Integrated Capacitors with Nb 2 O 5 Dielectric for Decoupling Applications
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Integrated Capacitors with Nb2O5 Dielectric for Decoupling Applications Susan Jacob1, Leonard W. Schaper1, and Mourad Benamara2 University of Arkansas, BELL 3217, Fayetteville, AR 72701, U.S.A. 2 University of Arkansas, Institute for Nanoscale Materials Science and Engineering, Fayetteville, AR 72701, U.S.A 1
ABSTRACT As electronic systems are scaling down further and further, there is the constant need to utilize all the board area with maximum efficiency. Since passive components occupy most of the space on boards, it is very important to scale them down. New techniques allow for “integrated” passives as opposed to their discrete counterparts. Integrated capacitors can be embedded within the substrate, leaving room for other components on the board surface. In order to improve the area efficiency of these integrated capacitors, researchers have formed multilayered capacitors in the past. This increases the capacitance density, but is time consuming and expensive due to too many process steps. With increased circuit density, a currently demonstrated dielectric, Ta2O5, could be replaced with a potential high-k dielectric that can store more charge in a smaller area than a capacitor with Ta2O5. Niobium pentoxide (Nb2O5) with k~41 is an emerging dielectric for high-k capacitor applications. This paper investigates niobium pentoxide as a next generation high-k planar capacitor dielectric. Niobium pentoxide dielectric was formed by reactive sputtering and anodization. Dielectric characterization was done using X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM). Thin film planar capacitor structures were fabricated using Nb2O5 dielectric and electrically characterized. The results presented include dielectric material characterization, design, capacitance, and breakdown voltage measurements. INTRODUCTION Niobium pentoxide (Nb2O5) has been investigated as a capacitor dielectric material for more than forty years. But, only recently, niobium capacitor technology gained appreciable interest. Tantalum pentoxide (Ta2O5) is a widely used dielectric for capacitor applications all over the world. This mature technology can render a planar capacitance density of 110 nF/cm2 with a 2000 Å dielectric. Increasing circuit density and power requirements call for higher capacitance densities. Multilayered Ta2O5 capacitors can give higher capacitance density, but there are cost issues associated with their fabrication [1]. Nb2O5 with a dielectric constant, k of 41 can give about 1.7 times the capacitance density obtained with single layer Ta2O5. Niobium pentoxide capacitors are currently available in the form of discrete electrolytic capacitors. In this study, we are evaluating the suitability of Nb2O5 thin films deposited by reactive sputtering and anodization to form integrated capacitors, through material and electrical characterization. EXPERIMENTAL PROCEDURE Film Preparation
Two types of films were formed for characterization; reactively sputtered and ano
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