Contact area as the intuitive definition of contact CD based on aerial image analysis

Netanel Polonsky; Amir Sagiv; Shmoolik Mangan

doi:10.1117/12.814275

23 March 2009 Contact area as the intuitive definition of contact CD based on aerial image analysis

Netanel Polonsky, Amir Sagiv, Shmoolik Mangan

Proceedings Volume 7272, Metrology, Inspection, and Process Control for Microlithography XXIII; 727237 (2009) https://doi.org/10.1117/12.814275
Event: SPIE Advanced Lithography, 2009, San Jose, California, United States

Abstract

As feature sizes continue to diminish, optical lithography is driven into the extreme low-k₁ regime, where the high MEEF increasingly complicates the relationship between the mask pattern and the aerial image. This is true in particular for twodimensional mask patterns, which are by nature much more complicated than patterns possessing one-dimensional symmetry. Thus, the intricacy of 2D image formation typically requires a much broader arsenal of resolution enhancement techniques over complex phase shift masks, including SRAFs and OPC, as well as exotic off-axis illumination geometries. This complexity on the mask side makes the printability effect of a random defect on a 2D pattern a field of rich and delicate phenomenology. This complexity is reflected in the dispute over the CD definition of 2D patterns: some sources use the X and Y values, while others use the contact area. Here, we argue that for compact features, for which the largest dimension is not wider than the PSF of the stepper optics, the area definition is the natural one. We study the response of the aerial image to small perturbations in mask pattern. We show that any perturbation creates an effect extending in all directions, thus affecting the area and not the size in a single direction. We also show that, irrespective of the source of perturbation, the aerial signal is proportional to the variation in the area of the printed feature. The consequence of this effect is that aerial inspection signal scales linearly with the variation of printed area of the tested feature.

Citation Download Citation

Netanel Polonsky, Amir Sagiv, and Shmoolik Mangan "Contact area as the intuitive definition of contact CD based on aerial image analysis", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 727237 (23 March 2009); https://doi.org/10.1117/12.814275

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KEYWORDS

Critical dimension metrology

Photomasks

Inspection

Airborne remote sensing

Signal detection

Image analysis

Semiconducting wafers

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