Contour-based two-dimension mask pattern metrology

Abstract

Mask pattern measurement becomes one of the main challenges for the quality evaluation of the mask which is applied with complex lithography optical effect correction. Traditional straight edge mask pattern is evaluated with 1-dimension Critical Dimension (CD) method. But for 2-dimension pattern especially the mask full filled with complex shapes OPC pattern, many special approaches are studied attempt to characterize 2D pattern from different points of view [1-5]. A simple CD’s information and the traditional mask performance evaluation parameters, such as CD mean-to-target and CD uniformity, are no longer suitable to such 2D pattern due to lacking of the pattern’s character descriptions. Therefore the CD performances may not represent the actual wafer printing result in many cases. In addition, non-straight pattern edge induces significant CD measure error which makes it difficult to clarify the real mask pattern making quality. This paper investigates a pattern contour based solution for 2D structure performance evaluation. The basic contours of GDS and CD-SEM image are extracted, overlapped and processed and then the edge roughness of SEM contour and the bias between the above two kinds of contour are adopted on 2D individual pattern performance’s statistics. By utilizing this solution, the 2D pattern quality can be described quantitatively as two main aspects, shape and size with the results of edge roughness and bias. Generalize this solution, the 2D pattern’s uniformity, mean size, or other performances, can be evaluated quantitatively in the similar way as well. This solution calculation bases on pattern contour, therefore the measure pattern is not restricted by its shape.