Photomask metrology using a 193nm scatterfield microscope

R. Quintanilha; B. M. Barnes; Y. Sohn; L. P. Howard; R. M. Silver; J. E. Potzick; M. T. Stocker

doi:10.1117/12.829693

30 September 2009 Photomask metrology using a 193nm scatterfield microscope

R. Quintanilha, B. M. Barnes, Y. Sohn, L. P. Howard, R. M. Silver, J. E. Potzick, M. T. Stocker

Proceedings Volume 7488, Photomask Technology 2009; 74881L (2009) https://doi.org/10.1117/12.829693
Event: SPIE Photomask Technology, 2009, Monterey, California, United States

Abstract

The current photomask linewidth Standard Reference Material (SRM) supplied by the National Institute of Standards and Technology (NIST), SRM 2059, is the fifth generation of such standards for mask metrology. The calibration of this mask has been usually done using an in house NIST ultra-violet transmission microscope and an Atomic Force Microscope (AFM). Recently, a new optical reflection scatterfield microscope has been developed at NIST for wafer inspection, Critical Dimension (CD) and overlay metrology purposes. Scatterfield microscopy relies on illumination engineering at a sufficiently large Conjugate Back Focal Plane (CBFP) of the microscope.1 Our new scatterfield reflection microscope uses 193 nm excimer laser light as well as sophisticated configurations to allow measurement of both the image plane and the Fourier plane using full-field and angle-resolved illumination. By reducing the wavelength compared to many current metrology tools that work in the visible light and near ultra-violet range, we have made substantial improvements in image resolution2 and commensurate gains in sensitivity to geometrical parameters. We present a preliminary study on the use of this new microscope to calibrate and measure features of this SRM photomask. The 193 nm scatterfield microscope is used in full-field mode with a NA range from 0.12 to 0.74 using our scatterfield imaging method. Experimental results obtained on isolated lines for different polarization states of the illumination are presented and discussed. Pitch measurements are compared to the measurements done on our NIST Ultra-Violet (UV) transmission microscope.

Citation Download Citation

R. Quintanilha, B. M. Barnes, Y. Sohn, L. P. Howard, R. M. Silver, J. E. Potzick, and M. T. Stocker "Photomask metrology using a 193nm scatterfield microscope", Proc. SPIE 7488, Photomask Technology 2009, 74881L (30 September 2009); https://doi.org/10.1117/12.829693

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KEYWORDS

Microscopes

Photomasks

Calibration

Metrology

Ultraviolet radiation

Charge-coupled devices

Quartz

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