Scanning coherent scattering methods for actinic EUV mask inspection

Y. Ekinci; P. Helfenstein; R. Rajeev; I. Mochi; I. Mohacsi; J. Gobrecht; S. Yoshitake

doi:10.1117/12.2242961

5 October 2016 Scanning coherent scattering methods for actinic EUV mask inspection

Y. Ekinci, P. Helfenstein, R. Rajeev, I. Mochi, I. Mohacsi, J. Gobrecht, S. Yoshitake

Proceedings Volume 9985, Photomask Technology 2016; 99851P (2016) https://doi.org/10.1117/12.2242961
Event: SPIE Photomask Technology, 2016, San Jose, California, United States

Abstract

Actinic mask inspection for EUV lithography with targeted specifications of resolution, sensitivity, and throughput remains a big hurdle for the successful insertion of EUVL into high volume manufacturing and effective solutions are needed to address this. We present a method for actinic mask inspection based on scanning coherent scattering microscopy. In this method, the mask is scanned with an EUV beam of relatively small spot size and the scattered light is recorded with a pixel detector. Customized algorithms reconstruct the aerial image by iteratively solving the phaseproblem using over-determined diffraction data gathered by scanning across the specimen with a finite illumination. This approach provides both phase and amplitude of actinic aerial images of the mask with high resolution without the need to use high NA (numerical aperture) lenses. Futher, we describe a reflective mode EUV mask scanning lensless imaging tool (RESCAN), which was installed at the XIL-II beamline and later at the SIM beamline of the Swiss Light Source and show reconstructed aerial images down to 10 nm (on-wafer) resolution. As a complementary method, the a-priori knowledge of the sample is employed to identify potential defect sites by analyzing the diffraction patterns. In this method, the recorded diffraction patterns are compared with the die or database data (i.e. previously measured or calculated diffraction data from the defect-free mask layout respectively) and their difference is interpreted as the defect signal. Dynamic software filtering helps to suppress the strong diffraction from defect-free structures and allows registration of faint defects with high sensitivity. Here, we discuss the basic principles of these Fourier domain techniques and its potential for actinic mask inspection with high signal-to-noise ratio and high throughput.

Citation Download Citation

Y. Ekinci, P. Helfenstein, R. Rajeev, I. Mochi, I. Mohacsi, J. Gobrecht, and S. Yoshitake "Scanning coherent scattering methods for actinic EUV mask inspection", Proc. SPIE 9985, Photomask Technology 2016, 99851P (5 October 2016); https://doi.org/10.1117/12.2242961

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available