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Proceedings Paper

Dimension controlled CNT probe of AFM metrology tool for 45-nm node and beyond
Author(s): Satoshi Sekino; Takafumi Morimoto; Toru Kurenuma; Motoyuki Hirooka; Hiroki Tanaka
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Paper Abstract

Atomic Force Microscope (AFM) is a powerful metrology tool for process monitoring of semiconductor manufacturing because of its non-destructive, high resolution, three-dimensional measurement ability. In order to utilize AFM for process monitoring, long-term measurement accuracy and repeatability are required even under the condition that probe is replaced. For the measurement of the semiconductor's minute structure at the 45-nm node and beyond, AFM must be equipped with a special probe tip with smaller diameter, higher aspect ratio, sufficient stiffness and durability. Carbon nanotube (CNT) has come to be used as AFM probe tip because of its cylindrical shape with small diameter, extremely high stiffness and flexibility. It is said that measured profiles by an AFM is the convolutions of sample geometry and probe tip dimension. However, in the measurement of fine high-aspect-ratio LSI samples using CNT probe tip, horizontal measurement error caused by attractive force from the steep sidewall is quite serious. Fine and long CNT tip can be easily bent by these forces even with its high stiffness. The horizontal measurement error is caused by observable cantilever torsion and unobservable tip bending. It is extremely difficult to estimate the error caused by tip bending because the stiffness of CNT tips greatly varies only by the difference of a few nanometers in diameter. Consequently, in order to obtain actual sample geometry by deconvolution, it is essential to control the dimension of CNT tips. Tip-end shape also has to be controlled for precise profile measurement. We examined the method for the measurement of CNT probe tip-diameter with high accuracy and developed the screening technique to obtain probes with symmetric tip-ends. By using well-controlled CNT probe and our original AFM scanning method called as Advanced StepInTM mode, reproducible AFM profiles and deconvolution results were obtained. Advanced StepInTM mode with the dimension- and shape-controlled CNT probe can be the solution for process monitoring of semiconductor manufacturing at the 45-nm node and beyond.

Paper Details

Date Published: 3 April 2008
PDF: 12 pages
Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69220L (3 April 2008); doi: 10.1117/12.772433
Show Author Affiliations
Satoshi Sekino, Hitachi Kenki FineTech Co., Ltd. (Japan)
Takafumi Morimoto, Hitachi Kenki FineTech Co., Ltd. (Japan)
Toru Kurenuma, Hitachi Kenki FineTech Co., Ltd. (Japan)
Motoyuki Hirooka, Hitachi, Ltd. (Japan)
Hiroki Tanaka, Hitachi Kyowa Engineering Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 6922:
Metrology, Inspection, and Process Control for Microlithography XXII
John A. Allgair; Christopher J. Raymond, Editor(s)

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