Characterization of Overlay and Tilt in Advanced Technology Nodes using Scatterometry

Optical scatterometry or optical critical dimension (OCD) is a well-known inline metrology technique in semiconductor manufacturing especially in advanced technology nodes. OCD metrology technique has high precision, throughput, accuracy, and process integrability. OCD is predominantly used to measure the feature dimensions such as line-width, height, side-wall angle, etcetera of the patterned structures after different manufacturing steps such as lithography, etch, deposition, chemical mechanical polishing (CMP), diffusion and others. However, use of OCD for characterizing patterning defects such as overlay and tilt is fairly limited. Precise measurement and control of these features is very important for reliable functionality of the device. This report is an overview of applications and benefits of using generalized ellipsometry or Mueller matrix spectroscopic ellipsometry based OCD for characterizing patterning defects like overlay and tilt in advanced nodes. Mueller matrix (MM) elements provides important additional information of complex anisotropic patterned structures as compared to conventional ellipsometry and reflectometry parameters. Also, due to patterning process errors such as, overlay and tilt, the complex patterned structures have induced structural asymmetry. The symmetric- antisymmetric properties associated with MM elements provide an excellent means of measuring asymmetry present in these complex nano-structures. This report provides details and insights of using appropriate approaches and strategies to characterize overlay and tilt present in patterned nano-structures of advanced semiconductor technology nodes.