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With wide application of low-dielectric constant (low-k) dielectric materials in multilevel VLSI circuits, the long-term reliability of such materials is rapidly becoming one of the most critical challenges for technology development. Among all the reliability issues, low4 time dependent dielectric breakdown (TDDB) is commonly considered a crucial problem. In this study, the effect of process variations on chemical-vapor deposited (CVD), carbon doped oxide dielectrics comprised of Si, C, 0, and H (SiCOH) TDDB degradation at the 65nm technology node is investigated. SiCOH TDDB is found to be sensitive to all aspects of integration.Based on extensive experimental data, an electrochemical-reactioninduced, three-step degradation model is proposed to explain the SiCOH dielectric breakdown process. Finally, we demonstrate that with careful process and materials optimization, a superior SiCOH TDDB performance at the 65nm technology node can be achieved for 300" fabrication. The projected lifetime, based on a conservative modeling approach and aggressive test structure is far beyond the most stringent reliability target. [

Eisenbraun, E.T.; Upham, A.; Dash, R.; Zeng, W.; Hoefnagels, J.P.M.; Lane, S.; Anjum, D.; Dovidenko, K.; Kaloyeros, A.E.; Arkles, B.; Sullivan, J.J.

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As-deposited and annealed tantalum films, grown by plasma-promoted chemical vapor deposition (PPCVD) using pentabromotantalum and hydrogen as coreactants, were evaluated as diffusion barriers in copper metallization. Stacks consisting of 500-nm-thick sputtered Cu/55-nm-thick untreated PPCVD Ta/Si were annealed in argon in the range 450 to 650 °C, in 50 °C intervals, along with sputtered Cu/preannealed PPCVD Ta/Si and sputtered Cu/sputtered Ta/Si stacks of identical thickness. Pre- and postannealed stacks were characterized by x-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, hydrogen profiling, x-ray diffraction, atomic force microscopy, sheet resistance measurements, and Secco chemical treatment and etch-pit observation by scanning electron microscopy. The sputtered and preannealed PPCVD Ta films acted as viable diffusion barriers up to 550 °C, while the as-deposited PPCVD Ta films failed above 500 °C. In all cases, breakdown occurred through the migration of Cu into Si, rather than an interfacial reaction between Ta and Si, in agreement with previously reported results for sputtered Ta films. The accelerated barrier failure for as-deposited PPCVD Ta might have been caused by the presence of approximately 20 at.% hydrogen in the as-deposited PPCVD Ta, an observation which was supported by the enhanced performance of the same PPCVD Ta films after annealing-induced hydrogen removal.

Results are presented from in situ, real-time, mass spectral, and infrared studies of the gas-phase evolution and decomposition pathways of the copper(II) ~-diketonate precursor bis (l,l,l,5,5,5-hexafluoroacetylaeetonato) copper(II),Cun(hfac)2, during plasma-assisted CVD (PACVD) of copper. Quadrupole mass spectrometry (QMS) investigations focused on determining the ionization efficiency curves and appearance potentials of Cu~(hfac)~ under real CVD processing conditions. The resulting curves and associated potentials were then employed to identify the most likely precursor decomposition pathways and examine relevant implications for thermal and plasma-assisted CVD of copper from Cu~(hfae)2. The QMS studies were complemented with real-time Fourier-transform infrared (FTIR) spectroscopy of the CVD processing environment to establish a basic understanding of plasma effects on copper precursor evolution and decomposition, and to determine optimum plasma CVD processing windows. Real-time FTIR absorption spectra of the gas-phase species in the CVD reactor were collected and analyzed for various plasma power densities. Key changes in precursor stretching and bending infrared (IR) bands were subsequently identified through a systematic comparison of the spectra of hydrogen plasma-exposed Cu~(hfac)2, collected as a function of varying plasma power density, and the fingerprint spectra of nonplasma-exposed H(hfac) and Cun(hfac)~. The resulting FTIR findings were used to develop optimum plasma processing conditions for providing the high concentration of reactive hydrogen species needed for the clean and efficient reduction of the precursor, without inducing undesirable gas-phase reactions. The results demonstrated that FTIR does provide a reliable in situ, accurate, and nonintrusive technique for monitoring the gas-phase evolution of metallorganics and associated reactants in the CVD reactor and allowing critical adjustments for optimal copper film quality.

This paper describes a comprehensive characterization of a 65 nm, 300" wafer size interconnect technology with SiCOH material (k=2.8). Excellent film properties of SiCOH material and precise process optimization enable the minimization of damaged layer during etching and strip processes. 3D modeling reveals that the k-value of SiCOH material was maintained at its initial value after the integration. Electrical yield, reliability and chip-to-package (CPI) evaluation are also presented. The results were comparable with conventional SiCOH integration scheme.