Systematic Measurement Uncertainty of Critical Dimension Scanning Electron Microscope

概要

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Critical dimension (CD) bias between a critical dimension scanning electron microscope (CD-SEM) and a reference tool is the most important error factor for more accurate CD measurement. The systematic measurement uncertainty was evaluated by experiment and electron beam simulation. The CD bias variation is caused by the change in secondary electron signal intensity. CD bias variation of an isolated 150 nm silicon substrate space pattern with space width change is 1.7 nm per 10 nm space width. The CD bias difference of the silicon substrate between with and without the native oxide layer is 30 nm at 150 nm space width. The CD bias change is 1.4 nm per 10 nm pattern height. This is caused by an interaction between space width and pattern height. We identified that measurement uncertainty includes not only random error but also systematic error in actual pattern shape, material, and layout variation quantitatively. The impact of systematic error on CD bias is very large compared with the metrology requirement for next-generation devices.
2010-06-25