AVS 49th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN-ThA

Paper PN-ThA5
Field Emitter Arrays with Sharp Tips for THz Microwave Source

Thursday, November 7, 2002, 3:20 pm, Room C-109

Session: Charged Particle Patterning and Emission
Presenter: C. Peng, The University of Michigan
Authors: C. Peng, The University of Michigan
S.W. Pang, The University of Michigan
Correspondent: Click to Email
Ballistic tunneling transit time device consists of a field emitter cathode, a drift region, and a collecting anode. These new transit time devices can produce mW level power in THz range with optimized operating voltage and anode to cathode separation. The field emission devices also need to have sharp tips, high emission current, low threshold voltage, and small dimensions for high packing density. In this work, nanofabrication technology to generate large arrays of sharp Si field emitters is developed. Sharp Si tips with tip radius of 20 nm are fabricated by dry etching with Cl@sub2@ in an inductively coupled plasma system. The tip sharpness, height, and profile are controlled by balancing the lateral etch rate of the SiO@sub 2@ mask and the vertical etch rate of the Si substrate. It is found that tip height and tip radius vary with rf power applied to the plasma source and the etch time. Tip height decreases with rf power and increases with etch time, while tip radius increases with source power and decreases with etch time. Uniform, large arrays of Si field emitters are formed with tip density of 1.1x10@super7@ tips/cm@super2@ and tip height varying from 2 to 4 µm. For these field emitters to function as THz microwave source, close tip to anode spacing in the range of 0.5 to 2 µm is needed. Etch time, spacer, and bonding technology are used to provide flexible and precise control of the tip to anode distance. In addition, emitter tip sharpening by oxidation and coating the tips with low work function materials will be studied to improve the emission current characteristics.