Taming Pattern and Focus Variation in VLSI Design

Copyright 2004 Society of Photo-Optical Instrumentation Engineers. This paper was (will be) published in and is made available as an electronic reprint [preprint] with permission of SPIE. Single print or electronic copies for personal use only are allowed. Systematic or multiple reproduction, distribution to multiple locations through an electronic listserver or other electronic means, duplication of any material in this paper for a fee or for commericial purposes, or modification of the content of the pater are all prohibited. By choosing to view or print this document, you agree to all the provisions of the copyright law protecting it.

Tight ACLV control has become increasingly difficult due to the diminishing process constant, K1. Focus variation and pitch variation are two major systematic components of ACLV. In this paper, we demonstrate these systematic effects and propose a design flow which exploits the systematic effect.

We demonstrate the systematic ACLV by showing a Bossung plot for a nominal 90nm technology node. The plot is generated by simulation with lithographic parameters closely resembling a production technology node.

Traditionally, tight CD control is achieved by sophisticated RET such as OPC, SRAF, AltPSM and more recently the Dense Template Design. The CD variation is specified in the design manual and the circuit designs will ensure functionality by building in enough margin to account for the variability. Even though, the systematic components of CD variation are understood, they have always been considered together with other random components as being random. This approach has left design performance on the table.

We propose a holistic design flow by integrating the technology development process, design process and the manufacturing process. This holistic approach is aiming to tame the systematic through-pitch and through-focus CD variation. We quantify the design timing benefit using this approach by circuit design experiments. Results of our experiments show that timing uncertainty can be reduced by up to 30%.

We also discuss other possibilities which are infeasible to carry out in traditional approach with silos of technology development, design and manufacturing.

By: Fook-Luen Heng, Puneet Gupta, Kafai Lai, Ron Gordon, Jin-Fuw Lee

Published in: SPIE Proceedings, volume 5379, (no ), pages 139-48 in 2004


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