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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).
>>
>> 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)
>>
>>
>> 1. AZ Developer 1:1 ? 90 s
>> 2. Rinse (DI water) and dry (N2+spin) ? 60-120 s
>> 3. MF-319 ? 5 s
>> 4. 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 sostrow at stanford.edu Tue May 9 21:29:56 2023
From: sostrow at stanford.edu (Sara Ostrowski)
Date: Wed, 10 May 2023 01:29:56 +0000
Subject: [labnetwork] Stanford University - Job opening - Scanning Probe
Microscopy Support Scientist
In-Reply-To: <SN4PR0201MB872656E397A88759E78DE4C5C6779@SN4PR0201MB8726.namprd02.prod.outlook.com>
References: <BY5PR02MB6883B77BC70855F8C8E738BEA7769@BY5PR02MB6883.namprd02.prod.outlook.com>
<SN4PR0201MB8726486D092A2DFE7202D8E2C6769@SN4PR0201MB8726.namprd02.prod.outlook.com>