The properties of iron in n-type and p-type silicon were studied by means of DLTS, carrier lifetime measurements, and infrared absorption spectroscopy. Only one donor level was observed, situated at Ev § 0.43 eV and correlated to iron on an interstitial site. In p-St: B iron-boron pairs were formed at room temperature. Their activation energy was determined to be Ev -6 0.10 eV. The reaction proceeded in two phases. In the second phase a thermal equilibrium between iron and iron-boron pairs was found which could be shifted by annealing and illuminating the specimen, respectively. In aluminum-doped silicon crystals two levels were observed after iron diffusion correlated to iron-aluminum pairs. Their activation energies were determined to be Ev -60.21 and 0.13 eV. It is assumed that iron-boron pairs form also two levels, a donor and an acceptor. The acceptor must be situated in the upper half of the silicon bandgap. Reaction mechanisms are discussed.

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A new method is presented which is suitable to check gettering processes and to evaluate gettering efficiencies. This method is based on an intentional contamination of the respective silicon wafer by means of palladium or any other haze forming metal. The palladium is diffused and haze is revealed by preferential etching. In order to determine gettering efficiency the sizes of the haze areas on gettered and non-gettered wafers are compared. The quantity of the gettered palladium can be deduced from lateral palladium profiles.In contrast to procedures published in the literature this method is very simple and fast. Therefore it is suitable for routine application to check back side damaged wafers or internal gettering.

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Carrier lifetime measurements were performed in silicon crystals in order to characterize the quality of the material and to control the device production process. For process monitoring, floating-zone n-type silicon of high resistivity was used, since p-type silicon in general exhibits pronounced axial and radial profiles of carrier lifetime. The influence of various atmospheres during heat treatment on the final carrier lifetime in n-type silicon was investigated. Oxygen with and without additional hydrochloric acid increased the carrier lifetime, while hydrogen, in comparison with inert gas atmospheres, decreased it. Gold, copper, and iron were found to be the main heavy metal impurities introduced into silicon specimens by heat treatment. The iron content varied considerably with the atmosphere used during annealing, showing the highest concentrations for hydrogen. Fast cooling of specimens after heat treatment produced carrier lifetimes that were unstable with the time elapsed after quenching.