Focus and CD Control by Scatterometry Measurements for 65/45 nm Node Devices

A method using scatterometry for simultaneous focus and critical dimension (CD) control method has been developed. Our focus and CD measurement method uses a five-layer scatterometry model and provides stable focus measurement when the exposure dose fluctuates. We utilize this feature and consider applying it to the response surface methodology model for focus and CD control. This control optimizes focus and calculates the correct dose allowing for the focus effect. We have confirmed that this method controls photoresist shape accurately and reduces the CD variation for 65 nm devices by 80%.