High work-function metal gate and high-κ dielectrics for charge trap flash memory device applications

We report the impact of high work-function (Φ_M) 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 Φ_M 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 Φ_M 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.