Ni/4H-SiC Ohmic Contact Formation Using Multipulse Nanosecond Laser Annealing

Abstract:

Nowadays, the growing worldwide electrification requires new materials for power management. SiC currently dominates the market thanks to excellent energy efficiency and broad operating capabilities. The present paper proposes an experimental study of the Ni-SiC backside ohmic contact formation using 308 nm nanosecond laser annealing (NLA). After Nickel (80 nm) sputtering over 4H-SiC wafers, various laser conditions are investigated, with energy density (ED) ranging from 2.4 to 5.4 J/cm², pulse number from 1 to 20 and chuck temperature from 25 °C (RT) to 400 °C. For all series, a common scenario is noticed as the ED increases, with first solid-state reactions, then local melt and, finally, complete top layer melt and de-wetting at high ED. An in-depth understanding of the impact of laser conditions on these stages is achieved, based on electrical data, Raman spectroscopy, optical microscopy, Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). Results reveal that both high pulse numbers and the use of a hot chuck enable to significantly reduce the ED needed to form low resistance contacts. In addition, sheet resistances and contact resistivities are linked to the microstructure evolution upon NLA exposure. As a proof-of-concept, an acceptable process point yields a contact resistivity around 5×10^-5 Ω cm² when the wafer is processed at 25 °C and a value as low as 10^-5 Ω cm² for 400 °C processing. The mechanisms involved and discussed in the present work may very likely pave the way for other contact formation with limited thermal budget.

• Periodical: Solid State Phenomena (Volume 359)
• Pages: 65-70
• DOI: https://doi.org/10.4028/p-k5uqJc
• Online since: August 2024
• Authors: Mathieu Opprecht*, Sébastien Kerdilès, Jérôme Biscarrat, Philippe Godignon, Cédric Masante, Romain Laviéville, Nicolas Vaxelaire, Patrice Gergaud, Adeline Grenier, Carl Jung, Fabien Roze, Zeinab Chehadi, Louis Thuries, Lu Lu, Toshiyuki Tabata
• Keywords: Contact Resistance, Laser Annealing, Multipulse, Ni-4HSiC, Ohmic Contact

References

[1] P. Badalà et al., « Ni/4H-SiC interaction and silicide formation under excimer laser annealing for ohmic contact », Materialia, vol. 9, p.100528, 2020.

DOI: 10.1016/j.mtla.2019.100528

[2] Rascuna et al., « Morphological and electrical properties of Nickel based Ohmic contacts formed by laser annealing process on n-type 4H-SiC », Materials Science in Semiconductor Processing, vol 97, pp.62-66, 2019.

DOI: 10.1016/j.mssp.2019.02.031

[3] F. Mazzamuto et al. , « Low Thermal Budget Ohmic Contact Formation by Laser Anneal », Mater. Sci. Forum, vol. 858, p.565‑568, 2016.

DOI: 10.4028/www.scientific.net/msf.858.565

[4] T. Kimoto et J. Cooper, Fundamentals of Silicon Carbide Technology, 2014, Singapore;Wiley.

[5] Z. Zhou et al., « Characteristics of Ni-based ohmic contacts on n-type 4H-SiC using different annealing methods », Nanotechnol. Precis. Eng., vol. 4, no 1, p.013006, 2021.

[6] S. Liu et al., « A method to improve the specific contact resistance of 4H-SiC Ohmic contact through increasing the ratio of sp 2 -carbon », Appl. Phys. Lett., vol. 117, no 2, p.023503, 2020.

DOI: 10.1063/5.0009813

[7] F. La Via et al., « Schottky ohmic trantition in nickel silicide 4h-SiC system Is it really a solved problem », Microelectronic Engineering, p.519‑523, 2003.

DOI: 10.1016/s0167-9317(03)00464-7

[8] D. Mangelinck et al., « Mechanisms of Silicide Formation by Reactive Diffusion in Thin Films », Diffus. Found., vol. 21, p.1‑28, 2019.

DOI: 10.4028/www.scientific.net/df.21.1

[9] I. P. Nikitina et al., « Formation and role of graphite and nickel silicide in nickel based ohmic contacts to n-type silicon carbide », J. Appl. Phys., vol. 97, no 8, p.083709, 2005.

DOI: 10.1063/1.1872200

[10] S. Y. Han et al., « Ohmic contact formation mechanism of Ni on n-type 4H–SiC », Appl. Phys. Lett., vol 79, p.1816 (2001).

[11] F. Roccaforte et al., « Emerging trends in wide band gap semiconductors (SiC and GaN) technology for power devices », Microelectron. Eng., vol. 187‑188, p.66‑77, 2018.

DOI: 10.1016/j.mee.2017.11.021