Electron tunneling in non-planar floating gate memory structure

Until recently, detailed understanding of tunneling from a textured surface through a thick oxide layer for the non-volatile write mechanism has been limited by poor agreement between theory and experimentally observed emission currents. A recent paper which modelled the structure with an emitting surface of varying curvature combined with a planar collecting surface succeeded in obtaining a good fit to the current-voltage characteristic for electron emission from the non-planar surface. In real textured memory structures, the deposited poly on which the oxide is grown has convex structures. The poly deposited on top of the thermally grown oxide has topological features which are concave and of lesser curvature. These differences lead to asymmetric tunneling characteristics. The previous model for the one-sided case has been extended to the more complex double non-planar case and is able to quantitatively describe the observed characteristics.