Proceedings Article | 25 August 1999
Proc. SPIE. 3748, Photomask and X-Ray Mask Technology VI
KEYWORDS: Semiconductors, Electron beams, Error analysis, Diffusion, Photomasks, Optical simulations, Mask making, Critical dimension metrology, Standards development, Chemically amplified resists
In electron beam writing with high accelerating voltage on photomask blanks, resist heating effect, which is the main factor of CD error in a localized area, is one of the serious problem that must be solved or ameliorated. In this study, the dependence of CD error on the types of resists and the dependence of CD error on the writing conditions of EB writer, were investigated. In this experiment, ZEP7000 (Nihon Zeon), a typical standard of non-chemically amplified resist for electron beam and two chemically amplified resists (CARs) were selected. As a result, the CD error caused by the resist heating effect for the CARs was smaller than that for ZEP7000. The efficiency of multi-pass writing for all of the evaluated resists was observed. The multi-pass writing was very effective in reducing the CD error for both ZEP7000 and the CARs, and especially so for ZEP7000. The dependence of the CD error caused by the resist heating effect on the various writing parameters was investigated using Ralf's model simulation, which is the calculation tool of the temperature rise during the exposure of electron beam including the heat diffusion equation. The CD error for the CARs was smaller and more stable than that for ZEP7000 in various writing conditions. Current density and shot size influenced CD error in sub-field strongly, however, settling time of each shot don't almost influence CD error in sub-field for ZEP7000. The fact that the results for CARs, which have high sensitivity, didn't depend on the current density and shot size indicates the ability to fabricate more accurate mask with higher throughput.
