Limitation current in Si 3N 4/SiO 2 stacked dielectric films

Abstract

The limitation current in Si 3N 4/SiO 2 stacked dielectric films has been investigated systematically for both field directions by using n + and p + polycrystalline Si (poly-Si) gate capacitors and by varying the bottom oxide thickness. It can be explained by the combination of Poole–Frenkel current in nitride layer and Fowler–Nordheim current in bottom oxide layer for all the cases. The trap depth for Poole–Frenkel current, the thickness of bottom oxide for Fowler–Nordheim current, and the barrier heights at the interfaces are the factors to determine the limitation current. The trap depths of holes and electrons for Poole–Frenkel current in nitride layer are calculated to be 0.6 and 0.9 eV, respectively. The limitation current with negative gate bias is thought to be Poole–Frenkel of holes and electrons both in nitride layer for thin (⪋30 Å) and thick (>30 Å) bottom oxides, respectively. On the other hand, the limitation current with positive gate bias is thought to be Poole–Frenkel of holes in nitride layer and Fowler–Nordheim of electrons in bottom oxide layer for thin and thick bottom oxides, respectively.