I'm using heavily doped p-type silicon (boron), and i was wondering if there is a dopant redistribution at the surface of the etched substrate.
I was able to find this for wet thermal growth of SiO2, but not for etching silicon.
Any ideas will be much appreciated.
Thanks
Hemi
Dear Hemi,
If on the surface of silicon due to the treatment an oxide film is formed then some amount of boron (dopant) can diffuse to the oxide film. At that, near-surface area of silicon can be depleted, accordingly. At some modes, the plasma treatment can result in generation of radiation defects at near-surface area.
Anyway, I suppose you may want to check the following book: https://www.elsevier.com/books/plasma-processing-for-vlsi/einspruch/978-0-12-234108-3 . I hope this will be helpful. If it will not be, please let me know.
p.s. For a more precise answer to the question, it is important to know the modes of plasma treatment you use.
Best regards,
Dmitrii
Besides, you may want to check the following paper: Article The influence of etching conditions on surface contamination...
Hi Dmitrii,
Thank you so much fer getting back to me.
For etching, i use SF6 and CHF3 (flow- 10:20), 600W ICP and 60W bias.
This probably introduces many defects to the surface. However, I'm using SOI wafers (2-5 um device thickness)and after etching i HF the device layer off and flip them. So I'm actually using the other side of the device layer that wasn't exposed to the plasma.
The problem is that i have inconsistencies with the membranes i get in term of their photo-electrical properties, and i'm trying to find the reason.
The interesting thing is that the front side of SOI wafers as is, don't have any photo-electrical response. However, oxygen plasma treatment, or wet thermal oxide growth (1-2um) severally increases the effect. Do you have any thoughts for what might influence this?
Many thanks
Do you have access to an XPS? You may be able to see if the doping is occurring, chemical state, and/or, relative concentration with XPS.
Dear Hemi,
Maybe it is worthable to apply an annealing to the sample after the plasma treatment. An annealing usually remove all defects caused by a plasma treatment. Maybe, you have to try an annealing in Nitrogen, Oxygen or Hydrogen atmosphere at 800 oC (a usual temperature from my experience). I hope this will be helpful.
Best regards,
Dmitrii
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