Atomic layer deposition (ALD) raises global interest through its unparalleled conformality. This work describes new microscopic lateral high-aspect-ratio (LHAR) test structures for conformality analysis of ALD. The LHAR structures are...
Surface
recombination of plasma radicals is generally considered
to limit film conformality during plasma-assisted atomic layer deposition
(ALD). Here, we experimentally studied film penetration into high-aspect-ratio
structures and demonstrated that it can give direct information on
the recombination probability r of plasma radicals
on the growth surface. This is shown for recombination of oxygen (O)
atoms on SiO2, TiO2, Al2O3, and HfO2 where a strong material dependence has been
observed. Using extended plasma exposures, films of SiO2 and TiO2 penetrated extremely deep up to an aspect ratio
(AR) of ∼900, and similar surface recombination probabilities
of r = (6 ± 2) × 10–5 and (7 ± 4) × 10–5 were determined for
these processes. Growth of Al2O3 and HfO2 was conformal up to depths corresponding to ARs of ∼80
and ∼40, with r estimated at (1–10)
× 10–3 and (0.1–10) × 10–2, respectively. Such quantitative insight into surface recombination,
as provided by our method, is essential for modeling radical-surface
interaction and understanding for which materials and conditions conformal
film growth is feasible by plasma-assisted ALD.
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