Method and device for setting and correcting errors of an electron optical condenser of a microprojector

摘要

A method and device for correcting errors and setting the focus of an electron optical condenser of a microprojector which condenser produces a bundle of axially parallel electron rays for illuminating a large surface transmission mask to create an image which is projected by means of an electron optical lens system on a surface of a wafer characterized by placing an annular field stop or diaphragm which passes a bundle of rays having a ring-shaped or annular cross section and recording the image in a plane preferably adjacent the surface of the wafer. The recording can be accomplished by utilizing a photographic plate or by utilizing a detector arrangement. When the image on the recording unit is the same size and shape as the annular field stop, then the electron optical condenser has the correct focal length and the source is disposed on the front focal plane.