Oxide-trap-enhanced Coulomb energy in a metal-oxide-semiconductor system

Coulomb energy is essential to the charging of a nanometer-scale trap in the oxide of a metal-oxide-semiconductor system. Traditionally the Coulomb energy calculation was performed on the basis of an interfacelike trap. In this paper, we present experimental evidence from a 1.7-nm oxide: Substantial enhancements in Coulomb energy due to the existence of a deeper trap in the oxide. Other corroborating evidence is achieved on a multiphonon theory, which can adequately elucidate the measured capture and emission kinetics. The corresponding configuration coordinate diagrams are established. We further elaborate on the clarification of the Coulomb energy and differentiate it from that in memories containing nanocrystals or quantum dots in the oxide. Some critical issues encountered in the work are addressed as well.

Figure 1

Measured mean capture time to mean emission time ratio versus gate voltage for two devices labeled Traps $A$ and $B$. The inset shows the time records of RTS drain current at a fixed gate voltage of 0.3 V. The fitting lines from Eq. (2) are also shown.

Figure 2

Capacitive coupling equivalent circuit, accounting for the effect of the trap depth and the charge sharing between gate, inversion layer, and silicon depletion region.

Figure 3

Simulated results of the key capacitance components versus gate voltage.

Figure 4

Calculated gate image charge and Coulomb energy versus gate voltage for two trap depths in the oxide.

Figure 5

Comparison of the measured and calculated capture time constants and emission time constants versus gate voltage.

Figure 6

Schematic configuration coordinate diagrams used for a phenomenological description of the capture and emission kinetics encountered in Traps $A$ and $B$. The corresponding energy band diagrams in flatband conditions are also given, schematically showing the trap depth and its energetic level in the oxide.