Juwon Seo

Reliability for recessed channel structure n-MOSFET

Recessed channel (Rch) structure n-MOSFET has been stressed under hot carrier injected condition and constant voltage stress (CVS). The degraded data are compared with planar channel (Pch) structure. We discuss difference of hot carrier (HC) degradation and oxide lifetime, which can be explained by the electrical field suppression and gate oxide thickness (tox) reduction in recessed channel area.

Structural health monitoring system of a cable-stayed bridge using a dense array of scalable smart sensor network

This paper presents a structural health monitoring (SHM) system using a dense array of scalable smart wireless sensor network on a cable-stayed bridge (Jindo Bridge) in Korea. The hardware and software for the SHM system and its components are developed for low-cost, efficient, and autonomous monitoring of the bridge. 70 sensors and two base station computers have been deployed to monitor the bridge using an autonomous SHM application with consideration of harsh outdoor surroundings. The performance of the system has been evaluated in terms of hardware durability, software reliability, and power consumption. 3-D modal properties were extracted from the measured 3-axis vibration data using output-only modal identification methods. Tension forces of 4 different lengths of stay-cables were derived from the ambient vibration data on the cables. For the integrity assessment of the structure, multi-scale subspace system identification method is now under development using a neural network technique based on the local mode shapes and the cable tensions.

Enhancement of the effective viewing window for holographic display with amplitude-only SLM

We propose the effective viewing window enhancement method for a holographic display with an amplitude-only SLM by using algorithmic approach. The basic concept is the superposition principle of holography. The multiple computer generated holograms (CGH) can be displayed on the SLM, and multiple 3D images are reconstructed at different positions within a viewing window simultaneously. In the experiments, we have implemented the holographic display using an amplitude-only SLM, a field lens, and laser light sources. We can observe the holographic 3D image in the frustum formed by the field lens through the viewing window located in the Fourier plane of the hologram. To enhance the effective viewing window, we generate multiple CGHs with an observer’s eye positions, and then overlap them to make the final CGH. Multiple 3D images can be reconstructed in different positions within the theoretical viewing window from the CGH displayed on SLM. This makes the enlargement of viewing zone that can observe the holographic images. The multiple holograms can be also made for enlargement of the viewing window along both horizontal and vertical direction (2D enlargement viewing zone). We confirmed that the experimental results and the simulation based on Rayleigh-Sommerfeld theory match well.

Ultra-slim coherent backlight unit for mobile holographic display

We propose slim coherent backlight unit for a mobile holographic display. This backlight unit consists of glass substrate for waveguide and two surface gratings produced by two-beam interference. The area of backlight illumination is 150 by 85 mm, and the thickness is 0.7 mm, which is thin compared to other conventional coherent backlight units. This backlight unit exhibits a total efficiency of 0.1%, preserving the collimation and a uniformity of 80% over the whole area. The proposed slim coherent backlight can be applied to a mobile holographic display.

A simple solution of the WSi x peeling issue at MDDR technology

In this paper, the advanced process has been presented to remove the WSix peeling which was brought in sub-100 nm DRAM SRCAT(sphere-shaped-recess-channel-array transistor). The source of WSix peeling was proved to be the groove of gate poly film. We have completely solved the problems to adopt the gate-poly CMP (chemical mechanical polishing) process.

Investigation of Hot carrier Degradation in Grooved Channel Structure nMOSFETs: Sphere shaped Recess Cell Array Transistor (SRCAT)

In this paper, first, it has been discussed hot carrier reliability in both Pch, RCAT and SRCAT. Second, we showed the origin of electric field suppression where the supply-voltage is applied at the same bias condition. Furthermore, we discuss the effects of ion implant process

Dielectric reliability of stacked Al2O3–HfO2 MIS capacitors with cylinder type for improving DRAM data retention characteristics

Abstract Dielectric reliability in Al2O3(2–3.1nm)–HfO2(3nm) stack capacitor with Metal–Insulator–Si(MIS) structure is investigated in this paper. We propose an optimized capacitor process through the Time–Dependent Dielectric Breakdown (TDDB) data under various process conditions. Furthermore, due to asymmetric current at both negative and positive voltage stress polarities, we show different lifetime extrapolation by a fluence–driven model. As a result, the maximum allowed operating voltage is projected to be 1.7V (failure rate 10ppm during 10year @ 85°C) for Data “0” retention lifetime.