Kt. Kohlmannvonplaten et al., RESOLUTION LIMITS IN ELECTRON-BEAM-INDUCED TUNGSTEN DEPOSITION, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 11(6), 1993, pp. 2219-2223
Electron-beam induced deposition of tungsten from the precursor gas W
(CO)6 was investigated with the aim of determining the resolution limi
ting parameters. By exploring the effect of the beam energy and curren
t, the resolution was found to correlate to the expected behavior of t
he beam diameter. To achieve a more accurate description of the deposi
tion process, the time dependence of the needle height and diameter at
the base was determined for deposition times ranging from 5 to 180 s.
The measurements enabled a mathematical description of the needle sur
face as a function of time, and, therefore, the determination of the s
urface growth. The results exhibit that electron scattering cannot exp
lain the observed growth. For that reason, the surface growth was corr
elated to the number of secondary electrons (SE) emitted by the primar
y e beam from the needle surface considering the Gaussian intensity di
stribution of the e beam and the angle dependence of the SE yield. The
se assumptions result in a good agreement of the number of SE with the
surface growth and demonstrate that the beam diameter mainly limits t
he deposit resolution. As a consequence, by using a proper e-beam syst
em, a resolution of 1 mum high needles in the order of 50 nm is obtain
able.