PECVD vs. PVD morphology
Recently, SiMPore has been exploring alternate ways for depositing our film stack. We’ve finished our initial testing of a plasma-enhanced chemical vapor deposited film by Rogue Valley (OR), and it appears that the pore formation process is inhibited with the standard 1000 C RTP 100 C/s anneal.
The most striking difference (besides the difference in porosity) is the size of the nanocrystals; the crystals in the PECVD sample are many times smaller than the PVD deposited porous membrane. The PECVD membrane appears to have a much higher density of crystals as well. My initial guess is that a difference in film stress is responsible for this phenomena. We have seen that by tweaking the stress in our films (deposition temp, substrate bias) we can greatly tune the morphology of the membrane. Interestingly, a recent anneal of a PECVD film at 700 C yielded flat membranes. I have not imaged them under EM, but this could be another piece of evidence that the PECVD films are more easily crystallized.
What method will you be using to measure the stress?
We still don’t know the degree of oxide stress difference in bias/no bias conditions and deposition temperature…
JP – have you figured out how to extract numerical data from the 3D plot of the Veeco tool at RIT? For compressively strained films that wrinkle as membranes, this would provide a direct measure of strain. I’d settle for strain at the moment, until we can measure Young’s modulus.