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Interferometric Evaluation of Line Width Stability As a Direct Write E-Beam System Diagnostic Aid

IP.com Disclosure Number: IPCOM000062701D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Moszkowicz, L: AUTHOR

Abstract

Line width variations beyond the accuracy and precision of measurement tools can be instantaneously observed across a wafer using an optical distortion tester (interferometer). This technique is a valuable aid in diagnosing E-beam tool-related problems. Normally an optical distortion tester is used to measure local distortion errors of photolithographic tools, i.e, magnification and orthogonal errors. Thus, the distortion tester can be used as a print quality maintenance tool. Here, a plurality of grating pattern fields, made up of 1.5/2.5 um line/space pairs, are imaged across a test wafer using an E-beam system. The imaged wafer is placed in an interferometer designed to create an interference pattern.

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Interferometric Evaluation of Line Width Stability As a Direct Write E-Beam System Diagnostic Aid

Line width variations beyond the accuracy and precision of measurement tools can be instantaneously observed across a wafer using an optical distortion tester (interferometer). This technique is a valuable aid in diagnosing E-beam tool- related problems. Normally an optical distortion tester is used to measure local distortion errors of photolithographic tools, i.e, magnification and orthogonal errors. Thus, the distortion tester can be used as a print quality maintenance tool. Here, a plurality of grating pattern fields, made up of 1.5/2.5 um line/space pairs, are imaged across a test wafer using an E-beam system. The imaged wafer is placed in an interferometer designed to create an interference pattern. Light intensity variations in the interference pattern can be observed when the slightest line width variations exist in the grating patterns. As shown in the photograph, the darkened squares indicate regions of the wafer having varying line widths. The
1.5/2.5 um line/space ratio is set as a function of the angle of incidence of the two interfering beams in the interferometer. This results in an enhanced light intensity relationship between the interference pattern variations to the 1.5 /2.5 um grating constant. Because of this sensitivity, it is possible to evaluate line width variations across an entire wafer instantaneously. The above interferometric technique a...