As the advanced IC device process shrinks to below sub-micron dimensions (65nm, 45 nm and beyond), the overall CD error budget becomes more and more challenging. The impact of lithography process parameters other than exposure energy and defocus on final CD results cannot be ignored any more. In this paper we continue the development of an advanced control system, which can be used to detect, classify and correct up to 5 lithography parameters. Sets of focus exposure matrix (FEM) models are first set up with different DOE process conditions split. And photoresist profiles of specially designed scatterometry CD mark are then fitted to models (Neural Network Model or standard polynomial model). Based on these calibrated models, not only exposure and defocus but also PEB temperature, lens aberration, etc. can be estimated. This approach utilizes information of resist CD, height, sidewall and feature type dependent bias to classify different lithography parameters and therefore can give very accurate estimation of lithography parameters like energy, focus, PEB, spherical aberration and coma aberration. The new approach does not need phase shift mask or other specially designed mask, so it can be used by most of mass production Fabs and used for process monitoring and matching on inline production wafer.

Date Published: 5 April 2007
PDF: 11 pages
Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 651823 (5 April 2007); doi: 10.1117/12.702270

Published in SPIE Proceedings Vol. 6518:
Metrology, Inspection, and Process Control for Microlithography XXI
Chas N. Archie, Editor(s)