| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF+EM+MI-WeM |
| Session: | Thin Films for Microelectronics |
| Presenter: | Orlando Cortazar-Martínez, CINVESTAV-Unidad Queretaro, Mexico |
| Authors: | O. Cortazar-Martínez, CINVESTAV-Unidad Queretaro, Mexico J.A. Torres-Ochoa, CINVESTAV-Unidad Queretaro, Mexico C.L. Gomez-Muñoz, CINVESTAV-Unidad Queretaro, Mexico A. De Luna-Bugallo, CINVESTAV-Unidad Queretaro, Mexico A. Herrera-Gomez, CINVESTAV-Unidad Queretaro, Mexico |
| Correspondent: | Click to Email |
We investigated the effect of soft nitridation on the electrical properties of hafnia-based MOS capacitors. Starting from a cleaned Si (100) wafer a 2 nm of HfO2 thin film is grown by ALD using tetrakis (dimethylamido) hafnium(IV) and water type I as precursors. The growth was performed at a temperature of 250 °C with a 20 sccm flow of ultra-high purity nitrogen (UHP-N). Hafnium oxide soft nitridation was performed by a remote plasma (Litmas) using a power of 2500 W, a substrate temperature of 500 °C, the ultra-high purity nitrogen flow was set at 140 sccm and the working pressure is fixed at 3.5x10- 2 Torr. A 300 nm titanium nitride (TiN) layer is deposited in-situ after nitration in a sputtering system, avoiding undesired contamination. Finally, MOS capacitors were defined using photolitography and etching process.
Capacitance vs voltage measurements characterization was carrying out at different frequencies (1 kHz to 1 MHz). MOS capacitors before nitriding shows a decreasing value in their accumulation capacitance when the frequency is increased. This behavior is attributed to the defects states located inside the oxide layer1. In contrast, MOS capacitors measured after nitriding barely shows dispersion in their accumulation regime as the frequency was varied. Also, it can be noted that the threshold voltage remains unchanged.
Films thickness and composition were characterized by ARXPS2. The initial thickness and composition were 20.7 Å and HfO2.09. After nitridation the thickness changed to 19.8 Å with a composition of HfO1.4N0.48. XPS spectra show that the N 1s peak observed at 396.8 eV is associated with the N-Hf bond3, showing a robust evidence of a substitutional incorporation of nitrogen species into the HfO2 with a saturation process like the one reported in silicon oxide nitridation4. Results can be correlated with the soft nitridation process used during fabrication with the remote plasma in which the substitutional nitrogen to oxygen interchange in the HfOxNy films keeping the tetrahedral structure from the ALD hafnium as the same as the original but decreasing the amount of the defect states inside the oxide layer.
1 A. Herrera-Gómez, A. Hegedus, and P.L. Meissner, Appl. Phys. Lett. 81, 1014 (2002).
2 P.-G. Mani-Gonzalez, M.-O. Vazquez-Lepe, F. Espinosa-Magaña, and A. Herrera-Gomez, J. Vac. Sci. Technol. A Vacuum, Surfaces, Film., vol. 31, no. 1, p. 010601, 2013.
3 K.-S. Park, K.-H. Baek, D.P. Kim, J.-C. Woo, L.-M. Do, K.-S. No, Appl. Surface Science 257, 1347, 2010.
4 A. Herrera-Gómez, A. Hegedus, and P.L. Meissner, Appl. Phys. Lett. 81, 1014 (2002).