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The rapid shrink of device dimensions requires not only excellent 1D CD precision, but also characterization of corner rounding and line end shape. To meet this on-going trend the industry is in a quest for higher resolution metrology tools, which in-turn drives the use of SEM metrology as more crucial. The industry challenge is to reduce corner rounding and area loss. The metrology challenge, is to be able to measure accurately and precisely these characters, in order to be able to control your process. In our study we will introduce the development of a new algorithm for general shape analysis. The purpose of this algorithm is to allow effective control of the correspondence of the feature’s shape to the design geometry. The disadvantage of the standard CD SEM metric such as contact area was discussed widely in the literature but new metrics were not discussed yet. We consider the following issues and challenges related to the development of a generic algorithm for general shape 2D analysis.
First stage of this algorithm is a generic segmentation of the two dimensional features. It should be robust to noise, as well as brightness and contrast changes. Output of this phase will be the contour representing the bottom of the feature. The second stage is the obtaining of new CD metrics for these contours, especially for contours corresponding to contacts with OPC structures. We consider the corner rounding as an example of such new metric. The same techniques can be elaborated for a large range of 2D structures with different levels of complexity. The obtaining of new metrics can be useful as handles for advanced process control (i.e. what to measure on the 2D feature with complex shape such as contact with OPC structures). We consider in this paper the application of the developed metrics for reticle contact with OPC structure monitoring problem that simulates a high level of complexity.
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