[labnetwork] Gas Purity Grade for RIE

Fri May 14 12:10:07 EDT 2021

Hi Loik,

One area to make sure you have high purity gas is the gas cabinet purge gas. When you purge your gas cabinet process panel or perform a cylinder change you are introducing nitrogen to displace the chlorine and fluorine chemistries. If that purge gas isn't completely dry, the trace moisture will react with the acids and start corroding/contaminating your panel. The first place this typically shows up is in the regulators with the inability to hold a setpoint, and the outlet pressure starts to increase. This happens because the pressure drop is higher through the regulator, and this causes the moisture to fall out and the corrosion starts. If this happens, you can look in the outlet fitting of the regulator and you'll see the corrosion. Usually by this time, the panel is in bad shape.

For these types of gases, when our customers can't guarantee that their nitrogen will be 5 nines, or if there is a chance that the wrong bottle of nitrogen can make its way to the purge panel, we recommend a purge gas purifier to remove the trace moisture. It will make your panels last a lot longer. Also, if possible, order your gas cabinets with a "trickle purge" on the automated N2 purge inlet valve connected to your process panel as this will keep the nitrogen flowing through the cylinder connection when you are replacing the process cylinders. This keeps atmosphere from going into the process lines when you remove the spent cylinder. Also, if possible, order your purge cylinders with DISS cylinder connections. It's very unusual to order general purpose nitrogen with DISS cylinder fittings and is cheap insurance to assure that the wrong grade of nitrogen doesn't end up connected to your chlorine or fluorine gas cabinets.

Hope this helps,

Tom

Tom Britton
Director of Sales
Critical Systems, Inc.
Direct: 208.890.1417
Office: 877.572.5515
Skype: tombrittoncsi
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-----Original Message-----

From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Lewis,William

Sent: Friday, May 14, 2021 7:41 AM

To: Dr. Loïk Gence <loik.gence at fis.puc.cl<mailto:loik.gence at fis.puc.cl>>; labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>

Subject: Re: [labnetwork] Gas Purity Grade for RIE

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Hi Loïk,

Four nines is definitely clean enough for plasma etch processes.....and, I seriously doubt 3 nines would be an issue for most processes.  The cost jumps quite a bit from 4 nines to 5 nines.  Filtration and purification matters much more for PVD, PECVD etc...

-----Original Message-----

From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Dr. Loïk Gence

Sent: Thursday, May 13, 2021 4:16 PM

To: labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>

Subject: [labnetwork] Gas Purity Grade for RIE

[External Email]

Hi All,

I hope you are all fine and safe.

We are planning the installation of our first RIE with chlorine and Fluorine chemistries.

I was wondering, what are purity grade of the gases you are using.

Always electronic grade, 5.0 grade or above ?  To avoid potential contamination of the gas lines, chamber, etc...  of course, choosing the best purity available is a solution. However, thinking about the cost/utility for standard etching processes, and with potential problem of local availability of high grade, what grade range would you consider safe for the equipment and standard processes?

Thanks in advance for your comment.

Best,

Loïk

--

Dr. Loïk Gence

Assistant Professor

Instituto de Física

Pontificia Universidad Católica de Chile Avda. Vicuña Mackenna 4860, CP 7820436 Santiago

Lab: +56 95504 9648

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