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Accurate Overlay between Patterns Written by E-Beam and Light Optical Lithography Systems

IP.com Disclosure Number: IPCOM000051962D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Michail, MS: AUTHOR [+2]

Abstract

This is a technique for providing accurate overlay patterns by adjustin the field deflection of an E-beam system to match the field distortion of any optical system.

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This is the abbreviated version, containing approximately 53% of the total text.

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Accurate Overlay between Patterns Written by E-Beam and Light Optical Lithography Systems

This is a technique for providing accurate overlay patterns by adjustin the field deflection of an E-beam system to match the field distortion of any optical system.

A scanning E-beam system is utilized as a tool for manufacturing semiconductor devices by writing patterns to overlay other patterns which were written previously by other E-beam systems or light optical means. The accuracy with which patterns can overlay other patterns is determined not only by the E- beam deflection accuracy, but also by the distortion of patterns to be overlayed as they have been introduced by the optical systems. When patterns are written by light optical systems, i.e., projecting patterns from masks to wafers, the exposed pattern will suffer from field distortion imposed by lens distortion, etc.

One method is to calibrate the E-beam deflection to a calibration grid made by the optical system to be compensated. Another method is to correlate the measured E-beam deflection errors to a deflection similar to the distorted optical field and generate corrections based on the difference.

The E-beam distortion is measured by scanning a calibration grid made of holes in gold over silicon. Having previously characterized the grid so that the relative position of the holes are known precisely, the true position of the beam within the field is determined. Since the optical field distortion is basically a static phenomena, it can be measured and determined. This distortion may be represented as beam position shifts at every measurement point within the deflection field of the E-beam system. These beam position shifts, due to optical distortion, are then added to the characteristics of the reference target. The result is a virtual reference target whose characteristics are the same as the optical system distortion.

The...