Understanding the Origin of Dipole Layer Formation at Interfaces between Two Dielectric Materials

这项研究的目的是了解在栅介质界面上形成的偶极层的起源，它改变了先进MOSFET的阈值电压。因此，本文研究了Al_2O_3/Al_xO_y和Al_2O_3/Al_2O_3两种介电界面。通过实验和经典分子动力学模拟，研究了Al_2O_3/Al_2O_3和Al_2O_3/Al_2O_3界面偶极层的形成。AlFxOy/Al_2O_3形成正偶极层，而MgO/Al_2O_3形成负偶极层。模拟结果表明，在AlFxOy/Al_2O_3上，氧迁移对电荷分离起着重要作用，而在MgO/Al_2O_3上，镁离子迁移起着重要作用。这两个界面上离子运动的不同作用被认为是界面性质的结果。AlFxOy/Al_2O_3上的离子运动主要是由应力松弛决定的，而化学稳定化合物的形成决定了在MgO/Al_2O_3上的离子运动。结果表明，在介电界面形成过程中，正负离子运动共同作用导致介电界面电荷分离，对不同介电界面偶极层形成的研究有助于理解介电界面偶极层形成与界面离子运动之间的关系

The purpose of this study is to understand the origin of dipole layer formation at gate dielectric interfaces which shifts the threshold voltage of advanced MOSFETs. Therefore two dielectric interfaces, Al2O3/AlFxOy and MgO/Al2O3, were studied.Dipole layer formation at AlFxOy/Al2O3 and MgO/Al2O3 interfaces was studied by both experiments and classic Molecular Dynamics simulation. Positive dipole layer formation was observed for AlFxOy/Al2O3 while negative for MgO/Al2O3. The simulation has suggested oxygen migration playing an important role on charge separation at AlFxOy/Al2O3 and Mg cations migration playing an important role at MgO/Al2O3. Different roles of ionic motion at these two interfaces are considered to be the result of the properties of the interfaces. The ionic motions are mainly determined by stress relaxation at AlFxOy/Al2O3 while formation of chemically stable compound determines the ionic motions at MgO/Al2O3. The results indicate a combined effects of cation and anion motion during the dielectric interface formation to caused charge separation at dielectric interfaces.The study on dipole layer formation at various dielectric interfaces provides us with an insight in understanding the relationship between the dipole layer formation at dielectric interfaces and interface ionic motions