The objective of this article is to evaluate low-voltage electron-beam (e-beam) resists suitable for direct write on wafer and mask fabrication in the sub-100 nm regime. Low kV exposure provides the advantages of high sensitivity, reduced charging, and a lack of proximity and heating effects. However, a major concern is whether a low-voltage e-beam is capable of patterning sub-100 nm features in resist with a thickness substantially greater than the penetration range of the electrons. At 1–2 kV, the penetration range is between 30 and 100 nm, while typical resist thickness is >200 nm. In an effort to overcome this limitation, thin film layer techniques are evaluated for low kV e-beam exposure. Preliminary 1 kV results on two thin imaging schemes, the bilayer CARL process and top surface imaging with NTS-4 resist, are reported here. Important results achieved are high sensitivity (1–2 μC/cm2), high contrast (γ>10), high resolution (70 nm in ∼300 nm thick resist), good critical dimension (CD) linearity (range=7 nm, mean=8 nm), large exposure latitude (ΔCD/Δdose=0.5 nm/% change in dose), and absence of proximity effects.
Propagation and post-acceleration of a pseudospark-sourced electron beam Distributed, multiple variable shaped electron beam column for high throughput maskless lithography A raster-shaped beam writing strategy has been tested on a prototype 50 keV electron-beam lithography workstation. The test stand was constructed to prove the raster-shaped beam concept by exposing patterns at full throughput over small areas. Patterns are composed in a raster-scanned array of variably shaped flashes at 100 MHz flash rate, with 0.9 A full beam current, and 2200 A/cm 2 current density using a thermal field emission source. Writing speed is independent of resist sensitivity and pattern complexity. By comparison, a typical variably shaped beam system with a LaB 6 source would have a current density of 10-30 A/cm 2 and a flash rate of 2-10 MHz, depending on resist sensitivity and deflection settling time.
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