TITANIUM ALKOXIDES- ALKYLAMIDES

Titanium bis(isopropoxide) bis(dimethylamide) Ti(OiPr)2(NMe2)2

Fig. ALD of TiO2 using Ti(OiPr)2(NMe2)2 - growth rate per pulse vs deposition temperature and pulse length (insert)

   Titanium bis(isopropoxide) bis(dimethylamide) Ti(OiPr)2(NMe2)2  (M=) is liquid at room temperature and has high volatility, thermal stability and reactivity. Due to these properties, it was proposed as potential Ti precursor for the growth of Ti-contaning layers, and indeed it was successfully applied for the depositiuon of TiO2 films by ALD. [i],[ii],[iii]

 [i] Timothee Blanquart, Academic Dissertation (University of Helsinki, Finland), 2013, « Atomic Layer Deposition of Groups 4 and 5 Transition Metal Oxide Thin Films: Focus on Heteroleptic Precursors. », https://helda.helsinki.fi/bitstream/handle/10138/38958/blanquart_dissertation.pdf?sequence=1

[ii] J. Niinistö, T. Blanquart, S. Seppälä, M. Ritala, M. Leskelä, 2014, ECS Transactions, 64 (9) 221-232, « Heteroleptic Precursors for Atomic Layer Deposition », http://ecst.ecsdl.org/content/64/9/221.short, http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.850.4157&rep=rep1&type=pdf

[iii] T. Blanquart, J. Niinistö, M. Ritala, M. Leskelä, Chem. Vapor Dep., 2014, Vol.20, Iss.7-8-9, p.189-208, Special Issue: Atomic‐Scale‐Engineered Materials (ASEM), Atomic Layer Deposition of Groups 4 and 5 Transition Metal Oxide Thin Films: Focus on Heteroleptic Precursors, https://doi.org/10.1002/cvde.201400055  

Ti(OiPr)2(NMe2)2 for TiO2 films by ALD

Fig. ALD of TiO2 using Ti(OiPr)2(NMe2)2 - Quartz Microbalance measurements

     Ti(OiPr)2(NMe2)2 was successfully applied for the ALD of TiO2 thin films. Though corresponding homoleptic alkoxide (Ti(OiPr)4) and alkylamide (Ti(NMe2)4) precursors of Ti have thermal stabilities «300°C, their heteroleptic combination Ti(OiPr)2(NMe2)2 demonstrated self-limiting growth at temperatures >300°C. At low temperatures (<325°C) no temperature region of constant growth rate (ALD window) was observed for the growth of TiO2 from Ti(OiPr)2(NMe2)2 (neither with O3 nor with H2O as the oxygen source). However, at 325 °C self-limiting growth with quite high growth rate for ALD (0.75-0.9 Å/cycle) was confirmed. (Fig.). High conformality TiO2 layers in the deep trenches (aspect ratio 60:1) were grown using Ti(OiPr)2(NMe2)2 precursors at 275°C. The as-deposited films were crystallized in the anatase phase; thickness-dependent phase change from anatase to rutile at 875–975 °C was observed by high-temperature XRD. The deposited TiO2 films had high purity pure and close to the stoichiometric composition, according to XPS. Spectroscopic ellipsometry was used to measure the refractive indices and absorption coefficient of the layers. Quadrupole mass spectrometry (QMS) and quartz crystal microbalance (QCM) studies were used for in situ investigation of the reaction mechanisms taking place during the ALD process using Ti(OiPr)2(NMe2)2  as precursor [i], [ii]

[i] T. Blanquart, J. Niinistö, M. Gavagnin, V. Longo, V. R. Pallem, C. Dussarrat, M. Ritala and M. Leskelä, Chem. Mater., 24, 3420 (2012), DOI: 10.1021/cm301594p, «  Novel Heteroleptic Precursors for Atomic Layer Deposition of TiO2 », https://pubs.acs.org/doi/abs/10.1021/cm301594p?journalCode=cmatex

[ii] M. Kaipio, T. Blanquart, Y. Tomczak, J. Niinistö, M. Gavagnin, V. Longo, H.D. Wanzenböck, V.R. Pallem, Ch. Dussarrat, E. Puukilainen, M. Ritala, M. Leskelä, Langmuir, 2014, 30 (25), pp 7395–7404, « Atomic Layer Deposition, Characterization, and Growth Mechanistic Studies of TiO2 Thin Films », DOI: 10.1021/la500893u, https://pubs.acs.org/doi/10.1021/la500893u

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