On the Influence of Hydrocarbon Precursors and Elemental Composition on the Dielectric Properties and Conduction Mechanism of Hydrogenated Silicon Carbonitride Thin Films
Authors: Abdelal Aysegul , Khatami Zahra , Abishek Allen , Mascher Peter 
Published: December 2020

Ternary compound thin films have drawn interest since intermediate forms can be developed for materials with tunable properties. Among them, thin films of silicon carbonitride (SiCN) are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another area of application of SiCN thin films is as low dielectric constant materials, which are desired for replacing silicon oxide (SiO2) or silicon nitride (Si3N4) in integrated circuits (IC) and charge trapping capacitors. In general, SiCN is an intermediate compound between Si3N4 which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with high mechanical durability [1].

One of the most common techniques for the fabrication of SiCN thin films is plasma enhanced chemical vapour deposition (PECVD) with alkylsilazane precursors for high composition control [2]. Recently, we reported the compositional and mechanical properties of SiCN:H thin films, which were deposited using electron cyclotron resonance (ECR) PECVD with two different hydrocarbon precursors, acetylene (C2H2) and methane (CH4) [3, 4]. In the present work, we explore how film composition affects the electrical behaviour of the thin films. More specifically, we investigate the dielectric properties of SiCN:H thin films and the charge transportation and trapping mechanisms for different stoichiometries and film densities, as a function of the hydrocarbon precursor.

Metal-insulator-semiconductor (MIS) capacitor type structures were formed on p-type (100) silicon substrates. Following the deposition, aluminum (Al) gate electrodes were sputtered for current-voltage (I-V) and capacitance-voltage (C-V) measurements operated at 1 MHz. The results were correlated with composition and density of SiCN:H thin films obtained from Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD), and variable angle spectroscopic ellipsometry (VASE) measurements. Finally, finite element modeling was performed by COMSOL to compare the capacitance characteristics in MIS structures of the thin films.

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[2] S. Bulou, L. Le Brizoual, P. Miska, L. de Poucques, R. Hugon, M. Belmahi, J. Bougdira. The influence of CH4 addition on composition, structure and optical characteristics of SiCN thin films deposited in a CH4/N2/Ar/hexamethyldisilazane microwave plasma. Thin Solid Films, 520(1), 245-250 (2011).

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