Electron conduction mechanism and band diagram of sputter-deposited Al∕ZrO2∕Si structure

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Abstract
Metal-oxide-semiconductor capacitors that incorporate ZrO2 gate dielectrics were fabricated by radio frequency magnetron sputtering. In this work, the essential structures and electrical properties of ZrO2 thin films were investigated. C-V, energy dispersive x-ray spectrometry, and transmission electron microscopy analyses reveal that an interfacial layer was formed, subsequently reducing the k value of the annealed ZrO2 thin films. Additionally, the mechanisms of conduction of the Al∕ZrO2∕p-Si metal/zirconium oxide/semiconductor structure were studied with reference to plots of standard Schottky emission, modified Schottky emission, and Poole–Frenkel emission. According to those results, the dominant mechanisms at high temperatures (>425K) are Poole–Frenkel emission and Schottky emission in low electric fields (1MV∕cm), respectively. Experimental results indicate that the Al∕ZrO2 barrier height is 0.92eV and the extracted trap level is about 1.1eV from the conduction band of ZrO2. The modified Schottky emission can be applied in an electric field to ensure that the electronic mean free path of the insulator is less than its thickness. According to the modified Schottky emission model, the extracted electronic mobility of ZrO2 thin films is around 13cm2∕Vs at 475K. The mean free path of transported electrons in ZrO2 thin films is between 16.2 and 17.4nm at high temperatures (425–∼475K).