Electrostatic sensing chuck using area matched electrodes

An electrostatic sensing chuck for attracting particles to a portion of a particle contact surface near a deposition electrode, the electrostatic sensing chuck comprising a pixel comprising:

• a deposition electrode for selectively establishing an attraction field at the particle contact surface;
• a shield electrode oppositely biased with respect to the deposition electrode;
• a charge sensing circuit to measure charge accumulated on each of the deposition electrode and the shield electrode, wherein the charge sensing circuit subtracts a second charge it senses at the shield electrode from a first charge it senses at the deposition electrode, thereby determining accumulated charge at the deposition electrode balanced by accumulated charge at the shield electrode,
• wherein the shield electrode is sized and oriented with respect to the deposition electrode as needed to achieve cancellation of drift in output from the sensing circuit, and
• dielectric insulating the shield and deposition electrode sufficiently to reduce leakage voltages therefrom to achieve cancellation of drift in output from the sensing circuit.

A charge sensing circuit is a driving circuit for driving and interfacing with a deposition electrode and a shield electrode of an electrostatic sensing chuck, the driving circuit comprising:

• [a] a two wire AC coupled circuit, having a first wire and a second wire;
• [b] a Wheatstone bridge connected to the first and second wires of the AC coupled circuit, the Wheatstone bridge having a low pole and a high pole for DC extraction, wherein the high pole is connected to one of the deposition electrode and the shield electrode and low pole is connected to the other of the deposition electrode and the shield electrode;
• and
• [c] a charge measuring device connected to either of the first and second wires of the AC coupled circuit;
• wherein the sum of the detected respective charges in the electric charge distribution and in the similarly created electric charge distribution of opposite polarity are balanced to reduce sensing error.