Hello everyone and welcome to "Ask the Staff." This is a new forum within the Purdue Engineering Intranet where researchers within Purdue can post questions to the Birck engineering and facility staffs on a variety of topics: processes, equipment, procedures, safety, etc. This is your forum to post questions, comments, and concerns. We will route specific posts to the appropriate staff member for discussion and answers, and threads on a variety of topics will develop and evolve.

Please don't be hesitant to use this forum. We look forward to helping all our users with their research experiences here at the Birck Nanotechnology Center!

Ron

Vapor HF etch system would make my etching process easier. But I cannot find one at Birck. Could anyone tell me if we have this system at Birck or other labs?
Thanks,
Yuqiang

Is it possible to have PMMA delivered and used in a Birck general lab? If so, who should I contact about the supply?

Hi,

Do we have stereolithography capability to fabricate some 3D MEMS device.

Or do we have the same or some similar capability like "Nanoscribe" ?
http://www.nanoscribe.de/


Thanks a lot for the reply.

Wuming

Dear Staff,

Who is currently in charge of the maintenance and training for the electrodeposition and anodization equipment? The equipment information pages indicate a person who no longer works in Birck. I would like to discuss the growth of a material as well as receive training and permission to use the equipment.

Thank you.

I have a question about the capabilities available in Birck. I am currently working with a facility outside of Purdue to fire a porous coating applied to a large (1 inch x 1 inch by 1.5 inches) copper block. The coating is not sintered in the traditional sense, but consists of silver-coated copper particles that adhere to the copper substrate at a firing temperature of 850 C. The facility is currently firing the part under a relatively high vacuum <0.1 mTorr, but the copper block and porous layer is becoming brown and oxidized. From talking with the manufacturer of the porous coating, firing in a reducing atmosphere can cleans the copper of oxide and result in superior adhesion and a clean looking final part.

Is it possible to fire this part in a reducing atmosphere in a furnace in Birck? If so, with whom might I discuss this further?

Thank you for your help,
Matthew Rau

I have a question/suggestion regarding the evaporators in the cleanroom. My impression is that it is not uncommon for the evaporators to be contaminated by oil from the roughing pump back-streaming into the chamber (I say this is not uncommon because there have been two times I know of where the CHA went down due to back-streaming the day before I was scheduled to use it ). Contamination issues like this obviously waste a lot of staff time and source material as well as interfere with user processing runs (my samples for instance can't sit around oxidizing for days once I start processing them). My suggestion is to switch all of the evaporators over to rough pumping with LN2 sorption pumping systems like the Varian uses. The sorption pumps have zero chance of contaminating the chamber (this is why we use them for the MBE's), no moving parts/maintenance, and are almost impossible to break. There would of course be an initial cost to buying new pumps and LN2 lines (though the dewars can also be manually filled quite easily as we do with the MBE's), but I don't think it would take too many contaminated gold crucibles or days of staff maintenance time to make up the cost. Just a suggestion...

John

I have functionalized and unfunctionalized SiNWs that I would like to get measurements for the surface potential. I was wondering if there was an instrument in Birck that could give me a readout in eV or mV to compare.

Thanks,
Kelly

I have devices meant for in-vitro measurements. So, I was thinking of using parylene as a passivation layer for the metals lines. Is it possible to deposit CVD parylene at Birck and can I use any of the plasma etching systems to etch it ?

I heard some people used to etch Au nanoparticles from Si nanowires by Plasma etching. Does anybody know that? I have some InAs nanowires and I want to remove Au particles on them. Thank you very much.

Hi

Do we have any Ultra High Vacuum CVD system at Birck (other than Prof.Capano's) or any Plasma Enhanced CVD System? In continuation with my previous thread on thin film Ge deposition, it seems like we need a CVD system for our purpose instead of the e-beam systems (like CHA).

Prof. Chen Yang in Chemistry has a CVD system that can deposit Ge but we've tried using it and it seems like it is not a UHV CVD system and is not the most ideal scenario for our work. She suggested that I should try to find out if Birck has a UHV or Plasma enhanced CVD system that we can talk about regarding thin film Ge deposition.

Dear all,

I am going to deposit/pattern a layer of AZ9260 with thickness of 11um for doing some electroplating experiments. As I could not find any useful recipe online, I was wondering if you could help me with the photoresist spinning condition, prebaking, exposure time, and finally developing time/ratio (AZ400k:DI).

Thanks,
Aida E

Hello!

I am trying to do electrical measurements on graphene FETs in solution medium. Going to perform the experiments in the Bio-wing.
However, I am not completely sure how to proceed with it. I have large area graphene which is contacted through silver paint. How do I go about passivating these contacts before exposing the sample to the solution. Also, what kind of instruments are available in Birck for these kind of liquid medium measurements? Just want to know the best strategy forward.

Any kind of help would be appreciated !
Thank you.

-
Ruchit

Hello!

I am looking to deposit a thin film of Germanium on an insulating substrate like SiO2 or sapphire. I am trying to find out what are my options here at Birck. I suppose we could do e-beam evaporation of Ge in one of the e-beam systems. Maybe the CHA? What are the other options? Can we do a thermal breakdown of GeH4 like we do for SiH4 to deposit Silicon? Does anyone know if we can do a CVD growth of Germanium?

Ideally I am looking for sub-100nm think Germanium films.

Any help would be greatly appreciated.

Sahil

I'm working on setting up a process flow for etching a mesa and evaporating ohmic contacts, and I've got a question about how to determine the exposure time for different photoresists apart from "the last guy in the group told me this worked." The manufacturer's specs I have found online seem to call for much lower exposures than what other people (including people who are good at processing) have told me. What is the trade-off between over-exposing or under-exposing for etching and lift-off processes? As a specific example, for AZ1518 the datasheet lists 339 mJ/cm^2 at g-line as the "Dose to print". Is it safe to assume that 34 seconds at 10 mW/cm^2 with the aligner set to the g-line will correctly expose the resist? Thanks!

Is there anyway to have a setup to anneal CVD oxide samples annealed at 1200 deg C for 3 hrs in N2 environment?

I have a aperiodic pattern which results in a large VEP file (~100's of MB). Currently the EMMA machine is not able to fetch this file because insufficient disk space. Can some data be cleared to accommodate my pattern file?


More importantly, is there any hardware related limitation on size on *.VEP file that VB6 machine can handle? This information will be useful to plan my design.

Thanks

Dear Staff,

I like to perform a yearly clean of all my glassware and in the past have used an acidic peroxide solution (H2O2/H2SO4, 3:1). Are there more effective solutions you recommend, e.g. aqua regia? My main goal is to remove organics, residuals, and even metal leftover from lift-off. Also, is there an effective way to clean metal tweezers?

Thank you!

I am having trouble lifting off Ti/Au (5nm/50nm) from graphene surface using optical lithography. I use AZ1518 (6000rpm 55sec / 85C 5min softbake) to pattern hall bar structures of 12um x 40um and have no liftoff after hot PG remover soak for 2 hrs. I have used Lesker as well but liftoff does not work on graphene(poor adhesion) but works on SiO2. The problem is I need in-situ liftoff and cannot use force from acetone bottle or gun as this damages graphene and peels it off. Any ideas as to if the issues are with photoresist or otherwise. Thanks!

We'd like to use ellipsometry or similar technique to measure oxide thickness on SiC. I think in the past we've had poor results using elliposometry, due to differences in SiC optical parameters relative to silicon, which usually works well. The technique needs to be quick and non-destructive, to allow us to continue processing after the measurement. Would the Filmetrics be appropriate? Would the wide band gap and short absorption wavelength of SiC be a problem?

Any advice or suggestions would be appreciated.