Alignment system for particle beam lithography

US4370554A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Harald Bohlen · Eppelheim, DE
• Johann Greschner · Neckartenzlingen, DE
• Werner Kulcke · Eppelheim, DE
• Peter Nehmiz · Stuttgart, DE

Key dates

• Filing date: Sep 2, 1980
• Grant date: Jan 25, 1983
• Expiry date: Sep 2, 2000

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01L21/682
• WIPO field: Electrical machinery, apparatus, energy
• WIPO sector: Electrical engineering

Abstract

The mutual alignment of mask and substrate patterns of a specific semiconductor structure are attained by use of a plurality of individual marks in a specific geometric position with respect to each other. By the arrangement of openings in the alignment pattern of the mask, the broad electron beam is split into a multitude of individual beams which interact with alignment marks on the substrate. The interaction is used to generate a coincidence signal. The signal to noise ratio of this arrangement is determined by the overall current and is comparable to that of a thin concentrated electron beam. Registration is effected in a small amount of time and the disadvantageous effects of the high current density used in the raster process are not a factor. In a preferred embodiment, the alignment pattern of the mask is a matrix with center spacings of openings increasing upon advance in two directions perpendicular to each other such that no distance can be represented by the sum of smaller distances. Alignment signals are provided by detecting either absorbed or reflected electrons. A plurality of detectors in the mask are used to detect the reflected electrons.