Deposition of Low Stress Amorphous Zinc Tin Oxide at Ambient Temperature Using a Remote Plasma Sputtering Process Suitable for Delicate Substrates

Abstract

ZnxSnyOz thin films (<100nm thickness), deposited by remote sputtering from a metal target using a confined argon plasma and oxygen gas jet near the sample, were investigated for their material properties. No visible deformation or curl was observed when deposited on plastic. Materials were confirmed to be amorphous and range between 5 and 10 at.% Sn concentration by x-ray diffraction, x-ray photoemission spectroscopy and energy-dispersive x-ray spectroscopy. Factors affecting the material composition over time are discussed. Depletion of the Sn as the target ages is suspected.

High-resistivity metal-oxide films through an interlayer of graphene grown directly on copper electrodes

“…Thickness was measured by surface ellipsometry and surface profilometry. Composition uniformity was confirmed [19].…”

“…Furthermore, in the HiTUS system, unlike in conventional RF-magnetron sputtering, the plasma density and energy of the plasma can be decoupled for a gentle (in terms of bombardment and temperature) yet quick deposition, in this case 4 min and 30°C. The material here was confirmed to be amorphous using X-ray diffraction [19]. A piece of silicon with a native oxide (*2 nm) was placed with the samples during deposition.…”

“…These five patterns were replicated in batches at seven locations on each wafer (Supplementary Figure S1 is a location map of these batches). Subsequently, the zinc tin oxide was deposited into the pattern using a remote plasma deposition High Target Utilization System (HiTUS) [19][20][21], i.e. the metal oxide is only found bridging each of the pre-patterned pair of contacts.…”

“…A metal ZnSn target was sputtered and oxidation of the channel material occurred during sputter deposition through a continual shower of oxygen placed in between the sample and the target. The percentage of tin relative to zinc after deposition is 8 as measured by X-ray photoemission spectroscopy [19]. The main advantage of this system is that the charged plasma is directed away from the sample such that the damage that would normally occur to carbon-based layers in traditional systems where the sample sits in the plasma is reduced [38].…”

“…Even so, the metal oxides remain sensitive to oxygen content during fabrication, to within a fraction of a per cent. The films presented here are made of zinc tin oxide (ZnSnO), where the main purpose of the tin in this study is to ensure that the layer is amorphous and thus encourage uniformity across the wafer, as verified previously [19].…”