<title>Contact hole litho correlation with shape analysis</title>

Abstract

For the near future generations of lithography we investigate the reticle measurements of contact holes with respect to their lithographic performance. The difficulty with the shrinking size of contact holes is that their X and/or Y measurement on reticle does not correlate with the lithographic results. The shape of the contact hole will have a large impact. This paper considers the several types of reticle SEM measurement on isolated contact holes, the simulations on asymmetric contact holes, reticle photo analysis of contact hole shape, and lithographic result of 1 15-nm contact holes.A set of contact holes has been measured with a CD SEM in several ways as x-size, y-size, area, diameter in various angles. Only area measurement will suffice to judge contact hole size and shape. A second step simulates the behaviour of asymmetric contact hole shapes. For attenuated phase shifted contact holes of 1 3Onm (lx) and smaller, shape asymmetry can lead to small CD deviations. The third step correlates lithographic performance with the reticle measurements. Contact hole area or effective circular diameter correlates with wafer results. A better correlation results from reticle CD uniformity profile. The attenuated (6%) PSM that we used, has a large variety of sizes and pitches in contact holes. The reticle was exposed using the ASML Step and Scan PAS5SOO/1100 system. The reticle was measured with a KLA SEM.