Impact of the TiN electrode deposition on the HfO2 band gap for advanced MOSFET gate stacks

The impact of the deposition of a TiN electrode on the high-k oxide HfO2 has been investigated, focussing on the dielectric band gap. After the gate elaboration, a non-destructive approach combining Spectroscopic Ellipsometry (SE), Reflection Electron Energy Loss Spectroscopy (REELS) and X-ray Photoelectron Spectroscopy (XPS) was developed to probe the buried metal/high-k interface. The overall optical band gap is 5.9 ± 0.1 eV with no change after the metal gate deposition. A local reduction of 1 eV is measured near the TiN layer, due to N diffusion at the interface creating N 2p states at the top of the HfO2 valence band. Increased disorder and defects are identified in the high-k after gate elaboration by XPS, REELS and SE.