mwiemer at sj-solar.com
Tue Mar 17 10:37:48 PDT 2009
Iodic Acid Procedure
1.) We will mix the powder into solution using the acid hood in the dicing saw room (0.2M/L solution).
2.) The powder will be stored in the acid vault.
3.) The acid will be brought into the lab either through the chemical passthrough or the cleanroom "back door" using a bottle carrier
4.) The mixed acid will be stored in the chemical passthrough in a dark brown bottle (with a yellow label of course)
5.) All etch waste will be collected and tagged and placed in the proper chemical passthrough area
6.) Waste acid which has not etched material will be aspirated
From: Mary Tang [mailto:mtang at stanford.edu]
Sent: Tuesday, March 17, 2009 9:53 AM
To: Mike Wiemer
Cc: specmat at snf.stanford.edu; Senyo Dogbe
Subject: Re: Iodic Acid
Hi Mike, Senyo --
Thanks for the reminder... Just a couple of things.
1. Powders (including crystals -- as well as free nanoparticles and nanotubes) aren't allowed in the cleanroom. It's just too difficult to handle powders (dispensing, weighing, mixing) when there's laminar flow and exhaust blasting in different directions. You can, however, mix solutions from powders outside the cleanroom, in the wafersaw room, and bring them in, either through the chemicals passthrough (get a staff member to help you with access) or using a single bottle carrier through the service area in the back. Alternatively, if you can find a source of pre-mixed solution, you won't have to mix it up yourself.
2. Can you store the solution for an appreciable time or does it have to be mixed up just before use? If you store the bottle of solution, it should be kept in the chemicals passthrough. Make sure to get a yellow label. I take it that a brown bottle should be sufficient for excluding light -- if you decide to also wrap it in foil or other covering, make sure to label the outside of the foil with all the critical info as well.
3. Crystals should be stored outside the lab. We have a corrosives room where this can be stored. However, you'll need staff help to access the vault, so this will limit availability to working hours.
4. How will you be disposing of the waste? If you are etching III-V's, then etchant waste should be collected locally and appropriately tagged. The unused acid itself, I believe, can disposed of by aspirating at the bench.
5. Could you write up a procedure for this (like what you have below, but with the where's and how's)?
Mike Wiemer wrote:
We would like to use Iodic Acid in SNF. This chemical is commonly used as an echant for III-V materials like InP. MSDS attached.
Iodic Acid comes in dry crystal form
One mixes the crystals with water to form the acid (0.2 M/Liter) in a glass, non-transparent bottle (Iodic acid should be kept from light)
We will mix the crystals & water to create the solution at the GaAs bench
At the GaAs bench, we will combine: HIO3 (0.2M/L) : HCl : H2O - 1:1:x where x goes from 1 to 100.
All work will be done at room temp
We will store the mixed solution in the personal chemical pass-through area, along with the dry crystals
What do you think?
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA 94305
mtang at stanford.edu<mailto:mtang at stanford.edu>
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