Compensation Of Indication Currents In Deflection Yokes
Original Publication Date: 1979-Nov-01
Included in the Prior Art Database: 2005-Feb-20
In the design of magnetic deflection coils for lithography systems, a large field, high speed and accuracy are primary goals. This necessitates high precision in wire placement in the coil and large deflection currents which, in turn, require many parallel conductors. One large solid conductor would create excessive eddy currents while a series connection of fine wires using lower current introduces prohibitive inductance for the driver. In parallel configurations detrimental induction currents are generated between adjacent windings, even when the unexited winding is open-circuited. Fig. 1 shows a single layer from two such windings as well as the geometry of their magnetic fields and induced currents. In actual systems each deflection yoke contains many windings, e.g., 20, each with many layers of wire, e.g., 25.