More than 100 Layers to make a Mirror
To coat the substrates SCHOTT LITHOTEC has set up an “Advanced Quality Production Line” using modern sputtering technology under clean room conditions. From its very conception, emphasis was placed on achieving low reject rates. On the journey from the substrate to the mask blank more than 100 layers are applied – each only a few atoms thick. As no material reflects EUV radiation naturally, artificial crystal grids have to be generated which produce the necessary mirror effect by means of interference. This also explains the high number of layers required. SCHOTT LITHOTEC is also cooperating with external partners in this area. These include the Fraunhofer Institute for Applied Optics and Precision Mechanics (IOF, Jena) and the PTB (Federal Physical and Technical Office) in Berlin. The metrology required to test the reflection behavior of the mask blanks while they are still in the production stage is being developed especially for SCHOTT LITHOTEC by Jenoptik Mikrotechnik and AIXUV GmbH of Aachen, the first supplier of commercially available EUV radiation sources for laboratory use.
SCHOTT LITHOTEC and SCHOTT GLAS EUVL programs have been running since May 2001 with financial support from the Federal Ministry for Research and Education (BMBF). These activities are also part of both a total German concept for EUVL and in the European MEDEA+ research initiative. MEDEA is the successor program to JESSI.
Together to the Target
Those involved in the EUVL consortium are:
- SCHOTT LITHOTEC
- SCHOTT GLAS
- Carl Zeiss
- XTREME Technologies (a merger of Lambda Physik and Jenoptik for the development
of EUV sources)
- ASML (as stepper manufacturer)