Investigating the Impact of Hydrogen Bonding on Silicon Nitride (SiNx) Film

Abstract

The deposition of amorphous hydrogenated silicon nitride (a-SiN_x:H) via plasma-enhanced chemical vapor deposition is critical for optimizing the performance of crystalline silicon (c-Si) solar cells. This study investigates the impact of varying gas ratios (GR = NH₃/SiH₄) on the optical and physical properties of deposited SiN_x films. Results show that the refractive index (RI) ranges from 1.8 to 2.3 with changing gas compositions. Fourier transform infrared Spectroscopy reveals shifts in [SiNH] and [SiH] stretching modes, indicating changes in hydrogen passivation and nitrogen incorporation. Hydrogen bonding densities of [SiH] and [SiNH] correlate positively with the RI. For example, the hydrogen bonding density [N_H] ranges from 4.53 × 10²³ to 6.32 × 10²³ cm⁻³ for [SiNH] bonds while [Si-H] varies from 6.93 × 10²³ to 1.06 × 10²⁴ cm⁻³. Secondary ion mass spectrometry (SIMS) analysis shows stable hydrogen intensity, contrasting with a decrease in nitrogenhydrogen bonds. These findings highlight the key role of hydrogen bonding in determining SiN_x film properties, with significant implications for semiconductor and photovoltaic applications.