Interfacial reactions in epitaxial Al/TiN(111) model diffusion barriers: Formation of an impervious self-limited Wurtzite-structure ALN(0001) blocking layer

Single-crystal TiN(111) layers, 45 nm thick, were grown on MgO(111) by ultrahigh vacuum reactive magnetron sputter deposition in pure N-2 discharges at T-s=700 degreesC. Epitaxial Al(111) overlayers, 160 nm thick, were then deposited at T-s=100 degreesC in Ar without breaking vacuum. Interfacial reactions and changes in bilayer microstructure due to annealing at 620 and 650 degreesC were investigated using x-ray diffraction and transmission electron microscopy (TEM). The interfacial regions of samples annealed at 620 degreesC consist of continuous similar or equal to7-nm-thick epitaxial wurtzite-structure AlN(0001) layers containing a high density of stacking faults, with similar or equal to 22 nm thick tetragonal Al3Ti(112) overlayers. Surprisingly, samples annealed at the higher temperature are more stable against Al3Ti formation. TEM analyses of bilayers annealed at 650 degreesC (10 degreesC below the Al melting point!) reveal only the self-limited growth of an similar or equal to3-nm-thick interfacial layer of perfect smooth epitaxial wurtzite-structure AlN(0001) which serves as an extremely effective deterrent for preventing further interlayer reactions. <(C)> 2001 American Institute of Physics.