Critical Area Analysis Of Litho Distortion Due To Metal Fill

With the scaling down of technology nodes of semiconductor and the continuous development of Very Large Scale Integration (VLSI) technologies and the fierce increment of System on Chip (SoC) scale, Design for Manufacturing (DFM) has acquired more and more concern in the sub-wavelength nanometer design. In order to improve the planarity of the surface of chip layout which belongs to DFM, it requires the uniformity of chip layout density, the most common way of which is using dummy metal fill method in the current IC design industry.Dummy metal fill not only can exacerbate the electrical parameters of the chip design, but also will influence the chip’s critical area. At the same time, lithography will also bring great influence which could not be neglected. Filling dummy metal in close proximity to signal interconnects may have greater line-width variations due to lithographic process comparing with no metal fill and it can lead to a scenario where a defect particle of a particular size may cause a defect in the presence of metal fill, which increases the probability of failure and hence the Critical Area (CA) of the design. So, dummy metal fill will make great influence of critical area after lithography, the influence of which will become more rigorous with the shrinking of technology nodes. Thus, it is of great significance to do the CA analysis of lithography distortion due to metal fill from the perspectives of different defect particles.In this paper the influences of dummy metal and lithography distortion due to metal fill on open CA from the perspectives of three different defect particles are studied based on45nm technology node. And it takes the space between dummy metal and signal interconnect into account and focuses on meta13(M3) and metal4(M4) of OR1200’s layout. In addition, based on the actual experiments the relationships between lithography distortion due to metal fill and open CA led by different defect particles are obtained, effectively explaining the reason of reducing open CA through spreading the space between dummy metal and signal interconnect. And this paper vividly convinces the necessary of taking lithography into consideration to evaluate total CA due to metal fill.The results reveal that dummy metal fill can increase total open CA after lithography and the increment percentage of total open CA due to the defect particle with a diameter of0.066um is the largest, the maximum of which will take up almost10%. And with the increasing of the defect particle size, the total open CA increment due to defect particles reduces. Thus, the influence of lithography must be taken into account when evaluating critical area caused by metal fill. This paper is instructive in researching the influence of lithography on CA due to metal fill or related field in the future.