Selective deposition for "chamber clean-free" processes using tailored voltage waveform plasmas

Tailored Voltage Waveforms (TVWs) have been proven capable of creating plasma asymmetries in otherwise symmetric CCP reactors. Particularly, sawtooth TVWs (described as having strong slope-asymmetry due to different voltage rise/fall slope) can lead to different sheath dynamics, thus generating strongly asymmetric ionization near each electrode. To date, research concerning the slope-asymmetry has only focused on single-gas plasmas. Herein, we present a study looking at SiF$_{\mathrm{4}}$/H$_{\mathrm{2}}$/Ar mixtures to investigate silicon thin film deposition. The resulting surface process depends strongly on multiple precursors, and the deposition requires a specific balance between surface arrival rates of SiF$_{\mathrm{x}}$ and H. For a certain gas flow ratio, we can obtain a deposition rate of 0.82{\AA}/s on one electrode and an etching rate of 1.2{\AA}/s on the other. Moreover, the deposition/etching balance can be controlled by H$_{\mathrm{2}}$ flow and waveform amplitude. This is uniquely possible due to the mixed-gas nature of the process and localized ionization generated by sawtooth TVWs. This encourages the prospect that one could choose process conditions to achieve a variety of desired depositions on one electrode, while leaving the other pristine.