plasmas for atomic precision processing*

Plasma-enhanced atomic layer deposition (PE-ALD) is a low temperature, conformal, layer-by-layer deposition technique that is based on a pair of self-terminating and self-limiting gas-surface half-reactions, in which at least one half-reaction involves species from a plasma.  This approach generally offers the benefit of substantially reduced growth temperatures and greater flexibility in tailoring the process conditions to achieve desirable film characteristics. However, tight control over the flux and energy of ions is needed to avoid unwanted damage and process drift can limit the successful implementation of plasma-enhanced schemes.

 

Often, in the pursuit of reduced ion energy at surfaces, PEALD reactors are operated at relatively high pressures (> 200 mTorr) with the intent to attenuate ion energy at surfaces through collisions in the sheath above the substrate. In this work, we present an alternative approach that involves temporally modulating the power to obtain a similar reduction in energy while maintaining greater control over the plasma parameters. Here we use spatio/temporally-resolved plasma diagnostics to assess the production of species within the plasma source, the variation of plasma properties in the transport region, as well as the flux and energy of ions reaching the substrate surface, under a variety of operating conditions.