Wafer-based optical pattern recognition targets using regions of gratings

US7564554B2 · kind B2 · utility

Assignee

• Intel Corporation · US

Inventor

• Martin Weiss · Margertshausen, DE

Key dates

• Filing date: Jun 30, 2006
• Grant date: Jul 21, 2009
• Expiry date: Jan 30, 2027

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F9/7076
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Pattern recognition targets including regions of one or more layers of gratings are used for semiconductor fabrication wafer alignment. Grates of the gratings are below the resolution limit of the alignment microscopes, and have dimensions compatible with design rules applied to actual device circuitry. Targets may be located by the contrast of light reflected and diffracted back from the regions and through a numerical aperture of the microscope. Target contrast may be achieved by controlling the diffractive properties of the regions. A grating with a pitch that causes a significant amount light to diffract out of the numerical aperture will appear darker, while a grating with a pitch that produces minimal diffraction with appear much brighter. Moreover, for a darker causing pitch, a region of layers gratings having grates stacked on each other can appear even darker, while a region having layers of grates interleaved can appear even brighter.