Reduced N2 TiN causes rougher, very pitted structure

Cause of reduced stress?

Film Stress proportional to Tc

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:N2Tc=5.1KVery small , 25nm grainsRMS=0.25nm

MV028, 15:10 Ar:N2Tc=4.5KVery small, 25nm grainsRMS=0.4nm

Slightly reduced N2 TiN keeps smooth surface

DSW019, 15:2.5 Ar:N2Tc=4.7k~20nm grainsRMS=0.7nm

DSW024, 15:2.0 Ar:N2Tc=4.6K~20nm grainsRMS=0.4nm

Further reducing N2 leads to deep crevasses

45nm deep pits, comparable to film thicknessRMS roughness ~5nmSmall grains still visible if look very closely

DSW023 15:1.5 Ar:N2Tc~2K, ΔTc~1KMeso-scale nonuniformity causing broad Tc?

Lower Tc TiN similar, with deep crevasses

DSW021, 15:1.0 Ar:N2Tc=1.550nm deep pitsRMS=7nm

DSW022, 15:0.7 Ar:N2Tc=0.750nm deep pitsRMS=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?