[mems-talk] silicon nitride windows/membranes

[Joseph Grogan]

Hi all,

I have a question for anyone who makes silicon nitride 
windows/membranes. I plan on making nitride windows for TEM applications.

I will be purchasing LPCVD nitride coated silicon wafers which I'll 
pattern myself to produce freestanding windows. I need to decide between 
low-stress nitride and stoichiometic nitride and I've heard differing 
opinions on which makes better windows. The argument I've heard for 
low-stress nitride is that the film is less likely to break because it 
isn't as stressed. But the argument I've heard for stoichiometic nitride 
is that it's more selective in KOH so I'm less likely to over-etch and 
since its pre-stress is tensile, this actually helps make the membrane 
flatter.

My film thickness will be 50nm. If anyone can share some advice I'd 
appreciate it.

thanks,
Joe