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Proceedings Paper

Mask-to-wafer alignment using x-ray-printed alignment marks in x-ray lithography
Author(s): S. E. Liang; Alex L. Flamholz; John F. Conway
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Paper Abstract

X-ray lithography can be used to achieve deep sub-micron design groundrules. With X-ray, as with other lithographic systems, mix and match techniques are often used to achieve timely, cost effective implementation. This can, in some cases, reduce overlay accuracy and complicate mask and wafer layout. In this paper we will present methods which will facilitate the use of X-ray lithography in mix and match environments to simplify layout and improve overlay accuracy. An alignment scheme for 0.35 micron CMOS device fabrication and a method for printing alignment marks for the next X-ray level are described. In this scheme all the critical levels such as oxide isolation, polysilicon gate, contact, and first metallization levels are printed using X-ray lithography with the same X-ray stepper (Karl Suss XRS200/2). All other noncritical levels are printed optically. The initial wafer lot using this scheme has been successfully processed to the first metallization level. The X-ray stepper alignment system can compensate for the first order overlay components such as translation and rotation. This feature is very useful for compensating for certain mask difference and process induced distortion. However, mask magnification difference must be compensated otherwise. A linear regression method has been used to analyze the overlay data and the results are fed back to the stepper for correction. A 3-sigma overlay distribution +/- 180 nm has been achieved.

Paper Details

Date Published: 24 June 1993
PDF: 11 pages
Proc. SPIE 1924, Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing III, (24 June 1993); doi: 10.1117/12.146512
Show Author Affiliations
S. E. Liang, IBM Corp. (United States)
Alex L. Flamholz, IBM Corp. (United States)
John F. Conway, IBM Federal Systems Co. (United States)

Published in SPIE Proceedings Vol. 1924:
Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing III
David O. Patterson, Editor(s)

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