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    Biosensor integration on Si-based devices: Feasibility studies and examples

    Year: 2013

    Journal: Sensors and Actuators B: Chemical, 179, pp 240-251, 20130926

    Authors: S. Libertinoa, S. Conoci, A. Scandurra, C. Spinella

    Organizations: CNR-IMM Sede, Strada VIII Z.I. 5, 95121 Catania, Italy, STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy, Laboratorio Superfici e Interfasi (SUPERLAB), Consorzio Catania Ricerche, Stradale Primosole 50, 95121 Catania, Italy

    Feasibility studies and examples of integration of Si-based miniaturized biosensors are discussed. Weinvestigated three main issues: (i) device surface functionalization, (ii) biological molecule functionalityafter immobilization and (iii) biosensor working principle using electrical transduction mechanism inorder to fabricate electrolyte-insulator-semiconductor (EIS) and, in the near future, ion-sensitive fieldeffecttransistor (ISFET) biosensors.We compared a well established method for the immobilization of bio-molecules on Si oxide with anew immobilization protocol, both providing a covalent bonding on SiO2 surfaces of proteins (metallothioneines)enzymes (glucose oxidase, horse radish peroxidase), or DNA strands. The process steps werecharacterized by means of contact angle, XPS and TEM measurements. The compatibility with Ultra LargeScale Integration (ULSI) technology of the two protocols was also studied. The results strongly encourageto use the new optimized protocol to accomplish both ULSI compatibility and biological molecules correctfunctionalization. The electrical characterization of MOS-like capacitors with ssDNA anchored on theSiO2 dielectric, allowed us to conclude that the structures tested are sensitive to DNA immobilization andhybridization, as demonstrated by a positive shift in the VFB of +0.47±0.04 V after ssDNA immobilizationand by a further +0.07±0.02 V shift when hybridization occurs. Device working principle was proved inthis way. However, our results seem to indicate that bare SiO2 surfaces cannot be used as anchoring sitesfor DNA in transistor applications. In fact, the immersion in solution causes the migration of H+ ions inthe oxide and the formation of defects at the SiO2/Si interface.