Chemical deposition and mechanical application of semiconductors thin films
Abstract
Features and main technological methods of forming thin layers of semiconductor materials by methods of chemical deposition and mechanical application are analyzed. The disadvantages of thermal sputtering and cathodic sputtering of thin films in vacuum for multicomponent semiconductor compounds are indicated. Features of chemical deposition of semiconductor films from the gas (steam) phase are presented. Such deposition involves the transfer of source material from the evaporator zone with higher temperature in the form of volatile compounds to the colder surface of the substrate, where the film growth occurs as a result of reaction of transported compounds or their decomposition. It is shown that the growth of the film during chemical vapor deposition is a process of layer-by-layer condensation of atoms or molecules, with the advantageous difference that during chemical deposition the latter are formed as a result of a heterogeneous chemical reaction when there is no need for average free path length of the gas molecules to be larger than the size of the deposition chamber, i.e. no need for critical degree of vacuum. Chemical deposition of thin films from solution is characterized as a process of precipitation of solute which occurs due to the fact that the ionic product exceeds the product of solubility, i.e. it is greater than the constant value characteristic of a saturated solution in the equilibrium state. We emphasize, that chemical deposition from an water solution allows to obtain homogeneous in thickness and structure fine-grained non-textured mechanically stable polycrystalline films with good adhesion to substrates and the required set of properties. The method of pulverization with subsequent pyrolysis is described. This is deposition from intracomplex organometallic compounds, which is based on thermally stimulated reactions between clusters of atoms, chemically active substances of liquid or vapor phase. The method of electrolytic deposition on electrically conductive substrates is characterized. The method is using appropriate salt solutions by co-deposition of individual components, or by deposition on the cathode of one of the components with its subsequent interaction with others present in the solution. We also describe the method of obtaining epitaxial thin films of semiconductor deposition materials. We note that the analyzed methods or their modifications are necessary tool today to create thin-film semiconductor structures with predetermined properties. In the same time, in each particular case the features of each method of obtaining thin semiconductor films should be comprehensively evaluated and, depending on the chemical composition, structure, topology and complex of expected properties, the most effective method should be applied.
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