Monitoring and control of RF driven PVD, PECVD and etching plasmas using Fourier components of discharge voltages
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| Year of publication | 2012 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | PVD and PECVD require monitoring and control of the deposition process in order to reproducibly prepare coatings of desired quality. RF driven magnetron sputtering as well as RF driven PECVD processes use capacitively coupled plasma to deposit various types of thin films. Due to the nonlinearity of sheaths, higher harmonics of discharge voltage and current are produced in capacitive discharges. Since the sheaths are in contact with bulk plasma, higher harmonics are strong in particular when their frequencies are close to the series plasma–sheath resonance. Also, the harmonics are strong when they are not damped by collisions between electrons and neutrals. Both conditions are fulfilled at pressures typically below 10 Pa used in majority of PVD and PECVD applications. Fourier components of discharge voltages were measured in two different reactive plasmas and their response to creation or destruction of a thin film was studied. In reactive magnetron sputtering the effect of transition from the metallic to the compound mode accompanied by the creation of a compound film on the sputtered target was observed. The amplitudes of certain harmonics change almost one order of magnitude during the transitions from the metallic to the compound mode and vice versa, thus react with the similar sensitivity as OES on the changes in the deposition process. Further, deposition and etching of a diamond-like carbon film and their effects on amplitudes of Fourier components of the discharge voltage were studied. It was shown that the Fourier components, including higher harmonic frequencies, sensitively react to the presence of a film. Therefore, they can be used as a powerful tool for the monitoring of deposition and etching processes. The behavior of the Fourier components can be explained by the difference between the coefficients of secondary electron emission of the film and its underlying material in both experiments. |
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