The ORIONTM series of test reticles have been used for many years as the photomask industry standard for evaluating contamination inspection algorithms. The deposition of Polystyrene Latex (PSL) spheres on various reticle pattern
designs allow STARlightTM tool owners to measure the relative contamination inspection performance in a consistent and quantifiable manner. However, with recent inspection technology advances such as shorter laser (light source)
wavelengths and smaller inspection pixels, PSL spheres were observed to physically degrade over relatively short time
periods: especially for the smallest sized spheres used to characterize contamination inspection performance at the most
advanced technology nodes.
Investigations into using alternative materials or methods that address the issue of PSL shrinkage have not yet proven
completely successful. Problems such as failure to properly adhere to reticle surfaces or identification of materials that
can produce consistent and predictable sphere sizes for the reliable manufacture of these critical test masks are only some
of the challenges that must be solved. Even if these and other criteria are met, the final substance must appear to
inspection optics as pseudo soft defects which resemble actual contamination that inevitably appears on production
In the interim, programmed pindot defects present in the quartz region of the SPICATM test reticle are being used to characterize contamination performance while a suitable long-term solution to address the issue of shrinking PSL
spheres on ORION masks can be found. This paper examines the results of a programmed pindot test reticle specifically
designed to evaluate contamination algorithms without the deposition of PSL spheres or similar structures. This
alternative programmed pindot test reticle uses various background patterns similar to the ORION, however, it also
includes multiple defects sizes and locations making it more desirable than the limited range of defects found on the
Chromeless PSM photomasks have been successfully applied to a production memory application. This 248-nm application has allowed an extremely aggressive, dense design to be successfully deployed without changing wavelength. This was achieved with an advanced resolution enhancement technique, a chromeless phase-shifting mask, to provide a more cost-effective total lithographic solution. The key to this technology is a mask that delivers high wafer-die yields, while delivering resolution at low k1. Therefore, the mask must have zero printing defects. In order to understand printing defects, many types of potential defects were analyzed and correlated back to the mask locations using both a 248-nm AIMs tool and SEM images. These defects were also correlated to a 257-nm KLA 576 tool using die-to-die inspection runs. This paper will examine chromeless mask phase-defect printing effects by using inspection capture at the key manufacturing steps (post-Cr etch, post-Qz Etch, and post-Cr removal). These defects will then be tracked through processes using SEM, AIMs, RAVE repair, and post-repair AIMs.
Photomasks with small dense features and high mask error enhancement factor (MEEF) lithography processes require stringent reticle quality control. The ability to quickly and accurately measure reticle defects on a high-resolution inspection system and to simulate their impact on wafer printing are key components in ensuring photomask quality. This paper discusses the correlation of measurements made with UV and DUV-based inspection systems; simulation performed with a 193nm aerial image review tool and aerial image simulation software. Ease-of-use is discussed for each technique. Data accuracy is compared to measurements performed by a Scanning Electron Microscope (SEM) on mask and wafer. Tests show that the inspection system can quickly and accurately determine sizes of most defects. The study also indicates that the simulation techniques can accurately tract the lithographic results, and can be used to reduce or eliminate the use of test wafers and expensive lithography and wafer metrology time. The outcome of this study leads to better defect dispositioning by providing techniques to determine the size and printability of reticle defects.