Philips Electronics North America Corporation

Fei Comapny

Thomas A Hardt

W Ralph Knowles

Peter Smith

An environmental scanning electron microscope is provided which is capable of maintaining a specimen at a temperature up to approximately 1500.degree. C. In this environmental scanning electron microscope, a specimen chamber maintains the specimen enveloped in gas in registration with a final pressure limiting aperture of the objective lens assembly. The specimen chamber includes a specimen stage having a sample platform for supporting the specimen under examination at a first vertical height and a specimen heating assembly which includes a non-inductively wound heater coil which is positioned closely adjacent to the sample platform and extends to a second vertical height which is significantly above the first vertical height so that the top of the specimen is maintained at a high temperature. In this environmental scanning electron microscope, a heat shield assembly is positioned above the specimen heating assembly in the specimen chamber to avoid radiant heat loss and which has an adjustable bias voltage applied thereto to accelerate secondary electrons through its central opening to be collected by an electron detector. Moreover, in order to enhance image quality, the final pressure limiting aperture and the electron detector are biased at different voltages with the bias applied to the final pressure limiting aperture floated to provide for automatic compensation. A specimen stage moving assembly is also provided to move the specimen stage with respect to the heat shield assembly to enhance the field-of-view of the specimen.

High temperature specimen stage and detector for an environmental

An environmental scanning electron microscope is provided which is capable of only detecting backscattered electron signals emanating from the specimen with the detector assembly be positioned within the gaseous environment of the ESEM specimen chamber. This detector assembly includes a biased converter plate and a collection grid/collection plate/collector ring arrangement. The primary beam passes through the final pressure limiting aperture formed in the converter plate and then through a central aperture of the collection grid/plate/ring before striking the sample. The collection grid is held at ground potential and therefore does not collect secondary electron signals generated at the sample. The backscattered electrons are not collected by the collector grid/plate/ring and strike the converter plate creating converted backscattered electrons. The converted backscattered electrons are amplified in the gas by the electric field created between the converter plate and the collection grid. As a result, the collection grid/plate/ring will not collect secondary electron signals from the sample but will collect only an amplified converted backscattered electron signal. This dedicated gaseous backscattered electron detector can also be utilized to make a simple, low cost electron detector that can easily be switched between secondary electron detection, backscattered electron detection or both together.

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Tewksbury, MA, United States of America

Thomas A Hardt