This study demonstrated our prototyped Micro Electro Mechanical System (MEMS) electron emitter
which is a nc-Si (nanocrystalline silicon) ballistic electron emitter array integrated with an active-matrix driving
LSI for high-speed Massively Parallel Electron Beam Direct Writing (MPEBDW) system. The MPEBDW
system consists of the multi-column, and each column provides multi-beam. Each column consists of emitter
array, a MEMS condenser lens array, an MEMS anode array, a stigmator, three-stage deflectors to align and to
scan the multi beams, and a reduction lens as an objective lens. The emitter array generates 100x100 electron
beams with binary patterns. The pattern exposed on a target is stored in one of the duplicate memories in the
active matrix LSI. After the emission, each electron beam is condensed into narrow beam in parallel to the axis
of electron optics of the system with the condenser lens array. The electrons of the beams are accelerated and
pass through the anode array. The stigmator and deflectors make fine adjustments to the position of the beams.
The reduction lens in the final stage focuses all parallel beams on the surface of the target wafer. The lens
reduces the electron image to 1%-10% in size.
Electron source in this system is nc-Si ballistic surface electron emitter. The characteristics of the
emitter of 1:1 projection of e-beam have been demonstrated in our previous work. We developed a Crestec
Surface Electron emission Lithography (CSEL) for mass production of semiconductor devices. CSEL system is
1:1 electron projection lithography using surface electron emitter. In first report, we confirmed that a test bench
of CSEL resolved below 30 nm pattern over 0.2 um square area. Practical resolution of the system is limited by
the chromatic aberration. We also demonstrated the CSEL system exposed deep sub-micron pattern over
full-field for practical use.
As an interim report of our development of MPEBDW system, we evaluated characteristics of the
emitter array integrated with an active-matrix driving LSI on the CSEL system in this study. The results of its
performance as an electron source for massively parallel operation are described. The CSEL as an experimental
set consisted of the emitter array and a stage as a collector electrode that is parallel to the surface of the emitters.
An accelerating voltage of about -5 kV was applied to the surface of the emitter array with respect to the
collector. The target wafer and the emitter array were set between two magnets. The two magnets generated
vertical magnetic field of 0.5 T to the surface of the target wafer. A gap between the emitter array and the target
wafer was adjusted to a focus length depending on electron trajectories in the electromagnetic field in the system.
The emitter array projected 100x100 electron beams with binary patterns and a dots image of its original size on
the target wafer. The certain array was examined in order to evaluate the property of the e-beam exposure.