Evaluations of optical performance for micro- trench on quartz etch in ArF lithography

As promising technologies for ArF optical lithography, CLM(Chrome-Less Mask) and alternating phase shift mask(PSM) technologies among RETs(Resolution Enhancement Techniques) for low k, have been researched worldwide for a couple of decades [1]. Quartz dry etching has become more critical to manufacture the mask with those technologies in the ArF lithography. Alternating PSM and CLM require the formation of 180-degree phase difference by quartz dry etch. There are many error factors, which can influence CD uniformities on mask and wafers, in dry etch step such as micro-trench, depth uniformity, sidewall angle, and morphology. Furthermore, quartz depth is hard to control because there is no stopping layer for quartz etch. Micro-trench, one of the important factors on quartz etch, can drop light intensity on wafer. Therefore, micro-trench can deteriorate the RET. We investigated characteristics of micro-trench during quartz dry etch process and the influences on resolution, which can be improved by dry etch parameters.