Paper PS-ThM2
Towards Plug-and-Play Tailored Voltage Waveform Plasma Sources: Progress in Matching and Calibration

Thursday, November 2, 2017, 8:20 am, Room 22

The use of non-sinusoidal Tailored Voltage Waveforms (TVWs) to excite a plasma process has proven to be a rich field. Performing deposition or etching using such TVWs been shown to provide (1) a greater degree of control over outcomes, (2) more understanding of those processes, and even (3) processes unachievable by any other means, such as electrode-selective deposition.

The dream design for a Tailored Voltage Waveform plasma source is one that can ensure that an exact version of a given waveform appears on the RF electrode, but without increasing the complexity and cost of the source far beyond that of a single frequency RF source (including matchbox). These requirements are challenging due to the multi-harmonic nature of TVW's; the matching network must simultaneously provide efficient impedance matching at multiple frequencies, and as the phase between harmonics matters, for certain systems the waveform appearing at the RF feedthrough will not be a scaled version of the one on the electrode.

We address these two challenges directly. For the multi-frequency impedance matching challenge, we present progress on the design and fabrication of a high-power multi-frequency matchbox. This system allows the semi-independent tuning of the matching condition at each harmonic. For the second challenge involving uncertainty in the waveform appearing at the electrode, we present results using the plasma properties themselves to eliminate potential sources of error in the waveform. This technique avoids the need for probes located within the vacuum chamber, optical access to the plasma, or limiting the waveforms to lower frequencies.