Infrared-measurement of X-ray mask heating during SR-lithography

For the fabrication of ULSI circuits, it is necessary to master sub-half micron design rules which include an efficient patterning procedure and critical dimensions related overlay requirements. In addition to the alignment accuracy, the overlay budget is determined by the pattern placement precision on X-ray masks. There are two kinds of absorber pattern displacements-those having static and others having dynamic causes. Static displacements are produced by e-beam patterning or during mask fabrication; dynamic distortions can be induced for example by temperature rise of X-ray masks in synchrotron radiation lithography. The authors used an in-situ thermographic system to determine the temperature distribution during the exposure.