Charged-particle-beam optical components and systems including ferrite exhibiting reduced image displacement from temperature fluctuations

Abstract

Charged-particle-beam (CPB) optical components (e.g., electromagnetic lenses and deflectors) are disclosed that exhibit very low to no image displacement or loss of focus accompanying changes in temperature of the optical components during use. An optical component includes a unit of ferrite (typically in a ferrite stack). The ferrite is configured to exhibit substantially no permeability change with a change in temperature relative to normal operating temperature, thereby maintaining image displacement caused by permeability changes to below a predetermined threshold. As the ferrite temperature T rises to T′, the saturation magnetic flux density B of the ferrite decreases while the initial permeability &mgr; increases. Thus, the initial magnetization curves of the ferrite intersect at a particular magnetic field intensity H, which exhibits substantially no change from T to T′. With H being the particular magnetic field intensity, the ferrite is selected so that the magnetic field intensity acting on the ferrite during operation is near H .