Porous low-k materials are required in the construction of 45 nm node large-scale integrated devices. However, the extremely low Young's modulus values of these materials results in a high number of previously unreported defects. A porous low-k film stacked with a dense low-k film showed pronounced cracking in its Cu wiring, which was concentrated in isolated lines 0.18 m in width and was accelerated with longer chemical-mechanical polishing ͑CMP͒ times. Denser lines showed less cracking and the single structure of a dense low-k film showed no cracking. We hypothesized that this cracking might be categorized as stress corrosion cracking ͑SCC͒. Accordingly, we investigated the relation between stress and corrosion in certain kinds of slurry. We have also researched the effects on corrosion of temperature and various metals. In all of the slurry that we tested, tensile stress increased corrosion current in Cu samples. Furthermore, both finite element method analysis of stress during CMP and measurements of friction on the Cu/low-k surface by scanning probe microscopy indicated concentration of stress on low-k materials, especially at the edges of isolated wiring. Thus, we concluded that stress enhances corrosion during CMP and that there was a high possibility of SCC.
The growth mechanism of the passivation layer in the cryogenic process used for silicon deep etching is explored experimentally in an inductively coupled plasma reactor. In particular, the role of SiF4 etching by-products on the SiOxFy layer deposition is investigated. The deposition of a SiOxFy layer using SiF4 and O2 gases is studied by in situ ellipsometric spectroscopy in different experimental configurations to devise the deposition mechanism: SiF4/O2 plasma mixture, alternation of SiF4 plasma and O2 plasma steps and alternation of SiF4 flow without plasma and O2 plasma steps. The refractive index and the thickness of the deposited layer are measured for different substrate temperatures, from −125 °C to 20 °C. Although some of the passivation layer is removed during the wafer warm up, a residual amount remains at the surface. The deposited SiOxFy layer forms more efficiently at low temperature with an optimal temperature of −100 °C in our experimental conditions. The passivation layer was etched by a SF6 plasma without bias versus the deposition temperature, to evaluate its resistance to plasma etching steps. The passivation layer was analyzed by ex situ EDX and XPS. We investigated the role of SiF4 low temperature physisorption in the formation of the passivation layer on the sidewalls of the features that are being etched, which are not submitted to ion bombardment. It is shown that physisorption of SiFx species play an important role because their residence time at the surface is longer, thus increasing the probability of reaction with oxygen.
A metallic Mn layer was successfully formed on tetraethylorthosilicate (TEOS)–SiO2 substrate at the deposition temperature of 250 °C by chemical vapor deposition (CVD) using a newly developed Mn precursor, bis[1-(tert-butylamide)-2-dimethylaminoethane-N,N ']manganese. A thin and uniform Mn oxide layer was simultaneously formed at a CVD-Mn/TEOS–SiO2 interface, and was partially embedded in the TEOS–SiO2. This Mn oxide layer was composed of a bilayer of MnO
x
and MnSi
x
O
y
. After annealing at 400 °C in vacuum for 10 h, the interface Mn oxide layer showed a good barrier property and thermal stability.
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