Optical Scatterometry Modeling of 5 nm Logic Metal Gate Structures

Optical scatterometry, owning to its noncontact and nondestructive nature, has become one of the most important metrology techniques in semiconductor manufacturing. At 5 nm technology node, as the high-k metal gate structure consists of nanometer scale layers, the detection of such small structure is very challenging. In this paper, we built a scatterometry model based on Rigorous Coupled Wave Analysis (RCWA) method, and explored the parameter space to find an optimized combination for grid size, illumination angle, illumination wavelength, number of orders, etc. From our study, we recommend a set of parameter settings which will provide a balance between sensitivity and efficiency for 5 nm FinFET structures.