Increasing mask yield through repair yield enhancement utilizing the MeRiT

Abstract

The push toward smaller feature size at 193 nm exposure has been enabled by resolution enhancement techniques (RET) such as phase shifting technologies and optical proximity correction (OPC) which require more costly and time intensive resources to fabricate. This leads to a higher overall cost associated with each mask, making it more important than ever for the mask shop to fully utilize and improve its repair capabilities as the presence of defects on the final product is the major yield reducing factor. An increase in repair capability leads to a direct enhancement in repair yield which translates to an improvement in overall mask yield and a reduction in cycle time. The Carl Zeiss MeRiT® MG 45 provides numerous benefits over other techniques that can lead to an increase in repair yield. This paper focuses on methods utilizing the MeRiT® MG 45 that can be employed in a production environment in order to increase mask repair yield. The capability to perform multiple repairs at a single site without optical degradation enables defects that were not successfully repaired the first time to be corrected on a subsequent attempt. This not only provides operator mistakes and inexperience to be corrected for, but eliminates the need to hold up production in order to start a new mask which can cause a cascading effect down the line. Combining techniques to approach difficult partial height and combination defects that may have previously been classified as non-repairable is presented in an attempt to enable a wider range of defects to be repaired. Finally, these techniques are validated by investigating their impact in a production environment in order to increase overall mask yield and decrease cycle time.