Influence of X-ray mask repair on pattern placement accuracy

Compared to photomasks, X-ray masks are much more sensitive to mechanical damage, especially to process-induced distortions due to the use of thin silicon membranes (typically 2 mu m). One of several possible causes for such distortions is the repair of opaque defects using focused ion beams (FIB). The extent to which distortions are induced by the repair process has been investigated. Extensive experiments have shown that the repair process of opaque defects using focused ion beams does not significantly influence the pattern placement accuracy on X-ray masks.