Application of a develop end point detector as a timely and cost-effective alternative to using an SEM for CD measurement in production photolithography

Dimitri L. Velikov; Mark Goldman; Dee Hester; Alan W. Kukas; Clifford H. Takemoto; Ken Goetz; Hua Zhang; Linard Karklin

doi:10.1117/12.240114

21 May 1996 Application of a develop end point detector as a timely and cost-effective alternative to using an SEM for CD measurement in production photolithography

Dimitri L. Velikov, Mark Goldman, Dee Hester, Alan W. Kukas, Clifford H. Takemoto, Ken Goetz, Hua Zhang, Linard Karklin

Author Affiliations +

Proceedings Volume 2725, Metrology, Inspection, and Process Control for Microlithography X; (1996) https://doi.org/10.1117/12.240114
Event: SPIE's 1996 International Symposium on Microlithography, 1996, Santa Clara, CA, United States

Abstract

This paper focuses on the use of a track-mounted, in-situ develop end point (EP) to reduce CD measurement via scanning electron microscope (SEM) in the production environment. Commonly, a few wafers are selected from a lot and examined to ensure conformance with desired CDs. Typically, the wafer's image linewidth is measured. If required, a corresponding adjustment is made to the stepper's exposure energy in order to obtain the targeted CD. While this methodology works, it does have its shortcomings such as: incomplete determination of wafer-to-wafer variations, the impossibility of detecting random 'problem' wafers, and the additional backlog CD measurement adds to the SEM station -- which generally results in production bottlenecks. The use of a track-mounted, in-situ develop end point detector facilitates rapid and accurate measurement of photoresist characteristics. Due to the direct correlation between develop end point time and CDs, a detector can be used to signal out-of- spec conditions. The nature of the data collected and analyzed by the detector allows exposure and other process variations to be revealed. In addition to providing this 'watchdog' function, some detectors can be programmed to automatically correct out-of-spec CDs by varying the development cycle time. Use of an in-situ detector, as described, will have a direct bearing on reducing the use of high-cost SEMs in the production environment as well as minimizing the number of scrapped wafers.

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Dimitri L. Velikov, Mark Goldman, Dee Hester, Alan W. Kukas, Clifford H. Takemoto, Ken Goetz, Hua Zhang, and Linard Karklin "Application of a develop end point detector as a timely and cost-effective alternative to using an SEM for CD measurement in production photolithography", Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); https://doi.org/10.1117/12.240114

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KEYWORDS

Critical dimension metrology

Semiconducting wafers

Scanning electron microscopy

Sensors

Cadmium

Detector development

Photoresist developing

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