The statistics of electrical breakdown field (Ebd) of HfO2 and SiO2 thin films has been evaluated over multiple length scales using macroscopic testing of standardized metal-oxide-semiconductor (TiN∕SiO2∕Si) and metal-insulator-metal (TiN∕HfO2∕TiN) capacitors (10−2mm2–10μm2 area) on a full 200mm wafer along with conductive-atomic-force microscopy. It is shown that Ebd follows the same Weibull distribution when the data are scaled using the testing area. This overall scaling suggests that the defect density is ∼1015cm−2 and Ebd is ∼40MV∕cm for nanometer-length scales; as such, breakdown in these materials is most likely initiated by bond breaking rather than punctual defects.

Statistics of electrical breakdown field in HfO2 and SiO2 films from millimeter to nanometer length scales

We present a quantitative physical model describing degradation of poly-crystalline HfO2 dielectrics subjected to electrical stress culminating in the dielectric breakdown (BD). The model accounts for the morphology of the hafnium oxide film and considers the interaction of the injected electrons with the atomic defects supporting the charge transport to calculate the 3-D power dissipation and temperature maps across the dielectric. This temperature map, along with that of the electric field, is used to self-consistently calculate the stress-induced defect generation rates in the dielectric during stress. The model quantitatively reproduces the evolution of the currents measured on HfO2 MIM capacitors during constant voltage stress, up to the onset of BD, and the dependencies of the time-dependent dielectric breakdown distributions on stress temperature and voltage. It represents a powerful tool for statistical reliability predictions that can be extended to other high-κ materials, multilayer stacks, and resistive RAM devices based on transition metal oxides.

Microscopic Modeling of Electrical Stress-Induced Breakdown in Poly-Crystalline Hafnium Oxide Dielectrics

By employing plasma-assisted atomic layer deposition, thin films of Al2O3 and TiN are subsequently deposited in a single reactor at a single substrate temperature with the objective of fabricating high-quality TiN/Al2O3/p-Si metal-oxide-semiconductor capacitors. Transmission electron microscopy and Rutherford backscattering spectroscopy analyses show well-defined interfaces and good Al2O3 stoichiometry, respectively. Electrical investigation of as-deposited test structures demonstrates leakage current densities as low as ∼1 nA/cm2. Current-voltage (I-V) measurements demonstrate clear Fowler–Nordheim tunneling with an average TiN/Al2O3 barrier height of 3.3 eV. Steep Weibull distributions of the breakdown electric field around 7.5 MV/cm indicate good reliability of these devices. Time-dependent dielectric breakdown measurements demonstrate that the devices can sustain high operating electric fields of 3–4 MV/cm for the 10 year lifetime criterion. From capacitance-voltage (C-V) measurements, a dielectric co...

https://pure.tue.nl/ws/files/3039456/Metis235625.pdf

Plasma-assisted atomic layer deposition of TiN/Al2O3 stacks for metal-oxide-semiconductor capacitor applications

Effects of annealing temperature on the characteristics of ALD-deposited HfO2 in MIM capacitors

Dispersion in accumulation is a widely observed phenomenon in technologically important InGaAs gate stacks. Two principal different interface defects were proposed as the physical origin of this phenomenon—disorder induced gap states and border traps. While the gap states are located at the semiconductor side of the interface, the border traps are related to the dielectric side. The study of Al2O3, HfO2, and an intermediate composition of HfxAlyO deposited on InGaAs enabled us to find a correlation between the dispersion and the dielectric/InGaAs band offset. At the same time, no change in the dispersion was observed after applying an effective pre-deposition treatment which results in significant reduction of the interface states. Both observations prove that border traps are the physical origin of the dispersion in accumulation in InGaAs based metal-oxide-semiconductor gate stacks.

F. Mondon

Papers

Electrical characterisation and reliability of HfO2 and Al2O3–HfO2 MIM capacitors