CALCULATION OF A PROXIMITY RESIST HEATING IN VARIABLY SHAPED ELECTRON-BEAM LITHOGRAPHY

In variably shaped electron beam (EB) lithography, the horizontal thermal diffusion in a resist cannot be neglected when, high-current density, a high-speed deflector amplifier, and a multiple-layer resist system are used. These cause a horizontal-mode resist heating (labeled ''proximity resist heating''). Calculation of proximity resist heating is accomplished by a finite element method, using ANSYS (Ver.4.4A) program. The calculation results suggest that the proximity resist heating is caused by the horizontal thermal flux from previous EB shot through a top layer resist. Especially, in case a high-current acceleration voltage is used, the thermal effect is not caused by the vertical-mode resist heating, but by the horizontal-mode resist heating. It is also shown that the shorter settling time, which is the interval between shots, results in a higher resist temperature and a closer position of maximum resist temperature to the previous EB shot position, and that a high-acceleration voltage in case of using a fixed current density brings out the reduction in resist heating.