Environmental scanning electron microscope

Abstract

An environmental scanning electron microscope which achieves image resolution comparable to that of a conventional SEM. A biased ring electrode which detects secondary electron signals emanating from the surface of the specimen is provided in the specimen chamber. A biased pressure limiting aperture electron detector is also provided to reduce signals emanating from backscattered electrons and to reduce signal noise generated by the electron beam. This environmental SEM also optimizes the signal amplification of the secondary electrons following detection thereof, such that the detector noise is reduced below the noise in the signal itself, while still maintaining an overall bandwidth that is suitable for setting up the image. An optical window system is also provided in this environmental SEM which allows the user to easily switch between the normal environmental SEM electron image (limited to 0.5 mm in diameter) to an optical light view of the sample that covers a field-of-view of up to about 7 to 10 mm. Moreover, the construction of this environmental SEM provides for a take-off angle for the X-ray detectors (EDX detectors) which is comparable to the take-off angle in for an EDX detector in a conventional SEM. Additionally, the arrangement of the scanning coils and magnetic focusing lens in this environmental SEM provides for an enhanced field-of-view of the specimen.