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The performance of an IC device, as we know, depends upon excellent linewidth control in lithography as the geometry of circuits is being decreased. The quality of the mask always plays an important role in this issue. As far as a wafer fab is concerned, the defective mask can lead to not only a dramatic drop in production yield, but also fatal damage for single-chip products. It is observed that a loss of transmission on a mask, detected by a reticle inspection system KLA303-UV STARlight (Simultaneous Transmitted And Reflected light) can bring about unacceptable CD variation on wafers. One major reason for the loss of transmission on masks is from the defect repair process, during which Gallium stain (Ga+) deposits onto the quartz on the chrome side of mask. This problem will become more and more critical for both mask houses and wafer fabs as long as the linewidth keeps shrinking and the design of denser pattern is inevitable. This purpose of this paper is to detail the correlation between wafer CD variation and the relative loss of transmission on the mask. By way of a designed test reticle processed with Gallium deposition by repair tool, inspection, exposure, CD data collection and analysis, we can clearly define the relationship based on I-line mask inspection light source. Following this work, the fab will be able to set up the inspection specifications for any incoming masks to prevent poor CD uniformity occurring in wafers. More importantly, with the design of a variety of patterns with different line/space ratios and device characteristics on this test reticle, we can try to predict the feasibility and severity of the transmission rate loss of mask for 0.15, 0.13 micrometers generations or beyond in order to help mask houses as well as wafer fabs get prepared and work out this problem prior to the advent of the next IC generation.
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