Effects of process parameters on the refractive index of F-doped SiOC:H films grown by PECVD

F-doped SiOC:H films were deposited on P-type (100) Si wafers by plasma enhanced chemical vapor deposition (PECVD) method using an SiH₄, CF₄ and N₂O gas mixture. The refractive index of the F-doped SiOC:H film continuously decreased with increasing deposition temperature and rf power. As the N₂O gas flow rate decreases, the refractive index of the deposited films decreased down to 1.3778, reaching a minimum value at an rf power of 180 W and 100 °C without flowing N₂O gas. The fluorine content of F-doped SiOC:H film increased from 1.9 at.% to 2.4 at.% as the rf power was increased from 60 W to 180 W, which is consistent with the decreasing trend of refractive index. Also, the maximum fluorine content of the deposited film was 5.5 at.% when it was deposited under the identical process condition exhibiting the lowest refractive index. The surface roughness (root-mean-square) significantly decreased to 0.6 nm with the optimized process condition without flowing N₂O gas.