EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Silicon nitride (SiNx) and hydrogenated silicon nitride (SiNx:H) thin films have widespread applications, including passivation films for semiconductor devices in microelectronics industry or antireflective layers for solar cells. The most common deposition techniques of SiNx:H thin films are different types of chemical vapor deposition methods, such as plasma enhanced chemical vapor deposition (PE-CVD) or hot wire chemical vapor deposition (HW-CVD). Due to the hydrogen content of the precursor gases (most often silane) CVD-deposited films always contain hydrogen and its amount cannot be controlled directly during the preparation process. Therefore, sputtering methods could be interesting as alternative fabrication techniques for controlled hydrogen concentration in direct way from zero by adjusting the applied hydrogen gas flow to the chamber.
In this work amorphous SiNx and SiNx:H films were deposited by radio frequency (RF) sputtering on single-side and double-side polished crystalline (001) Si wafers. Hydrogen free films were deposited in pure nitrogen, while hydrogenated thin films were fabricated by applying various hydrogen gas to the chamber while all other deposition parameters were kept constant. Optical properties were investigated as a function of hydrogen concentration of the plasma. Structural investigation revealed correlation between hydrogenation process and the layer porosity. 4 at% of bounded hydrogen content was proved by Fourier Transform Infrared Spectroscopy (FTIR) while Elastic Recoil Detection Analysis indicated 6 at% hydrogen which suggests the presence of molecular hydrogen in the films. Annealing measurements showed that molecular hydrogen was released at temperature of ~65 oC while blisters with approximately 100 nm diameter were created on the thin film surface.