METHOD OF DETERMINING A FOCUS OF A PROJECTION SYSTEM, DEVICE MANUFACTURING METHOD, AND APPARATUS FOR DETERMINING A FOCUS OF A PROJECTION SYSTEM

Methods and apparatus for determining a focus of a projection system are disclosed. In one arrangement, a method includes obtaining first data derived from a first measurement of one or more selected properties of a target pattern formed on a substrate by exposing the substrate using the projection...

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Bibliographische Detailangaben
Hauptverfasser: LAENENS, Bart, TEL, Wim Tjibbo
Format: Patent
Sprache:eng
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Beschreibung
Zusammenfassung:Methods and apparatus for determining a focus of a projection system are disclosed. In one arrangement, a method includes obtaining first data derived from a first measurement of one or more selected properties of a target pattern formed on a substrate by exposing the substrate using the projection system. The first measurement is performed before the substrate is etched based on the target pattern. The method further includes obtaining second data derived from a second measurement of the one or more selected properties of the target pattern. The second measurement is performed after the substrate is etched based on the target pattern. The method further includes determining the focus of the projection system using the first data and the second data.