Room Temperature Precursor Vaporization for ALD
Room temperature vaporization of Titanium isopropoxide (TTIP) precursor was performed using ultrasonic atomization module installed in TTIP precursor bubbler for ALD TiO2 thin films. In-situ quartz crystal microbalance (QCM) data shows significantly higher growth rate with TTIP ultrasonic atomizer than that without it because ultrasonic atomization of TTIP occurs even at room temperature. TiO2 growth rates at different ALD reactor temperatures remain unchanged up to 180 oC. Two dimensional TiO2 film thickness mappings were performed by Spectroscopic Elliposometry (SE). The thickness variation of TiO2 film by atomized TTIP is worse than that of TiO2 grown by thermally vaporized TTIP because some droplets of atomized TTIP are quite heavy to touch the back of ALD reactor with a cross-flow configuration. However, with a perpendicular flow configuration of ALD, the thickness uniformity will be significantly improved.
Also, ALD coating for heterogeneous catalysts will be discussed.