Optimization of CD-SEM Imaging Sequence to Achieve High-speed and Multi-point Measurement

Abstract

Critical dimension scanning electron microscope (CD-SEM) is widely used as an essential tool for measuring semiconductor patterns. It is necessary to set imaging sequence including corrections of imaging position and focusing of electron beam in evaluation point (EP) for the reliable measurement. Previously, addressing point (AP) and autofocus point (AF) suitable for these processing are selected by the hand and this is a drop factor of SEM operation rates. In our previous work, we developed a multifactor layout analysis (MLA) method, which automatically generate imaging sequence for each EP from design data of the pattern layout. In this paper, we propose an enhanced MLA method, which optimizes the imaging sequence to share AP and AF between multiple EPs. For 203 EPs, the imaging time of the proposed method is twice as fast as that of conventional MLA method. Without the hard improvement of the SEM apparatus, the proposed method can realize significant throughput improvement for numerous EPs