The effects of rapid thermal oxidation (RTO) on the chemical vapor deposited nitride/oxide layer for thin gate dielectrics were studied. Successful growth of a top oxide of ∼25 Å was confirmed using x-ray photoelectron spectroscopy and no punchthrough of the chemical vapor deposited nitride was observed for a nitride thickness of 60 Å. Changes in electrical properties after RTO were studied using current-voltage and charge-to-breakdown measurements. Results indicate that the top oxide reduces the leakage current under positive gate bias and increases the leakage current at high fields for negative gate bias. In addition, the charge to breakdown of the layer is increased after RTO.

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The electrical properties of thin nitrided oxide (∼100 Å) formed by rapid thermal nitridation (RTN) in pure NH3 have been studied. It is found that the current-voltage characteristic of RTN oxides follows a Fowler–Nordheim tunneling behavior with modifications caused by electron trapping processes at the oxide surface and interface. The trapping density is dependent on the RTN conditions. At the interface, both fixed charge (Nf) and interface state (Dit) densities exhibit turnaround phenomena when the RTN process proceeds. The maximum values of Nf and Dit at the turnaround points are lower for the higher temperature RTN, suggesting a viscous flow related strain relieving mechanism associated with RTN of thin oxides. Films with superior endurance behavior (QBD=20.4 C/cm2 compared with QBD=5.1 C/cm2 of thermal oxide under 10 mA/cm2 constant current stress) have been obtained by RTN at 1000 °C, 10 s.

Recently, SONOS high-k memories have attracted much attention for the application in the next-generation nonvolatile memories [1] due to fast program/erase speed, low programming voltage and small power consumption. Rare-earth oxide and yttrium oxide materials have attracted the great potential candidates for metal-oxide-high-k material-oxide-silicon (MOHOS)-type memory based on thermodynamic compatibility with Si considerable, moderately high dielectric constant, high conduction band offset over 2 eV [2][3]. In addition, it has been reported [4] that lanthanide (Nd, Tb, or Dy) doped TiO x dielectric films shows excellent electrical characteristics.