To the best of our knowledge, no earlier study has investigated or described a detailed reaction mechanism for TDMAA, making its surface chemistry less understood. Studies of other dimethylamido precursor can provide insights into the TDMAA surface chemistry. Hence, in this study, the surface chemistry of TDMAA for ALD of AlN was investigated for both plasma and thermal ALD, with NH3 as the co-reactant, using mass spectrometry. Comparisons between TDMAA and TDMAT was also done to probe similarities between the possible reaction pathways of the two dimethylamido precursors.