[labnetwork] Etch rate of expired BOE solution

[Matthias Pleil]

We use BOE, 6:1 or 20:1 occasionally.  We have actually kept a batch for a few years with little degradation in etch rates.  We add water to keep the level constant.


Kind Regards,

Matthias Pleil, Ph.D.
Research Professor & Lecturer III of Mech. Eng - UNM
UNM MTTC Cleanroom Manager
PI - Southwest Center for Microsystems Education
scme-nm.org
(505)272-7157
________________________________
From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> on behalf of Savitha P <savithap at iisc.ac.in>
Sent: Tuesday, October 10, 2017 10:05:49 PM
To: Mac Hathaway; labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Etch rate of expired BOE solution


Hi Mac:


We have been doing test pieces to find the etch rate every week, but have been seeing it going down, hence the thought of adding fresh HF.


Thank you for your suggestions.


Regards,


Savitha

________________________________
From: Mac Hathaway <hathaway at cns.fas.harvard.edu>
Sent: Tuesday, October 10, 2017 7:42:31 PM
To: labnetwork at mtl.mit.edu; Savitha P
Subject: Re: [labnetwork] Etch rate of expired BOE solution

Hi Savitha,

I don't have personal experience with old BOE, but since HF is made by bubbling HF gas through water, I would expect the HF gas to come out of solution and evaporate over time, lowering the HF concentration.  If the bottles have been sealed, I don't know why it would weaken.

While adding fresh 49% HF to the existing stock would increase the etch rate, figuring out the concentration of your "resultant" mixture would be challenging, since you don't know the current (weakened) concentration.

If you are doing an etch where knowing the precise etch rate is important, you might try just doing a rate test on each bottle as it is opened and put into use, marking the rate on the side of the bottle, and letting that suffice.

I am unaware of any other issues that can arise from the use of old HF or BOE, such as surface roughening, or things like that.  Other more experienced hands will no doubt weigh in...


Mac

Mac Hathaway
Senior Process and Systems Engineer
Harvard Center for Nanoscale Systems
11 Oxford St.
Cambridge, MA  02138
617-495-9012


On 10/9/2017 1:05 PM, Savitha P wrote:

Hi all,


We have a lot of BOE(13:2) solution expired in 2014, which has been seeing declining oxide etch rates since sometime.  Is there some way of improving the etch rate, like by adding fresh HF (50%).


Kindly let me know if anyone has information on this.


Regards,


Savitha

________________________________

Dr. Savitha P
Chief Operating Officer
National Nanofabrication Centre
Centre for Nanoscience and Engineering
Indian Institute of Science
Bangalore - 560012
India.
Ph. +91 80 2293 3254
www.cense.iisc.ac.in<http://www.cense.iisc.ac.in>
*Please note the change in my e-mail id*



_______________________________________________
labnetwork mailing list
labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20171011/12d23a83/attachment.html>