Characterization of Atomic Layer Deposited Thin Films: Conformality in High Aspect Ratio Pores and the Electrical Properties of Capacitors

In this work the characterization of atomic layer deposited (ALD) Al2O3, TiO2 and ZnO thin films is presented by introducing their conformality in high-aspect ratio pores and their electrical properties in capacitors, followed by the experimental results. In addition, a literature survey on thin films and ALD technology is presented. Trimethyl aluminium (TMA), titanium tetrachloride (TiCl4), diethyl zinc (DEZ) and water vapor (H2O) were used as precursors. The conformality of high aspect ratio pores was studied by deposition of Al2O3, TiO2 and ZnO films in closed and open end pores and analysis by using scanning electron microscope (SEM). The ALD deposition process was confirmed conformal in closed pores, but in open end pores the conformal deposition process was non-ideal. The electrical properties of Al2O3 and Al2O3-TiO2 laminates in planar capacitors were studied by deposition of the thin films as the dielectric layer in capacitors with varying deposition temperature, film thickness, surface area and TiO2 content in the laminate films. The results were analyzed by measuring the capacitance value, leakage current and breakdown strength of the planar capacitors. The higher deposition temperature increases growth rate and produces thicker films, which have lower capacitance values than thinner films. However, higher deposition temperature resulted in low leakage current. The smaller surface area of the capacitor resulted in low leakage current density. Laminates with low TiO2 content resulted in low leakage current. The key finding was that capacitors prepared with TiO2 in the dielectric thin film layer exhibited ability to short energetic peaks without irreversible failure. Also, low leakage current in ALD Al2O3 dielectric capacitors was achieved with use of relatively low deposition temperature.