Distributed, multiple variable shaped electron beam column for high throughput maskless lithography

The ultimate resolution obtainable with focused electron beams is, for practical purposes in lithography, unlimited. Existing e-beam lithography systems are too slow to be practical for high volume manufacturing of semiconductor devices, however. The usable current in probe forming systems is limited by the stochastic Coulomb interaction in the beam path, which causes loss of resolution at high current. This is due to the need to pass all of the writing current through an aperture. Distributed systems, by contrast, do not suffer from this problem, as the current is spread over a large volume. The purpose of this article is to propose a distributed system, employing multiple, variable shaped beams for direct write (maskless) lithography. We call this system DiVa, to emphasize the key attributes of distributed writing current, and variable beam shaping. It utilizes a planar cathode, patterned with a rectilinear array of square emitters. Focusing is accomplished by a uniform, axial magnetic field, oriented along the optic axis. This transfers a one-to-one image of the emitters onto the writing surface. Deflection plates between adjacent rows of beamlets effect motion in one Cartesian axis, while mechanical translation of the stage effects motion in the orthogonal axis. Theoretical resolution is diffraction limited to 4.6 nm at 50 kV. Experimental results are presented which demonstrate the first order optics using a rudimentary apparatus. (C) 1998 American Vacuum Society. [S0734-211X(98)14406-2].