While using MW PECVD to deposit SiNx on Si wafers, I came across the "phase shift" setting. Based on the manual, my understanding is that if I set the phase shift at 20%, the oscillation from the second MW source will start 20% after the first MW source started. Is this correct?
I was informed that, higher phase shift would dissociate more gases, hence improve the deposition rate, since both MW sources are not competing and able to utilize more gases to generating plasma, resulted in more gas dissociation. I am not sure how true this is, as it was conveyed verbally.
As of now, I am still unable to fully understand how phase shift would effect the MW generation, and how would it effect the thin film deposition and optical parameters of the deposited thin films. I came across journals using the term "duty cycle" (e.g. Pulsed PECVD deposition of diamond-like carbon films G. Fedosenkoa, A. Schwabedissen, J. Engemann, E. Braca, L. Valentini, J.M. Kenny, 2002) and was wondering if it "duty cycle" and "phase shift" are actually the same.
I would appreciate it if someone can help me understand more regarding this term.
Thank you.
Dear Dr. Reza,
I believe the phase shift is actually the shift between voltage and current. I.e. the amount of mismatch between plasma input impedance and power supply output impedance you allow. The duty cycle in a pulsed (DC) refers to the amount of plasma on time compared to the total time.
Thank you for explaining the difference between those 2 terms, Dr Lippens. I really appreciate it.
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