Characteristics of Tungsten Nitride Atomic Layer Depostiion

Abstract

Atomic layer deposition method for binary or ternary metal nitride film such as TiN, W-N, and TaN has been proposed to get a nano-scale diffusion barrier thin film. In this work, we have prepared W-N atomic layer by using WF6, NH3, and dry N2 gases diffused through a shower head. The residuary gases in the chamber were removed out by nitrogen as a purging gas. A cycle time was varied from 1 ~ 5 sec for an atomic layer and deposition rate per cycle, crystal structure, and atomic lattice image for interface were determined with high resolution transmission electron microscopy (HR-TEM). First, we have investigated the atomic layer deposition windows, resistivity and deposition rate per cycle at temperature between 250 ~ 450 oC. The diffusion barrier properties of both as-deposited post-annealed W-N films at temperatures between 500 and 700 oC were investigated against evaporated Cu films using interfaces analysis. The W-N/Si and Cu/W-N/Si interfaces show not any inter-diffusion and reaction up to 600 oC for 1 hr. As a nano scale thin diffusion barrier for Cu interconnect, we have investigated the composition change and interface reaction of W-N atomic layer and Cu after post-annealing with medium energy ion spectrometry (MEIS) as well as HR-TEM. As a result, the W-N atomic layer shows not any composition change or reaction with Cu at high temperature.