Effect of H₂ addition during PECVD on the moisture barrier property and environmental stability of H:SiN_x film

Abstract

A hydrogenated silicon nitride (H:SiN x ) film with enhanced moisture barrier property and environmental stability was developed using plasma-enhanced chemical vapor deposition (PECVD) with the addition of H 2 gas at 100°C. The moisture barrier property and film density of the 100-nm-thick H:SiN x film were ameliorated by increasing the H 2 gas flow rate during PECVD. X-ray photoelectron spectroscopy and Fouriertransform infrared spectroscopy studies demonstrated that the improved performance was a result of an increase in the amount of Si-N bonds compared to hydrogenterminated bonds with an increase in the H 2 gas flow rate. It is believed that H 2 gas assisted the formation of aminosilane, which contributed to the condensation of silicon nitride by lowering the activation energy for radicalization reactions of silane and ammonia. After the 85°C/85% RH test, the optimized H:SiN x film maintained a water vapor transmission rate lower than 5 × 10 −5 g/m 2 /day owing to the suppression of oxidation. The optimized H:SiN x film was rarely oxidized owing to the decrease in hydrogen-terminated bonds and increase in the film density. The results indicated that the introduction of H 2 gas during the PECVD process strengthened the environmental stability of the H:SiN x film.

Long-term stability of low-temperature deposited Cat-CVD SiN x thin film against damp-heat stress

“…Note that the SiN x films formed by PECVD are fully oxidized under DH testing for only 7 days. 35) The main Si-N peaks were completely replaced by a strong peak at ∼1080 cm −1 corresponding to a Si-O stretching mode, along with the disappearance of the Si-H and N-H vibration modes. A possible explanation for the higher stability of Cat-CVD SiN x films under the DH test is due to their high film density.…”

“…In fact, our XRR measurement revealed that the film density of the Cat-CVD SiN x is as high as ∼2.5 g cm −3 , which is much higher than that of the PECVD SiN x deposited at the same T sub . 35) The density of SiN x films is inversely proportional to the hydrogen content in the film, i.e. hydrogen in bonding with Si and N (Si-H and N-H bonds).…”