Je. Schneider et al., Patterned negative electron affinity photocathodes for maskless electron beam lithography, J VAC SCI B, 16(6), 1998, pp. 3192-3196
This work focuses on two issues crucial to achieving high throughput with a
negative electron affinity semiconductor photocathode source. Monte Carlo
simulations indicate that for a 50 kV system, as much as 8 mu A of current
may be delivered to the wafer to achieve a raw throughput of 20 8 in. wafer
s per hour with 0.1 mu m minimum feature size (assuming a resist sensitivit
y of 10 mu C/cm(2)). In order to achieve the throughput potential of this a
pproach, suboptical emission areas are required; this suggests the use of c
athode patterning. Two patterning alternatives have been investigated exper
imentally, and both approaches have been used to generate arrays of more th
an 100 electron beams with source sizes as small as 150 nm. However, each t
ype of patterned cathode presents unique challenges to fabrication and perf
ormance in a practical multibeam system. Different source configurations (n
umber of beams, beam current, beam spacing, etc.) create a system-level tra
deoff between resolution and throughput. Results from patterned cathode exp
eriments and system modeling are presented. (C) 1998 American Vacuum Societ
y. [S0734-211X(98)15806-7].