Effects of illumination wavelength on the accuracy of optical overlay metrology

Jae-Seong Han; Hak Kim; Jeong-Lim Nam; Myung-Soo Han; Soon-Kwon Lim; Shimon D. Yanowitz; Nigel P. Smith; Andrew M.C. Smout

doi:10.1117/12.276027

7 July 1997 Effects of illumination wavelength on the accuracy of optical overlay metrology

Jae-Seong Han, Hak Kim, Jeong-Lim Nam, Myung-Soo Han, Soon-Kwon Lim, Shimon D. Yanowitz, Nigel P. Smith, Andrew M.C. Smout

Author Affiliations +

Proceedings Volume 3051, Optical Microlithography X; (1997) https://doi.org/10.1117/12.276027
Event: Microlithography '97, 1997, Santa Clara, CA, United States

Abstract

As the integration density in the manufacturing of IC's increases and tighter design rules are implemented, the accuracy of overlay in the photolithography process is becoming all the more important. Consequently, investigation and characterization of the accuracy (as well as precision) of the overlay measurement are being required to insure that the overlay metrology tool qualifies for the new technologies. In this paper, we analyze the relationship between wafer substrate types and the respective characteristic overlay measurement errors associated with them. We compare results using different illumination wavelengths in the overlay tool. We define the Wafer Induced Shift (WIS) contribution to the measurement accuracy error and introduce a metric for it. And we analyze the relationship between the TIS and WIS. We show that the wavelength of the optical overlay measurement (OL, for short) should be fitted separately to each of the various kinds of overlay measurement targets, or marks. Buried type targets, covered by transparent materials, for which the measurement is made through the transparent interlayer, benefit from wavelength selection due to the possible improvement in contrast associated with an interference effect. Open type targets, on the other hand, in which the measurement signal is collected off the substrate shape itself, do not benefit from that. There is another problem to consider, however. Such targets may show a considerable WIS, even thought TIS and precision are good both before and after etch. The WIS error can be as high as 100 nm. This could create serious OL problem and it means that TIS and precision are not enough to characterize the quality of measurement, and WIS is equally important, it not more so. We look into the causes of WIS in the substrate shape, overlay mark design and fabrication method. We show that with careful selection of illumination wavelength, some layers produce no WIS. On the other layers WIS remains a problem and other methods are still required to control it.

Citation Download Citation

Jae-Seong Han, Hak Kim, Jeong-Lim Nam, Myung-Soo Han, Soon-Kwon Lim, Shimon D. Yanowitz, Nigel P. Smith, and Andrew M.C. Smout "Effects of illumination wavelength on the accuracy of optical overlay metrology", Proc. SPIE 3051, Optical Microlithography X, (7 July 1997); https://doi.org/10.1117/12.276027

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