Patent ID: 6149774
Filing Date: 2000-11-21
Classification: B01J,G01N,H02N,Y10S,Y10T

Abstract:
An electrostatic chuck for attracting charged grains to a bead collection zone on a bead contact surface comprising:a bead electrode for selectively establishing a grain attracting field to the bead collection zone, the bead electrode shaped and configured in such a manner so that when an AC waveform potential is applied thereto, the grains are influenced by it and guided to selective retention by the bead electrode to the bead collection zone; andan electronic driver programmed to deliver the AC waveform potential configured to provide a repeated effective grain attraction potential at the bead collection zone, wherein the AC waveform potential comprises a grain-attracting potential pulse followed by a recovery period adapted to allow, in the case where the bead collection zone is formed on a substrate with a resistivity below 10.sup.11 .OMEGA.-cm, an effective grain attraction field at the bead collection zone on activation of a subsequent grain-attracting potential pulse, wherein the AC waveform potential has a frequency of 100 Hz or less.