Multi-tone mask (MTM) consists of more than two layers having different transmittance modulation layers. A novel method is proposed to manufacture a MTM based on two kinds of transmittance modulation materials such as chromium and molybdenum. Different modulation materials cannot be only act as etch-stopper to each other, but also they play a role as a separator between the layers consisted of MTM. Furthermore, clearly classified modulation layers contribute to define one of the targeted transmittance according to different etching process. Especially, a conventional MTM requires three mask writing processes to form three patterns whereas the proposed MTM structure makes it possible to form three patterns by using only two mask writing processes. It is found that the turnaround time of proposed MTM is remarkably decreased as value of 30% compared to that of conventional MTM. MoSi-/Cr-based tri-tone mask configuration having 37, 15, and 0% of transmittance had been demonstrated based on the optimized thin-film conditions. Optical uniformity characteristics were also carried out to evaluate the photomask performance. Consequently, the proposed MTM is not only expected to extend the variation of objective transmittance, but also it is a very promise method for achieving a high performance photo-mask by reducing its fabrication cost.
Recently, the development of semiconductor process for 14nm node and beyond is in progress. The mask-making
process demands higher resolution and CD accuracy to meet requirements. Current conventional ArF PSM has several
problems such as higher 3D effect and higher loading effect due to the thicker film. These problems cause the CD
This study is about the manufacturing of advance ArF PSM, which has thinner phase shift layer and higher etch rate Cr
absorber film. The thickness of phase shift film is less than 60nm and the total etch-time for the Cr absorber film is
reduced more than 30%.
The mask CD performance of this new blank was evaluated in terms of CD uniformity, CD linearity, pattern resolution,
and loading effect and so on. Adapting to this new blank, we can achieve better CD performance by reducing the loading
effect. In addition, the chemical durability and ArF exposure durability were also improved.
In conclusion, the mask-making process margin was extended by using this new blank, and it is expected that we can
achieve the required specifications for 14nm node and beyond.