RvT comparison shows two distinct regions Sharp transitions, High N2, high stress, smooth Broad transitions, Low N2, lower stress, huge crevasses Assume that measurement geometry is roughly constant, reasonable as chips identical and bonding likely to be similar.
High N2 fraction, high Tc TiN very smooth, irrespective of chamber DSW016, 15:10 Ar:N2 Tc=5.1K Very small, 25nm grains RMS=0.25nm MV028, 15:10 Ar:N2 Tc=4.5K Very small, 25nm grains RMS=0.4nm
Further reducing N2 leads to deep crevasses 45nm deep pits, comparable to film thickness RMS roughness ~5nm Small grains still visible if look very closely DSW023 15:1.5 Ar:N2 Tc~2K, ΔTc~1K Meso-scale nonuniformity causing broad Tc?
Lower Tc TiN similar, with deep crevasses DSW021, 15:1.0 Ar:N2 Tc=1.5 50nm deep pits RMS=7nm DSW022, 15:0.7 Ar:N2 Tc=0.7 50nm deep pits RMS=5nm
Open questions Is the reduced stress in the lower Tc films intrinsic or does the fractured surface relieve the stress? Does the fractured, rough surface matter? DSW026 similar to DSW023, and Jiansong saw high enough Qs at high power. If necessary, mitigate through thicker amorphous seed layer? Higher DC sample bias?