Abstract
The specification of mask global CD uniformity (GCDU) is ever tightening. There is no exception at the 65-nm node. Some of the key contributors affecting GCD non-uniformity is pattern-density effects such as fogging effect from the e-beam writer and macro loading effect from the etcher. In addition, the contributions from position-dependent effects are significant, and these contributions included resist developing, baking, as well as aberrations of the wafer-imaging lens. It is challenging to quantify these effects and even more so to correct them to improve the GCDU. Correction of the fogging and etch loading effects had been reported 1-4 by various authors. In addition to correction for these effects, we are reporting the position-dependent effects in this paper. Currently, the fogging effect induces 5 nm of CD error and an additional 5-15 nm of CD errors is induced by the etch-loading effect within a 60-mm radius area. We improved the GCDU by pattern-dependent corrections. Using position-dependent dose correction in mask writing, we managed to effectively compensate for intra-field non-uniformity on wafer, which is induced by lens aberrations and illumination non-uniformity.