APPARATUS FOR CALIBRATING A CAPACITANCE HEIGHT GAUGE

摘要

Disclosed is a highly accurate capacitance height gauge which is applied in the presently preferred embodiment in a reticle position detection system for an electron beam lithography apparatus. The capacitive height gauge circuitry includes a hybrid circuit substrate which carries four measuring capacitor circuits and two reference capacitor circuits. The driven plates of the four measuring capacitors are disposed on the bottom of the substrate opposite to the object surface to be measured. The driven plates of the two reference capacitors are disposed on the top surface of the substrate under caps which support oppositely disposed grounded capacitor plates at a nominal distance from the driven plates. The object surface comprises the grounded plate for the four measuring capacitors. The reference capacitors provide voltage regulation to ensure that a stable signal drives the measuring capacitors. The reference capacitors also set zero points for the measurements from the four measuring capacitors. These zero points are set at the nominal distance from the measuring capacitor sensors. The four measuring capacitors provide readings with respect to the object surface to determine the position of the object surface with respect to the nominal zero points. This information can be used by a suitable control system to manipulate the object surface or tools used to work on the surface in response to the position information as appropriate to the task being performed.