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Azimuth Insensitive System for Line Width Measurement

IP.com Disclosure Number: IPCOM000045719D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Goodman, DS: AUTHOR

Abstract

In the ordinary measurement of line widths, it is necessary either that the distance from one line edge to the other be measured in a direction perpendicular to the line length or, if the measurement direction is not perpendicular, then its angle must be known. An azimuthal-independent measurement scheme is described.

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Azimuth Insensitive System for Line Width Measurement

In the ordinary measurement of line widths, it is necessary either that the distance from one line edge to the other be measured in a direction perpendicular to the line length or, if the measurement direction is not perpendicular, then its angle must be known. An azimuthal-independent measurement scheme is described.

A line width can be found from two width measurements taken at different angles if the angle between these measurements is known, even if the angle of the pair of width measurements relative to the line is not known. If A is the angle between the measurement directions (Fig. 1) and if the two measurements across the line have lengths D1 and D2, then the line width is W=(D1 x D2 x SIN A) / (D1/2/ + D2/2/ - 2 x D1 x D2 x COS A) /1/2/.

One embodiment of this method is shown in Fig. 2. The object 10 under inspection is imaged by lens 12 onto a plane containing a pair of linear detector arrays 14 and 16, which have an included angle of A. These act as the "rulers" which give D1 and D2. Array outputs 18 and 20 are shown on oscilloscope 22 for the case of a line which is lighter than its surrounding area. The first and last high diode outputs are found by comparison with an electronic threshold, and the separation between the two is proportional to D1 and D2, where the proportionality constant depends upon the magnification and the dimensions of the detector array. From these numbers, the line width is...