Assessment and application of focus drilling for DRAM contact hole fabrication

Conference: EMLC 2008 - 24th European Mask and Lithography Conference
01/21/2008 - 01/24/2008 at Dresden, Germany

Proceedings: EMLC 2008

Pages: 10Language: englishTyp: PDF

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Noelscher, Christoph; Jauzion-Graverolle, Franck; Henkel, Thomas (Qimonda Dresden GmbH & Co.OHG, Koenigsbruecker Straße 180, D-01099 Dresden, Germany)

By assessment of options for the fabrication of small contact holes in DRAM devices the method of focus drilling was identified and investigated to overcome the depth of focus limitations. By use of ArF-dry lithography a practical shrink of the target CD by 15nm can be achieved both with a focus offset double exposure (FODEX) and with a tilted stage approach. This was optimized in simulation and demonstrated by CD measurement on wafer, as well as by electrical measurement on integrated lots. Application of dual λ focus drilling is limited by the chromatic magnification error of the lens. The increase of hole-to-hole CD variations due to a lower dose latitude and to increased MEEF was characterized. As improvement option the use of a high transmission attPSM was identified.