I want to make a reactive ion etching of silicon carbide. I would like to get holes with a size of around 200nm in diameter.
So far I have made a first try with a recipe from 'Etching in Microsystem Technology' - Michael Köhler with SF6/O2 but I have got side etching comparable with vertical etching. (See attached picture.)
The question now is how to make systematics tests to find a suitable recipe?
What parameters are most crucial for etching with vertical walls? (Gases flows, ICP power, RF power, pressure)
What is better - having high or low BIAS (and what is 'high' and 'low')?
Is there a difference in which mask I use? Now it is Cr layer, but in literature I saw mainly SiO2 masks. Is it possible that because of the mask I will not get vertical walls or selectivity is the only parameter for how the masks are usually chosen?
Hi Viktoriia
you can not simply transposate a recipe because this Last one depends also on Tool caracteristics.
To get an anisotropic profile the main parameters are:
-Reducing pressure ( a few mtorr.)
-and increasing bias voltage (max That you can get on your tool...ie...several 100W.)
Concerning the mask nature, it should not be a problem to use Cr to get the anisotropy.
To begin, and because the process tuning depends on tool, i advice you to begin with a simple chemistry of SF6. O2 can be added later. ..it Will help in tuning the ER and selectivity.
Not easy to advice in a few Words in that subject.
Regards
Mohamed
Thank you for the answer.
The pressure I used and it minimum I can get in this setup is around 6 mTorr. And bias I had was around 300 V. But the result as shown on the picture is not good. So from the first view it should work.
And for the chemistry. Isn't is so that if I use only SF6 then only first nanometers of Si will be etched and then because carbon will cover the surface the process would be stopped? I thought that oxygen is necessary to etch carbon or SF6 also does it?
Yes SF6 can etch SiC at only one condition...you must bombarde the surface to help in the removing of CxFy polymer that forms and deposits on surfaces. This CxFy Will remains on profile sidewalls allowing you to get anisotropic profiles. I Will try to find you a paper on That.
Regard
Mohamed
Here it is some data about anisotropic etching on SiC...two articles That can help you:
regards
Mohamed
I will try to do just SF6 etching and see what is going on then.
Thank you for the papers!
Hello,
You can have a look on this publication.
But, to my knowledge, the role of oxygen for SiC plasma etching is still unclear.
Best regards.
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