensive chamber cleans were necessary to remove the metal from the ceramic liners.  

 

I don’t personally have any experience with GeSbSe, but I would have concerns about the Sb and Se components (the Ge should form a volatile compound) contaminating the chamber.  In addition, selenium hexafluoride is an acutely toxic and corrosive substance.  If you decide to use this material, I would work with your environmental health and safety group to figure out a way to properly treat the exhaust (also check whether your pump can handle corrosive exhaust).  If they don’t have any experience in this area, you may want to consult some companies that sell abatement systems (Critical Systems, Ebara, Edwards, etc.).  

 

Best Regards,

 

Matt

 

-- 
Matthew T. Moneck, Ph.D.
Executive Manager, Carnegie Mellon Nanofabrication Facility
Electrical and Computer Engineering | Carnegie Mellon University
5000 Forbes Ave., Pittsburgh, PA 15213-3890
T: 412.268.5430
F: 412.268.3497
 <http://www.ece.cmu.edu> www.ece.cmu.edu
nanofab.ece.cmu.edu

 

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Tzu-Min Ou
Sent: Wednesday, May 18, 2016 1:20 PM
To: Labnetwork Mailing List <labnetwork at mtl.mit.edu>
Subject: [labnetwork] Plasma etch of chalcogenides

 

Dear Colleagues in the LabNetwork,

 

Good day! I got a request for the plasma etch of a chalcogenide that I have zero experience with. So, I figure I should consult LabNetwork's professional opinions before making any rush decision. Your response will be extremely helpful to us.

 

We have a STS ICP etcher dedicated for Si DRIE. The chamber is carefully kept clean that only photoresist and Si-based dielectrics are allowed to present so far. Now, a faculty member wanted to etch a thin film of GeSbSe in the chamber using CHF3 + Ar on a regular basis. I remember that both Sb and Se are poisonous to the vacuum systems, but I cannot recall exactly why. Here are my qestions:

 

1. Can anyone let me know how those elements are harmful to the vacuum systems, please? 

 

2. I tried to ask our EH&S people about the compatibility of the exhaust, but they are not sure either. Is there a foreseeable compatibility issue in the exhaust? Is it likely that we will need to have an inspection from the authority, such as the fire department, etc., to be permitted to emit the byproducts of this chalcogenide film?

 

3. Is it likely that the etch will cause any irreversible contamination/change to the ICP system that cannot be recovered by a standard cleaning process? (I was just worried that the Si DRIE will be runined after this etch.)

 

Again, your opinion will be deeply appreciated. Thank you so much for your time and help.

 

Sincerely,

 

Tzu-Min


-- 

Tzu-Min Ou, Ph.D.

Lab Manager

Colorado Nanofabrication Laboratory

Department of Electrical, Computer, and Energy Engineering

University of Colorado at Boulder

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