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Reduced metal contamination levels become ever more critical as ultralarge scale integrated device feature sizes shrink to 0.25 p.m. Wafers may be contaminated with metals during their manufacture, but metals are more likely to be introduced at the wafer surface during integrated circuit processing. During high-temperature processing steps, the surface contaminants diffuse rapidly into the wafer bulk. Because carrier lifetime and diffusion length are strongly affected by the presence of parts per trillion levels of electrically active metal-related defect centers in the bulk of the wafer, these properties can be used to detect the presence of metal contamination. Unfortunately, these techniques are sometimes misused and misinterpreted. The more common techniques, their benefits, and limitations on their interpretation are discussed. A unified taxonomy to describe carrier lifetime characteristics is also proposed.

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Materials Characterization by Electrical Methods 7 3.1. U Through MIPR FY76 167600366 (NBS Cost Center 4259560). # Code SP-23, through project order N0016475P070030 administered by Naval Weapons Support Center, Crane, Indiana (NBS Cost Center 4251533).

Measurements of the magnetoresistance, Hall, and planar Hall coefficients have been made on oriented single crystals of w-type germanium at 77° and 300°K. At 77 °K measurements made as a function of the magnetic field strength and of the angle between the current and the magnetic field are found to be in agreement with theoretical calculations based on an energy-independent mean free time TO which has the same form of anisotropy as the effective mass at the bottom of the conduction band. The value of ro is determined from previously described Hall measurements and the anisotropy factor K is determined from the high-field longitudinal magnetoresistance. K decreases from about 16 to about 12 or 13 as the electron density increases from about 5.4 X10 13 cm" 3 to about 5.2 X10 14 cm" 3 .At 300 °K measurements were made for selected orientations of current and field on samples whose resistivities varied from 0.016 to 8.9 ohm-cm. The usual low-field symmetry relations are