Variability Modeling and Process Optimization for the 32 nm BEOL Using In-Line Scatterometry Data

Abstract

Process variability is a great concern when it comes to the fabrication of nano-scaled devices precisely. The effect of any imprecision can be directly translated into uncertain behavior of the devices. To address the process related issues, it is now essential to identify physical variability properly for a quality end product. If the effects of the variations are not correctly characterized, there is no other way of guaranteeing that the design will meet the specified budgets. This paper describes the essential variability modeling and analyses for the BEOL critical parameters. We used AQUAIA, to model end-of-the-line electrical resistances and capacitances based on 32 nm technology assumptions. By using scatterometry and reference metrology data, we have compared the correlations among the physical in-line measurements and end of the line electrical measurements which eventually address the potential variability issues between them specifically for the 32 nm technology node. It shows good correlation between scatterometry measurement results and results obtained from the AQUAIA simulation. Fitting parameters are generated with the help of AQUAIA's simulation results and physics model. Finally, we have developed a spreadsheet for the RC graph using those fitting parameters to manipulate and optimize the BEOL specification for 32 nm technology. This spreadsheet can be used as a guideline for the process development and control.