Translator Disclaimer
Paper
20 April 2011 Reconciling measurements in AFM reference metrology when using different probing techniques
Author Affiliations +
Abstract
CD-AFM can report CD measurements to several nanometer differences when different probing techniques including probe types, scan methods, or data analyses are employed on the same sample despite using standard calibration techniques. This potentially weakens the assertion that this instrument is inherently accurate. It is particularly important to resolve these discrepancies given the measurement challenges where multiple probing techniques need to be employed to get complete CD information. Probe type refers to tip construction methods that can significantly affect geometrical aspects of probe such as effective length, width, and edge height as well as material composition and coating. Scan code refers to CD or DT mode of tool operation. Analysis includes probe geometry deconvolution and measurement algorithms. These challenges in measurement accuracy are especially significant for the foot or bottom CD metrology of 3D structures. This paper explores the impact of these different probing techniques on the measurement accuracy. In one series of experiments, measurements for different probing techniques are compared when the test and the referencing structures are composed of similar material and possess smooth vertical profiles. The investigation is then extended to explore the accuracy of bottom CD measurement of non vertical profiles encountered in actual process development. A hybrid method using CD and DT modes has been tested to measure the bottom CD of challenging pitch structures. The limited space for the probe is particularly problematic for CD mode but the accuracy of DT mode for CD measurement is a concern. Other challenges will also be discussed along with possible solutions. CD-AFM has increased uncertainty when it comes to measuring within 15 nm of the bottom of a structure. In this regime details of the shape of the probe and the method by which this shape is extracted from the raw data become important. Measured CDs can vary by a few nanometers depending upon the algorithm employed for data analysis. These algorithms apply approximate methods for probe shape deconvolution from the raw data. Given all these sources of variation in CD determination it important to understand their impact on the accuracy of measurement in order to properly estimate uncertainty and drive improvement. Overall this paper provides a practical guideline in pursuit of accurate CD metrology and scope for improvements for upcoming technology nodes.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Narender Rana, Charles Archie, and Johann Foucher "Reconciling measurements in AFM reference metrology when using different probing techniques", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 797117 (20 April 2011); https://doi.org/10.1117/12.879516
PROCEEDINGS
13 PAGES


SHARE
Advertisement
Advertisement
RELATED CONTENT

Determination of spatial CD signatures on photomasks
Proceedings of SPIE (October 20 2006)
Photomask CD metrology at the 100-nm node
Proceedings of SPIE (August 01 2002)
Sidewall slope sensitivity of CD-AFM
Proceedings of SPIE (September 20 2011)

Back to Top