Jaewhan Kim

Reactive ion etching mechanism of plasma enhanced chemically vapor deposited aluminum oxide film in CF4/O2 plasma

Aluminum oxide film prepared by plasma enhanced chemical vapor deposition (PECVD) is one of the promising candidates for an etch mask or an etch barrier material in very large scale integrated fabrication. We have investigated the reactive ion etching mechanism of the PECVD aluminum oxide films in the CF4/O2 plasma. The dependences of the aluminum oxide etch rate on the atomic fluorine concentration and the incident particle bombardment energy are studied at various etching conditions. The etch products and their depth distribution are also determined by analyzing the surface layer of the etched aluminum oxide films with Auger electron spectroscopy. The CF4/O2 plasma fluorinates the aluminum oxide surface layer through the particle bombardment activated reaction, producing etch products in the form of AlF3 or AlOXFY, which is nonvolatile but has a higher sputtering yield than aluminum oxide. The reactive ion etching of aluminum oxide proceeds by the formation and the sputter removal of the etch product. T...

CHARACTERIZATION OF PBTIO3 THIN FILMS DEPOSITED ON PT/TI/SIO2/SI SUBSTRATES BY ECR PECVD

The electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) method is used to prepare ferroelectric PbTiO3 films. Single-phase perovskite PbTiO3 films with smooth surfaces and fine grain size were successfully fabricated on Pt/Ti/SiO2/Si substrates at low temperatures of 400-500 °C using metal-organic (MO) sources. The chemical compositions, structural phases, surface morphologies, and depth profiles of the PbTiO3 thin films were investigated using EDS, XRD, SEM, RBS, and AES. Variations of those properties with process temperature and gas supply ratio are discussed. When the process temperature was above 450 °C, the stoichiometric perovskite PbTiO3 films could be obtained even though the MO source supply ratio was varied in a wide range if the oxygen supply was sufficient.

Composition control of lead zirconate titanate thin films in electron cyclotron resonance plasma enhanced chemical vapor deposition system

Lead zirconate titanate (PZT) thin films were fabricated on Pt/Ti/SiO2/Si substrates by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). Lead ?-diketonate ( Pb(DPM)2, zirconium t-butoxide ( Zr(OC4H9)4) and titanium i-propoxide ( Ti(OC3H7)4) were used as metalorganic (MO) precursors. Perovskite single-phase PZT films were obtained at temperatures below 500? C when the Pb/(Zr+Ti) concentration ratio was close to 1. The cation concentrations in the PZT films were successfully controlled by adjusting the flow rate of each MO source. The variation in composition and structure with the process temperature and the MO source flow rates was discussed.

Study on Diagnosis Error Assessment of Operators in Nuclear Power Plants

The purpose of this study is to suggest a framework to assess diagnosis error of operators in nuclear power plants. In nuclear power plants, human error caused by inappropriate performance due to inadequate diagnosis of situation by operators have been considered to be critical since it may lead serious problems. In order to identify and estimate the human errors, various human error analysis methods were developed so far. Most human error analysis methods estimate diagnosis error through time reliability curve or expert judgments. In this study, a new framework to assess diagnosis error was suggested. It is assumed that diagnosis error is caused by inadequate quality of data and diagnosis error can be observed by using information processing model of human operators. Based on this assumption, we derived the assessment items for the quality of data and diagnosis error taxonomy here.

A simulator study and its application to an HRA in NPPs

A plant specific data is indispensable for a human reliability analysis (HRA) in order to meet the requirement fo risk-informed activities. This paper introduces a human performance analysis of the emergency tasks in nuclear power plants (NPPs) to support an HRA. More than 110 simulation records were gathered from a full-scope simulator of a reference plant and analyzed to generate an operators’ performance time during emergency situations with six accident scenarios. A sensitivity analysis for an HRA has been undertaken by using an operators’ performance time.

Analysis of Human Decision-based Errors of Commission in Accident Scenarios

This paper presents a new methodology for identifying and analysing errors of commission (EOC) in accident scenarios of nuclear power plants. The proposed method focuses on the EOC events caused from the failure in situation assessment and decision-making of human operators. Results from a pilot application to a reference plant in Korea are presented.

A Study on the Development of a Systematic Framework to Construct Diagnosis Procedures

A diagnosis procedure that allows operators to identify the nature of an on-going event is very important for complex systems such as the nuclear and chemical industry, because appropriate countermeasures or remedial actions can be initiated by it. Unfortunately, a systematic framework that can suggest a unified and consistent process for constructing diagnosis procedures seems to be scant. In this paper, the systematic framework that can provide a sound way in constructing a diagnosis procedure is suggested. To demonstrate the appropriateness of suggested framework, in addition, the diagnosis procedure of the reference nuclear power plant (NPP) is reformed based on it. Subjective ratings are conducted to compare reformed procedure with the original one, and results support that operators’ performance in an event diagnosis could be improved. Thus, it is expected that suggested framework could be applied to provide a consistent process in constructing useful diagnosis procedures.