Changhyun Kim

A low jitter dual loop DLL using multiple VCDLs with a duty cycle corrector

A low jitter dual loop DLL with multiple VCDLs has been developed. This DLL whose locking range is 150-600 MHz, allows unlimited phase shift without noise sensitivity issues. A built-in duty cycle corrector guarantees 50% duty cycle under severe transistor mismatch.

Improving the Barrier Height Uniformity of 4H—SiC Schottky Barrier Diodes by Nitric Oxide Post-Oxidation Annealing

We improved the characteristics of 4H-SiC Schottky barrier diodes (SBDs) by post-oxidation annealing in nitric oxide ambient (NO POA). Unlike the sacrificial oxidized SBDs, the SBDs with added NO POA exhibited highly uniform Schottky barrier height and nearly ideal breakdown voltage of 1990 V. Time-of-flight secondary ion mass spectroscopy revealed nitrogen pileup at the sacrificially oxidized SiC surface after NO POA. We believe that NO POA electrically passivated the detrimental residual carbon at the SiC surface by forming C-N bonds, improving the performance of the SBDs.

Improved 4H-SiC MOS Interface Produced by Oxidized-SiN Gate Oxide

We have investigated the electrical and physical properties of the oxidized-SiN with or without post oxidation annealing (POA) in N2 gas. A significant reduction in interface-trap density (Dit) has been observed in the oxidized-SiN with N2 POA for 60 min if compared with other oxides. The reason for this has been explained in this paper.

Effects of rapid thermal annealing on Al2O3/SiN reaction barrier layer/thermal-nitrided SiO2 stacking gate dielectrics on n-type 4H-SiC

In this letter, we have reported electrical and physical properties of rapid thermal annealed (RTA) Al2O3 stacking dielectric on n-type 4H-SiC. The effects of SiN-reaction barrier layer (RBL) between Al2O3 and thermal-nitrided SiO2 on SiC-based metal-oxide-semiconductor characteristics have been investigated and compared. A significant reduction in oxide-semiconductor interface-trap density (Dit), improvement in dielectric breakdown field and reliability has been observed after the SiN-RBL has been introduced between Al2O3 and SiO2. High-resolution transmission electron microscope and Auger electron spectroscopy analyses reveal that the SiN-RBL suppresses Al diffusion into the nitrided SiO2 during RTA process.

Preparation and Characterization of IZO Transparent Conducting Films by the Sol-Gel Method

Indium-zinc oxide (IZO), with Zn/(Zn+In)=0.33 - 0.78, films were deposited by the sol-gel method. Effects of Zn/(Zn+In) atomic ratio and annealing temperature on the structural, electrical and optical properties of IZO thin film were investigated. Films of Zn/(Zn+In)=0.33 prepared at 600°C had the lowest resistivity value, 4.48X10 -2 Ω cm (carrier concentration=3.83X 1018 cm-3 and mobility=25.54 cm2/Vs), and the structure of these films matched that of Zn2In2O5 film. Average optical transmittances of all films were above 80% in the visible range. The highest average transmittance was observed at Zn/(Zn+In)=0.5, with 86.8% in the visible range.

16.6 Double-side CMOS-CNT biosensor array with padless structure for simple bare-die measurements in a medical environment

CMOS sensors using nanomaterials on the surface are very effective for early detection of diseases. Among the nanomaterials, carbon nanotube (CNT) is an ideal biosensor material since it has a small diameter (~1nm) directly comparable to the size of biomolecules and excellent electrical characteristics. Because CNT is formed chemically in a special environment, to use it in a CMOS process, many electrodes are formed as an array and the CNT solution is coated on the electrode array. However, to prevent electrical shorts between bonding pads, very complicated area-selective CNT coating processes are required. Furthermore, chip packaging steps - such as wire bonding, chip passivation against reactions to the wire, microfluidic channels on the chip, etc. - should be carefully applied [1].

Low Temperature Homoepitaxial Growth of 4H-SiC on 4° Off-Axis Carbon-Face Substrate Using BTMSM Source

Homoepitaxial 4H-SiC thin films were grown on (0 0 0 -1) C-face substrate by cold-wall chemical vapor deposition (CVD) using bis-trimethylsilylmethane (BTMSM, C7H20Si2) precursor. Because of the polarity difference of C-face and (0 0 0 1) Si-face, epitaxial growth conditions of C-face was quite different from those of Si-face. To improve the quality of C-face epitaxial films, effects of epitaxial growth conditions on surface morphology and crystallinity of epitaxial films were investigated.

Relay selection for amplify-and-forward systems with differential and double-differential modulation

Most of existing research on cooperative diversity systems have assumed that the destination node and the relay node have perfect channel state information. However, it is difficult to obtain all the channel state information in the systems, especially in a multi-relay node environment. To greatly reduce the cost required for those channel estimations, a differential modulation technique can be applied to multi-node cooperative communications. However, the performance of this system can be severely degraded if the transmission among the relays is not synchronized. Therefore we first combine relay selection schemes with differential modulation. Even if some existing literatures considered how to select a relay, the selection methods in those papers still require the channel state information. In this paper, we propose a simple relay selection scheme which does not require any channel state information. Our method is based only on the received signal power at the destination. This selection method can also be applied to double-differential modulation and show that the proposed selection scheme can work well for both differential modulation schemes. Our relay selection scheme combined with these differential modulation can significantly reduce the receiver complexity and also improve data throughput by eliminating pilot symbol period needed for channel estimation.