Investigation of copper metallization induced failure of diode structures with and without a barrier layer

Impact of the Unique Physical Properties of Copper in Silicon on Characterization of Copper Diffusion Barriers

“…Since it is known that copper usually does not form deep levels at concentrations sufficient to affect the leakage currents of p±n junctions through generation of minority carriers, we would argue that the leakage current of p±n junctions increases only when copper forms precipitates in the junction area, most likely starting from n-side of the junctions, where its precipitation is facilitated by Fermi level effects discussed above. Recently reported studies of Baumann et al [90] and Miyazaki et al [91] confirm this model. Miyazaki et al [91] reported extensive Cu precipitation in the n area of Cu-contaminated p±n junction devices.…”

“…Miyazaki et al [91] reported extensive Cu precipitation in the n area of Cu-contaminated p±n junction devices. Baumann et al [90] reported that a 120 min annealing of silicon samples with Cu deposited on its surface in air at 120 C did not cause a change of the electrical behavior of the p±n junctions formed by As + implantation at a depth of 400 nm. However, XTEM investigation showed that Cu diffusion into the Si already has happened.…”

“…Dark shadows, reaching up to 260 nm deep into the Si bulk, were visible in the cross-sectional TEM micrograph and were identified by EDX as Cu-rich regions. Only after annealing at 200 C did the p±n junction leakage current increase by several orders of magnitude [90]. The authors concluded that the detection of electrical breakdown of p±n junctions was possible only after destruction of the entire vertical diode structure through the formation of Cu 3 Si spikes [90].…”

“…Only after annealing at 200 C did the p±n junction leakage current increase by several orders of magnitude [90]. The authors concluded that the detection of electrical breakdown of p±n junctions was possible only after destruction of the entire vertical diode structure through the formation of Cu 3 Si spikes [90]. The final comment in this section will be that to the best of our knowledge, no quantitative data are available as to what dissolved Cu concentration is required to affect the properties of p±n junctions.…”

“…Some groups have applied such analysis techniques as SEM (scanning electron microscopy) and even optical microscopy to detect the first signs of degradation of barrier integrity by appearance of defects on the surface of the barrier layer or the copper film, or appearance of etch pits after chemical removal of the barrier layer and selective etching of silicon (see, e.g., [5,15,18,20,82,99,100,103]). Plan view and cross-sectional TEM analyses (see, e.g., [11,14,19,21,71,93,96,98,101,104]) were used to detect interaction at the interfaces, degradation of the interface sharpness, and formation of spikes of Cu-silicide at the interface, or to measure Cu or Al concentration at different depths of the barrier layers using EDX (energy-dispersive X-ray spectroscopy) [90,99,105].…”