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Observation of IC operation using nematic liquid crystals and the laser scanning microscope

: Fritz, J.; Lackmann, R.

The International Congress on Optical Science and Engineering 1990 Technical Program
International Congress on Optical Science and Engineering <1990, The Hague>
Fraunhofer IMS ()
DAP-effect; ECB-effect; electrically controlled birefrigence; nematic liquid crystals; nondestructive testing; observation of IC operation

One important operation mode of electron beam testers used for IC failure analysis is qualitative voltage c"ntrast. The laser scanning microscope (LSM) offers an alternative observation mode without the need of a vacuum chamber. The addition, the proposed analysis method with nematic liquid crystals (NLC) is nondestructive, cheap and also applicable using a simple polarizing microscope. To ensure a homogeneous electric field distribution we propose the use of a conducting field plate. Device handling and preparation according to the IC scale can be extremly simplified with special microscope manipulator developed by us. The operating principles in reflective mode bases on voltage tuable birefringence. When a field above a critical threshold is applied, the liquid crystal begins to turn away from the direction of E due to the interaction of its dipole moment and the electric field. The basic principles of static and dynamic deformations are discussed and theoretical and experimental re sults treating the voltage and frequency response of NLC are presented. As a typical application exapmple we have observed CMOS ICs under working conditions.