https://gistexel.com/wp-content/uploads/2014/08/logo_exel.gif00exelhttps://gistexel.com/wp-content/uploads/2014/08/logo_exel.gifexel2014-09-03 14:16:112014-09-03 14:16:19 "Semiconductor device having X-ray lithographic mask and method for manufacturing the same,” US patent No. 5700603, 1997.