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Electrical Vernier Alignment Measurement

IP.com Disclosure Number: IPCOM000047110D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Voge, JB: AUTHOR

Abstract

An electrical vernier alignment measurement system for measuring the alignment of two metal layers, i.e., two levels of metallurgy, is shown in the drawing. Conductor #2 is the upper level, and conductors #1 and #3 are the lower level. A misalignment would shift conductor #2 left or right (Wx). Conductor #1 is the measurement, and conductor #3 serves as a reference. Conductors #1 and #3 are equivalent such that the resistance of one zig-zag (one period) of conductor #1 may be calculated by measuring conductor #3 and dividing its resistance by the number of periods. In a perfectly aligned system, conductor #2 would short out conductor #1 from the slider to Tab #0. Thus, the resistance of conductor #1 would be reduced by 5 periods.

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Electrical Vernier Alignment Measurement

An electrical vernier alignment measurement system for measuring the alignment of two metal layers, i.e., two levels of metallurgy, is shown in the drawing. Conductor #2 is the upper level, and conductors #1 and #3 are the lower level. A misalignment would shift conductor #2 left or right (Wx). Conductor #1 is the measurement, and conductor #3 serves as a reference. Conductors #1 and #3 are equivalent such that the resistance of one zig-zag (one period) of conductor #1 may be calculated by measuring conductor #3 and dividing its resistance by the number of periods. In a perfectly aligned system, conductor #2 would short out conductor #1 from the slider to Tab #0. Thus, the resistance of conductor #1 would be reduced by 5 periods. A left shift (-Wx) would cause an open circuit at Tab #0, increasing the resistance of conductor #1 by one period, and a larger -Wx would cause additional open circuits at Tab -1, then Tab -2, etc., such that the resistance would increase as a step function. A right shift (+Wx) would have an opposite effect on the resistance of conductor #1. As Wx became more positive, Tab 1, then Tab 2, etc., would short out an increasing number of periods in conductor #1. The number of periods and the resistance of each period can be adjusted for optimum effect. A perfectly aligned system will result in conductor #1 being 50% of the resistance of conductor #3. For each increment of alignment shift, the resistanc...