Method of measuring focus of a lithographic projection apparatus

摘要

A method of measuring focus of a lithographic projection apparatus includes exposure of a photoresist covered test substrate with a plurality of verification fields. Each of the verification fields includes a plurality of verification markers, and the verification fields are exposed using a predetermined focus offset FO. After developing, an alignment offset for each of the verification markers is measured and translated into defocus data using a transposed focal curve. The method according to an embodiment of the invention may result in a focus-versus alignment shift sensitivity up to 50 times higher (typically dX,Y/dZ=20) than conventional approaches.