Global CD uniformity improvement using dose modulation pattern correction of pattern density-dependent and position-dependent errors

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 are pattern-density effects such as fagging 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 by various authors. In addition to correction for these effects, we are reporting the position-dependent effects in this paper.