Silicon nitride thin film deposited by plasma-enhanced chemical vapour deposition technique for various device applications

Anayesu Bariki Malisa, Department of Physics, CoNAS, University of Dar es SalaamFollow

Section

Physical Sciences

Abstract

This work reports on silicon nitride (SiNx) thin film deposited by the Plasma-Enhanced Chemical Vapour Deposition (PECVD) technique. The film was characterized by Variable Angle Spectroscopic Ellipsometry (VASE) to obtain optical constants 𝑛, 𝑘 and thickness using the Cauchy layer built on the Lorentz oscillator model and the B-spline model. The determined optical band gap 𝐸𝑜𝑝𝑡𝑖𝑐𝑎𝑙 for direct transition was 3.2 𝑒𝑉 and that for indirect transition was 2.13 𝑒𝑉. Film characterization was performed by Fourier Transform Infra-Red spectroscopy (FTIR) at two different angles of incidence of 15 degrees to probe deep layers and 65 degrees (Brewster’s angle) to excite both Longitudinal and Transversal Optical (LO and TO) modes, respectively. In the FTIR experiment photons in the IR region revealed dominant bond vibrations of excited covalent bonds e.g. 𝑆𝑖 − 𝑁 stretching mode at 850 𝑐𝑚−1 (TO) and the 𝑆𝑖 − 𝑁 rocking mode at 1180 𝑐𝑚−1 (LO). We could also see the 𝑁 − 𝐻2 scissors and 𝑆𝑖 − 𝐻 stretching mode at 2180 𝑐𝑚−1 and 3350 𝑐𝑚−1 , respectively. X-ray Photoemission Spectroscopy (XPS) characterization assisted us in performing elemental composition analysis of the sample. In the XPS spectrum 𝑆𝑖 2𝑝 peak of 𝑆𝑖𝑁𝑥 was located at 101.4 eV, and that of 𝑆𝑖𝑂2 due to oxygen contamination was located at 102.764 eV. High-Resolution Scanning Electron Microscope (HR-SEM) and Atomic Force Microscope (AFM) characterization indicated good surface roughness suitable for optical device fabrication based on 𝑆𝑖𝑁𝑥 as an antireflection coating and passivation layer for Si-based solar cells, as well as an insulating layer in microelectronics. A Hall-effect Measurement System (HMS) was used to obtain the film carrier concentration of 1.595 × 1017 𝑐𝑚−3 , mobility of ~1.155 1 𝑐𝑚2 𝑉𝑜𝑙𝑡−𝑠𝑒𝑐 , resistivity of ~3.387 × 101 Ωcm and the conductivity of 2.952 × 10−2 . Film compressive and tensile Ωcm stress was determined using a Veeco Dektak Stylus profilometer. The measured stress induced in the film in the directions 𝑥 − and 𝑦 − are 𝜎𝑥 = 93.46 𝑀𝑝𝑎 and 𝜎𝑦 = 137.13 𝑀𝑝𝑎, respectively. Such films are also common in microelectronics as diffusion barriers and low-temperature superconducting devices where amorphous 𝑆𝑖𝑁𝑥 films exhibit less dielectric loss than silicon dioxide (𝑆𝑖𝑂2 ) films.

Recommended Citation

Malisa, Anayesu Bariki (2026) "Silicon nitride thin film deposited by plasma-enhanced chemical vapour deposition technique for various device applications," Tanzania Journal of Science: Vol. 52: Iss. 3, Article 16.
Available at:https://doi.org/10.65085/2507-7961.1040