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Proceedings Paper

Shape control using sidewall imaging
Author(s): Bo Su; Ramiel Oshana; Mina Menaker; Yogev Barak; Xuelong Shi
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Paper Abstract

As gate widths shrink below 0.18 micrometer, the SPC (Statistical Process Control) based CD (Critical Dimension) control in lithography process becomes more difficult. Increasing requirements of a shrinking process window have called on the need for advanced CD control using a closed-loop feedback mechanism. This concept has been gaining momentum and shows promising advantages in shortening the time of feedback control. However, the current closed-loop feedback links only the average CD of a lot and the exposure dose (E), leaving out another critical lithography parameter -- stepper, or scanner, defocus (F). Up until now, F has been assumed constant while E has been shown to have one-to-one correlation with CD. Such an assumption is justified for feature sizes larger than 0.25 micrometer with a usable DOF (Depth Of Focus) of more than 1 micrometer. For 0.25 micrometer and below technologies, stepper defocus induces rapid feature profile, as well as CD, changes. Therefore, one parameter (exposure dose versus CD) feedback is not adequate enough to control CD in photolithography and a two-parameter (exposure dose and stepper defocus versus CD) feedback is needed. For stepper defocus variation, resist feature shape needs to be monitored in-line. We will present an innovative way of shape monitoring through sidewall imaging. The scanning beam is bent up to 5 degrees, so that a feature can be viewed from a tilted angle. Such tilted view greatly enhances edge resolution. Shape monitoring applications based on sidewall imaging will be presented. With both CD and shape are monitored in photolithography process, two critical parameters, i.e., exposure dose and defocus, can be easily controlled. Such shape control mechanism provides the base for two-parameter feedback loop.

Paper Details

Date Published: 2 June 2000
PDF: 7 pages
Proc. SPIE 3998, Metrology, Inspection, and Process Control for Microlithography XIV, (2 June 2000); doi: 10.1117/12.386476
Show Author Affiliations
Bo Su, Applied Materials (United States)
Ramiel Oshana, Applied Materials (United States)
Mina Menaker, Applied Materials Ltd. (Israel)
Yogev Barak, Applied Materials Ltd. (Israel)
Xuelong Shi, Motorola (United States)

Published in SPIE Proceedings Vol. 3998:
Metrology, Inspection, and Process Control for Microlithography XIV
Neal T. Sullivan, Editor(s)

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