Optical and Electrical Properties of ECR-PECVD Grown SiCN Thin Films

Abstract

Recent progress in scaling down the metal-oxide semiconductor (MOS) devices accompanied limitations arising from quantum effects, which leads to a search for new materials. Silicon oxide (SiO2) thin films have been a favourable dielectric for more than 4 decades. Their usage have become impractical due to the power dissipation and delay in interconnects. To increase the electrical performance, low extinction coefficient (low-k) dielectric materials are being developed as a substitute to SiO2. Those materials draw considerable attraction due to their advances in the integrated circuit technology to increase the transistor density. Among numerous materials, silicon carbonitride (SiCN), which is an intermediate compound between silicon nitride (SiN) and silicon carbide (SiC), has become noteworthy with its unique properties as low-k, robustness, high thermal stability, and wide bandgap of 2.2eV- 5eV1. In this work we present the optical, structural, and electrical analysis of SiCN thin films grown using electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD). The influence of the precursors (SiH4, C2H2, and N2 gases) on the composition and electronic structure of thin films which were characterized by Rutherford backscattering spectroscopy (RBS) and Fourier transmission infrared spectroscopy (FTIR). Furthermore, current-voltage characteristics were studied in dark and illuminated environment at room temperature. We studied the variation of photodiode characteristics with the thin film compositions. These results were also compared with the SiCN thin films growth using identical parameters except for the carbon source (CH4 gas) which has been reported in earlier studies2. Our findings showed that the hydrogen content influenced the optical coefficients of these two set of samples. Index of refraction and extinction coefficients were characterized by variable angle spectroscopic ellipsometry (VASE). In addition to our works on developing low-k matrix to enhance the performance of the integrated circuits, the wide gap feature of SiCN thin films enable us to consider the ultraviolet (UV) photo responsivity effect which is studied for photodetector device application.