Focus and CD control by scatterometry measurements for 65/45nm node devices

Focus and CD simultaneous control method using scatterometry has been developed. Our focus and CD measurement technique consists of five layers scatterometry model that achieves the stable focus measurement at the exposure dose fluctuation. We utilize this feature and consider applying to the RSM (Response Surface Method) model for the focus and CD control. This control realizes a focus optimization and calculates the correct dose allowed for the focus effect. We´ve confirmed this method realizing high accuracy PR (Photo Resist) shape control and obtaining the CD variation reduction effect to 1/5 at the 65nm device.