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. 2023 Mar 22;16(6):2539.
doi: 10.3390/ma16062539.

Studies of Electrical Parameters and Thermal Stability of HiPIMS Hafnium Oxynitride (HfOxNy) Thin Films

Mirosław Puźniak  1   2 , Wojciech Gajewski  2 , Aleksandra Seweryn  3 , Marcin T Klepka  3 , Bartłomiej S Witkowski  3 , Marek Godlewski  3 , Robert Mroczyński  1
Affiliations

Studies of Electrical Parameters and Thermal Stability of HiPIMS Hafnium Oxynitride (HfOxNy) Thin Films

Mirosław Puźniak et al. Materials (Basel). .

Abstract

This work demonstrated the optimization of HiPIMS reactive magnetron sputtering of hafnium oxynitride (HfOxNy) thin films. During the optimization procedure, employing Taguchi orthogonal tables, the parameters of examined dielectric films were explored, utilizing optical methods (spectroscopic ellipsometry and refractometry), electrical characterization (C-V, I-V measurements of MOS structures), and structural investigation (AFM, XRD, XPS). The thermal stability of fabricated HfOxNy layers, up to 800 °C, was also investigated. The presented results demonstrated the correctness of the optimization methodology. The results also demonstrated the significant stability of hafnia-based layers at up to 800 °C. No electrical parameters or surface morphology deteriorations were demonstrated. The structural analysis revealed comparable electrical properties and significantly greater immunity to high-temperature treatment in HfOxNy layers formed using HiPIMS, as compared to those formed using the standard pulsed magnetron sputtering technique. The results presented in this study confirmed that the investigated hafnium oxynitride films, fabricated through the HiPIMS process, could potentially be used as a thermally-stable gate dielectric in self-aligned MOS structures and devices.

Keywords: HfOxNy; HiPIMS; MOS; electrical parameters; reactive magnetron sputtering; structural characterization; thermal stability.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
Graphing methodology used in orthogonal tables, employed during the analysis of dependencies between process and material parameters; the example shows the trend (dashed line) of the influence of pressure in the reactive chamber on the permittivity value of HfOxNy films (see Figure 2).
Figure 2
Figure 2
Most essential trends (dashed lines) obtained according to the Taguchi approach employed in this study, which are taken into account to set the ultimate process parameters for fabrication of HfOxNy layers.
Figure 3
Figure 3
Comparison of the hysteresis loop (a) and frequency dispersion (b) of C-V characteristics of MOS structures with HfOxNy films, fabricated using designed sets of parameters for reactive magnetron sputtering processes, i.e., optimal and non-optimal processes.
Figure 4
Figure 4
Qeff/q and Ditmb values, estimated from analysis of C-V characteristics of MOS devices with HfOxNy, as the gate dielectric film fabricated employs optimal and non-optimal HiPIMS processes.
Figure 5
Figure 5
Cumulative breakdown statistics of MOS structures with examined hafnium oxynitride thin films, fabricated employing optimal and non-optimal HiPIMS processes; dashed lines indicate obtained trends.
Figure 6
Figure 6
Morphology of HfOxNy films characterized by AFM; RMS values of the investigated dielectric layers are also shown.
Figure 7
Figure 7
GIXRD patterns (a) and N1s photoelectron spectra (b) of HfOxNy thin films (as-grown and annealed at 300 °C or 800 °C).
Figure 8
Figure 8
Variation of Tauc’ plots of HfOxNy thin-films. Inset: the extracted band-gap (Eg) value, based on the relation (αhν)2 versus hν of particular hafnium oxynitride films.
Figure 9
Figure 9
Comparison of GIXRD patterns of dielectric thin films (as-grown and annealed at 800 °C) (a) and C-V characteristics of MOS devices with HfOxNy films fabricated using PMS and HiPIMS processes and annealed at 800 °C (b); the inset to (b) shows the leakage current density vs. breakdown electric field intensity (Ebr) of MOS structures.
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