New Design and operation of Photon Energy Source for the Low Temperature Atomic Layer Deposition Process; Deposition of TiO_2 on Polymer Substrates

摘要

The design and operation of a new photon energy source for the atomic layer deposition (ALD) process is presented. Results suggest its use is feasible in industrial application areas for ALD, such as in printed electronics and packaging, where roll-to-roll ALD is necessary for large industrial scale production. Moving towards faster production sets requirements for optimization and improvement of the ALD cycle steps. Deposition at low temperatures is required for polymer substrates. Photon energy assistance can be used to enable these requirements. The commonly used plasma assisted processes may have drawbacks such as polymer photodegradation and unwanted effects on the film due to a presence of vacuum ultraviolet photons and ions. The photon energy source developed in this study allows the control of photon energy level by filtering the wavelengths using optical windows with defined absorption characteristics to cut off the wavelengths that are harmful to polymers. Here, the window materials studied were quartz, borosilicate glass and several transparent polymers. These materials enable the photon energy cut off wavelength to be varied from 170 nm to close to 400 nm. The metal oxide film growth showed similar characteristics to typical plasma assisted ALD. The effect of different photon energy on the molecular oxygen gas dissociation to produce radicals, on polymer substrate photodegradation and on the film growth characteristics will be further discussed.