Automatic focus and deflection correction in E-beam system using

Details Automatic focus and deflection correction in E-beam system using Automatic focus and deflection correction in E-beam system using

1981-12-31

1984-08-28

Howell, Janice A.

Radiant energy

Means to align or position an object relative to a source or...

2504923, 219121ES, 219121EW, B23Q 1512, G01B 1114

Patent

active

044685653

ABSTRACT:
An automatic focus correction system for E-beam lithography uses optical light from a narrow angle light source to illuminate a horizontal slit, the image of which is projected onto a target surface. Prior to and after reflection of the slit image from the target surface the light beam is projected parallel to the target surface to minimize vertical space requirements in the E-beam column. Variations in height, z-position, cause the slit image to move vertically and the focus of reflection to shift laterally and this image is redeflected in the horizontal plane by a prism to a linear diode array used to produce a video-type output signal. Autofocus electronics are used to convert the video output signal into an analog correction signal to the E-beam fine focus coil. The video-type signal is also converted to a digital height value to be used for corrections in beam magnification and rotation.

REFERENCES:
patent: 4039824 (1977-08-01), Nanba
patent: 4334139 (1982-06-01), Wittekoek
S. Wittekoek "Step and Repeat Wafer Imaging" Semiconductor Microlithography V SPIE Proceedings, vol. 221 (Mar. 17-18, 1980) pp. 5-6.

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