In situ diagnostics for studying gas-surface reactions during thermal and plasma-assisted atomic layer deposition

Abstract

The authors have constructed a novel experimental setup to investigate the surface reaction mechanisms during thermal and plasma-assisted atomic layer deposition (ALD) of thin films by employing in situ surface and gas-phase diagnostic techniques. Specifically, we have used a real-time attenuated total reflection Fourier transform infrared spectroscopy setup to detect the surface adsorbates as well as gas-phase species in each half-reaction cycle during ALD. In this article, we describe the reactor construction and the in situ diagnostics with sufficient details that it can be a useful reference for researchers in the field. To illustrate the use of these in situ diagnostics, we present our results for the ALD of TiO2 from titanium tetraisopropoxide in conjunction with H2O, O3, and a O2 plasma. For O2 plasma-assisted ALD, our measurements are complimented with optical emission spectroscopy to identify the radicals and excited molecular species in the plasma, some of which are produced by the dissociation of the surface reaction products. The authors show that in O3- and O2 plasma-assisted ALD processes, the surface reaction products play an important role in determining the surface chemistry.