Preparation of High-Quality Low-Temperature PECVD Silicon Nitride Films: Effect of NH3 Precursor on Film Properties and RF Response Mechanism

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With the shift in advanced packaging toward 3D integration and flexible electronics, it is becoming critical to produce high-quality silicon nitride films under low thermal budgets. To overcome the limitations of low-temperature deposition, this study compares two gas mixtures—SiH4/NH3/N2 and SiH4/N2—in plasma-enhanced chemical vapor deposition of silicon nitride coatings. We systematically evaluated how the NH3 precursor affects deposition kinetics, chemical bonds, non-uniformity, optical properties, and internal stress at different RF powers and electrode gaps. The test results show that NH3, with its lower dissociation energy, avoids the high activation barrier associated with pure N2 plasma, leading to a higher reactive nitrogen flux and a doubled deposition rate. In the SiH4/NH3/N2 system, raising RF power from 300 W to 900 W reduced hydrogen content from 23.58% to 12.25%. This suppression of hydrogen promoted structural densification, shifting the mechanical stress from 173.3 MPa to −989.7 MPa. At a larger electrode gap of 19 mm, NH3’s better diffusion characteristics offset the electric field sensitivity typical of N2 systems, reducing large-area film non-uniformity by 28.7% compared to a 13 mm gap. This work offers a practical, mass-production-friendly approach for depositing robust, low-hydrogen, highly uniform silicon nitride films at low temperatures.