Sub-Half Micron Exposure System with Optimized Illumination

Akiyoshi SUZUKI  Miyoko NOGUCHI  

IEICE TRANSACTIONS on Electronics   Vol.E76-C   No.1   pp.13-18
Publication Date: 1993/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Opto-Electronics and LSI)
Category: Opto-Electronics Technology for LSIs
photolithography,  resolution,  depth of focus,  illumination,  quadrupole illumination,  

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New illumination principle for photolithography is investigated. As the optical microlithography approaches its own limit, it becomes apparent that the simple extrapolation of the present technology is not sufficient for the future demands. This paper introduces the new imaging technology that overcomes such a boundary. First, the basic imaging formulae are analyzed and the illumination light is classified into 4 cases. 3-beam case and 2-beam case carry the object information, and the comparison of these 2 cases is carried out theoretically. It can be shown that the 2-beam case has greater depth of focus than that of the 3-beam case, though it has inferior contrast at the best focus. Since this degradation, however, has little effect, the enlargement of the depth of focus can be achieved. In reality, 2-dimensional imaging must be considered. Quadrupole effect can be deduced by the results of the analysis. It shows great improvement in the depth of focus near resolution limit. As it can be applied to the conventional masks, it can be a promising candidate for fhe future lithography. Experimental results are also shown to demonstrate the analysis.