This invention relates to a ceramic membrane device which is suitable for a photomask and to a method for producing the ceramic membrane device.
When processing an integrated circuit, a photomask is used for the purpose of forming a pattern of electronic circuits or masking a pattern on a wafer. A conventional ceramic membrane device is composed of a ring-shaped base plate made of silicon and a circular ceramic coating supported on the base plate.
In the conventional ceramic membrane device, the ceramic coating is formed on only one face of the base plate. Thus, the base plate is apt to be disadvantageously curved or bent because there is a difference in magnitude of thermal expansion between the silicon base plate and the ceramic coating. If the base plate is curved, the ceramic coating is also curved so that its flatness deteriorates. In case of a curved ceramic membrane on which a masking pattern is formed, the pattern formed on a wafer by means of an X-ray will be faulty.