[labnetwork] Pre-oxidation furnace clean

[Vito Logiudice]

Hi Kurt,

If I recall correctly from my experience working in a CMOS industrial fab many years ago, critical thermal oxidation runs (i.e.., gate oxides) had to begin within 30 minutes of the preceding RCA clean/HF dip step. Beyond 30 minutes, an additional HF dip (10:1) was required,  with no repeat of the RCA clean step deemed necessary. This could only be performed a limited number of times (3?) before the affected production lot required special attention from engineering.

I also coordinated several extended production plant shutdowns which lasted anywhere from a few days up to 1.5 weeks. In all cases, production lots at critical production steps had to be "parked" at specific process locations and always in dry boxes with constant N2 purges. We never permitted wafer batches to be parked with exposed silicon. Specifically, wafers could not be parked before a gate oxidation run: the gate oxide had to be grown before the shutdown.

Hope this helps.

Best regards,
Vito
--
Vito Logiudice  P.Eng.
Director of Operations, Quantum NanoFab
University of Waterloo
Lazaridis QNC 1207
200 University Avenue West
Waterloo, ON           Canada N2L 3G1
Tel.: (519) 888-4567  ext. 38703
Email: vito.logiudice at uwaterloo.ca<mailto:vito.logiudice at uwaterloo.ca>
Website: https://fab.qnc.uwaterloo.ca


From: Kurt Kupcho <kurt.kupcho at wisc.edu<mailto:kurt.kupcho at wisc.edu>>
Date: Wednesday, 18 March, 2015 3:58 PM
To: "labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>" <labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>>
Subject: [labnetwork] Pre-oxidation furnace clean

Hi everyone –

For a traditional thermal oxidation furnace, for things like building gate oxides, the general practice is to do a pre-furnace clean using piranha, RCA 1, RCA 2, and HF in successive cleanings beforehand.  I was wondering for other academic cleanrooms following this practice what rules do you have in place for once the students clean their samples and how long they can store these samples before putting into the oxidation furnace.  Let’s assume that the students redo the HF dip to remove the native oxide layer that has reformed, and they stored the samples in a clean container in a N2 dry box inside the cleanroom.  Do you require them to put the sample in the oxidation furnace immediately after pre-furnace clean? 1 day? 1 week?  Also, if you do have a specific rule for this do you have any cleanliness data to back it up?  Thank you ahead of time for your insightful responses!

Best,

Kurt


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Kurt Kupcho
Microelectronics Engineer

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