Natsuko Nabeoka

Instantaneous Generation of Many Flaked Particles by Impulsive Force of Electric Field Stress Acting on Inner Wall of Mass-Production Plasma Etching Equipment

To elucidate the mechanism of instantaneous generation of many flaked particles in plasma etching equipment, we investigate the relationship between the generation of flaked particles from deposited films (consisting of etching reaction products on the ground electrode) and the plasma stability under mass-production conditions. Many particles are observed with our particle monitoring system when plasma instability occurs. The generation of such flaked particles correlates well with the occurrence of a large, rapid change in floating potential on the chamber wall. Our results indicate that many flaked particles from films deposited on a ground electrode are generated by electric field stress acting instantaneously and working as an impulsive force.

Many flaked particles caused by impulsive force of electric field stress and effect of electrostriction stress in mass-production plasma etching equipment

To investigate the mechanism of instantaneous generation of many flaked particles in plasma etching chambers, we study the relationship between particle generation from deposited films and electric field stress acting on the films under mass-production conditions. The particles are formed by stress working as an impulsive force due to rapid changes in floating potential on the chamber walls. The results indicate that Maxwell’s stress and electrostriction stress both affect particle generation in terms of the impulsive force of electric field stress. Although Maxwell’s stress mainly influences the outbreak of particles, the electrostriction stress also acts with considerable intensity.

Numerous flaked particles instantaneously generated by micro-arc discharge in mass-production plasma etching equipment

The relationship between the instantaneous generation of flaked particles and micro-arc discharge is investigated in mass-production plasma etching equipment. To investigate the mechanism of such particle generation, we simultaneously detect particle generation from deposited films on a ground electrode and occurrence of micro-arc discharge under mass-production conditions. The results indicate that the deposited films are severely damaged and flake off as numerous particles when micro-arc discharge occurs. The rapid changes in floating potential on the films due to micro-arc discharge cause electric field stress, which works as an impulsive force. The particles are generated not from the melting of chamber parts by micro-arc discharge but from the flaking of deposited films by electric field stress acting as an impulsive force.

Estimation of Marbling Score in Live Cattle Based on ICA and a Neural Network

To accurately estimate the Beef Marbling Standard(BMS) number of live cattle using ultrasound echo imagings, we have developed a image recognition method by use of a neural network. This paper examines the efficiency of applying Independent Component Analysis(ICA) to the compression of multidimensional image features. ICA can accurately separate a target signal because of its independence assumption, while Principal Component Analysis(PCA), a conventional method, involves decorrelation of the components. We have implemented the estimation tests by use of ultrasound echo imagings of 103 live cattles. Multidimentional texture features extracted from the imagings were compressed by ICA, and then the estimation of BMS number was conducted by using a neural network. The estimation accuracy was evaluated based on the cross validation method. We caluculated the correlation coefficient between the actual and estimated values using 100 different data sets. The results confirmed that the correlation coefficient between the actual and the estimated values was higher by ICA (R = 0.70, p <; 0.01) than by PCA (R = 0.62, p <; 0.01). Also, we conducted the comparison experiments between the ICA based estimation and the estimation by an experienced inspector. The both methods examined the same ultrasound images. Even the experienced inspector failed to estimate BMS number because the estimation requires highly professional skill. The correlation coefficient between the actual and the estimated values was R = 0.70 (p <; 0.01). As a result, we confirmed that the proposed method had much the same capability as the experienced inspector to estimate BMS number.

In-situ detection method for wafer movement and micro-arc discharge around a wafer in plasma etching process using electrostatic chuck wafer stage with built-in acoustic emission sensor

We report an electrostatic chuck (ESC) wafer stage with a built-in acoustic emission (AE) sensor for detecting anomalies occurring around a wafer during plasma etching. The built-in AE sensor detects acoustic waves caused by wafer movement and micro-arc discharge with high sensitivity, and identifies these anomalies based on the frequency characteristics of the waves. The results demonstrate the effectiveness of using an ESC wafer stage with a built-in AE sensor for in-situ anomaly detection, which can improve the production yield and overall equipment efficiency in large scale integrated circuit (LSI) manufacturing.