CD uniformity improvement by loading effect correction (LEC) function for 90-nm reticle

Abstract

The etching loading effect is always a big issue for mask maker to get excellent critical dimension (CD) uniformity. For etching process, with different loading area density the etching rate is different and then micro-loading issue exists. In accordance with the shrinking of patterns on ultra-large scale integration (ULSI), higher CD accuracy on photomask is required. For the 130nm technology node, the SPEC of CD uniformity range is about 17 ~ 22nm. At common poly layer, the distribution of pattern density is from 50% ~ 90%. The CD variation with different pattern density is 15 ~ 20nm. Besides adjusting the etching recipe to minimize the loading effect, we provide another solution. With loading effect correction (LEC) function on HL-950M, it offers a software method to calculate the pattern density and produce a dosage map to compensate the CD variation which is resulted from etching loading.