Keiji Yoshimura

Performance of the FPA-7000AS7 1.35 NA immersion exposure system for 45-nm mass production

Canon has developed an immersion exposure tool, the FPA-7000AS7 (AS7), with the industrys highest NA of 1.35. This paper reports on its performance. The AS7s projection lens achieves ultra-low aberration with total RMS of less than 5 mλ and flare of less than 0.5%. The resolution capability is 37 nm with k1 = 0.259, and DOF of 0.8 μm was obtained owing to the ultra-low aberration and low flare. Regarding focus performance, a 3σ value of 19.3 nm for Lstage and 16.1nm for R-stage were attained in a whole area. The result of CD uniformity of 1.91nm (3σ) was obtained across the wafer with a total of 4032 measurement points. Distortion was 3.9 nm at the worst value. On the other hand the most critical issue of immersion is defects, so the nozzle, lens and stage must be cleaned to reduce defects. The result of defect evaluation of the AS7 was an average of 0.042 defect/cm2 from 25 wafers in a lot and average 0.046 defect count/cm2 from long-term defect evaluation for two months. From these results, we are confident that the AS7 is capable of 45-nm node device production.

The solutions for 3D-NAND processes with Canon's latest KrF scanner

The NAND type flash-memory is now used not only on smart phones or tablet PCs, but also adopted on infrastructures such as servers, etc.