Color mixing in overlay metrology for greater accuracy and robustness

Mathijssen, Simon G. J.; Noot, Marc; Bozkurt, M Murat; Javaheri, Narjes; Hajiahmadi, Reza; Zagaris, Antonios; Chang, Ken; Gosali, Benny; Su, Eason; Wang, Cathy; Boef, Arie den; Bhattacharyya, Kaustuve; Huang, Guo-Tsai; Chen, Kai-Hsiung; Lin, John C.

doi:10.1117/12.2514949

Cited by 5 publications

(1 citation statement)

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“…Process-and target-specific wavelength optimization, measurement quality metrics, and calibration to scanning electron microscope-based overlay (SEM-OL) measurements are being pursued. [8][9][10] Tool-induced shift (TIS) is evaluated to estimate the impact of tool asymmetry on measurement error. 11 TIS can be obtained by measuring overlay at 0 deg and 180 deg of wafer rotation and the difference of the two divided by 2.…”

Section: Introductionmentioning

confidence: 99%

Review of scanning electron microscope-based overlay measurement beyond 3-nm node device

Ito

Hasumi

2019

J. Micro/Nanolith. MEMS MOEMS

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Overlay control has been one of the most critical issues for manufacturing of leading edge semiconductor devices. Introduction of the double patterning process requires stringent overlay control. Conventional optical overlay (Opt-OL) metrology has technical challenges with measurement robustness, solving overlay discrepancy between overlay mark and device pattern, and measuring smaller marks laid out in large numbers within the die accurately for high-order correction. In contrast, scanning electron microscope-based overlay (SEM-OL) metrology can directly measure both overlay targets and actual devices or device-like structures on processed wafers with high spatial resolution. It can be used for reference metrology and optimization of Opt-OL measurement conditions. SEM-OL uses small structures, including actual device patterns, which allows insertion of many SEM-OL targets across a die. Precise overlay distribution can be measured using dedicated SEM-OL mark, improving measurement accuracy and repeatability. To extend SEM-OL capability, we have been developing SEM-OL techniques that can measure not only surface patterns by critical dimension SEM but also buried patterns for leading edge device processes. There are two techniques to detect buried patterns. One is to use high-acceleration voltage SEM, which detects backscattering electron emphasizing material contrast. It has been adopted for overlay measurements for memory and logic devices at after-etch inspection or even after-develop inspection. The other is to utilize charging effect, which reflects voltage contrast at the surface depending on the material properties of underneath structure. SEM-OL measurement using transient voltage contrast has been developed and its capability of overlay measurement has been proven. An overlay measurement algorithm using template matching method has been developed and was applied to dynamic random access memory (DRAM) process monitor in manufacturing. In order to extend SEM-OL metrology to beyond 3-nm node logic and cutting-edge DRAM devices (half pitch = 14 nm), we are improving measurement precision of detecting buried patterns and measurement throughput by developing optimized SEM-OL mark.

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