Hello,
I am trying to wet etch ITO on glass (100 nm thick) to make interdigitated electrodes of circa 10um resolutions.
I read that HCl is a convenient etchant. I tried a mixture HCl:H20 1:1 and it etches indeed, although I have encountered 2 problems: the etch rate varies greatly in time (a couple of nm per minute at beginning up to 10-20 nm/min after a few minutes) and the resist (AZ1512HS) tends to delaminate when glass is reached. In consequence ITO is etched away under the resist at some points as can be seen on the picture.
Hardbaking the photoresist - 5 min @ 200°C - helps but it is still not perfect. Do you have any suggestions to improve my result?
I am going to try a longer dehydration bake as well as depositing LOR resist under AZ1512 to improve the adhesion.
Greetings.
Very interested,but so sorry and excute me.I does not have the experianse for this topics.
Thank you for attention.
http://transene.com/tino/, it did not delaminate my photoresist (but it also did not etch my FTO).
Thanks for your answers.
I moved to another solution of etchant that yields better results: 20 % HCl, 5% HNO3. The etching is very slow (90 minutes to etch 120 nm) but the result is better than with HCl only. I still have some parts of my electrodes that are etched away, probably to local poor adhesion of the resist.
I will try different adhesion promoter as well as a thicker photoresist. Will keep you posted.
I managed to get nice results with the following:
- Dehydratation 180°C 5 min
- Cleaning acetone/IPA
- HMDS spinning
- Lithogrpahy with AZ1512HS
- HardBake 5 min 150 °C
- Etching HCl 20 % / HNO3 5%
Etch rate is very low at room temperature, takes 100 minutes to etch 100 nm and I need to flip the slides over at mid-time to get a conformal etching. Heating the etching solution would gratly reduced the etching time, but I did not have access to a htplate at the time.
I etch commercial ITO (10 Ohm/sq, 140nm) on glass with HCL 37% for 7 min. Prior etching I clean with Acetone-IPA-DI water in ultrasonic bath, dry with N2 gun, bake for 1 min at 115C. I used S1813 photoresist baked 1min at 115C after deposition and another 1min at 115C after developing, then I etch the ITO for 7 min. This works for me
Antoine Legrain is AZ1512 HS the best option to coat on ITO. i have tried other photoresist by sigma but i got a very bad result. i am planing to buy new positive photoresist any suggestion please.
i faced same problems u faced at bigger scare and i am plan to achieve interdigitated electrodes with 10um-30um spacing
Thank you
Indeed, indium tin oxide (ITO) thin films coated on glass can be etched with HCl (diluted ~1:1 v/v, concentrated acid/water) with either added FeCl3 (2─5% wt/wt) or mixed with HNO3 (i.e. aqua regia).
Only HCl was sufficient to etch the ITO in my case. I have used S1813 as photoresist with HMDS pre-coated. I have diluted the HCl to approx. 9M and kept it for 10 minutes for a thickness of 120 nm ITO. You can also refer to the article published in 2004 https://pdfs.semanticscholar.org/b3df/af578948ac6dda3ad1464ff3061234ee7b5a.pdf
Note: Sometimes it doesn't etch in the exact time. in those cases I have prepared a fresh solution and kept it for some more time. May be the dissolution of InCl3 saturates the solution to retard the etching rate.
Norberto Hernández-Como What was the mixing rate (HCl:H2O) you used to dilute the HCl?
Hoang-Phuong Phan, you need to try different mixing rates (HCl:H2O). Example: when I use commercial ITO, I use HCl with the concentration from the bottle (about 37%); when I use ITO deposited in my sputtering system I normally need to dilute 1:5 (HCl:H2O). I also heat the solution depending of the etch rate that I want, my etching temperature is 40 celsius degrees. I recommend to try these recommendations in order to fit to your materials and methods. Regards
Hi Phan, we had a working recipe at UQ many years ago using AZ1518 as an etch mask. See below for the details:
The working electrode consisted of a 20x20 mm sodalime (thickness??) glass cover slip coated with 100 nm of Indium Tin Oxide (ITO 90/10 wt%, 99.99% from Testbourne Ltd.) deposited using an electron beam evaporator (Temescal BJD2000) at 1.5 Å/s at 10-6 mTorr. In the fabrication process the samples were first spincoated (CEE200X, Brewer Science Inc.) with 1.8 µm thick AZ1518 photoresist (Microchem GmbH), soft-baked at 100 °C for 2 min and patterned by a chromium photomask containing the design of the electrodes using a mask aligner (EVG 620, EV Group) with dose of 250 mJ/cm2. After the samples were developed in a 2.38% TMAH developer (AZ 726, Microchem GmbH) for 45s the exposed ITO surfaces were etched away in a 1 M Oxalic acid for about 1 min. The samples were then undergone thermal annealing at 500 °C using an oxidation furnace (Hi Tech Inc.) with O2/N2 flow rate of 2/2 SLPM. The patterned ITO substrates then become electrically conducting and optically transparent for testing.
Han-Hao Cheng Thank you for your suggestion. I have tried with 9M HCl and it worked, thought the etching rate is still not optimized.
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