Improvement of a DUV mask inspection tool to hand over the baton for next-generation tool smoothly

Various technologies such as multiple patterning (MP) are being developed to extend the current DUV optical lithography to deal with the delay of next generation lithography such as EUV and NIL. Likewise, it is necessary to continue to develop technologies for mask inspection tools for masks fabricated for the DUV optical lithography so that they can be appropriately inspected, until the next generation EB or EUV actinic inspection tools is put into practical use. To fabricate 1x nm devices with the present lithography process, the industry will likely further extend double patterning (DP) to multiple patterning (MP). For MP, the requirements for the inspection sensitivity of traditional defects such as intrusions or extrusions do not change much, but those for CD control and overlay tolerances will become more critical. In this paper, we will discuss the main features of NPI-7000, a DUV based mask inspection tool for the 1x nm node devices, and our challenges in enhancing the CD error sensitivities to enable the inspection of masks.