High resolution electron beam imaging (E-beam) has found wide usage in industry in photolithography and semiconductor inspection systems. E-beam inspection, which takes place in vacuum, is very sensitive to magnetic fields, and requires highly dynamic and accurate actuators Piezo "walking" motors are an option, but have, apart from being relatively slow and rather expensive, the disadvantage of repetitive mechanical contact generating particles which contaminate and damage the products. Electromechanical actuators operate contactless, but have the drawback of generating magnetic fields. The distribution of the magnetic fields brings to the appearance of the space varying leakage fluxes dependent on the actuator position. These "stray fields" deteriorate the accuracy of E-beams and should be lower than 10-8 T at the location of the beam. Most actuators do not fullfill this requirement. Their strayfield levels are typically in the range of 10-5 T at (mechanical) practical distances of 100 mm. This paper explores the possibilities to reduce the magnetic fields outside linear electromechanical actuators to such extend that application in e-beam inspection is possible.
|Title of host publication||Proceedings of the 7th International Symposium on Linear Drives for Industry Applications, LDIA 2009, 20-23 September 2009, Incheon, Korea|
|Publication status||Published - 2009|