Mechanisms of defect generation in chemically amplified resist processes

Abstract

As the minimum feature size of electronic devices continues to shrink, the industry is moving from 248-nm wavelength KrF excimer laser sources to shorter wavelength 193-nm ArF excimer and 157-nm F2 excimer sources to achieve the higher resolution lithographic processes that are required. This requires optimum control over CD(critical dimension), but also the ability to minimize and reduce device defects is critically important. Satellite defects and various other kinds of defects were found to occur in the development process when chemically amplified resists are used in 248-nm lithography, and these defects clearly have an adverse effect on yields. Now that the industry is moving from KrF (248- nm) to ArF (193- nm) exposure systems, this means the requirements to control and reduce these micro defects are more exacting than ever before. In this paper we describe the generation behavior of defects caused by bottom anti-reflective coating (BARC) and the adherence behavior of defects onto the BARC. In this work we show that the generation behavior of defects is clearly affected by the thickness of the BARC, and the adherence behavior of defects is well explained by potential analysis measurements. With the transition toward shorter wavelength exposure systems, varying the thickness of the BARC is likely to have a major impact on the CD in lithography processes, but controlling the thickness of BARC layers is also extremely important from the standpoint of controlling defects. While we certainly must continue in our efforts to develop better resists that minimum defects, our results suggest that we must also focus attention on optimizing and closely controlling the entire lithographic process.