Atmospheric pressure plasma enhanced spatial atomic layer deposition of SnOx as conductive gas diffusion barrier

Abstract

The authors report the preparation of transparent conductive gas permeation barriers based on thin films of tin oxide (SnOx) grown by spatial atomic layer deposition (ALD) at atmospheric pressure. They present a comparative study using tetrakis(dimethylamino)tin(IV) and various oxidants (atmospheric pressure oxygen plasma, ozone, and water) at process temperatures in the range of 80–165 °C. Specifically, for oxygen plasma or ozone as oxidant, the authors confirm self-limited ALD growth with a growth per cycle (GPC) of 0.16 and 0.11 nm for 80 and 150 °C, respectively, comparable to the classical vacuum-based ALD of SnOx. On the contrary, for water-based processes the GPC is significantly lower. Very notably, while SnOx grown with water as oxidant shows only a very limited electrical conductivity [10−3 (Ω cm)−1], atmospheric pressure oxygen plasma affords SnOx layers with an electrical conductivity up to 102 (Ω cm)−1. At the same time, these layers are excellent gas permeation barriers with a water vapor transmission rate as low as 7 × 10−4 g m−2 day−1 (at 60 °C and 60% rH). ALD growth will be demonstrated at substrate velocities up to 75 mm/s (i.e., 4.5 m/min), which renders spatial plasma assisted ALD an excellent candidate for the continuous manufacturing of transparent and conductive gas permeation barriers based on SnOx.