Deflector contamination in E-beam mask writer and its effect on pattern placement error of photomask for sub 20nm device node

Abstract

One of the concerned phenomena that influencing to the performance of electron beam mask writer is contamination of deflector. Previous studies show that the relation between the deflector contamination and pattern placement error. In fact, the source of the contamination of deflector was not defined clearly yet. However, the fact that of deflector contamination clearly influences the pattern placement error on mask fabrication. We think that there is no detailed investigation about the effect of deflector contamination on the pattern placement error of production photomask. This paper will describe the effect of e-beam positioning error due to the contamination of deflector in electron optic system. To reduce the placement error by the deflector contamination circumstance the e-beam drift was evaluated in various conditions of deflection based on the theoretical assumption and our own modeling, and optimization of the deflection condition. Furthermore, we will present the requirements on position accuracy of deflector for the photomask of sub 20nm device node.