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Investigating the Causes of Reduced Stress in TiN Films

This study delves into the factors behind the reduced stress in TiN films, analyzing N2 levels, transitions, and surface structures. The research explores film stress proportional to TiN composition and its impact on surface smoothness. The investigation highlights meso-scale nonuniformity leading to deep crevasses and broad transitions in the films, with implications for TiN quality and stress relief mechanisms. The study poses open questions regarding the intrinsic nature of stress reduction and the significance of fractured surfaces.

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Investigating the Causes of Reduced Stress in TiN Films

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  1. Reduced N2 TiN causes rougher, very pitted structureCause of reduced stress?

  2. Film Stress proportional to Tc

  3. RvT comparison shows two distinct regions Broad transitions, Low N2, lower stress, huge crevasses Sharp transitions, High N2, high stress, smooth Assume that measurement geometry is roughly constant, reasonable as chips identical and bonding likely to be similar.

  4. High N2 fraction, high TcTiN very smooth, irrespective of chamber MV028, 15:10 Ar:N2 Tc=4.5K Very small, 25nm grains RMS=0.4nm DSW016, 15:10 Ar:N2 Tc=5.1K Very small , 25nm grains RMS=0.25nm

  5. Slightly reduced N2 TiN keeps smooth surface DSW024, 15:2.0 Ar:N2 Tc=4.6K ~20nm grains RMS=0.4nm DSW019, 15:2.5 Ar:N2 Tc=4.7k ~20nm grains RMS=0.7nm

  6. Further reducing N2 leads to deep crevasses DSW023 15:1.5 Ar:N2 Tc~2K, ΔTc~1K Meso-scale nonuniformity causing broad Tc? 45nm deep pits, comparable to film thickness RMS roughness ~5nm Small grains still visible if look very closely

  7. Lower TcTiN 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

  8. 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?

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