The first intrinsic process monitoring system for 90nm device with Focus and Dose Line Navigator (FDLN)

摘要

Focus and exposure dose control in lithography is a key challenge for CD (critical dimension) control at 90 nm technology node and beyond. Specially, more high accurate focus control will be necessary for low power MOS devices. Focus and dose line navigator (FDLN) is one of the candidates as in-line controller. The FDLN methodology involves two steps: first, create a focus-dose matrix (FEM) for building the library as supervised data using test wafer. The library means relational equation between the topography of photoresist patterns (line width: CD, height: HT, a side wall angle: SWA) and FEM exposure conditions, second, measure standard production wafer and feed the raw data into the library (which extrapolate focus and dose), which is then provided to the user. Using FDLN, current volume production's focus and dose deviation from the best condition can be obtained. In this time, we have evaluated FDLN using an optical CD measurement tool and process wafer. STI, Cu-CMP, metal wafers are used in this time as actual process. We acquired several FEM set of image feature from wafers, which were exposed by ArF scanner. According to our experiment, the estimation precision for focus and dose are below 24nm and below 1.7% respectively. And CD difference in a chip can reduce to one third as compared with the conventional QC method. These results suggest that FDLN can be the solution as in-line focus controller for volume production, enabling the progression toward Advanced Process Control (APC)