Browse Prior Art Database

Photomask Inspection System

IP.com Disclosure Number: IPCOM000078877D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Wuestenhagen, J: AUTHOR

Abstract

The method serves to automatically detect defects on photomasks used in different process steps, during the manufacture of integrated circuits.

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Photomask Inspection System

The method serves to automatically detect defects on photomasks used in different process steps, during the manufacture of integrated circuits.

It is assumed that masks are produced by a pattern generator assembling the Bask pattern from rectangles, the centers of which are arranged on points of a square grid. The lengths of the rectangle sides can only be integral multiples of the grid spacing. From this fact, a layout rule is derived which consists in particular in the minimum distances between the structures and in the minimum widths of the structures being prescribed.

The mask to be tested is placed on an x-y table, magnified by a microscope and projected onto a TV camera, with magnification being chosen so that the line spacing is approximately equivalent to the grid spacing of the pattern generator. For line-by-line scanning of the mask, video signals consisting of a pulse sequence corresponding to the pattern are provided. The pulse widths and spacings of a mask free from defects must be in compliance with the layout rules. Nonpermissible pulses, i.e., pulses originating from defects. are filtered out by a suitable defect detector and are displayed on a TV monitor. By moving the table in meander fashion, the full mask is passed by the field of the microscope. The defects can be counted and individual ones can be observed through the microscope by stopping the table.

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