Improving critical dimension accuracy and throughput by subfield scheduling in electron beam mask writing

Sergey Babin, Andrew B. Kahng, Ion I. Măndoiu, Swamy Muddu
2005 Journal of Vacuum Science & Technology B Microelectronics Processing and Phenomena  
Resist heating in high-voltage, high-throughput electron beam ͑e-beam͒ mask write is a significant source of critical dimension ͑CD͒ distortion. Excessive heating on the reticle determines changes in resist sensitivity, which in turn cause significant CD variation. CD distortions on the reticle are replicated onto the wafer with increased magnitude as determined by the mask error enhancement factor ͑MEEF͒. As designs enter the sub-90 nm regime, CD variation has a significant impact on
more » ... e, performance variation, and product yield. Previous methods for reducing CD distortion include usage of lower e-beam current density, increased delays between electron flashes, and multipass writing. However, all of these methods lower mask writing throughput, which is increasingly becoming a limiting factor in semiconductor industry productivity. In this paper, we propose a novel method for minimizing CD distortion and maximizing mask writing throughput. By scheduling the writing of subfields, we perform simultaneous optimization of mask writing order and e-beam current density. We perform subfield scheduling by evaluating resist temperature of subfield orderings using a fast analytical temperature model. Simulation experiments show that the new subfield scheduling method can reduce the maximum resist temperature up to 12°C over existing sequential writing methods with unchanged mask writing throughput. Alternatively, improved subfield scheduling can enable the use of higher beam current densities, leading to increased writing throughput without compromising CD control.
doi:10.1116/1.2132330 fatcat:syeeufiyhbhfzkiwnt5a4niz5a