The study to enhance the mask global CD uniformity by removing local CD variation

Abstract

As pattern size is shrinking, required mask CD specification is tighter and it's effect on wafer patterning is more severe. Recent study showed that the effect of mask local CD variation of mask on wafer is much smaller than that of global CD variation.[1] 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) or polynomial fitting method is introduced to represent global CD variation on mask.[2][3][4] These methods are removing local CD variation on mask. The local CD variation will be remained as residual CD after approximation. In this paper, local CD variation of mask and wafer is evaluated and 2 kinds of 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. And the repeatability of field to field CD uniformity of wafer is evaluated to correct the fields CD uniformity of wafer by controlling the selective changing of transmittance of mask or to feed back to mask process. Higher correlation between fields of wafer, more accurate correction can be possible.

Generation of large field SEM image by panorama composition technology for nano-order measurement

“…Thus, high accuracy measurement of the shape of this complicated photomask pattern and the appropriate feedback to the design data of the pattern layout are needed to expose the pattern shape correctly on a silicon wafer. A critical dimension scanning electron microscope (CD-SEM) is widely used as an essential tool for measuring microstructures [7][8][9][10].…”