Effect of Alignment Marks Design and Processing Factors on Overlay Accuracy

Egil D. Castel; Nader Shamma

doi:10.1117/12.953150

25 July 1989 Effect of Alignment Marks Design and Processing Factors on Overlay Accuracy

Egil D. Castel, Nader Shamma

Proceedings Volume 1088, Optical/Laser Microlithography II; (1989) https://doi.org/10.1117/12.953150
Event: 1989 Santa Clara Symposium on Microlithography, 1989, San Jose, CA, United States

Abstract

A series of alignment experiments was carried out in order to specify and optimize the design parameters for the site-by-site alignment marks used in an advanced single polysilicon bipolar process (ASPECT**). An Ultratech model 900 projection stepper which employs a dark field alignment system was used as the exposure tool. Alignment evaluations were performed for all masking levels of the ASPECT process with special emphasis placed on polysilicon and metal masking levels. The use of optimized targets resulted in a drastic improvement in registration accuracy: alignment statistics collected on a large number of samples with optimized targets for polysilicon to isolation alignment indicated a registration accuracy of +/- 0.27 um (2 sigma), whereas standard targets yielded +/- 0.50 um (2 sigma). For alignments of metal levels the values were +/- 0.40 um and +/- 1.0 um, respectively; thus the use of optimized targets allowed on reflective layers an alignment accuracy equal to or better than the stepper capabilities published by the manufacturer: Ultratech specifies an overlay budget of +/- 0.40 um (2 sigma) for a single stepper. This improvement in overlay accuracy translated into a large decrease in number of reworks and a significant improvement in product yield.

Citation Download Citation

Egil D. Castel and Nader Shamma "Effect of Alignment Marks Design and Processing Factors on Overlay Accuracy", Proc. SPIE 1088, Optical/Laser Microlithography II, (25 July 1989); https://doi.org/10.1117/12.953150

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