With the advent of copper metallization in interconnect structures, new barrier layers are required to prevent copper diffusion into adjacent dielectrics and the underlying silicon. The barrier must also provide adequate adhesion to both the dielectric and copper. While Ta and TaN barrier layers have been incorporated for these purposes in copper metallization schemes, little quantitative data exist on their adhesive properties. In this study, the critical interface fracture energy and the subcritical debonding behavior of ion-metal-plasma sputtered Ta and TaN barrier layers in Cu interconnect structures were investigated. Specifically, the effects of interfacial chemistry, Cu layer thickness, and oxide type were examined. Behavior is rationalized in terms of relevant reactions at the barrier/dielectric interface and plasticity in adjacent metal layers.

We describe the evolution of microstructure during ultrahigh vacuum ion beam sputter deposition of Cu (001) at room temperature on hydrogen-terminated Si (001). In situ reflection high energy electron diffraction indicates growth of an epitaxial Cu (001) film on Si (001) with the intensity of the Bragg rods sharpening during 5–20 nm of Cu film growth. Post-growth x-ray diffraction indicates the Cu film has a mosaic spread of (001) textures of about ±2° and that a small fraction (0.001–0.01) is of (111) textures. High-resolution transmission electron microscopy shows an abrupt Cu/Si interface with no interfacial silicide, and reveals an evolution in texture with Cu thickness so as to reduce the mosaic spread about (001). Moiré contrast suggests a nearly periodic elastic strain field extending into the Cu and Si at the interface. Other aspects of film growth which are critical to epitaxy are also discussed.

Single-crystal films of permalloy ( Ni 80 Fe 20) were grown on Cu (001) seed layers oriented epitaxially with Si (001). The microstructural properties were measured using in-situ reflection high-energy electron diffraction, and ex-situ transmission electron microscopy, x-ray diffraction, and atomic force microscopy, whereas the magnetic properties were probed using in-situ magneto-optic Kerr effect and ex-situ vibrating sample magnetometry. Anisotropic magnetoresistance and resistivity for some of the samples were also measured. The coercivity for thinner (≤5 nm) Ni 80 Fe 20 was significantly higher (10–20 Oersteds) than polycrystalline films deposited on SiO 2/ Si , and was also higher than films deposited on lattice-matched Cu x Ni 1–x alloys. These magnetic properties were explained using a theoretical model involving interaction of domain walls with defects such as misfit dislocations and coherent islands, due to the mismatch between Ni 80 Fe 20 and Cu .

The agglomeration of thin (10 nm) Cu films suitable for use as electroplating seed layers has been investigated on ultrathin (<4 nm) Ta, Ta1-xNx, Tal-xOx, and composite Ta/Ta1-xNx, diffusion barriers. Copper films on clean 3.6nm Ta barriers deposited by ultrahigh vacuum sputter deposition at up to 120°C are stable against agglomeration during 30 minute anneals at 360°C and display strong (022) crystallographic texture. Similar Cu films deposited on thinner Ta, Ta0 85N0 15, Ta0.95O0 05, and residual gas contaminated (∼ 1 Langmuir) Ta barriers agglomerate during annealing, and Cu films on Ta0 85N0 15 and contaminated Ta have random biaxial crystallographic texture. The density of agglomerated regions in Cu films on SiO2 and Ta0 85N0 15 is characterized as a function of thickness of an ultrathin Ta adhesion layer.

We have investigated structural and magnetic properties of epitaxial (100) N&Feel0 films grown on relaxed Cu/Si(lOO) seed layers. The crystallographic texture and orientation of these films was analyzed in situ by reflection high energy electron diffraction (RHEED), and M situ by x-ray diffraction and cross-sectional transmission electron microscopy (XTEM). In particular, RHEED intensities were recorded during epitaxial growth, and intensity profiles across Bragg rods were used to calculate the surface lattice constant, and hence the film strain. XTEM analysis indicated that the epitaxial films had atomically abrupt interfaces The magnetic properties of these epitaxial films were measured in situ using magneto-optic Kerr effect magnetometry. Large N, (10-20 Oej was observed for epitaxial Nis,,Fez,, (100) films less than 10.0 nm thick whereas for larger thicknesses, W, decreased to a few Oe with the appearance of a uniaxial anisotropy. Correlations were made between magnetic properties of these epitaxial films and the strain in the film.