Surface Smoothing And Roughening Effects of High-k Dielectric Materials Deposited by Atomic Layer Deposition and Their Significance for MIM Capacitors Used in DRAM Technology

Abstract

Previously, the author suggested that the atomic layer deposition (ALD) of an amorphous high-k dielectric thin film has a surface smoothing effect on a rough surface. In this paper, the author points out that for ALD high-k dielectric materials which tend to be polycrystalline, the situation is different. When the film is very thin, it can be amorphous with a surface smoothing effect; when the film is thicker than a critical thickness, it can be polycrystalline with a surface roughening effect. An asymmetry in interfacial roughness will lead to an asymmetry in the top and bottom Schottky barrier heights, resulting in I-V polarity asymmetry. The significance of this theory on the leakage current mechanism of ZAZ MIM capacitors used in DRAM technology will be explained.