The Defect Structure of Buried Oxide Layers in SIMOX and BESOI Structures

Abstract

Both SIMOX [1] and BESOI [2] structures are potentially important for future SOI devices. A common feature of these structures is that two Si layers are separated by an SiO2 layer. Thus, the oxide layer is buried or confined between the Si layers. As a result of this confinement, some of the properties of these two types of buried oxide (BOX) layers are similar, even though the preparation conditions are very different. Although both BOX layers are similar to the widely used thermally grown SiO2 films in the sense that they are noncrystalline, some properties are quite different; this is particularly true for the SIMOX BOX layers. The primary reason for this difference is the difference in their defect structures. The defect structure of the BOX layers plays an important role in determining various properties of the completed SOI devices, particularly fully-depleted transistors, as well as the yield of the fabrication process and, very likely, the reliability of the devices. In this paper the properties of these BOX layers are reviewed with emphasis on their defect structure.