Capability of eco-friendly cleaning strategy corresponding to advanced technology
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In sub-60nm technology node, cleaning process becomes specialized to clear the defects without pattern damage as decreasing critical particle size to control. While cleaning process has to meet the primary requisite, removal of particle including organic residue and prevention of particle re-deposition, it should enable to suppress haze phenomena for a long life of photomask. However, to solve the problem of haze, the chemical materials caused haze seed should be hardly used and physical force becomes strengthen as the compensation for cleaning efficiency. Unfortunately it brings about another problem, pattern damage seriously. In this paper, adequate cleaning conditions which are applicable in sub-60nm technology node are evaluated to meet the dilemma among three requirements, high cleaning efficiency, and prevention of pattern collapse, and prevention of haze phenomenon. All cleaning steps in photomask process were set up using only 172nm UV irradiation for degradation of organic contaminants and deionized water (DI) with acoustic power for particle lift-off. The effect of UV and DI cleaning on cleaning efficiency and haze phenomena was derived from carrying out chemical and physical analysis simultaneously. Also, we could quantify the statistical probability of pattern collapse in each of technology node and layer shape as different condition of megasonic frequency and its power. As a result, it was known that this cleaning process have various merits to make out dilemma mentioned above, if it satisfies optimized conditions.
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