Hello, I am an Etch Engineer.
I am performing etching with high T_ox/Nit selectivity using remote plasma.
Etching plasma is formed using only NH3/NF3/H2.
1. I wonder if it would be advantageous to add Ar or N2 as inert gas to increase the stability of plasma. (There is an ion filter, but I am concerned about damage caused by Ar)
1.1 Additionally, it is said that inert gases help maintain plasma density, but only the radicals of the reactive gases react, not the electrons or ions needed to form plasma. Is there a difference?
2. I suspect Nit etching due to F radicals when using that gas. I am curious about a way to reduce the concentration of F radicals. (Additional process gas, ratio, etc.)
3. Is there a pre-treatment process that can reduce Nit etching?)
Thank you very much.
I am NOT an etch engineer; usually adding helium to a plasma enhances stability, as it has the highest mobility (well, there would also be hyrogen, but that has a whole lot of other issues, among which its high flamability i sprobably the worst)
Sputtering with nominally inert gases enhances anisotropic etching, i.e. you etch more into the direction of your plasma power supply. The NX3 gases or also H2 will also etch to some extent give you a reactive etching component which may also attack in other directions thus creating e.g. pits depending on the crystal orientation.
So, if you use Ar for plasma stabilization, you will have to recalibrate your etching rates and may eventually get a different surface finish.
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