Kyu-Beom Kim

The threshold voltage fluctuation of one memory cell for the scaling-down NOR flash

The threshold voltage (Vth) fluctuation for the NOR flash memory scaling is investigated. The Vth fluctuations for one memory cell in 45nm node are dramatically increased to 350% compared to 90nm generation due to the reduction of channel area and the increase of channel doping level. Here, as the cell size is scaled, the impact due to random telegraph noise (RTN), Dopant Fluctuation and etc become more critical. In 45nm technology, the RTN results in the Vth fluctuations of 60% from the measurement results. Furthermore, we also propose one solution with the channel doping engineering to suppress the Vth fluctuations. It is confirmed that maximum RTS amplitude at the center can be significantly decreased to below 20% in 45nm technology by the modification of channel doping profile. From this result, the Vth fluctuations within one NOR flash cell are the most critical issue for the cell size scaling, and can be effectively suppressed by the optimal channel engineering.

Novel Self-Reference Sense Amplifier for Spin-Transfer-Torque Magneto-Resistive Random Access Memory

A novel self-reference sense amplifier with parallel reading during writing operation is proposed. Read access time is improved compared to conventional self-reference scheme with fast operation speed by reducing operation steps to 1 for read operation cycle using parallel reading scheme, while large sense margin competitive to conventional destructive scheme is obtained by using self-reference scheme. The simulation was performed using standard 0.18 mm CMOS process. The proposed selfreference sense amplifier improved not only the operation speed of less than 20 ns which is comparable to non-destructive sense amplifier, but also sense margin over 150 mV which is larger than conventional sensing schemes. The proposed scheme is expected to be very helpful for engineers for developing MRAM technology.

Impact of etch angles on cell characteristics in 3D NAND flash memory

Abstract We investigated the impact of etch angles on cell characteristics of 3D NAND flash memory structures. The cell characteristics were extracted from simulations with an empirical etch profile, which was analyzed through comparisons to completely vertical conditions. Here, we observed that a narrowing of the poly-silicon channel width due to etch angles increased the channel resistance, which resulted in an on-current degradation of approximately 19% for an etch angle of 89.2°. The degradation in cell characteristics also became worse as the number of word-lines changed from low to high levels. Additionally, the difference in channel hole size between upper and lower stage aggravated the cell uniformity along the channel, hence the threshold voltage distribution was broadening in the smaller etch angle. We confirmed that critical dimensions should be well-controlled to minimize the etch angles, which provide significant on-current reduction and program characteristics distortion. These results led to an appropriated standard to implement high stack 3D NAND flash memory.

Acoustic Echo Cancellation using the DUET Algorithm Based Blind Separation in a Noisy Environment

In hands-free full-duplex communication systems, acoustic noises picked up by the microphones are mixed with echo signals, which may result in poor echo cancellation performance of the communication system. In such cases, a degenerate unmixing estimation technique, adjusted in the time-frequency domain, can be employed to separate undesired echo signals and noises. However, scaling and permutation ambiguities still have to be solved for blind source separation (BSS). In this paper, a new acoustic echo cancellation approach, utilizing the DUET algorithm based BSS, is proposed, whereby a new scale estimation method is introduced along with kurtosis-based desired signal selection. Simulation results demonstrate that the proposed approach yields better echo cancellation and noise reduction performance, compared with conventional methods

A capacitive biosensor using buried electrodes for the discrimination of whole-cells

This paper presents a capacitive biosensor that measures capacitances of living cells in electrolytic solution. The capacitive sensor was designed to consist of buried electrodes and was fabricated in Complementary Metal-Oxide-Semiconductor (CMOS) technology. Normal breast tissue cell MCF-10A, invasive breast cancer cell MDA-MB-231, and early-stage breast cancer cell MCF-7 were prepared. The capacitances of three cells were measured by LCR meter and calculated the capacitance differences from controlled experiment. Our results show that the capacitance changes of normal and breast cancer cells are different at whole-cell level. Furthermore, the capacitive difference of the cancer cells was observed by stage of cancer. This characterization may have useful developments for applications such as cancer diagnosis and treatment.

Nonlinear active noise control of systems with a linear noisy secondary path

In this paper, an adaptive 3rd-order Volterra filtering is proposed for nonlinear active noise control (ANC) of systems with a cubically nonlinear primary acoustic path and a noisy secondary path, whereby a Gauss-Seidel fast affine projection (GS-FAP) algorithm is employed as an adaptive scheme. The simulation results demonstrate that the proposed nonlinear ANC approach yields stable ANC performance and faster convergence, compared with those of conventional ANC approaches in case of a noisy secondary path.