The optimization of CD uniformity and measurement on mask and wafer

Abstract

As pattern size is shrinking, required mask CD specification is tighter and its effect on wafer patterning is more severe. To enhance the device performance, wafer CD uniformity should be enhanced and controlled by mask global CD uniformity. Mask global CD uniformity usually can be enhanced by mask process and optimal fogging effect correction. To enhance the mask global CD uniformity on mask, resist process and FEC (Fogging Effect Correction), reliable CD measurement tool and methods are necessary. Recently, group CD using OCD(Spectroscopic Ellipsometer) or AIMS(Aerial Image Measurement and Simulation) is used to represent global CD variation on mask. These methods are removing local CD variation on mask. Because local CD variation on wafer is large compared with the effect of local CD variation of mask, global CD uniformity can be measured with suppressed local CD variation [1]. In this paper, local CD variation of mask and wafer is evaluated, and area CD and smoothing methods are used to measure CD on mask and wafer, and the correlation of global CD of mask and field CD of wafer are evaluated. By these methods, CD measurement repeatability can be enhanced to get closer correlation of mask and wafer. Close correlation makes fine CD correction on mask to get better field CD uniformity on wafer. And the repeatability of field to field CD uniformity of wafer is evaluated according to measurement tool of CD-SEM and scatterometry.