Non-Contact Magneto-Optical Analyzer for IR Focal Plane Array Materials

Focal plane arrays (FPAs) are one of the most critical and expensive components in infrared imaging equipment, such as nigh vision, security and surveillance systems. In the device manufacturing processes, at present, it is not possible to determine if the final product is successful until all steps and materials have been incorporated. Since this entire manufacturing process can take up to 12 weeks to complete, much time and effort is spent on components which may ultimately prove to be defective. Current defect rates are in the order of 80% and are attributed to defective FPA chips/die. As a consequence, the availability of fully functional FPA modules is limited, and the price of those produced is unacceptably high. The Hall effect technique, particularly in conjunction with the van der Pauw theorem, is the most frequently used method of screening chips. In this technique at least four electrical ohmic contacts must be made to the semiconductor. This technique is labor intensive and frequently causes mechanical and electrical problems that result in inaccurate and non-repeatable results or damage. Furthermore, the measurement of carrier concentration as a function of position on the slice (mapping) is impossible since the Hall technique provides only the average value of the carrier concentration for area enclosed by the electrical contacts. For detector arrays, carrier concentration uniformity or doping homogeneity is necessary for uniform array operations. Any nonuniformity in the starting material would show up as a nonuniformity in the detectivity of each pixel in the detector array. The approach described in this proposal requires no physical contacts, is not labor intensive and can map electronic properties, such as carrier concentration and mobility, of a chip with high spatial resolution thereby identifying small areas of electronic nonuniformity that could not otherwise be found by conventional screening methods. This is accomplished by utilizing the Faraday rotation effect.