With continuously shrinking device structure sizes the photomask suppliers are facing increasing linewidth metrology control requirements. Therefore it is becoming more and more important for equipment suppliers to provide mask metrology tools capable of measuring 0.5 tm and smaller critical dimension (CD) features with high accuracy and repeatability, while offering high throughput for systems to be used in the production environment. CD measurement results obtained on the Leica LWM 250UV will be presented showing not only the considerably improved resolution power and measurement accuracy but also an extension ofthe linearity range to smaller feature sizes using UV light of 365 nm (I-line) instead of white light for illumination in transmitted mode. Results obtained after a system calibration against SEM measurement data show a further extension of the linearity regime. The higher lateral resolution of I-line compared to white light measurements also leads to a CD range value reduction for long term repeatability.
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