AC waveforms biasing for bead manipulating chucks
AssigneeDelsys Pharmaceutical Corporation
InventorsHoi Cheong Steve Sun, Eugene Samuel Poliniak, Dominic Stephen Rosati, Bawa Singh, Nitin Vithalbhai Desai
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Abstract
AC waveforms biasing of bead transporter chucks and their accumulated charge sensing circuits tailored for low resistivity substrates and beads where if traditional DC quasi-static biasing potentials were used, the bead attraction potentials of the chuck would undergo rapid RC decay and cause the bead transporter chuck to stop working. Methods for selecting AC waveforms are given, including those that maximize the time average of the bead attraction potential at the bead collection zone of the bead contact surface.
Claims22
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;
- and
- an 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.
An electrostatic chuck device with an accumulated charge sensing circuit having a charge sensing electrode for monitoring accumulated charge on the bead collection zone of the bead contact surface, comprising:
- an AC bias source;
- an electrostatic chuck comprising at least one a bead electrode for establishing a grain attracting field to attract charged grain s to a bead collection zone the electrostatic chuck further comprising a sensing capacitor electrically connected between a charge collector electrode and the AC bias source;
- and
- an electrometer electrically connected between the AC bias source and a coupling capacitor to measure the potential of the sensing capacitor.
A method for adhering charged trains to a bead collection zone on a bead contact surface comprising:
- (1) adhering a substrate with a resistivity below 10.sup.11 .OMEGA.-cm to an electrostatic chuck, with the substrate arrayed over a grain-attracting electrode of the electrostatic chuck so that a surface of the substrate defines the bead contact surface;
- (2) applying an AC waveform potential to the grain-attracting electrode to create a grain attracting field, wherein the AC waveform potential comprises a grain-attracting potential pulse followed by a recovery period adapted to allow an effective grain attraction potential 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;
- and
- (3) attracting and retaining a grain to the bead collection zone.
Dependencies are inferred from the claim text.