Nanometer-scale Gap Control for Low Voltage and High Current Operation of Field Emission Array (FEA)

Abstract

In this work, we propose a new technique to fabricate a polysilicon gap, cathode-to-anode spacing, in a few tens of nanometer scale and investigated for the possibility in vacuum microelectronic device application. The polysilicon is chosen as a field emitting material because of its excellent electro-mechanical properties. Although the polysilicon has rather higher work function than other low function metals or DLC, low voltage operation is expected by virtue of small inter-electrode distance. The tensile stress existing between the silicon nitride and the polysilicon layers forces initially connected slim polysilicon pattems to be separated into two parts, yielding wedgeshaped cathode and anode tips for a field emission array (FEA) with extremely small inter-electrode distance. The oxidation time and the polysilicon thickness are the key parameters to control the inter- electrode gap. The fabricated field emission devices show very high emission current with low turn-on voltage. The turn-on voltage was as low as 11 V and very high electron emission current of 12 ,uA/tip was measured at the voltage of 34 V for the device with average inter-electrode spacing of 23nm which is the smallest inter-electrode distance ever reported. The good linearity in the Fowler-Nordheim plot converted from the current-voltage data for the array clearly shows the confirmation of the field emission. The combined effects of small inter-electrode spacing and large emitting area, which is the nature of the wedgeshaped diodes, are responsible for the low turn-on voltage and high emission current.