At&t Bell Laboratories

Bell Telephone Laboratories

Michael G Thomson

Ruichen Liu

Robert J Collier

An electron emission system includes a high-brightness field-emitter cathode. Advantageously, the tip of the cathode is shaped to minimize structural variations caused by surface tension forces. In addition, an electrode assembly associated with the cathode is designed to establish electric field forces that are opposite and at least approximately equal to the surface tension forces acting on the tip. The electric field forces can be adjusted to establish a highly stable operating condition without altering the value of electron beam energy for which the overall system was designed. Moreover, the current density of the beam at a writing surface can be selectively varied without changing prescribed operating parameters of the cathode. The resulting system is characterized by excellent emission stability, low noise and a useful operating life of at least several thousand hours.

Electron emission system

For a given resolution or address dimension, the pattern-writing speed of an electron beam exposure system is increased by utilizing a new mode of raster scanning. In the new mode, the writing spot dimensions of the electron beam are varied rapidly during the scan. In an electron column designed for variable-spot raster scanning, an illuminated aperture is demagnified to form the writing spot. By imaging a first aperture upon a second aperture and rapidly deflecting the image of the first aperture, the portion of the second aperture that is illuminated by the electron beam is altered. In that way, the spot size is selectively varied in a high-speed way during the raster scanning process.

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Berkeley Heights, NJ, United States of America

Michael G Thomson