Development of etch rate uniformity adjustment technology for photomask quartz etch in manufacturing the 100 attenuated PSM

摘要

As the feature size of integrated circuits decreases, it is difficult to have a good resolution with an ordinary lithography technology. Resolution enhancement technologies(RETs), therefore, become prominent way to achieve better resolution. Among various RETs, Phase Shift Mask (PSM) can be one of the most useful technologies in these days and especially Chrome-Less Mask (CLM) or Phase Edge PSM (PE-PSM) is used for utilizing strong effect of PSM technology. In manufacturing the CLM or PE-PSM, the quartz layer of the photomask should be etched to 2480 □ in depth which is the equivalent value in phase, 180°. But quartz etch is one of the difficult processes in photomask manufacturing due to the absence of stopper layer. Moreover, the depth uniformity should be controlled within the tolerance of 5°. But there are etch rate variations from center to edge positions within the 6-inch mask area which originates from the deficit of plasma uniformity. As a result, phase deviation in those area occurs after quartz etch up to several degrees in phases and this problem makes the manufacturing of CLM or PE-PSM difficult. We thought there would be some relations between etch rate uniformity and hardware, such as focus ring which is used for confinement of plasma species. Various experiments, therefore, were executed with regard to the type of focus ring (shape, and height). As a result, the outstanding tendencies which show the relations, can be obtained. On this paper, the detailed descriptions of the experiments and their results will be presented.