Practical use of hard mask process to fabricate fine photomasks for 45nm node and beyond

摘要

New process with hard-mask (HM) blanks was evaluated as one of candidates for photomasks beyond 45nm-node. Through the fabrication of gate-layer photomasks, aptitude of the HM process for practical use was confirmed from the view of controllability on CDs and defects. Although conventional process for attenuated PSM was shown to have critical CD error which belongs to the "patterns" in bright-field masks, experimental data proved effectiveness of the HM process to control CDs after process optimization. With the HM blanks, remarkable reduction of CD error more than 80% of conventional process was confirmed. In this report, peculiar opaque defects are also shown to be a critical issue on the HM process. From results of design of experiment (DOE), combining the proper means to prepare the HM blanks with the optimized HM etching condition, these defects were proved to be controlled within the tolerance for production. Through the investigations, validity of the HM process on practical use for mask fabrication of 45nm-node and beyond is considered as conclusions.