| In this thesis several fundamental issues concerning the influence of wet chemical processes on silicon surfaces are addressed. As a result of the trend toward decreasing feature sizes in the semiconductor industry, there is increasing emphasis on the properties of silicon surfaces and interfaces. In front end of the line wafer processing, wet chemical cleaning and etching steps are commonly used and there is a need for improved understanding of the relationships between the electrical properties of the silicon wafers and the surface chemistry. Determination of the band bending in a semiconductor in contact with a solution is not straightforward since the potential is partitioned between the space charge layer in the semiconductor and the Helmholtz layer on the solution side of the interface. In deep depletion, a change in the applied potential usually appears across the space charge layer, however, under conditions of weak depletion or accumulation, the applied potential is partitioned between the two layers and the band bending is usually unknown. Microwave reflectivity can be used to probe the electrical properties of the semiconductor/solution interface by measuring the reflectivity response to a modulation in the band bending. The effectiveness of microwave reflectivity measurements to determine the potential distribution at the semiconductor/solution interface is demonstrated. Expressions for the dependence of the band bending on the applied potential are derived, and the consequences for charge transfer processes are discussed. A multiphase stratified media model is used to numerically calculate the microwave reflectivity for a semiconductor in contact with a solution. The reflectivity change produced by such systems is related to the frequency of the microwave source, the thickness of the semiconductor, the thickness of the space charge layer of the semiconductor, the dielectric constants and conductivities of the various media. The sensitivity factor of this model is compared to experimental results for silicon surfaces. A quantitative treatment of the carrier recombination lifetimes and minority carrier properties of silicon is presented. The general guidelines for minority carrier lifetime measurements are provided. The commonly used techniques such as radio frequency photoconductivity decay, electrolytical metal tracer, and microwave photoconductivity decay for determining minority carrier properties are reviewed and the feasibility of performing minority carrier measurements using in-situ microwave reflectivity is discussed. |
