Characteristics of tungsten nitride atomic layer for Cu interconnection technology

Abstract

Atomic layer deposition method for binary or ternary metal nitride film has been proposed to get a nano scale diffusion barrier thin film. However, there are few results regarding to tungsten nitride atomic layer. Generally, comparing with TiN thin film deposited with low pressure chemical vapor deposition method, the W-N layer has been deposited with plasma enhanced chemical vapor deposition and it seems to be an excellent diffusion barrier. In this work, we have prepared W-N atomic layer at 300~450 oC by using WF6 and NH3 gases diffused through a shower head without plasma discharge. A cycle time was varied from 2 ~ 5 s 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). As a nano scale barrier against 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.