Oto Brzobohatý, Vilma Buršíková, David Trunec

Mirror effect in PECVD reactor and its explanation via MC-PIC computer simulation

Czechoslovak Journal of Physics 54 (2004) C527-C532

We have studied thin film deposition from methane and thin film sputtering in argon in low pressure rf discharge. We have observed that thickness of a thin film deposited on the upper (grounded) electrode has mirrored substrates placed on the bottom rf powered electrode. This mirror pictures have not been quite sharp. The same effect was observed when the initially homogeneous film was sputtered in the argon plasma. Again the picture of object on bottom electrode was sputtered in the film on the upper electrode. The mirror effect has been studied via Monte Carlo - Particle In Cell (MC-PIC) computer simulation. In our explanation the mirror effect is caused by the difference between secondary electron emission coefficient of substrate material and material of the powered electrode. This difference in the secondary electron emission coefficient affects plasma density upon the substrates and this leads to higher or lower deposition rate on the upper electrode. In our simulation we have calculated distribution of impact position for electrons on grounded electrode that have flew from the powered electrode. We have calculated this distribution for ions created in ionization collisions (of secondary electrons with neutrals) too. We have carried out simulation of this distribution for different pressures.

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