Effect of the NH₃ Precursor on the Properties and Temperature-Pressure Response Mechanisms of Low-Temperature PECVD Silicon Nitride Film

The integration of advanced semiconductor architectures strictly mandates process thermal budgets below 200 °C, positioning low-temperature PECVD of silicon nitride (SiN_x) film as a critical layer. However, SiN_x film deposited at sub-200 °C inherently exhibits sluggish deposition kinetics and degraded spatial uniformity. To overcome these bottlenecks, this study systematically investigates the regulatory mechanisms of the NH₃ precursor within SiH₄/N₂-based plasmas under varying chamber pressures and substrate temperatures. The results show that the introduction of NH₃ at 2.1 Torr, leveraging its facile plasma dissociation, drastically enhances the deposition rate from 18.2 to 39.1 Å/s and improves thickness uniformity by 1.07%. Meanwhile, NH₃ supplies abundant highly reactive radicals that elevate the refractive index and reinforce compressive stress. Furthermore, film properties exhibit a higher sensitivity to pressure than to temperature, primarily due to the pronounced influence of pressure on plasma dynamics and collision frequencies, whereas the effect of temperature remains comparatively minor. This phenomenon is clearly demonstrated by the Si-H and N-H content. This study validates that operating at low chamber pressures maximizes the collision-free travel distance of SiN_x radicals, providing an optimized and quantified process window for high-volume manufacturing of low-temperature SiN_x film.