Improvement of pattern and position accuracies by multiple electron beam writing for X-ray mask fabrication

To study the improvement of position and line-width accuracies of resist patterns for X-ray masks, we tried to examine multiple writing with an electron beam (EB) exposure system. First, the uncertainty of the position measurement is checked and reduced to 0.03 µm (3σ) by the short-length measurement method. Then, it is found that by increasing the number of writing times from one to four, the overlay accuracy is improved from 0.04 µm to 0.02 µm (3σ) and the line-width of the pattern is exactly controlled. These results show that sub-quarter-micron patterns are formed by the multiple-writing method with the present EB machine.