updated 06/08/2015:
Hi Dear All,
I had several line patterns on the quartz wafer using negative lithography. This patterns will be used for future etching and deposition. So I would love to characterize several info:
1) the PR patterns after development
2) The etched depth after dry etching
3) The deposited depth after evaporation
The problem is the line width is small, around 200nm. While I am using the Leo 1550, the coating problem has been solved( the previous sputtering system has been problematic). It is able to view in detail.
The problem is the coating will flake, making the cross section of fine feature on the top surface not available. My process is crack it, coat it and image it.
Thanks in advance!
Letian
I think Pt coating is better in this case. You can try by sputtering Pt.
First of all, you should first make sure you're not limitied by the resolution of the equipment itself. I cannot advise much, because I don't have experience with your system, but general rules for SEM imaging of non-conducting specimens is to use a metallic coating, use silver (or other metal) paint to form a evacuate electrons from the sample surface to the metalic substrate, decrease beam voltage, decrease beam current. You might lose some resolution, especially changing the beam, but it's all about compromise.
If you do have image drifting or surface charging effects, try saturating the sample surface by holding the beam at small magnifications before zooming in on the are you wish to image. If charging is not too bad, it tends to gradually stabilize within one minute or so.
I agree with Daniel that you should check your SEM machine capability.
Another suggestion, try to lower as possible the current you use to avoid charging. Also use carbon paste to hold the sample into the stage.
good luck
200 nm features should not be a problem at all. I had similar problems with dielectric films ZrO2/Si.
I would recommend low acceleration ~2 KV. Reduce the sample distance below 5mm and use in-lens detector.
Low acceleration reduces the charging effect.
Lower distance improves the resolution
In-lens detector is not very sensitive to charging
Hope this helps.
Take a look at the SEM image taken with above settings at http://scitation.aip.org/content/aip/journal/jap/112/7/10.1063/1.4757924
- melisation with gold
- use SECONDARY DETECTEUR
- tilt your sample
- use < 5KV
- SPOTSIZE < 30
200 nm for your microscope should be an easy task.
We do not have your picture, so it is difficult to give a proper advice.
You mentioned etching and deposition. Etching could lead to smooth, curved transition from upper to lower level. Under SEM such transition will look "blurry". The same with deposition.
Dear All,
Thank you for your answer. The blurry turned out to be the problem of our sputtering system.
My new question is how to make cross-section to see the top feature on dielectric. I tried already. The problem is the coating will flake after 2 days store and some vibration upon transporting it around. This is making the cross section of fine feature on the top surface not available. My process is crack it, coat it and image it. Any suggestion on this process?
I uploaded my cross section picture and I am not sure what is the black regions beneath the coating and on top of the surface.
Thank you again!
Letian
Hi Letian.
I think you should try first to image it without coating at very low kV (
Hi Manuel,
I did found this low voltage possibility and tried like 1.3 kV, but it did not get rid of charging problem. I am not a experienced imaging people and I thought I need to adjust the current too. But currently I did not found this option in LEO 1550( correct me if you have experience with that).
Thank you for offering this option!
Letian
Hi Letian,
As long as I remember, the way to change current in LEO was with the aperture.
Try to select the smallest aperture, the lowest kV that gives you signal (even 500V), and if possible acquire with the in-lens detetector at a very low WD to increase the solid angle.
Good luck.
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