ELECTRON BEAM LITHOGRAPHY FROM 20 TO 120 kev WITH A HIGH QUALITY BEAM.

Electron beam lithography studies have been performed on thick substrates using beam energies of 20-120 kev and a nominal beam diameter of 2 nm in a Philips 400 electron microscope with scanning capability. Metal lines as narrow as 10 nm were fabricated on Si and GaAs substrates using liftoff of a single thin layer of resist. High resolution (approximately 10 nm) patterns could be written at all beam energies with an exposure latitude that remained approximately constant up to energies for which the range of the backscattered electrons became significantly larger than the pattern area. For large area patterns written with the small beam, the proximity effect is greatly reduced, even at 20 kev, because of the sharp edge of the exposure profile. At high beam energies, the range of backscattered electrons is large enough that they contribute only a slowly varying background dose, leading to a relatively simple proximity correction even for complex patterns.