Date of Award

6-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Electrical Engineering

Advisor

Harrell, William R

Committee Member

Harriss , James E

Committee Member

Wang , Pingshan

Abstract

Electrical characteristics of a new class of tantalum capacitor are presented. Specifically, this type of tantalum capacitor is manufactured by KEMET Electronics Corporation and utilizes Poly(3,4-ethylenedioxythiolphene) (PEDOT) as the cathode material. There are two capacitor varieties based on the polymerization method used for the PEDOT. One uses In-Situ polymerization, and the other uses Pre-Polymerization. Existing polymer Ta capacitors use In-Situ polymerization while Pre-Polymerization is a new technique of cathode application. We investigated both types of devices to determine what, if any, performance benefits were gained by using Pre-Poly.
In a basic form Ta capacitors consist of a Ta anode, Ta2O5 dielectric, and PEDOT cathode polymerized to be a semiconductor. Based on the simplified representation of the capacitor materials these devices were investigated as MIS structures and C-V, I-t, and I-V measurements were made. C-V measurements were used to observe characteristics of MIS operation in the devices. Measurements were made from room temperature down to 100K in attempts to suppress the leakage current in these devices. I-t and I-V measurements were used to identify dominating leakage current mechanisms. The Poole-Frenkel Effect, the Schottky Effect, and Space-Charge-Limited Current were observed in In-Situ polymerized devices, while the Poole-Frenkel Effect, the Schottky Effect, and Fowler-Nordheim Tunneling were observed in Pre-Poly devices. Overall, both devices showed voltage dependent capacitance. The Pre-Poly devices generally had lower levels of leakage current. However, due to differing properties of the polymer in each case In-Situ devices exhibited less capacitance loss at low temperatures.

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