Measurement of AC Ion Current from Ionizer by Using Faraday Cage
AC ionizer with high frequency became more common in semiconductor industries. Neutralization mechanism of such equipment is, however, not well understood because the measurement of extremely small ion current is interfered by AC induction. Our attempt is to use the Faraday cage that is directly connected to an AC ionizer. At frequencies of 1 Hz and 10 Hz, clear pulse shape ion currents were measured. The amounts of transported charges increase with both applied voltage and pressure. The effect of pressure is more significant than voltage. At higher frequency, the measured current changes from pulse to sinusoidal shape. From the delay time of 1 kHz, the average air velocity between the needle and Faraday cage was calculated. From DC corona measurement inside the nozzle, it became clear that the portion of transported charge to the Faraday cage is quite small.
Ion imbalances on the ionizer controlled work surface
This paper presents results of investigations carried out to test the influence of charged objects introduced into the vicinity of an ionizer-controlled work surface. The qualitative and quantitative distribution of ions on the surface was the main focus of the experiment. Experiments were conducted using ionizers with a feedback signal taken from a sensor at the output of the ionizer (factory installed internal feedback).
Comparison of germanium and silicon needles as emitter electrodes for air ionizers
Germanium (Ge) and silicon (Si) needles were tested as emitter electrodes for use in low particle generating static eliminators. The materials were found to oxidize with minimal incorporation of nitrogen, and the negative polarity enlitters oxidzed at a greater rate than the positive polarity emitters. The negative polarity silicon emitters generated severall orders of magnitude greater particle emissions than any of the other emitters tested. The mean particle size was about 0.015μm. Although the germanium emitters oxidized, no evidence was found to indicate particles were shed from h s material. Preliminary data indcates the emitters perform equally well in Class 100 cleanroom air, and lowest particle generation is achieved when germanium electrodes are purged with dry air.