| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+EM+MI+MS-TuM |
| Session: | ALD for Alternative Devices |
| Presenter: | Morteza Aghaee, Eindhoven University of Technology, Netherlands |
| Authors: | M. Aghaee, Eindhoven University of Technology, Netherlands P.S. Maydannik, Lappeenranta University of Technology, Finland P. Johansson, Tampere University of Technology, Finland M. Creatore, Eindhoven University of Technology, Netherlands T. Homola, Masaryk University, Czech Republic D.C. Cameron, Masaryk University, Czech Republic J. Kuusipalo, Tampere University of Technology, Finland |
| Correspondent: | Click to Email |
Spatial atomic layer deposition (S-ALD) is a technique which has been shown to lead to high quality moisture barrier films (e.g. Al2O3) in a roll-to-roll process1. However, TiO2 is expected to outperform Al2O3 because of its higher stability against long-term degradation than Al2O3. For high throughput S-ALD at low temperature, highly reactive precursors with high vapour pressure are necessary. Titanium chloride is typically used but has the disadvantages of residual chlorine incorporation in the film and generation of corrosive by-products. Titanium tetra-isopropoxide (TTIP) is a valid alternative because of its high vapour pressure at room temperature compared to other titanium organometallic compounds2. TTIP has not previously been used as a precursor for S-ALD.
In this work, a preliminary investigation has been carried out on the temporal ALD approach consisting of alternating exposure of a polyethylene naphthalate (PEN) substrate to the precursors TTIP and water, ozone or oxygen-fed plasma. The deposition was carried out at a substrate temperature of 80-120oC. The highest growth rate (0.056 nm/cycle) and refractive index (2.33) values have been obtained by using an O2- fed plasma. The water vapour transmission rates have been found to be lower than 5 × 10-4 g.m-2.day-1 at 38°C, 90% RH conditions for a film thickness of 20 nm. For the water process, WVTR values were found to be in the range of 10-3 for a 40 nm film.
Based on these results, a low pressure S-ALD process was developed using a Beneq TFS200R system. Titanium dioxide films were successfully deposited by TTIP and water as S-ALD precursors in the same temperature range as temporal, and their properties were characterised in terms of growth per cycle, refractive index and chemical composition. The growth rate saturated at precursor exposure time of 230 ms at every deposition temperature, which was slightly higher than the growth rate in temporal ALD mode at the same temperature range. Similar properties (refractive index and chemical composition) to temporal ALD have been obtained by adopting S-ALD.
1 P. S. Maydannik, T. O. Kääriäinen, K. Lahtinen, D. C. Cameron, M. Soderlund, P. Soininen, P. Johansson, J. Kuusipalo, L. Moro, and X. Zeng, J. Vac. Sci. Technol. A 32, 051603 (2014).
2 M. Aghaee, P. S. Maydannik, P. Johansson, J. Kuusipalo, T. Homola, M. Creatore, D. C. Cameron, Submitted to J. Vac. Sci. Technol. (2015)