| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF+EM+NS+PS+SM-ThM |
| Session: | Plasma ALD and Nano-applications |
| Presenter: | Martijn Vos, Eindhoven University of Technology, Netherlands |
| Authors: | M.F.J. Vos, Eindhoven University of Technology, Netherlands B. Macco, Eindhoven University of Technology, Netherlands N.F.W. Thissen, Eindhoven University of Technology, Netherlands A.A. Bol, Eindhoven University of Technology, Netherlands W.M.M. Kessels, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
In this contribution we present a novel plasma-assisted atomic layer deposition (ALD) process to deposit high-quality molybdenum oxide films, with a high growth per cycle (GPC) over a wide temperature range of 50 °C to 350 °C. This process complements existing (thermal) ALD MoOx processes, which are less suited for deposition at low temperature, due to low GPC and contamination. A decent deposition process is of importance as MoOx films have received great interest due to their remarkable optoelectronic and catalytic properties and find their use in many applications, including solid state lithium batteries, gas sensors, and more recently solar cells.
A variety of deposition techniques exists for the deposition of MoOx, such as evaporation, sputtering, chemical vapor deposition and ALD. While many of the applications of MoOx films can benefit from the merits of ALD, i.e. conformality and digital thickness control, only few ALD processes are known from literature [1, 2]. Recently bis(tert-butylimido) bis(dimethyamido) molybdenum ((NtBu)2(NMe2)2Mo) appeared as a promising precursor for ALD of MoOx films, using O3 as oxidant [2].
The plasma-assisted ALD process we report on uses (NtBu)2(NMe2)2Mo and O2 plasma and shows a relatively high GPC between 0.70 Å and 0.93 Å for amorphous films deposited at temperatures up to 250 °C. In comparison, the analogous O3 process is featured by a low GPC of 0.17 Å at 150 °C. For deposition temperatures above 250 °C polycrystalline growth was observed, accompanied by an increase in GPC to 1.88 Å for 350 °C. From Rutherford backscattering measurements it was determined that the C and N content in the films is below the detection limit (3 at.% and 2 at.% respectively) for all deposition temperatures, which demonstrates the high-quality of the films (while the aforementioned O3 process resulted in 9.2 at.% N). Furthermore the O/Mo ratio was found to be just below 3, indicative of oxygen vacancies, which are common for MoOx films and can lead to an increased conductivity, which is beneficial for many applications. Additional material properties such as band gap, work function and surface morphology will also be discussed and finally an outlook to the application of this ALD process in silicon solar cells will be given.
[1] M. Diskus et al., J. Mater. Chem. 21 (2011) 705
[2] A. Bertuch et al., J. Vac. Sci. Technol. 32 (2014) 01A119