Surface morphology of SiN film deposited by a pulsed-plasma enhanced chemical vapor deposition at room temperature

Silicon nitride (SiN) films were deposited by a pulsed plasma enhanced chemical vapor deposition system in a SiH ₄-NH ₃ chemistry. Surface morphology of SiN films at room temperature is first reported. Scanning electron microscope and atomic force microscopy were used for characterization. Radio frequency source power was varied from 200-800 W with an increment of 200 W. For each power, duty cycle was controlled as 40, 50, 70, 90%. Particularly, surface roughness was detailed in terms of a distribution of maximum pixel size or major pixel density, and a nonuniformity of pixel density. A consistent decrease in surface roughness with reducing duty cycle was observed in the ranges of 40-70% and 40-90% at 200 and 600 W, respectively. In contrast, surface roughness increased with reducing duty cycle at 800 W. Meanwhile, both maximum pixel size and distribution of major pixel density were highly correlated to surface roughness as a function of duty cycle at all powers. These two metrics are expected to effectively characterize the degree of surface densification as well as to support surface roughness variations.