The application of radiochemical research techniques for the analysis of semiconductor and ultrapure materials

Activation analysis techniques have proved highly suitable for the purpose to investigate the impurities and the local distribution of impurities and doping elements of ultrapure materials. Their advantages include extreme sensitivity of detection, the application of an absolute method of analysis and simultaneous coverage of a broad spectrum of elements. Autoradiography can be exploited to derive valuable analytical information about 50 elements on the periodic table. By employing radiotracer techniques it is possible to obtain important information leading to the optimization of manufacturing procedures. The advantages and the wide range of applications of these methods are demonstrated by the results of radiochemical investigations of about 30 problems in the semiconductor technology. Autoradiographs illustrate that doping and impurity elements deposit in swirls, striations and defects in the crystal lattice, e.g. in silicon, quarz, LiNbO3, which may result in undesirable crystalline properties. Results from activation analyses demonstrate the intrinsic gettering effect with oxygen segregations in silicon, the introduction of impurities in ion-implanted materials through sputtering in vacuum, increased take-up of impurities under high-pressure oxidation of silicon and the purifying effect of sapphire liquefaction and controlled silicon solidification. The capabilities of radiotracer techniques are demonstrated by investigations of zone refining and silicon water cleaning. (author)