US 4,683,366 A · All electrostatic electron optical sub-system for variable electron beam spot shaping and method of operation

Abstract

An all-electrostatic variable spot charged particle (electron) beam shaping sub-system which is compact and of much smaller size than known similar systems designed for the same purpose and operating with magnetic lenses. The improved electrostatic variable spot-shaping sub-system does not require mechanical rotation of the spot-shaping apertures for maintaining alignment or orientation. The improved sub-system includes both beam steering and beam blanking requiring less than 3 volts for operation of the blanking controls to turn the beam on and off. The novel system easily accomodates a variety of different beam-shaping apertures for use as the second beam shaping aperture in the sub-system including rectilinear triangles of different orientation to provide smooth 45 degree pattern delineation, rectangles, squares, and even different diameter circles where such configurations are required by a particular pattern to be written in the target plane.

Claims14

Dependent claims

An all electrostatic charged particle beam variable spot-shaping lens and deflector assembly to be mounted within an elongated evacuated housing along the optical axis of the undeflected charged particle beam path of a charged particle beam produced by a charged particle gun mounted at one end of the elongated housing;

said electrostatic charged particle beam spot shaping lens and deflector assembly including first and second spot shaping apertured plate members spaced apart a predetermined axial distance along the optical axis of the assembly and having spot shaping apertures formed therein, first and second electrostatic spot shaping lens sub-assemblies mounted between the first and second spot shaping apertured plate members along the optical axis of the assembly housing and spaced-apart a predetermined distance with relation to each other and the apertured plate members, and first and second spot shaping electrostatic deflector means mounted along the optical axis of the assembly with the first spot-shaping deflector means interposed between the first and second spot shaping electrostatic lenses for imaging the aperture of the first spot shaping apertured plate member onto the second spot shaping apertured plate member to thereby produce a partially truncated image of the first spot shaping aperture for application to a target surface, and said second spot-shaping electrostatic deflector means being mounted immediately following the second spot-shaping apertured plate member in the direction of the charged particle beam path for restoring the partially truncated charged particle beam image of the first spot shaping aperture back to the optical axis of the undeflected beam to thereby avoid the need to correct the beam spot position at the target plane as the charged particle beam shape is varied.

The method of precisely shaping the cross-sectional size and configuratin of an electron beam used for direct electron beam writing on a target surface in an electron beam lithography system using an all electrostatic electron beam spot-shaping lens and deflector assembly mounted within an elongated evacuated housing along the optical axis of the undeflected electron beam path of an electron beam produced by an electron gun mounted at one end of the housing, said electrostatic electron beam spot-shaping lens and deflector assembly including first and second spot-shaping apertured plate members spaced apart a predetermined axial distance along the optical axis of the elongated housing and having spot-shaping apertures formed therein, first and second electrostatic spot-shaping lens sub-assemblies comprised by three plate element Einzel lens structures having center, front and back plate elements, respectively, mounted between the first and second spot shaping apertured plate members along the optical axis of the elongated housing and spaced-apart a predetermined distance with relation to each other and the apertured plate members, and first and second spot shaping electrostatic deflector sub-assemblies mounted along the optical axis of the housing with the first spot shaping deflector sub-assembly interposed between the first and second spot shaping electrostatic lens sub-assemblies, and said second spot shaping electrostatic deflector sub-assembly being mounted immediately following the second spot shaping apertured plate member in the direction of the electron beam path;

said method comprising:
imaging the first spot shaping aperture onto the second spot shaping aperture while simultaneously imaging the electron beam source crossover point onto the principal plane of focus of the final lens or an intervening demagnification lens employed in an electron beam optical system with which the electron beam spot shaping lens and deflector assembly is used, maintaining the deflection center of the first spot shaping deflector a distance of double the focal length of the second electrostatic spot shaping lens measured from its rear principal plane and maintaining the deflection center of the second spot shaping deflector a distance of double the focal length of the second electrostatic spot shaping lens measured from its front principal plane to thereby cause the image of the first spot shaping aperture to remain stationary relative to a target surface and the superimposed image of the second spot shaping aperture appear to move relative to the stationary image of the first aperture to thereby vary the spot size and shape while always being confined within the full spot dimensions of the first spot shaping aperture.

Dependencies are inferred from the claim text.

All electrostatic electron optical sub-system for variable electron beam spot shaping and method of operation

Life of this patent

All electrostatic electron optical sub-system for variable electron beam spot shaping and method of operation

Life of this patent

Abstract

Claims14