Study for compensation of unexpected Image Placement error caused by VSB mask writer deflector

Abstract

The Electron Optical System (EOS) is designed for the electron beam machine employing a vector scanned variable shaped beam (VSB) with the deflector. Most VSB systems utilize multi stage deflection architecture to obtain a high precision and a high-speed deflection at the same time. Many companies use the VSB mask writer and they have a lot of experiences about Image Placement (IP) error suffering from contaminated EOS deflector. And also most of VSB mask writer users are having already this error. In order to use old VSB mask writer, we introduce the method how to compensate unexpected IP error from VSB mask writer. There are two methods to improve this error due to contaminated deflector. The one is the usage of 2nd stage grid correction in addition to the original stage grid. And the other is the usage of uncontaminated area in the deflector. According to the results of this paper, 30% of IP error can be reduced by 2nd stage grid correction and the change of deflection area in deflector. It is the effective method to reduce the deflector error at the VSB mask writer. And it can be the one of the solution for the long-term production of photomask.