Taisei Motomura

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.

Real-time characteristic impedance monitoring for end-point and anomaly detection in the plasma etching process

We propose a practical and highly sensitive characteristic impedance monitoring (CIM) system for detecting the etching end point and anomalies during the plasma etching process. The CIM system employs a directional coupler and a newly developed vector processing system. The etching end point was successfully detected when a SiO2/Si wafer was etched with CF4 plasma; the system also detected wafer fluttering occurring during SF6–N2 plasma etching. The reactance component of the characteristic impedance primarily changed with the transient response of the electric potential on the inner glass surface during SF6–N2 plasma etching.

Detection of microarc discharge using a high-speed load impedance monitoring system

A high-speed and practical load impedance monitoring system is developed for the detection of microarc discharge. The detection system measures forward and reflected rf powers, including phase information, simultaneously with capacitances of variable capacitors, which allows real-time monitoring of load impedance. The results demonstrate that the system can detect microarc discharges at high speed and high sensitivity from a 50 Ω transmission line, and reveal that a significant change in load impedance is caused by arcing. This method is expected to contribute to improvements in plasma processing, production yield, and overall equipment effectiveness in semiconductor manufacturing.

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.

Transport of a helicon plasma by a convergent magnetic field for high speed and compact plasma etching

A high density argon plasma produced in a compact helicon source is transported by a convergent magnetic field to the central region of a substrate located downstream of the source. The magnetic field converging near the source exit is applied by a solenoid and further converged by installing a permanent magnet (PM) behind the substrate, which is located downstream of the source exit. Then a higher plasma density above 5 × 1012 cm−3 can be obtained in 0.2 Pa argon near the substrate, compared with the case without the PM. As no noticeable changes in the radially integrated density near the substrate and the power transfer efficiency are detected when testing the source with and without the PM, it can be deduced that the convergent field provided by the PM plays a role in constricting the plasma rather than in improving the plasma production. Furthermore it is applied to physical ion etching of silicon and aluminum substrates; then high etching rates of 6.5 µm min−1 and 8 µm min−1 are obtained, respectively.

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.