Philips Electronics North America Corporation

Fei Comapny

Electro Scan, Inc.

W Ralph Knowles

Thomas A Hardt

Peter Smith

Diane Stewart

Allen E Armstrong

William G Schultz

Brian T Kimball

A charged particle beam system uses an ion generator for charge neutralization. In some embodiments, the ion generator is configured to maintain an adequate gas pressure at the ion generator to generate ions, but a reduced pressure in the remainder of the vacuum chamber, so that another column can operate in the chamber either simultaneously or after an evacuation process that is much shorter than a process that would be required to evacuate the chamber from the full pressure required at the ion generator. The invention is particularly useful for repair of photolithography masks in a dual beam system.

Charged particle beam system

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.

Gaseous backscattered electron detector for an environmental scanning

An environmental scanning electron microscope with, field emission gun providing for a spatial resolution of the specimen under examination of 2nm which is comparable to the spatial resolution of high vacuum field emission scanning electron microscopes even though the specimen is contained in the gaseous environmental of the specimen chamber. The objective lens assembly of this environmental scanning electron microscope includes a differentially pumped aperture system having at least four differentially pumped vacuum zones to provide a pressure difference of up to approximately 10.sup.10 Torr between the field emission gun and the specimen. The differentially pumped aperture system further includes at least four pressure limiting apertures defining the differentially pumped vacuum zones through which the electron beam passes. One of the pressure limiting apertures is formed of a pressure limiting aperture assembly which includes a plurality of stacked annular apertures. Further, an electron detection assembly is provided for detecting signals emanating from the surface of the specimen. The electron detection assembly includes a printed circuit board having a signal ring electrode biased to collect secondary electrons emanating from the surface of the specimen and a final pressure limiting aperture integrally formed therewith which extends through the signal ring electrode so that the electron beam path through the gaseous environment of the specimen chamber is minimized.

Field emission environmental scanning electron microscope

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.

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North Andover, MA, United States of America

W Ralph Knowles