Biofunctionalized silicon nitride platform for sensing applications

Silicon nitride (SiN_x) based biosensors have the potential to converge on the technological achievements of semiconductor microfabrication and biotechnology. Development of biofunctionalized SiN_x surface and its integration with other devices will allow us to integrate the biosensing capability with probe control, data acquisition and data processing. Here we use the hydrogen plasma generated by inductively coupled plasma-reactive ion etching (ICP-RIE) technique to produce amino-functionality on the surface of SiN_x which can then be readily used for biomolecule immobilization. ICP-RIE produces high-density hydrogen ions/radicals at low energy, which produces high-density amino group on the SiN_x surface within a short duration of time and with minimal surface damage. In this work, we have demonstrated selective amination of SiN_x surface as compared to Si surface. The as-activated SiN_x surface can be readily biofunctionalized with both protein and oligonucleotide through covalent immobilization. N-5-azido-2-nitrobenzoyloxysuccinimide, a photoactivable amino reactive bifunctional crosslinker, was used and greater than 90% surface coverage was achieved for protein immobilization. In addition, ssDNA immobilization and hybridization with its complemented strand was shown. Thus, we demonstrate a uniform, reliable, fast and economical technique for creating biofunctionalized SiN_x surface that can be used for developing compact high-sensitivity biosensors.