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Subject: [labnetwork] Strange "sample memory" with LOR 5B |
Hello everyone, |
While working on a recipe for LOR 5B/AZ 1512 in our automatic development system, I encountered some intriguing effects when reusing wafers for my tests. This could be a problem for our users when developing their own process, so we'd appreciate it if anyone could help us to understand what is going on. |
Below is a picture of a sample right before exposure, taken using our MLA150. The dark/bright features you see are NOT etched on the wafer (these wafers were never etched). The marks are from a previous lithography test. They become apparent after coating the sample with LOR 5B and even more after adding AZ 1512. And I don't see them when coating only with AZ 1512 (I reused wafers for that process development without any issues). |
[cid:image001.png at 01D95E44.038894D0] |
And what is more intriguing is that these features affect exposure/development of my test mask. For instance, on a virgin sample I can expose and auto-develop with the same recipe (dose and development time) I use for the manual process. On a reused sample, the reisst stack behaves as if it were underexposed (a dose test made this very obvious). |
Here are the steps during my tests: |
1. Piranha clean |
2. HMDS prime on a YES oven |
3. Spin-coat with LOR 5B/AZ 1512 (marks show up on a reused sample) |
4. Expose using either a mask aligner or DWL |
5. Auto-develop in our Laurell EDC-650 (resist seems underexposed over the marks) |
* AZ Developer 1:1 ? 90 s |
* Rinse (DI water) and dry (N2+spin) ? 60-120 s |
* MF-319 ? 5 s |
* Rinse (DI water) and dry (N2+spin) ? 60-120 s |
1. Strip resist with Remover PG |
2. Repeat all steps for every iteration |
At first I thought that this could actually be some etching of my Si wafers by MF-319, even though unlikely given the low TMAH concentration (and I'm not sure why that would affect exposure/development). But the sample in the image above has 2 ?m thermal oxide, so practically impervious to TMAH. Not to mention that the brightest crossing marks come from testing a recipe where TMAH was not used at all. This must be some strange interaction between LOR 5B and the sample surface, which I'd expect to be practically reset after piranha and HMDS priming. |
My search for more information regarding LOR 5B and it's sensitivity to surface conditions has proven fruitless so far. And requiring a brand new sample for every iteration can get expensive quite quickly. We'd appreciate it if you could point us to some references where this was discussed in any form, or if you know of a method to avoid this from happening. |
I'm sorry for the long email, and thank you in advance for any comments. |
Best regards, |
-- |
Gustavo de Oliveira Luiz, PhD |
Applications/Research Specialist |
nanoFAB, University of Alberta |
+1 (780) 619-1463 |
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From deonc69 at illinois.edu Fri Mar 24 14:33:37 2023 |
From: deonc69 at illinois.edu (Collins, Deon) |
Date: Fri, 24 Mar 2023 18:33:37 +0000 |
Subject: [labnetwork] Dry Bed Scrubber for silane, etc |
In-Reply-To: <DM6PR04MB439672E86ED63FDBEB6FFD82BB849@DM6PR04MB4396.namprd04.prod.outlook.com> |
References: <DM6PR04MB439672E86ED63FDBEB6FFD82BB849@DM6PR04MB4396.namprd04.prod.outlook.com> |
Message-ID: <DM6PR11MB31626F29E33FF8CCAC0F4D29D7849@DM6PR11MB3162.namprd11.prod.outlook.com> |
Contact Critical Systems Inc. or BAZM. They both have these systems. CS Clean Solutions also offers dry bed systems. |
Deon D. Collins |
FACILITY MANAGER |
Holonyak Lab |
University of Illinois at Urbana-Champaign |
208 N Wright St Rm. 248 | 2250 |
Urbana, IL 61801 |
217-300-7531 | deonc69 at illinois.edu<mailto:deonc69 at illinois.edu> |
[cid:image001.png at 01D95E55.3BC66870]<http://illinois.edu/> |
Under the Illinois Freedom of Information Act any written communication to or from university employees regarding university business is a public record and may be subject to public disclosure. |
Life is not about watching other people live it. It's about you living your own! |
From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of James C. Sturm |
Sent: Friday, March 24, 2023 9:49 AM |
To: labnetwork at mtl.mit.edu |
Subject: [labnetwork] Dry Bed Scrubber for silane, etc |
We have a Si/Ge UHV CVD system for which we want to purchase a dedicated dry bed scrubber. |
Total N2 purges ~38 lpm (from several dry pumps, etc) |
Total H2 100 sccm when purging, but normally < 20 sccm |
Silane ~2 sccm, Germane < 0.05 sccm, Diborane and phosphine < 0.01 sccm. |
Running < 10 hours a week on average. |
We are looking into a Callisto dry bed scrubber (by Jupiter). We have no experience with such systems, having used a hot "combustion chamber" with air pumped in for 20+ years. |
Comments/suggestions/other manufacturers/"been there done that" are welcome. |
Thanks, |
Jim Sturm and Zoe Cyue, Princeton University |
******************************************** |
Prof. James C. Sturm |
Chair, Department of Electrical and Computer Engineering |
Stephen R. Forrest Professor in Electrical Engineering |
Princeton University |
B210 E-Quad, Olden St. |
Princeton, NJ 08540 |
609-258-5610, fax: 609-258-1177 |
sturm at princeton.edu<mailto:sturm at princeton.edu> |
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From spaolini at cns.fas.harvard.edu Fri Mar 24 16:05:46 2023 |
From: spaolini at cns.fas.harvard.edu (Paolini, Steven) |
Date: Fri, 24 Mar 2023 20:05:46 +0000 |
Subject: [labnetwork] Dry Bed Scrubber for silane, etc |
In-Reply-To: <DM6PR04MB439672E86ED63FDBEB6FFD82BB849@DM6PR04MB4396.namprd04.prod.outlook.com> |
References: <DM6PR04MB439672E86ED63FDBEB6FFD82BB849@DM6PR04MB4396.namprd04.prod.outlook.com> |
Message-ID: <BL0PR07MB4050F4CE30AB17CB79CCF26BDF849@BL0PR07MB4050.namprd07.prod.outlook.com> |
James, |
I would highly recommend a dry bed scrubber for a number of reasons. |
Electrical consumption will be seriously reduced since you are not keeping a large mass of "burn box" at elevated temperatures. |
If your present unit is of the "burn/wash" type, city water consumption will be eliminated. |
I have installed a dual Calisto system for our LPCVD systems and I am quite satisfied with it's performance and features. One outstanding feature is the built in TGMS sensor that will alert you to when the dry bed has reached its lifespan. Most other abatement systems simply monitor exhaust pressure as a trouble indicator. The dual Calisto will not only alert you of a dry bed (cannister) failure, it will automatically switch over to the second canister and you have the luxury of changing the spent one when you have the time. |
Hope this helps, |
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