Photoresist Shrinkage Caused by Single-Line Scan of Electron Beam

Abstract

Shrinkage behavior caused by a single-line scan of an electron beam over a photoresist line was observed, including shrinkage distribution in the photoresist-line direction. A new method for evaluating the minute amount shrinkage and the shrinkage distribution caused by a single-line scan was developed. According to the results of evaluations with this method, the shrinkage of an about 50-nm-wide photoresist line caused by a single-line scan is less than 0.1 nm under landing energies of 200, 300, and 500 eV and probe current of 8 pA. This shrinkage is more than ten times smaller than the typical amount of shrinkage caused by a standard two-dimensional scan. This result indicates the possibility of a significant reduction of photoresist shrinkage during scanning-electron-microscope measurements. The evaluation method also yielded the first observation of the shrinkage distribution in the photoresist-line direction. The results show that the shrinkage caused by a single-line scan distributes more than 30 nm, which is wider than the calculated electron-scattering range. This result suggests that there likely to be an additional mechanism involved in photoresist shrinkage other than the microscopic interaction between incident electrons and photoresist molecules. An elastic-relaxation effect and a contribution of back-scattered electrons are plausible additional mechanisms for photoresist shrinkage.