The analysis of oligonucleotide (ODN) loading over inorganic substrates is of fundamental importance to properly develop organic-inorganic systems such as biosensors. For this purpose, silicon is one of the most suitable substrates, but few works have been reported compared to other substrates such, for example, oxides, glasses or gold [1]. Crystalline silicon functionalization is a delicate process since the use of both basic and aggressive acidic solutions can damage the Si surface. A strict control of the functionalization process is of crucial importance both to preserve the high quality of the substrate surface (and its properties) and to optimize the final device performance. Functional parameters such as sensitivity and selectivity of the biosensor, depends on the ODN probe-target hybridization efficiency, which in turn depends on the optimization of ODN probe loading on the Si substrate.