An XPS study on the structure of SiN x film deposited by microwave ECR magnetron sputtering

Hydrogen-free SiN x films were deposited at N 2 flow rate ranging from 1 sccm to 20 sccm by microwave electron cyclotron resonance plasma enhanced unbalance magnetron sputtering system. We studied the influence of N 2 flow rate on the structural characteristics of deposited films in chemical structure, stoichiometry, composition at different depths in film, and hardness by using X-ray photoelectron spectroscopy and nano-indantation. The results indicate that the films deposited at low N 2 flow rate are Si-rich structure. The films deposited at 2 sccm N 2 flow rate show an excellent stoichiometry with 94.8% Si—N bond content and uniformity of composition in different depths. At the same time, the films display the highest hardness value of 22.9 GPa. The films deposited at high N 2 flow rate contain too much N—Si—O bond and Si—O bond, which is caused by chemical absorption both on and in film in atmosphere. The films present N-rich structure. In this situation, the films display poor mechanical properties with hardness of only 12 GPa.