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.
To control the CD precisely, inorganic "Hard-Mask" which we expect one of the candidates for 45nm-node and beyond
technology was evaluated. Hard-Mask which is inserted between resist and Cr layer of a photomask blank enable us to
use high anisotropic etch condition. Also it enhances the resist resolution because it can avoid the interaction between
resist and Cr. This time, we confirmed the benefit of Hard-Mask which could reduce the etch bias and proximity process
error. Especially proximity process error was reduced down to 1/4. And resolution enhancement effect was observed. We
also confirmed the blank quality such as defects, film stress, sheet resistance, optical properties and so on, and found that
Hard-Mask blank would not be a showstopper for this development.
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