Crystallization of amorphous WNx films

Abstract

The microstructural changes of WNx films during annealing were analyzed using transmission electron microscopy and x-ray diffraction. Amorphous WNx films eventually crystallized to a two-phase mixture of W and W2N through the primary crystallization and eutectic crystallization. The resulting microstructure after annealing at 800 degreesC consisted of large primary crystals with a eutectic mixture of W and W2N microcrystallites in the intergranular boundary region. In case of the amorphous film with near-eutectic composition of W0.79N0.21, it transformed directly into a two-phase mixture of W and W2N through the eutectic crystallization at 600 degreesC without the primary crystallization. On the other hand, polycrystalline W2N films had a columnar structure and did not undergo any microstructural change during annealing up to 800 degreesC. Barrier properties of WNx film versus Cu diffusion are discussed in relation with the microstructural changes of the films. (C) 2001 American Institute of Physics.