[labnetwork] Resist coating of tiny pieces

Tue Nov 17 11:46:29 EST 2020

Lots of good advice here - I can offer two other small observations.

1. Shimming really helps...this has worked much better than trying to
make a recessed holder, using scrap pieces works well
2. Spinning the piece off-center also helps - the shims then only need
to be on the outside.

This is discussed a bit here:
https://doi.org/10.1109/JMEMS.2017.2691585
(Fig 11)

There is another trick for contact lithography on these size pieces if
the shimming does not work for whatever reason and you can afford to
lose the edges....  You can make a mask pattern that removes the edge
bead (we have a mask with all relevant rectangles on it in 100 micron
steps), shoot that without contact and develop it.  Without that edge,
establishing contact is easier.  I've used this in the past, but we've
moved to the shimming/off center approach for more recent work.

Thanks,
-John

-----
Ioannis (John) Kymissis
Kenneth Brayer Professor of Electrical Engineering
Chair, Department of Electrical Engineering
Columbia University SEAS
500 W120th Street
Room 1300/MC 4712
New York, NY 10027
Tel: 347-850-0235
Fax: 212-932-9421
johnkym at ee.columbia.edu
http://kymissis.columbia.edu

On Mon, Nov 16, 2020 at 9:23 PM Price, Aimee <price.798 at osu.edu> wrote:
>
> Hi Lino,
>
> You are getting good ideas for the resist but you are correct that you’ll need to do something to level the sample during contact, if you are in fact using a contact aligner.  We were less concerned about breaking the sample/mask (although that is of course a concern) but more with the uniformity of the contact, which leads to poor resolution and/or definition.
>
>
>
> We had a post doc work out this plan.
>
> 1)      Pattern and etch a grid with alpha numeric labels across a full wafer.
>
> 2)      Place your sample piece onto the wafer above using a VERY small drop of DI water on the back of your sample (make sure it doesn’t wick to the front of the sample).  We use the size of a drip from the end of a pipette, so that it just barely spreads out across the sample (when in contact).
>
> 3)      Place dummy samples of the same thickness on the patterned alpha numeric wafer to ensure the mask/wafer pieces are level during wedge compensation.
>
>
>
> This has worked VERY well for me, even in the case of thin flexible materials (Kapton).  The reason for the labeled wafer is that you can use it again if you need to do alignment.  You have to note where you placed the sample the first time but it reduces the “search and find” alignment strategy on your subsequent layers.
>
>
>
> If you are interested I’ll look for those wafers tomorrow and send you a few images.  We made some to keep on hand.
>
>
>
> Good luck!
>
>
>
> Aimee Bross Price
>
>
>
> Sr. Research Associate
>
> The Ohio State University
>
> Nanotech West Lab
>
> Institute for Materials Research
>
> 1381 Kinnear Road
>
> Suite 100
>
> Columbus, OH 43212
>
> 614-292-2753
>
>
>
>
>
>
>
>
>
>
>
> From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> On Behalf Of Lino Eugene
> Sent: Monday, November 16, 2020 5:39 PM
> To: Orad Reshef <orad at reshef.ca>; Nathanael Sieb <sieb at 4dlabs.ca>; Michael Rooks <michael.rooks at yale.edu>; Carsen Kline <carsen at stanford.edu>
> Cc: 'labnetwork at mtl.mit.edu' <labnetwork at mtl.mit.edu>
> Subject: Re: [labnetwork] Resist coating of tiny pieces
>
>
>
> Dear Orad, Michael, Nathanael and Carsen,
>
>
>
> Thanks for your reply. It is good to know that mounting a tiny piece on a carrier wafer is sufficient for EBL.
>
>
>
> Sorry for not providing the context . We have currently an user who wants to plasma etch several microns of dielectric on a diced chip of ~3 mmx 3 mm. A thick photoresist is needed and I think that just mounting the chip on a carrier wafer would not work well. I was suggested to use dummy pieces placed all around the chip, which should work well for this process. Also, I believe that this would avoid also to break the chip or the carrier wafer (or the photomask?) because of the pressure applied during the wedge compensation on the mask aligner but maybe there is nothing to be worried about.
>
>
>
> Best,
>
>
>
> Lino Eugene, P.Eng., Ph.D.,
>
> Micro/nanofabrication process engineer
>
> Quantum Nano-Fabrication and Characterization Facility
>
> QNC 1611
>
> University of Waterloo
>
> 200 University Avenue West
>
> Waterloo, ON, Canada
>
> N2L 3G1
>
>
>
> Ph: +1 519-888-4567 #37788
>
> Cell: +1 226-929-1685
>
> Website: https://qnfcf.uwaterloo.ca/
>
>
>
>
>
>
>
> From: Orad Reshef [mailto:orad at reshef.ca]
> Sent: November 16, 2020 16:19
> To: Lino Eugene <lino.eugene at uwaterloo.ca>
> Cc: labnetwork at mtl.mit.edu
> Subject: Re: [labnetwork] Resist coating of tiny pieces
>
>
>
> Dear Lino,
>
>
>
> We need a little more context for what you consider a "tiny piece". I routinely work with 1x1 cm pieces, and for those we use chucks that have an o-ring about 0.5 cm in diameter.
>
>
>
> I have colleagues who have worked with 1mm x 1mm square diced samples. They mounted those on a large si handle wafer using double-sided carbon tape, like you would use to mount a sample on an SEM stub.
>
>
>
> Hope this helps,
>
> Orad
>
>
> Orad Reshef, PhD
>
>
> Département de physique | Department of Physics
> Université d’Ottawa | University of Ottawa
> boydnlo.ca | reshef.ca
>
>
>
>
>
> On Mon, Nov 16, 2020 at 11:44 AM Lino Eugene <lino.eugene at uwaterloo.ca> wrote:
>
> Dear colleagues,
>
>
>
> We are having more users who work on tiny pieces to be coated with photo and e-beam resist.
>
>
>
> I am thinking of different ways to coat these pieces:
>
> ·       custom chucks with a recess of the size of the chip
>
> ·       Si carrier wafer with recess etched by SF6 plasma
>
> ·       MicroSpray photoresist
>
>
>
> I am wondering if you could share the techniques you use to get uniform coating on very small pieces.
>
>
>
> Best,
>
>
>
> Lino Eugene, P.Eng., Ph.D.,
>
> Micro/nanofabrication process engineer
>
> Quantum-Nano Fabrication and Characterization Facility
>
> QNC 1611
>
> University of Waterloo
>
> 200 University Avenue West
>
> Waterloo, ON, Canada
>
> N2L 3G1
>
>
>
> Ph: +1 519-888-4567 #37788
>
> Cell: +1 226-929-1685
>
> Website: https://fab.qnc.uwaterloo.ca/
>
>
>
>
>
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