| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Monday Sessions |
| Session TF-MoA |
| Session: | Emerging Applications for ALD |
| Presenter: | Dan Alvarez, RASIRC |
| Authors: | D. Alvarez, RASIRC J. Spiegelman, RASIRC R. Holmes, RASIRC S. Allanson, RASIRC A.C. Kummel, University of California, San Diego S. Wolf, University of California, San Diego M. Kavrik, University of California, San Diego K. Andachi, RASIRC |
| Correspondent: | Click to Email |
Overview
New channel materials such as SiGe, Ge and InGaAs create challenging thermal budgets (<400°C) for metal nitride deposition. TiNx metal gate electrodes in particular need new low temperature ALD methods.
Hydrazine has shown viable reactivity in previous studies but practical use has been limited due to purity concerns, especially water contamination [1-3]. Commercially available anhydrous hydrazine typically has a water concentration ranging from 0.2-2.0%. In addition to this low purity issue, oxygen concentration in metal-nitride films made using hydrazine is a high 4-15% for SiNx and TiNx.
Previous reports detail the safe delivery of gaseous hydrazine using a solvent-based formulation and membrane delivery system [4]. This presentation details studies on water measurement and removal, plus low resistivity films resulting from hydrazine-based low temperature TiNx ALD.
Hydrazine Purification, Measurement
Studies show that water contamination levels can be reduced to <50 parts-per-million (ppm) using new hydrazine source purification methods as measured by Karl-Fischer and GC-MS methods. Gas phase output of the ultra-dry materials was measured below the FT-IR moisture measurement method lower detection limit of 0.83ppm (Figure 1). Standard commercially available hydrazine has a comparatively high gas phase moisture measurement of 31ppm.
Titanium Nitride Deposition
Sequential pulsing of TiCl4 and N2H4 precursors at substrate temperatures of 275°C-350°C achieved atomic layer deposition TiNx. Initial measured resistivity at 350°C was a low Raverage = 130 ohm, Rsheet = 50 ohm. Growth rate is approximately 0.5A per cycle. Films were characterized by XPS (Figure 2), AFM, KPFM, TEM and four-point sheet resistance. Little to no oxygen was present in the TiNx film, which had a near stoichiometric ratio of Ti/N. The presentation will include additional optimization to reduce residual chlorine content at lower temperatures. In addition, a correlation with regards to residual Chlorine content/Resistivity versus deposition temperature will be discussed.
References
[1] S. Wolf, M. Edmonds, T. Kent, D. Alvarez, R. Droopad A. C. Kummel, AVS (2015) EM+NS+PS-MoA7.
[2] K. Bernal-Ramos, T. Chen, R. Kanjolia, Y. J. Chabal, AVS ALD (2014).
[3] B. Burton, S. Kang, S. Rhee, S. George, J. Electrochem. Soc. 155(7) (2008) D508-D516.
[4] D. Alvarez Jr, J. Spiegelman, E. Heinlein, R. Holmes, C. Ramos, M. Leo, Sean Webb, ECS Trans. 72(4), (2016), 243-248.