Preparation of low-stress SiNx films by catalytic chemical vapor deposition at low temperatures

Silicon nitride (SiNx) films were prepared by catalytic chemical vapor deposition (Cat-CVD) at low substrate temperatures below 130 degrees C. The stress in the films was low, typically lower than 100 MPa, and could be varied from compressive to tensile by changing the deposition conditions used. The cause of the changes in stress was investigated from the relationship between film properties and deposition conditions. Stress was more compressive when the SiH4 flow rate was high, while it was more tensile when the substrate temperature and gas pressure were high. This is attributed to the shrinkage of the film accompanied by gas desorption from the growing surface. The gas desorption is enhanced by the elevation of substrate temperature and the attack of atomic hydrogen. The gas desorption also leads to low hydride densities and high mass densities. The SiNx films prepared by Cat-CVD can be used for passivating organic materials.