Lithography technologies promising for the half pitch (HP) 32 nm generation include 193 nm immersion with water,
extreme ultraviolet lithography (EUVL), and nano-imprint lithography (NIL). Among these, 193 nm immersion with
water is considered a mainstream for hp 32 nm device fabrication in terms of performance and device production costs.
Meanwhile, according to the International Technology Roadmap for Semiconductors (ITRS) 2009, the optical masks for
hp 32 nm devices need to meet extremely strict requirements; for example, an image placement accuracy of 3.8 nm (2.7
nm for double patterning), and CD uniformities of 1.5 nm (isolated lines) and 2.4 nm (dense lines).
To meet these accuracy requirements, we have developed JBX-3200MV, a variable shaped beam mask writer featuring
an accelerating voltage of 50 kV and a current density of 70 A/cm2. For this new writer, we developed a new
digital-to-analog converter (DAC) amplifier designed to reduce noises input to electron beam optics components such as
the main and sub positioning deflectors and the beam shaping deflectors. The stage and exposure chambers were
enhanced in rigidity to reduce mechanical noises. The position of the stage is measured by laser devices with a finer
resolution of 0.15 nm, and the measured results are fed back to the beam position. In addition, data transfer speed and
proximity correction speed were improved to handle larger data volumes.
Our exposure test results demonstrate that the new lithography system, installed at the leading-edge mask production
facility, achieved the hp 32 nm mask accuracies required by the ITRS 2009.
This paper presents an experimental study of resist charging of mask blanks written with a variable shaped electron beam
mask writer. Experiments were performed at a current density of 40 A/cm2 on mask blanks with a chemically amplified
resist. Test patterns were written to examine the magnitude of the pattern shift due to resist charging and the distance
within which the pattern shift is significant. To reduce the pattern shift due to resist charging, furthermore, similar test
patterns were written with a two-pass scanning in which both horizontal and vertical scanning directions are different
between the two passes. With this writing method, the pattern shift was successfully reduced to about half.
This paper presents an experimental study of resist heating effect in mask making with a variable shaped electron beam
mask writer. Experiments were performed at current densities of 40 and 80 A/cm2 on mask blanks with a chemically
amplified resist. At these levels of current density, the critical dimension change due to resist heating effect was obvious.
The critical dimension change was reduced with a checkerwise writing method, in which sub-fields were arranged in
main fields in an alternate fashion so that the average incoming heat per unit area due to beam exposure could be reduced.
The reduction factor was 2 or more.
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