QUANTIFYING LOCAL OXIDE DIELECTRIC BREAKDOWN FOR NANOPORE FABRICATION IN OXIDE FILMS

The failure of thin oxide films has been studied intensively over the years, due to its relevance to the semiconductor industry. Dielectric breakdown (BD) under electric field stress has been proposed to occur due to the formation of a percolation path of defects through the oxide, and dissipation of energy by hot electrons. The local nature of these BD processes has been utilized in recent years as an efficient tool to fabricate nanopores in free standing solid state membranes, which are attractive for use in bio-sensing applications. I will present here a work aiming at assimilating the BD process for the fabrication of local pores in ultra-thin oxide films thermally grown on silicon wafers. In these studies a conductive probe of atomic force microscope was used as a metal gate of a 20 nm thick oxide layer grown on a highly doped p-type silicon wafer. Our studies show that for a positive biased probe, a leakage current appears at a threshold voltage around 26 V, which gradually progress into a catastrophic BD with the increase in the voltage. The BD process is accompanied by the formation of hills around the BD point exhibiting higher conductivity as well. On contrary, when the probe is negatively biased there is no leak current and a sudden increase in the conductivity is observed at voltage of around 40V, manifesting a BD. This BD process is accompanied by the formation of a pore, hundreds of nanometers in diameter. EW envision that the gradual escalation of the BD process under a positive probe bias may open the way to the controlled fabrication of nanopores upon farther treatment of the films.