Radical analysis and residence-time effect of silicon nitride atomic layer deposition processes with trisilylamine and NH3 plasmas

The residence time effect of SiNx plasma atomic layer deposition processes was investigated. The reactive species (H-x, NHy, SiHz) were analysed by a mass spectrometer. In the NH3 plasma step, a strong SiH4 peak was observed and is attributed to the desorption of SiH4 from the SiNx surface. A relatively low N/Si ratio of 1.16 was identified owing to the re-deposition of the desorbed SiH4. The re-deposition was decreased by reducing the residence time of reactants. The re-deposition species were quantitatively analysed using optical emission spectrometry, and the N/Si ratio increased nearly to the ideal stoichiometric value of 1.33.