RESOLUTION LIMITS IN ELECTRON-BEAM-INDUCED TUNGSTEN DEPOSITION

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.