An Improved Approach to Locating Pinhole Defects in MOS and Bipolar Integrated Circuits Using Liquid Crystals

Routine failure analysis of dielectric defects using nematic liquid crystals is possible with the method described in this paper. The refinements on previously described implementations result in excellent definition of the pinhole site. The paper discusses the principle involved in liquid crystal pinhole detection and details a practical liquid crystal fixture and device preparation. The influence of cell voltage polarity is illustrated and shown to be an important factor in achieving satisfactory results. The effectiveness of using dark field illumination and polarized light is shown and compared with the conventional bright field illumination used by prior authors. CMOS, MOS capacitor, and bipolar device analyses are included. Results are presented in sufficient detail to allow the reader to easily implement the technique in his own laboratory.