ABSTRACT: By use of a combination of electrical measurements and
internal photoemission interface barrier characterization, the effective
workfunction (EWF) changes of nm-thin TiN layer deposited on top
of oxide insulators (SiO2, HfO2) have been correlated with atomic and
chemical composition of the metal/oxide interfaces characterized by
photoelectron spectroscopy and X-ray absorption. The major
mechanisms of the EWF tuning are shown to be correlated to
redistribution of light N and O atoms. Oxygen scavenging from the
underlying oxides changes the TiN EWF by forming a Ti oxynitride
layer at the interface and introducing charge traps in the near-interface
oxide layer. By contrast, significant (≈1 eV) reduction of EWF can be
achieved by introduction of a thin TiAl getter layer on top of TiN film.
The mechanism of this reduction can be traced to formation of metallic Ti caused by nitrogen scavenging by TiAl as evidenced by
AlN formation.