As the required accuracy of the mask arises, Cr shading film thickness has been thinner gradually. CD linearity with
the thinner Cr film thickness has better performance. However, it is difficult to apply thinner Cr film thickness simply
under the condition of OD > 3, which is needed for wafer printing. So, we tried to develop new shading film. We adopted
MoSi film, because MoSi film has almost no micro loading effect compared with Cr film. MoSi shading film with
att.PSM satisfied OD > 3 at 193nm wavelength with good resist profile. But the issue was dry-etching selectivity, because
shading layer material was the same of att. PSM layer material. Therefore super thin Cr etching stopper was inserted
between MoSi shading layer and MoSi att.PSM layer.
The mask CD performance of new blank was evaluated for CD linearity, CD through pitch, and global loading effect.
This blank and mask process reduce loading effect, therefore the mask CD performance is improved remarkably. In
conclusion, the mask manufacturing process margin was able to be expanded by this new blank and method, and it is
expected that we can achieve the required specifications for att.PSM in 45nm node and beyond.
The immersion lithography for 45 nm generation has been developing aggressively for smaller critical dimension of semiconductor devices. The polarization lithography system is indispensable to have an advantage to use the immersion lithography with hyper NA (>1.0). As pattern size becomes smaller, mask induced polarization effects to polarization of exposure image seems not to be negligible. There are several issues about mask induced polarization. But dominant factor for mask induced polarization effect is not understood well.
In this paper, in case of monolayer mask of att.PSM, degree of polarization (DoP) strongly depends on film thickness and extinction coefficient from simulation and experimental results. DoP depends on material factor. And in case of double layer mask, DoP depends on total film thickness and extinction coefficient of both upper layer and bottom layer. So, DoP depends also on structure of mask.
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