Synchrotron-radiation-induced formation of salt particles on an X-ray lithography mask

The suppression and removal of contaminants on X-ray masks are required for the application of X-ray lithography to practical semiconductor production, because contamination is easily transferred to the replicated resist patterns and degrades the LSI patterns. In order to study contamination of a Ta/SiN X-ray mask, its growth process was investigated using an atmospheric reaction chamber and in situ observation apparatus for gases at atmospheric pressure. It was found that the contamination particles were ammonium sulfate and oxalate. The sources of the salt particle were also identified.