| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+SS-WeM |
| Session: | ALD Surface Reactions and Precursors |
| Presenter: | Abraham Vega, The University of Texas at Dallas |
| Authors: | A. Vega, The University of Texas at Dallas C.E. Nanayakkara, The University of Texas at Dallas G. Liu, SAFC Hitech R. Kanjolia, SAFC Hitech Y.J. Chabal, The University of Texas at Dallas |
| Correspondent: | Click to Email |
Molybdenum nitride films have properties such as high hardness, high melting point, good chemical stability and high conductivity, which makes them suitable for a wide range of technological areas, as diffusion barriers or interconnections in microelectronics and even as catalysts in fuel cells. Molybdenum nitride films have been deposited by variety of techniques, such as chemical vapor deposition, magnetron sputtering, and atomic layer deposition among others.
For atomic layer deposition of molybdenum nitride, molybdenum complexes containing alkylamido and alkylimido ligands are being considered as potential molybdenum precursors. A notable advantage is that they do not produce corrosive byproducts compared to halide based transition metal precursors.1 A uniform growth has been achieved in the range 260 – 300 0C with bis(tert-butylimido)-bis(dimethylamido)molybdenum when used with NH3 as a co-reactant.1
In this study, in-situ IR and X-ray photoelectron spectroscopies are used to investigate ALD of bis(tert-butylimido)-bis(dimethylamido)molybdenum and hydrazine an alternative for NH3 as co-reactant for molybdenum nitride deposition on pre-annealed, oxidized and OH-terminated Si(100) surfaces. While bis(tert-butylimido)-bis(dimethylamido) molybdenum is expected to react with two surface OH groups leaving one amino groups with further reaction with hydrazine leading to a NHx-terminated surface, the details of the reactions have not been explored, hence the importance of in-situ IR spectroscopy.
Bis(tert-butylimido)-bis(dimethylamido) molybdenum reacts with surface Si-OH groups (loss at 3740 cm-1) to form the expected (O)2-Mo=(N-tBu)2structure, as evidenced by broad band from various CHx stretch bands in the 2900 cm-1 region and stretching of CN bonds at 1240 cm-1, respectively. The first hydrazine pulse leads to a loss of tBu vibrational bands [at 2900 and 1240 cm-1]. The steady state ALD process is characterized by tBu removal by hydrazine and formation of NHx groups driving the ALD process. A clear ligand exchange is observed at deposition temperatures of 225, 250 and 275 °C for 30 cycles. The ALD window for this process was found to be between 225 and 275 °C, with low carbon content determined by XPS, which is lower than the window when using NH3 (260-300 °C) instead of hydrazine. No growth is observed above 300 °C, and very poor quality films are obtained at 200°C.
This work confirms the reactivity of bis(tert-butylimido)-bis(dimethylamido) molybdenum with OH-terminated surfaces at low temperatures and illustrates the role of the co-reactant on the thermal window and the quality of the resulting molybdenum nitride films.
1. Chem. Mater., Vol. 19, No. 2, 2007