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Physical and Electrochemical Characterization of Crystalline Silicon Surfaces Modified by Aluminum

Crystalline silicon surfaces are modified by deposition of aluminum thin film that is sintered at 500 °C for different period of times. This treatment originates pyramidal pits and nanoparticles structures on the silicon surface. As a result, the sheet resistance of silicon surface increases. The analysis of the treated surfaces by Rutherford backscattering (RBS) and the impedance electrochemical spectroscopy (IES) reveals that, in addition to these defects, the aluminum atoms diffuse inside the silicon substrate, also contribute to the increase of the sheet resistance due to the formation of a high resistivity layer. In addition, the reflectance spectra of these samples reveal that after this treatment the complex refractive index of silicon crystal close to surface change and its surface becomes rough, as confirmed by the scanning electron microscopy (SEM). Although the higher sheet resistance of these substrates, they are more prone to be dissolved by HF attack when immersed into etchant composed by HF and HNO3, i.e., the etching rate of these samples becomes larger than in the case of the untreated substrate. This behavior is linked to the amount of oxygen incorporated within the silicon bulk during the thermal treatment.