Applying tailored waveform biasing to industrially-relevant etch processes for semiconductor fabrication

With the ever-increasing complexity of modern electronics, semiconductor fabrication requires precision on the atomic scale. Plasma etching, a well-established technique, is a crucial step in this process. When etching a wafer, control of the ion energy distribution function (IEDF) at the wafer surface is essential for minimising subsurface damage and processing time. This is commonly achieved in industry by applying a sinusoidal, radio-frequency (RF) bias voltage to the wafer table within a plasma chamber, with the IEDF tuned via the magnitude of the bias waveform. A limitation of this method is that the energy range of the resulting IEDF is challenging to minimise for sensitive etch processes. A promising alternative is tailored waveform biasing, in which low-frequency, ramped voltage waveforms are applied to the wafer table. Proper tuning of the voltage ramp generates monomodal IEDFs with significantly smaller energy ranges than conventional RF biasing [1].

In this work, tailored waveform biasing is applied to the table of a commercial plasma tool (PP100 Cobra, Oxford Instruments) supplied with industrially-relevant process gases. The benefits of tailored waveform biasing is demonstrated through experimental measurements of the IEDF and wafer outcomes, alongside validation from a hybrid computational model.

References

[1] Faraz, T., et al., 2020. Precise ion energy control with tailored waveform biasing for atomic scale processing. Journal of Applied Physics, 128(21).