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Super-steep switching is successfully demonstrated using positive feedback (PF) in fabricated diode-type 3-D NAND flash memory strings. Thanks to the PF, the subthreshold swing (SS) measured in a cell of a string during read operation is less than 1 mV/dec at turn-on voltage (Von) regardless of the polarity and the amount of the charge stored in the cell. This string has memory characteristics similar...
We extract the trap density (Nt) profile of the nitride storage layer in 3-D NAND flash memory cells. The adjacent cells which are programmed suppress significantly the lateral diffusion during retention measurement so that we can extract accurate Nt profile. The AC-gm method makes the Nt profiling in an EC-ET range of 1∼1.2 eV possible, and provides a Gaussian Nt profile together with the retention...
The AC-gm dispersions are measured to analyze trap profiles in a cell of 3-D NAND flash cell string before and after P/E cycling. After 4k P/E cycling, the trap density (Nt) near the interface between the poly-Si channel and the tunneling oxide is increased according to the extracted Nt profile. The temperature dependency of the AC-gm dispersion is also investigated.
Retention characteristics of a 3-D NAND flash cell with tube-type poly-Si body are investigated at a high temperature (T) depending on program (P), neutral (N), and erase (E) states of adjacent cells. The trap density (Nt) in the nitride storage layer of the cell is extracted by utilizing retention model and deriving related equations in cylindrical coordinate. By programming or erasing adjacent cells,...
The trap density (Nt) in nitride storage layer is extracted in 3-D NAND flash memory cells with tube-type poly-Si body. We extract the Nt by utilizing AC-gm method and deriving related equations in cylindrical coordinate. The AC-gm method makes the Nt profiling with distance from the interface possible. We also characterize the behavior of transient bit-line current (IBL) during reading after applying...
We characterized the behavior of transient bit-line current (IBL) during reading after giving a pre-bias (Vpre) to two different cells in 3-D stacked NAND flash memory having poly-Si body. Depending on the dominance of charge trapping in blocking dielectric or the interface between the tunneling oxide and the poly-Si body, opposite behavior was observed. To identify the cause, we systematically analyzed...
To reduce TSV coupling noise, a new guard-ring technique is proposed and implemented experimentally. We design the n+/n− well guard-ring butted to the TSV dielectric surrounding the TSV and utilize the inversion layer induced by a positive interface charge as a shield layer. The interface trap density responsible for the interface charge between the TSV dielectric and Si substrate was extracted. Proposed...
A new read method which suppresses the effect of read current fluctuation due to random telegraph noise was proposed to reduce read error in NAND flash memory by using hysteretic characteristic. By controlling the amplitude and polarity of a word-line (WL) bias applied to the gate of a selected cell in a cell string, we can predict stochastically RTN event at μsec time range. From measured transient...
Trap density (Dit) was extracted for the first time in 3-D stacked NAND flash memory with the tube-type poly-Si channel structure. We verified extracted Dit with conductance method and charge pumping method in 32 nm floating gate (FG) NAND flash memory device. In 3-D stacked NAND flash memory device, the Dit extracted by conductance method was 1∼2×1012 cm−2eV−1 in Ec-ET of 0.15∼0.35 eV. The simulation...
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