Analysis of pattern accuracy in submicrometer electron-beam direct writing

To create submicrometer patterns with high accuracy on thick single-layer negative resist, error factors that degrade pattern accuracy have been investigated. Pattern accuracy was analyzed using a new evaluation method based on the difference between the resist development energy and the exposure energy at points on the edge of each shape. By introducing a new evaluation parameter, we were able to clarify error factors from the exposure conditions, the proximity effect correction method, and the machine exposure fluctuation. The evaluation parameter
K
is
Q/Q_{0}
where
Q
is the exposure dose appropriate for the desired resist thickness and Q
0
is the interface gel dose. It was found that the resist resolution and the rounding error of the exposure dose were serious error factors, especially in delineation on submicrometer patterns. To achieve 0.5-µm patterns with ±0.1-µm accuracy on 1-µm-thick negative resist, the resist evaluation parameter
K
must be less than 2, the rounding error of the exposure dose must be less than 2.5 percent of the dose, and the beam addressing unit (LSB) must be less than 0.025 µm.