The wafer stage is the key system of motion in the lithography printing process. When the light is projected through a blueprint of the printing pattern or mask, the mask illuminates. To make sure the process goes seamlessly and ensure that individual components on the wafer illuminate, the lithographic devices move the wafer to the required position.
This requires a precise sensor that can measure nanometer displacement with ease and accuracy. Very small displacements, both static and dynamic, are normally generated by piezo actuators. High precision displacement sensors ensure that these displacements are measured to the required nanometre and sub-nanometre accuracies. Resolution and repeatability of up to 0.04nm are possible.
Non-contact, capacitive displacement sensors from Micro-Epsilon provide this sub-nanometre precision. The capaNCDT series combines high precision and the required stability, both in terms of long-term stability and particularly for temperature stability. Therefore, the capacitive displacement sensors compensate for the weaknesses of piezo actuators in position control loops. Interferences such as a non-linear actuator curve, temperature expansion, hysteresis and mechanical elasticity can be balanced.