The source collector module (SoCoMo) for the extreme ultraviolet (EUV) small-field exposure tool (SFET) had been operated for 1,700,000,000 pulse radiations using more than 20 electrodes, four debris mitigation tools (DMT), and three collector mirrors. After 600 million pulse radiations, it was found that the EUV light intensity at wafer plane had been decreased to less than 10% of the initial value and the pupilgram exposed by SFET had been drastically deteriorated. In order to study on the cause of the intensity reduction and to maintain the intensity highly, three new evaluation tools were introduced; collector position monitors, an intermediate focus (IF) spot position monitor, and an attachment of screen tool. Utilizing these tools, it was clarified that the main causes of EUV light intensity reduction at IF plane were the plasma fluctuation with electrode erosion, the degradation of DMT's optical transmissivity, and the degradation of collection efficiency. These results indicated that it would be necessary for future SoCoMo not only to achieve highpower, stable and long-life performance, but also to equip with the functions that these tools provided in order to maximize its own performance.

Date Published: 18 March 2009
PDF: 7 pages
Proc. SPIE 7271, Alternative Lithographic Technologies, 727135 (18 March 2009); doi: 10.1117/12.814004

Published in SPIE Proceedings Vol. 7271:
Alternative Lithographic Technologies
Frank M. Schellenberg; Bruno M. La Fontaine, Editor(s)