(Invited) In-Situ and Combinatorial Techniques for Spatial ALD

Abstract

Atmospheric-pressure spatial atomic layer deposition (AP-SALD) and chemical vapor deposition (AP-CVD) have been developed in recent years as scalable techniques for the rapid deposition of oxide thin films on different substrates for a variety of applications. The atmospheric nature of these techniques facilitates the integration of characterization tools and the modification of the experimental setup to produce novel materials. Here we report in-situ electrical and optical characterization methods that have been developed for our AP-SALD/CVD system, as well as new techniques to deposit oxide films with nanoscale thickness gradients. The in-situ electrical measurements are enabled by a custom-designed, flexible printed circuit board substrate and the optical measurements are performed via reflectometry techniques. The thickness, resistance, and optical constants of prototypical AP-SALD films (ZnO and Al2O3) were monitored during depositions, providing insight into film nucleation and growth. The nanoscale thickness gradient films facilitate combinatorial high-throughput screening of devices, where a multitude of devices with varying film thicknesses can be fabricated on a single substrate. This combinatorial approach was applied to study the role of Al2O3 film thickness as an insulating layer in quantum-tunneling metal-insulator-metal diodes and as an encapsulation layer in metal halide perovskite solar cells.