Characterization of e-beam patterned grating structures using Mueller matrix based scatterometry

Abstract

Scatterometry is one of the most useful metrology methods for the characterization and control of critical dimensions and the detailed feature shape of periodic structures found in the microelectronics fabrication processes. Spectroscopic ellipsometry (SE) and normal incidence reflectometry (NI)-based scatterometry are widely used optical methodologies for metrology of these structures. Evolution of improved optical hardware and faster computing capabilities led to the development of Mueller matrix (MM)-based scatterometry (MMS). Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light interacting with a sample. This gives MMS an advantage over traditional SE scatterometry due to the ability to characterize samples that have anisotropic optical properties and depolarize light. In this paper, we present the study of full MM (16-element) scatterometry over a wide spectral range from 245 to 1700 nm on a series of one-dimensional, two-dimensional symmetric, and asymmetric grating structures. A series of laterally complex nanoscale structures were designed and fabricated using a state-of-the-art e-beam patterning. Spectroscopic MM and SE data were collected using a dual rotating compensator ellipsometer. Commercial modeling software based on the rigorous coupled-wave approximation was used to precisely calculate the critical dimensions. Results from MMS were compared with scanning electron microscopy.