An Integrated Approach to the Determination of a Manufacturable Process Window in Advanced Microlithography

摘要

Resolution enhancement techniques (RET), immersion lithography, and Design for Manufacturing (DFM) are all geared towards increasing the lithographic process window to enable the ever more difficult processing demands of semiconductor manufacturing. It is well understood that there is a trade-off between depth of focus (DOF) and exposure dose latitude (EL), as well as best focus (BF) and best exposure dose (BE), in which a Manufacturable Process Window (MPW) must be established and centered. Oftentimes it is overlooked that this balance needs to be maintained across multiple dimensions including spatial (e.g. across field), density (e.g. dense, iso), temporal, tool-to-tool, etc. To maintain this critical balance, both test wafers and product wafers need to be monitored and analyzed in order to support Advanced Process Control (APC) and Automated Equipment Control (AEC). In this work we establish a method to optimize process window by using an integrated analysis workstation based on measurements from both optical and e-beam metrology. By applying this method, we demonstrate a MPW on daily FEM and nominal wafers already used at IMEC for daily process qualification.