We briefly review the controversy concerning the proper methodology for the assignment of soft x‐ray photoemission Si 2p core levels at Si/SiO2 interfaces. Evidence for Second nearest neighbor effects in the photoemission spectra of analogous free molecules in the gas phase are surveyed for the purpose of placing this controversy within a wider context. Physisorption experiments have been performed to inquire whether the second nearest neighbor effects found in free molecules are in any way reduced in their magnitude owing to the proximity to the highly polarizable Si surface. No evidence for such a diminution have been found.

The hydridospherosiloxane cluster H8Si8012 has been physisorbed onto Si(111)-H and soft X-ray Si 2p core-level photoemission spectra obtained. The results of these experiments provide strong support for previous binding energy assignments of HSi03 moieties at -3.6 eV.

The room temperature chemisorption of disilane on Ge(100) and subsequent reaction at elevated temperatures was investigated by core level photoemission spectroscopy. At room temperature Si2H6 chemisorbs dissociatively on Ge(100) forming a surface populated largely by Si-H groups. Annealing the sample to 300°C effectively reduces the Si-H species to elemental Si. An additional anneal to 580°C promotes the diffusion of Si into the bulk and restores the Ge surface to an atomically clean state.

The interaction between F atoms and crystalline Si, which is essential for etching processes in semiconductor device fabrication, is investigated with state-of-the-art theoretical techniques. The theory is based on the pseudopotential-density-functional method in a supercell geometry. A comprehensive picture of F reactions with the Si surface, the bulk, and the near-surface region is obtained, in terms of which the etching process is elucidated. Insertion of F into Si-Si bonds becomes possible because of relaxed steric constraints in the near-surface region. Dependence of the etch rate on doping follows naturally, in agreement with observations. Similarities and differences between F-Si and H-Si reactions are discussed.

Soft x-ray core-level photoemission was used to study the reaction layer formed on a Si(111) surface during steady-state etching by XeF2. These surfaces show shifted Si 2p core levels which correspond to particular silicon fluoride species residing in the reaction layer. Spectra were collected in constant final state (CFS) mode for electron kinetic energies ranging from 2 eV to 90 eV. The use of CFS mode allowed the electron escape length to remain constant during individual spectra. The electron escape length for the reaction layer as a function of kinetic energy was then determined by monitoring the intensity of the bulk silicon signal. Thus, by analyzing the proportions of each silicon fluoride species observed in the individual CFS spectra as a function of the electron escape depth in the reaction layer, the distribution of the silicon fluoride species in the layer was obtained. The distribution determined placed SiF at the interface between the reaction layer and the bulk silicon, and the remaining species, SiF2, SiF3 and SiF4, successively layered on top. This observation leads to a model for the structure of the reaction layer.