New Method for Observation of Interface States in the Semiconductor Band-Gap : XPS Measurements under Biases(Interfaces by various techniques)

概要

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The energy distribution of interface states for Si-based metal-oxide-semiconductor (MOS) devices with an ultrathin oxide layer has been obtained using a new method developed by us, i.e., measurements of X-ray photoelectron spectroscopy (XPS) spectra under biases between the metal overlayer and the Si substrate. By applying biases, the Si 2p peak due to the Si substrate is shifted because of charges accumulated in the interface states in the Si band-gap. By analyzing the energy shifts measured as a function of the bias voltage, the energy distribution of interface states is obtained. The energy distribution has one, two, or three peaked-structure, depending on the oxide formation methods. Comparison with the ab-initio calculation using cluster models shows that the interface state peak near the midgap is due to isolated Si dangling bonds which do no interact with any atoms in the oxide layer, and those above and below the midgap are due to Si dangling bonds with which a Si or oxygen atom in the oxide layer interacts weakly. The interface state density for the Si(111)-based MOS devices with an ultrathin oxide layer is lower than that for the Si(100)-based MOS devices, and this is attributed to smoother Si(111)/oxide interfaces.interface stateultrathin oxideXPSMOSbiassilicon
東北大学の論文
1997-03-31