Fabrication and characterization of singly addressable arrays of polysilicon field-emission cathodes

Polysilicon is a viable candidate material for field-emission microelectronics devices. It can be competitive for large size, cost-sensitive applications such as flat-panel displays and micro electro-mechanical systems. Singly addressable arrays of field-emission cells were fabricated in a matrix configuration using a subtractive process on polysilicon-on-insulator substrates. Matrix rows were fabricated as insulated polycrystalline silicon stripes with sharp emission tips; and matrix columns were deposited as gold thin film electrodes with round gate openings. Ion implantation has been used to provide the required conductivity of the polysilicon layer. To reduce radius of curvature of the polysilicon tips, an oxidation sharpening process was used. The final device had polysilicon emission tips with end radii smaller than 15 nm, surrounded by gate apertures of 0.4 tm in diameter. Field emission properties of the cathodes were measured at a pressure of about 10(-8) Torr, to emulate vacuum conditions available in sealed vacuum microelectronics devices. It was found that an emission current of I nA appears at a gate voltage of 25 V and can be increased up to I VA at 70 V. Over this range of current, no "semiconductor" deviation from the Fowler-Nordheim equation was observed. I-V characteristics measured in cells of a 10 x 10 matrix, with a cell spacing of 50 pm demonstrated reasonable uniformity and reproducibility. (C) 2001 Elsevier Science Ltd. All rights reserved.