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.
Shrinking of pattern size on photomask requires tight control on defects and CD qualities. Recent ultra resolution lithography requires tight criteria for defect. In this paper, we describe the main defect factor "re-adsorption of resist" on. This is dependent on the development process, the relationship between defect and development and/or rinse method. The hp90-65nm process needs to reduce re-adsorption of resist for improvement in defect level. The solution of this issue is the uniformed high flow for development and rinse fluid. We adopt modified development system as the intermediary to make high fluid flow possible. From our results, this system could reduce the number of defects around 70-80%. The defect size will also be reduced through this system. So, we propose that Noble development method is one of the effective process means for hp90-65nm photomask production.
For today’s advanced reticle production, process bias should be reduced as possible, and be “zero” ideally, because of its negative impacts on CD control and pattern fidelity against minute features. In this paper, blanks with Cr film thinner than 100 nm were examined as promising materials to meet this demand. Results from two aspects, reticle production and lithographic performance, are presented. Dry etching properties such as etching bias, CD Linearity, impact on pattern-pitch were investigated. Thin Cr film blanks showed excellent results in process bias less than 50 % of conventional ones with proper etching conditions. They also showed about 50 %’s decrease of etching bias variations for pattern-pitch with smaller CD error in CD Linearity at the same time. Results of aerial image simulations showed possibilities of them as substitute of conventional binary blanks in ArF lithography. There was no impact of Cr film thinning on depth of focus and optical proximity effect with optimized exposure condition. These experimental results imply that Cr film thickness plays an important role to decide the qualities of reticle CD. Thinner Cr film blanks have capability to realize a 90 nm-node reticle with minimized process bias enough to produce fine OPC features.
In mask making, ZEP 7000 resist process with MEBES writing tool is widely adopted to produce advanced masks. This time, we tried to improve resist pattern CD uniformity in ZEP process using our special techniques. Resist sensitivity uniformity of mask blank is one of the most significant parameters for resist pattern CD uniformity. In ZEP7000 coating process, our original cooling method waw adopted in consideration of its resist sensitivity properties. Resist film thickness loss (RTL) uniformity during development was examined in order to analyze the resists sensitivity uniformity within a mask blank. It was clearly seen that resist pattern CD uniformity was 15nm with the optimum cooling condition. RTL uniformity and resist pattern CD uniformity were also examined using blanks which were commercially available from two vendors. And these results were compared with the results of our original cooling method. Based on the results of our study, we confirmed that our original cooling method was very effective for improvement of resist pattern CD uniformity on ZEP process.
In mask manufacturing, resist coating is one of the most important processes for fine pattern making because the pattern CD uniformity largely depends on the resist film accuracy. In recent years, various spin coating methods, we have found that the rotary cup method is the best choice to meet our requirements. The method has various advantages in comparison with the other ones. On the other hand, there is a problem of film thickness variations, which are specific to certain types of resist, with this method. In our study, we established a new coating technique which solved the problem mentioned above, without sacrificing the advantages of the rotary cup method. This new method is very effective for resist coating and can be applied to mask fabrication for the next generation devices including 230 mm masks.