Advanced Atomic Layer Deposition Techniques for Metal-Insulator-Metal Diodes
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Date
2017-07-06
Authors
Alshehri, Abdullah H.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
Metal-Insulator-Metal (MIM) diodes are nanoelectronic devices that operate by quantum tunneling of electrons through a thin dielectric layer to rectify high frequency alternating current (AC) to usable direct current (DC). In this research, two fabrication techniques are explored to improve the MIM diode fabrication process; the introduction of a thickness gradient and doping of the insulator layer.
Atmospheric pressure spatial atomic layer deposition (AP-SALD) is used for the first time for the combinatorial fabrication of MIM diodes. This unique technique is used to deposit thin dielectric films with a thickness gradient. A plasma-assisted atomic layer deposition (PAALD) technique is utilized for deposition of nitrogen-doped TiO2 films. Tuning the electron affinity (χ) of the insulator by doping is expected to improve the rectification of the diode.
Pt-Al2O3-Al diodes have been fabricated by AP-SALD to demonstrate the capability of this method for rapid, scalable and atmospheric insulator layer deposition. Current-voltage measurements of these diodes exhibit high asymmetry and nonlinearity. In addition, AP-SALD was implemented to fabricate combinatorial and high-throughput Pl-Al2O3-Al diodes via the introduction of an Al2O3 thickness gradient. Current-voltage characteristics and figures of merit (FOM) for the MIM diodes show variations with the thickness gradient of the Al2O3 insulator.
A plasma assisted atomic layer deposition (PAALD) system was used to deposit nitrogen-doped titanium dioxide. A simple approach was developed that requires only a nitrogen plasma and short plasma exposure times to effectively dope TiO2. A range of nitrogen dopant concentrations were achieved by varying the flow rate and exposure times of nitrogen and oxygen plasmas. A nitrogen content as high as 27.2±0.5 at. % was observed when only the nitrogen plasma was used. The type of nitrogen doping can be varied from purely substitutional to entirely interstitial, as measured by X-ray photoelectron spectroscopy (XPS). UV-Visible spectroscopy measurements showed a shifting in the absorption edge from 350 to 520nm with doping, indicating band gap narrowing from 3.1eV to 1.8eV.
Description
Keywords
MIM diodes, Atomic Layer Deposition (ALD), Doping TiO2, Combinatorial Techniques