| Popis: |
Currently semiconductor industry drives the 193nm lithography to its limits, using techniques like double exposure, double patterning, mask-source optimisation and inverse lithography. These requirements trend to full in-die measurement capability of photomask metrology for registration. Especially, overlay becomes more and more critical and must be ensured on every die. For this, Carl Zeiss SMS has developed the next generation photomask registration and overlay metrology tool PROVE which is already well established in the market. To ensure in-die measurement capability, sophisticated image analysis methods based on 2D correlations have been developed. A key component for registration tool users is the cross site manufacturing flexibility given by the matching capability of all its metrology tools. Therefore all PROVE tools offer a tool matching procedure based on 2D Golden Grid references. In this paper we first review the optimal length standard and golden grid matching procedures of modern registration metrology tools. Systematic errors in fleet matching based on illumination differences, thermal expansionbased issues or line width roughness are addressed. The tool matching performance of PROVE tools is demonstrated by comparing up to 7 different tools. All tools are well within accuracy and long-term repeatability specification which considerably reduces the statistical error contribution of the tool matching performance. For grid matched tools the final cross tool registration error is shown to be below 1nm. |
