Braeken, E

Haukka, S

Kessels, WMM

Knoops, HCM

Pore, V

Potts, SE

Profijt, HB

Roelofs, R

English

UCL Discovery

  Room-Temperature ALD of Al2O3, TiO2, SiO2 and SiNx Enabled by Energy-Enhanced ALD Techniques  S. E. Potts,*,1 H. B. Profijt,1 R. Roelofs,1 E. M. J. Braeken,1 H. C. M. Knoops,1 S. Haukka,2 V. Pore2 and W. M. M. Kessels1  1Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands. 2ASM, Väinö Auerin Katu 12 A, 00560 Helsinki, Finland. *s.e.potts@tue.nl   Atomic layer deposition (ALD) is known to give high quality films at relatively low temperatures (≤200 °C) [1]; however, as ALD is driven by surface reactions, there is the potential to obtain saturating ALD at the lowest extreme of room temperature. For room-temperature ALD (RT-ALD), thermal ALD processes are generally not suitable due to a lack of thermal energy, especially with respect to the ligand removal step when using H2O or NH3, making the deposition times and purge times impractically long. Energy-enhanced ALD techniques [2], such as plasma-enhanced [3] or ozone-based ALD, can help to overcome these problems. However, despite employing energy-enhanced co-reactants, RT-ALD is not always possible. Using Al2O3, TiO2, SiO2 and SiNx as examples, we discuss here the mechanisms and fundamentals of RT-ALD processes.  To test the viability of RT-ALD processes, Al(CH3)3 (TMA), Ti(OiPr)4 (TTIP), SiH2(NEt2)2 (BDEAS) and SiH2(NHtBu)2 (BTBAS) were employed as high-vapour-pressure metalorganic precursors to Al2O3, TiO2, SiO2 and SiNx, respectively (Fig. 1). For oxides, an O2 plasma or O3 gas was used as the co-reactant [4]. All plasma-enhanced RT-ALD processes gave growth at room temperature (Fig. 1a-c), which was a result of the high reactivity of the O2 plasma. For the O3-based processes, growth was only observed for Al2O3 (1.1 Å/cycle). In the case of TiO2, the lack of growth with O3 was a result of insufficient thermal energy, which could also be the case for SiO2. However, the heteroleptic nature of the BDEAS precursor was also an important factor, as O3 exhibits a low reactivity towards Si–H surface groups [5] under ALD conditions. For SiNx, growth was obtained using a remote plasma (Fig. 1d), but the films contained significant quantities of C and O.  It is evident that the viability of an RT-ALD process is not straightforward. It is essential that both the metalorganic precursor and the co-reactant be sufficiently reactive with the surface groups left after the preceding respective RT-ALD half-cycle. High-vapour-pressure precursors and short purge times are desirable. Using these results, the practicalities and possibilities for RT-ALD will be demonstrated and discussed.   This work is supported by NanoNextNL, a micro and nanotechnology programme of the Dutch ministry of economic affairs, agriculture and innovation (EL&I) and 130 partners. Air Liquide and Air Products are thanked for the donations of BDEAS and BTBAS, respectively.  [1] S. E. Potts et al., J. Electrochem. Soc., 157, P66 (2010); [2] S. E. Potts and W. M. M. Kessels, Coord. Chem. Rev., submitted (2013); [3] H. B. Profijt et. al., J. Vac. Sci. Technol. A, 29, 050801 (2011); [4] S. E. Potts et al., Chem. Vap. Deposition, in press (2013); [5] C. K. Fink et al., J. Phys.: Condens. Matter, 21, 183001 (2009).  Fig. 1. RT-ALD saturation curves for (a) Al2O3, (b) TiO2, (c) SiO2 and (d) SiNx as measured by in situ spectroscopic ellipsometry. All plasma-enhanced RT-ALD processes gave saturating growth-per-cycle (GPC) values of (a) 1.5, (b) 0.6 and (c) 1.2 Å/cycle for Al2O3, TiO2 and SiO2, respectively. Growth was only obtained with O3 where TMA was the precursor (1.1 Å/cycle). RT-ALD of SiNx afforded a GPC of 1.3 Å/cycle. 

Room-Temperature ALD of Al₂O₃, TiO₂, SiO₂ and SiNₓ Enabled by Energy-Enhanced ALD Techniques

https://discovery.ucl.ac.uk/id/eprint/10114890/9/Potts_SEP_ALD2013_Abstract_Submitted.pdf

Room-Temperature ALD of Al₂O₃, TiO₂, SiO₂ and SiNₓ Enabled by Energy-Enhanced ALD Techniques

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