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Silicon nitride films with the best optical quality can be realized with low pressure chemical vapor deposition (LPCVD)[1]. However, high mechanical stress within the LPCVD silicon nitride films leads to formation of cracks and prevents thick films (> 400 nm) with high optical quality. A number of clever processes have been developed in order to prevent cracks, such as patterning of crack barriers, multi-step deposition and a Damascene process that deposits silicon nitride into trenches. In addition, to reduce material losses and achieve ultralow propagation losses (~ 1 dB/m), long-time high temperature annealing (1200 C for 3 hours) is needed, which can cause dopant diffusion and damage of prefabricated temperature-sensitive devices. Hence, LPCVD Si 3 N 4 is very challenging for applications in back-end-of-line processes and foundry compatible processes. In recent years, low-temperature deposited Si 3 N 4 …