Flare evaluation for 32-nm half pitch using SFET

Hajime Aoyama; Yuusuke Tanaka; Takashi Kamo; Nobuyuki Iriki; Yukiyasu Arisawa; Toshihiko Tanaka

doi:10.1117/12.771857

21 March 2008 Flare evaluation for 32-nm half pitch using SFET

Hajime Aoyama, Yuusuke Tanaka, Takashi Kamo, Nobuyuki Iriki, Yukiyasu Arisawa, Toshihiko Tanaka

Proceedings Volume 6921, Emerging Lithographic Technologies XII; 69213H (2008) https://doi.org/10.1117/12.771857
Event: SPIE Advanced Lithography, 2008, San Jose, California, United States

Abstract

Flare degrades critical-dimension (CD) control in EUVL, a promising technology for the 32-nm half-pitch node. To deal with flare, high-quality projection optics in the exposure tool and flare variation compensation (FVC) technology with proper mask resizing are needed. Selete has installed a small-field exposure tool (SFET) with the goal of assessing resist performance. Due to the high-quality optics, the SFET allowed us to determine the required flare specification to be 6.1% or 6.6%, as calculated from the residual part of the low- or middle-frequency region, respectively. The flare level was confirmed through experimental results and from calculations using the power spectral density (PSD) obtained from the mirror roughness by the disappearing-resist method. The lithographic performance was evaluated using 32-nm-halfpitch patterns in a new resist. The resist characteristics can be explained by modeling blur as a Gaussian function with a σ of 8.8 nm and using a very accurate CD variation (< ~6 nm) obtained by taking into account the influences of mask CD error and flare on evaluation patterns. Since FVC is needed to obtain flare characteristics that do not degrade the CD, we used the double-exposure method to eliminate the influence of errors, including nonuniform dose distribution and CD mask error. Regardless of whether there was an open area or not, there was no difference in CD as a function of distance up to a distance of 20 µm. In addition, CD degradation was observed at distances not far (< 5 µm) from the open area. In a 60-nm neighborhood of the open area, an 8-nm variation in CD appeared up to the distance at which the CD leveled off. When the influences of resist blur and flare on patterns was taken into account in the calculation, it was found that aerial simulations based on a rigorous 3D model of a mask structure matched the experimental results. These results yield the appropriate mask resizing and the range in which flare has an influence, which is needed for FVC. This research was supported in part by NEDO.

Citation Download Citation

Hajime Aoyama, Yuusuke Tanaka, Takashi Kamo, Nobuyuki Iriki, Yukiyasu Arisawa, and Toshihiko Tanaka "Flare evaluation for 32-nm half pitch using SFET", Proc. SPIE 6921, Emerging Lithographic Technologies XII, 69213H (21 March 2008); https://doi.org/10.1117/12.771857

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