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The impact of high work function metal gate and high dielectric on memory properties of NAND-type charge trap flash (CTF) memory devices are discussed. A key role is played by high work-function metal gate and high permittivity dielectric in the elimination of electron back tunneling though the blocking dielectric during the erase operation.

A sputter-deposited Al2O3/HfO2 stack as a blocking layer of metal-oxide-nitride-oxide-silicon capacitors is investigated. The study shows that the improvement of electrical characteristics can be explained by lower leakage current density and less voltage drop of high-k blocking layer which in turn increase the effective thickness of tunneling oxide.

Charge-trap flash- (CTF) memory structures have been fabricated by employing IrO2nanodots (NDs) grown by atomic-layer deposition. A band of isolated IrO2NDs of about 3?nm lying almost parallel to Si/SiO2interface is confirmed by transmission electron microscopy and x-ray photoelectron spectroscopy. The memory device with IrO2NDs shows much larger capacitance-voltage (C-V) hysteresis and memory window compared with the control sample without IrO2NDs. After annealing at 800?°C for 20?min, the ND device shows almost no change in the width of C-Vhysteresis and the ND distribution. These results indicate that the IrO2NDs embedded in SiO2can be utilized as thermally stable, discrete charge traps, promising for metal oxide-ND-based CTF memory devices. [ABSTRACT FROM AUTHOR]

We report the impact of high work-function (ΦM) metal gate and high-κ dielectrics on memory properties of NAND- type charge trap Flash (CTF) memory devices. In this paper, theoretical and experimental studies show that high ΦM gate and high permittivity (high-κ) dielectrics play a key role in eliminating electron back tunneling though the blocking dielectric during the erase operation. Techniques to improve erase efficiency of CTF memory devices with a fixed metal gate by employing various chemicals and structures are introduced and those mechanisms are discussed. Though process optimization of high ΦM gate and high-κ materials, enhanced CTF device characteristics such as high speed, large memory window, and good reliability characteristics of the CTF devices are obtained. [ABSTRACT FROM AUTHOR]

This letter reports the impact of metal work function (ΦM) on memory properties of charge-trap-Flash memory devices using Fowler-Nordheim program/erase mode. For eliminating electron back tunneling and hole back tunneling through the blocking oxide during an program/erase operation, a gate with ΦM of 5.1-5.7 eV on an Al2O3-SiN-SiO2 (ANO) stack is necessary. Compared to a thickness optimized + poly-Si/ONO stack, a high-work-function gate on an ANO stack shows dramatic improvements in retention versus minimum erase state. [ABSTRACT FROM AUTHOR]