The Perkin-elmer Corporation

John C Wiesner

Lee H Veneklasen

John W Vorreiter

William A Eckes

Russell H Rhoades

Charles E Shepard

An electrostatic cassette assembly comprising, a cassette body having a central opening for receiving a wafer to be processed in a particle beam lithographic system, a charge plate with a top surface having a coating of dielectric (nonconductive) material or a plurality of nonconductive means, or both, on which the wafer is supported, means for forcing said charge plate and wafer into contact with stop means to hold the wafer rigidly in said cassette assembly, and means for applying a potential difference between the wafer and the charge plate to flatten said wafer by Coulombic force so that the wafer is held both mechanically and electrostatically in said cassette assembly. Means are also provided for insuring a good electrical contact with the wafer and for aligning the wafer in the cassette assembly.

Electrostatic cassette

In particle beam optical instrumentation, an array of conventional sputter ion pump cells distributed in a ring shaped array about the circumference of the volume (optical column) to be pumped. An axially symmetrical, hollow, toroid magnetic circuit, formed by axially symmetrical magnets, either of the permanent type or of the electromagnetic type (or a combination of both), is used and the pumping action is outward from the central throughbore in the column so that the bore space could be occupied by other instrumentation. The magnetic circit may be used for particle beam focusing (optical lens) as well as for the pumping action by introducing magnetic gaps in either a series or parallel configuration.

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Hayward, CA, United States of America

John C Wiesner