New critical dimension optical metrology for submicron high-aspect-ratio structures using spectral reflectometry with supercontinuum laser illumination

The article presents a novel optical metrology method for accurate critical dimension (CD) measurement of sub-micrometer structures with high spatial resolution and light efficiency. The proposed method takes advantage of the spatially coherent nature of the supercontinuum laser to detect submicron-scale structures with high aspect ratios. By using the method, CD measurement of individual microstructures such as vias and redistribution layers (RDL) becomes achievable when a high magnification optical configuration is incorporated. Proved by a test run on measuring submicron structures with linewidths as small as 0.7 μm and an aspect ratio over 4, the measurement precision of the depth can be kept within a few nanometers.