Automatic Generation of Imaging Sequence for CD-SEM Using Design Data

Critical dimension scanning electron microscope (CD-SEM) is widely used as a measurement tool of semiconductor patterns. It is necessary to set imaging sequence including corrections of imaging position and focusing of electron beam for the reliable measurement. Conventionally, 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. We propose a technique to generate imaging sequence from design data of the pattern layout. Proposed method calculates selection indices for pattern complexity, uniqueness, and so on from design data and selects AP and AF templates automatically based on these indices. For 901 evaluation points, success rate of SEM imaging by proposed method was 100% and generation time of imaging sequence was 18 minutes. Compared with manual selection (conventionally, it takes 10 several hours by using SEM), large reduction of operation cost can be realized.