Enabling Scatterometry as an In-Line Measurement Technique for 32 nm BEOL Application

Conventional metrology tools are unable to precisely monitor some interconnect attributes such as trench sidewall angle either due to limited capability or excessive cycle time. But these attributes have great impact on interconnect performance for 32 nm technology node and beyond. Scatterometry, a non-destructive metrology technique, is proposed to address the shortcomings of current metrology tools while also potentially providing additional measurement capabilities that enable more comprehensive characterization of interconnect attributes. Enabling scatterometry for back-end-of-line metrology at 32 nm technology node is challenged by the inherent complexity of a multilayer film structure. The research reported describes the implementation of scatterometry measurements to explore the advantages of this technique for the 32 nm technology node. The results obtained demonstrate the superiority of scatterometry techniques over conventional semiconductor metrology tools such as throughput, process control capability, precision, and accuracy. The total measurement uncertainty of scatterometry results with tunneling electron microscope and cross-sectional scanning electron microscope results for line height shows 1.92 and 6.46 nm, respectively, which compare favorably to the reference metrology tools. Scatterometry techniques also exhibited impressive potential to estimate end-of-the-line electrical parametric data. Finally, physical dimensions obtained from scatterometry measurements are shown to be comparable to TEM results from product wafers.