The Variation of Crystalline Structure Induced by Gas Dilution and Thermal Annealing in Silicon Layers Deposited by PECVD Technique

We prepared hydrogenated thick silicon film by plasma enhanced chemical vapor deposition (PECVD) method using SiH4 and H2 gas mixture and we investigated the effect of the hydrogen dilution ratio defined as \( R=\frac{\left[{H}_2\right]}{\left[{SiH}_4\right]} \) on the as-deposited and annealed films. With increase in hydrogen dilution ratio, amorphous to microcrystalline transition has been observed. The crystallization has been confirmed from Raman spectroscopy, UV reflectance, low angle X-ray diffraction (XRD), spectroscopic ellipsometry and atomic force microscopy (AFM) analysis. Tauc band gap shows a decreasing trend with increasing H2 dilution of silane. It decreases from 1.8 to 1.57 eV. It has been concluded that H2 dilution of silane in PECVD enhances the crystallinity of the film and affects its optical and structural properties.