Patent Number: 052346099
Section: claims

1. An X-ray permeable membrane for an X-ray lithographic mask which is a membrane consisting of the elements of silicon, carbon and nitrogen and which has a chemical composition expressed by the formula SiC.sub.x N.sub.y, in which the subscript x is a number in the range from 0.25 to 0.86 and the subscript y is a number in the range from 0.18 to 1.0; and hydrogen in an amount not to exceed 1.0 atomic % of the membrane. 2. The membrane of claim 1 having a thickness of from 0.3 to 3.0 .mu.m. 3. The X-ray permeable membrane for X-ray lithographic mask as claimed in claim 1 in which the molar ratio of silicon to the total of carbon and nitrogen is in the range from 0.05 to 2.0 and the molar ratio of carbon to nitrogen is in the range from 0.2 to 5.0. 4. The X-ray permeable membrane for X-ray lithographic mask as claimed in claim 1 which is formed by the thermal chemical vapor-phase deposition method from a gaseous compound comprising the elements of silicon, carbon and nitrogen or a combination of gaseous compounds comprising, as a group, the elements of silicon, carbon and nitrogen.