New methodologies: Development of focus monitoring on product

Several focus monitoring methods for high volume manufacturing (HVM) have been developed to improve general tool stability maintenance, fleet matching and focus uniformity on product. One technique involving the usage of diffractive gratings requires special targets that need to be designed and optimized at the individual mask level, which will increase the development cycle time. Our approach — TurboShape: described in this paper is based on spectroscopic ellipsometry and measured design rule compatible (DRC) targets to extract focus/dose results from the spectral response. To suppress the process variation impact and minimize focus and dose crosstalk, multiple design targets in the scribe-line were selected during the metrology development. The applications of this methodology for on-product focus monitoring on critical layer will be presented. This paper will describe the inline on-product focus excursion detection, fleet matching data and new strategy for new tool matching based on TurboShape. The measured focus uniformity (3σ) will be analyzed to demonstrate the capability for inter-field fingerprint detection.