Method and apparatus for determining line centers in a microminiature element

US5063300A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Michael Kallmeyer · Eppelheim, DE
• Dietmar Wagner · Tauberbischofsheim, DE

Key dates

• Filing date: Jun 28, 1990
• Grant date: Nov 5, 1991
• Expiry date: Jun 28, 2010

Classification

• Technology area (CPC G): Physics
• CPC primary: G01B11/02
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Method and an apparatus for determining line centers in a microminiature element such as on a semiconductor wafer or a mask having linewidths and other spacings below the one micron range. The invention uses, two focussed laser beams which are directed across a line on the element, both beams being illuminated successively with a distance therebetween below the classic resolving power. A portion of the incident beam and a portion of the beam reflected from the line is conducted to respective detectors which respectively generate measurement and reference signals. These signals are treated to eliminate high frequency noise components therein. Subsequently, the filtered measurement and reference signals are digitized and synchronously processed to provide two sine shaped curves whose intersection point corresponds to the center of the scanned line.