New Process Development for Planar-Type

A planar-type conductor-insulator-conductor tun- neling diode is developed using a boiling water process for surface oxidation. First, microsized bow-tie patterns are transferred on a doped polysilicon layer using e-beam lithography. After reactive ion etching, the polysilicon bow-tie pattern has a very narrow knot between two triangles. Using a buffered oxide etchant (BOE) solution, hydrogen silsesquioxane patterns and native oxide layer are etched. The knot is oxidized by a boiling water oxidation process. By repeating the BOE etch and oxidation, the bow-tie pat- terns are transformed into tunneling diodes with a very thin oxide barrier separating two polysilicon conductors. We show that the resulting structures follow the Simmons tunneling current-voltage relationship after boiling. Moreover, a high sensitivity of 31 V −1 is achieved at a bias voltage of 80 mV. Index Terms—Bow-tie antenna, metal-insulator-metal (MIM) diode, optical antenna, surface plasmon, surface plasmon reso- nance (SPR), tunneling diode.