16 March 2009 Ultimate contact hole resolution using immersion lithography with line/space imaging
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Contact Hole (CH) resolution is limited by the low aerial image contrast using dark field masks. Moreover the 2- Dimensional character of CH is a limiting factor in the use of extreme Resolution Enhancement Techniques for reaching the smallest pitch. These limitations can be overcome if one deconvolves the 2D CH into two exposures of 1D structures (i.e. lines). These 1D structures can indeed be printed at the ultimate resolution limit of the scanner using dipole exposures. Recently, several materials have become available to pattern CH from such a double exposure of line patterns. It is shown in this paper how this concept of deconvolution can be used in different techniques: Two 1D aerial images can be recomposed in order to obtain 2D images which will subsequently be reversed into CH. We can distinguish, on the one hand, a reversal based on the positive development of line crossings into resist pillar patterns, on which are deposited or coated a gap-fill material layer. The pillars are then removed, leaving a masking material layer with holes. On the other hand, negative tone development can be used to reverse directly the recomposed 2D aerial image: while the classical positive development creates pillars, the negative tone development inverses immediately this image to create contact holes in the resist layer. In this paper, we demonstrate the potential of the double exposure method. We characterise three reversal techniques using a NA=1.35 immersion scanner for patterning 40nm or lower CH at pitch 80nm. We also show etch performance of these processes and address the complexity of each solution.
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V. Truffert, V. Truffert, J. Bekaert, J. Bekaert, F. Lazzarino, F. Lazzarino, M. Maenhoudt, M. Maenhoudt, A. Miller, A. Miller, M. Moelants, M. Moelants, T. Wu, T. Wu, } "Ultimate contact hole resolution using immersion lithography with line/space imaging", Proc. SPIE 7274, Optical Microlithography XXII, 72740N (16 March 2009); doi: 10.1117/12.814867; https://doi.org/10.1117/12.814867

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