(Invited) Vacuum Ultraviolet Photochemical Atomic Layer Deposition of Alumina and Titania Films

Abstract

Conventional atomic layer deposition (ALD) is a thermo-chemical process where co-reagents are sequentially pulsed in cycles onto a heated substrate. As an alternative to substrate heating, various forms of other "non-thermal" ALD processes are being investigated. Herein, the photochemical atomic layer deposition of Al2O3 and TiO2 thin films at 60°C is reported using a shuttered vacuum ultraviolet light source to excite molecular oxygen as a coreagent with the metal precursors. The growth mechanisms using trimethyl aluminium and titanium tetraisopropoxide precursors, are investigated using in-situ quartz crystal microbalance and postdeposition ellipsometric measurements. The photochemical ALD Al2O3 films exhibit different capacitance equivalent thicknesses for irradiated and masked regions respectively, even after postdeposition annealing. The photochemical ALD titania films are amorphous and when incorporated into Pt / TiO2 / Pt metalinsulator-metal structures, the titania exhibits a resistive switching behavior.

Vacuum Ultraviolet-Enhanced Oxidation—A Route to the Atomic Layer Etching of Palladium Metal

“…The idea of supplementing chemical reactions with light in the vacuum ultraviolet (VUV) region (λ < 160 nm) has been explored in atomic layer deposition (ALD) schemes involving Al 2 O 3 , where VUV photons interact with O 3 to deposit Al 2 O 3 at 60 °C and in the room-temperature deposition of Al 2 O 3 and TiO 2 . , Although the benefit of VUV exposure has been demonstrated in ALD and photodissociation for etching is possible, the potential utility of VUV-enhanced ALE is yet to be realized. Additionally, although many ALE techniques have been developed, few exist for many base or noble metals …”

UV-enhanced atomic layer deposition of Al2O3 thin films at low temperature for gas-diffusion barriers

“…ALD assisted by UV irradiation has also been used for enhanced growth of metal oxide thin lms. [40][41][42][43][44][45][46][47] In our previous report, uniform and conformal ZrO 2 thin lms were deposited on plastic substrates at room temperature (RT) by UV-enhanced ALD (UV-ALD). 43 One can expect that high-quality Al 2 O 3 thin lms may be obtained at low deposition temperature by using UV-ALD.…”

“…However, only a couple of cases have been reported for the use of the UV-ALD to prepare Al 2 O 3 thin lm and their deposition temperatures were not limited to low temperature. 42,44 Moreover, these works are focused on the effect of UV irradiation on growth mechanism or electrical properties of the lms, not on their barrier performance for OLEDs applications.…”