Conformality

Conformality → ALD >> PECVD >> Sputter >>> Evaporation

Transport of reactants to the substrate

• Case 1: direct $\left( S_c=1\right)$
• Case 2: re-emission $\left( S_c<1\right)$
• Case 3: Surface diffusion

Reactive sticking coefficient $S_c$

$$ S_c=\cfrac{incident-re\;emitted}{incident\;precursor} $$

If $S_c \approx1$, non-conformal

$S_c <1,$ conformal