Kyu S. Min

Frenkel-Poole trap energy extraction of atomic layer deposited Al2O3 and HfxAlyO thin films

Frenkel-Poole (FP) trap energies of atomic layer deposited Al2O3 and HfxAlyO thin films with various Hf∕Al compositions have been extracted. Using a method based on the field and temperature dependence of FP conduction, intrinsic trap energies under zero electric field can be extrapolated. Results indicate that FP trap energies increase from 0.56to1.48eV when adding more and more Al to HfO2. The trap energy seems to be inversely proportional to the square of the dielectric constant of the film, suggesting that traps may originate from the same type of defect, whose energy level is mediated by the dielectric constant.

Multi-Layer High-K Tunnel Barrier for a Voltage Scaled NAND-Type Flash Cell

Low-voltage program/erase (P/E) operations of a NAND-type flash cell have been demonstrated using a multi-layer tunnel barrier. The concept is to achieve low voltage P/E operations similar to a scaled tunnel barrier without compromising retention by exploiting a multi-layer tunnel oxide consisting of a low-k, high-k and low k material. In this study, barrier engineered tunnel oxides of SiO 2 -HfO x -SiO 2 and SiO 2 - ZrOx-SiO 2 were explored using a Metal-Insulator-Nitride-Oxide- Silicon (MINOS) capacitor with a TiN gate electrode. The device programmed/erased at 16/-22 V for 1 ms and it had a memory window of 6 V. The cell showed less than 2 V charge loss after 27 hours when programmed to a 5 V initial window. The proposed high-K tunnel barrier is a promising alternative for tunnel oxide for sub-35 nm NAND Flash technology.

Time-Resolved Programming Current Measurement and Modeling for nand -type Nanodot Flash Cell

The programming/erasing transient behavior of the NAND-type nanodot flash cell has been studied for the first time. By using an equivalent circuit model, the transient current through each layer in the dielectric stack can be monitored during the pulse programming/erasing. It is found that the oxide charging current leads the tunneling current during programming, and the charge built up at the storage node causes the gradual leakage current increase in the blocking dielectric. Parameters such as the current ratio of the tunnel oxide and the blocking layer and the programming efficiency of the nanodot cell can be calculated. The simulation result has been verified by the time-resolved current measurement.