Pulsed laser deposition of TiO2 for MOS gate dielectric

Titanium dioxide (TiO2)-based gate insulators for MOSFETs are of current interest in VLSI technology due to the high permittivity (k) of TiO2. In this paper, we present a study of metal–TiO2–SiO2–Si (MTOS) capacitors with equivalent dielectric thickness (EDT) in the range of 36–130 Å. Pulsed laser deposition (PLD) of TiO2 to realize this stacked dielectric is being reported for the first time. Interestingly, it has been observed that even though an additional TiO2 layer has been deposited, the capacitance of the MTOS structure actually increases or remains almost the same compared to the MOS device having the same SiO2 layer thickness. Secondary ion mass spectrometric (SIMS) analysis reveals that there is substantial penetration of titanium into the underlying SiO2 layer resulting in a reduction of EDT. In addition, the leakage current of the MTOS capacitor reduced by almost two orders of magnitude and the breakdown field strength nearly doubled after incorporating the TiO2 layer. Thus, PLD is shown to be a viable technique for controlled deposition of TiO2 to achieve lower EDT with smaller leakage current, the two most desirable parameters in present-day MOS devices.