Kazuo Okubo

Pattern matching for automated E-beam testing

Abstract Pattern matching between the LSI mask layout database and SEM image is essential for automated e-beam testing. Techniques for calibrating wiring width, compensating for layer misalignment, and generating template images taking into account the effect of passivation films have been developed. We combined these techniques with projection edge extraction correlation (PEC) and had registered wiring probed automatically. Positioning time, which includes stage movement, SEM image acquisition, and pattern matching, was less than 20 s. Positioning accuracy (3σ) was 0.19 μm for metal and 0.55 μm for passivated wiring of an IC with a 2-μm minimum wiring width.

Automatic probing system for electron beam tester

Abstract In developing an automatic probing system for a CAD-linked electron beam (e-beam) tester, there are two problems derived from the electric or magnetic fields over the device under test (the global fields). One is SEM (Scanning Electron Microscope) image degradation and the other is SEM image shift. We solved this by adjusting electron optical parameters automatically and devising a semi-2D pattern matching algorithm. Using these techniques we developed an automatic probing system that acquires the voltage waveforms for conduction lines registered in advance on a mask layout. This paper discusses the effect of the global fields on automated probing, and our system and its performance.

Automatic measurement with an electron beam tester

Abstract We have developed automatic positioning and waveform acquisition techniques for measurement with an electron beam tester (EBT). Automatic positioning is difficult due to stage movement, magnification, and wiring width error in a CAD-linked tester. To correct these errors, we developed an SEM image-to-layout matching technique. A waveform is obtained by averaging repeatedly acquired waveforms. However, it is impossible to obtain the waveform with the same resolution, because a waveform is acquired using specified averaging in a conventional EBT. We developed the technique that how to monitor the voltage resolution simultaneously in the acquisition sequence. This technique makes it possible to stop acquisition at specified voltage resolution for quick, correct measurement. Using these techniques, we were able to automatically measure the waveforms specified in a CAD layout at about 90 s/wiring.