EFFECT OF BEAM CONDITION IN VARIABLE-SHAPED ELECTRON-BEAM DIRECT WRITING FOR 0.25 MU-M AND BELOW

The effect of incident electron-beam conditions, which are acceleratio n voltage and beam blur of variable-shaped electron-beam direct writin g, is investigated using the deposited energy distribution to realize a fine pattern of less-than-or-equal-to 0.25 mum in trilayer resist pr ocess. The deposited energy distribution is calculated using a three-d imensional Monte Carlo method. In a trilayer resist system, a thin bot tom resist layer can be used, because the contrast value derived from the Monte Carlo calculation is independent of the bottom layer thickne ss. The beam blur of 0.05 mum does not degrade 0.25 mum line-and-space (L/S) patterns, but seriously degrades 0.1 mum L/S patterns. Higher a cceleration voltage is effective for improving the contrast. At lower acceleration voltage, the slope of the deposited energy profile define d at the resist bottom is mainly influenced by electron scattering. On the other hand, at higher acceleration voltage, the slope of deposite d energy profile mainly depends on the beam blur. The 0.1 mum L/S patt erns are expected to be resolved at 30 kV when there is less than 0.02 mum beam blur with trilayer resist system. The possibility of using a single layer resist process for 0.1 mum L/S pattern will be barely re alized at the conditions of 50 kV and 0.02 mum beam blur.