Provided herein are methods of depositing conformal silicon nitride films using atomic layer deposition by exposure to a halogen-free, N—H-bond-free, and carbon-free silicon-containing precursor such as disilane, purging of the precursor, exposure to a nitrogen plasma, and purging of the plasma at low temperatures. A high frequency plasma is used, such as a plasma having a frequency of at least 13.56 MHz or at least 27 MHz. Methods yield substantially pure conformal silicon nitride films suitable for deposition in semiconductor devices, such as in trenches or features, or for memory encapsulation.