Serge Blonkowski

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

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.

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

Abstract Current leakage and breakdown of MIM capacitors using HfO2 and Al2O3–HfO2 stacked layers were studied. Conduction in devices based upon HfO2 layers thinner than 8 nm is probably dominated by tunnelling. Al2O3–HfO2 stacked layers provide a limited benefit only in term of breakdown field. Constant-voltage wear-out of samples using insulating layer thicker than 6 nm is dominated by a very fast increase of the leakage current. A two step mechanism involving the generation of a conduction path followed by a destructive thermal effect is proposed to explain breakdown mechanism.

MIM capacitance variation under electrical stress

Abstract Due to strong requirement in term of capacitance voltage linearity, MIM capacitance stability during the whole operating lifetime of the product appears to be a key issue to warrant the reliability of this device. Using a constant current stress, two effects can be noticed on the evolution of the stressed C–V characteristics: a voltage shift to negative bias and a significant increase of the capacitance. Both phenomena have been demonstrated to be strongly correlated and to have the same origin: the trapped charges in oxide, which can generate new dipoles in the dielectric and, as a result, modulate the dielectric permittivity.

Nonlinear capacitance variations in amorphous oxide metal-insulator-metal structures

An analytical model for the electric field and temperature dependence of the nonlinear dielectric susceptibility of amorphous oxides is developed and compared with experimental measurements on metal-insulator-metal capacitors. Using the model, experimental capacitance variations with applied field, as well as temperature, are tied to an increase in system entropy due to thermal expansion of the lattice. In addition, our model explains the CV-curve sign reversal (slope of the capacitance versus voltage curve) that is frequently seen for metal oxide versus SiO2 capacitors.

Filamentary model of dielectric breakdown

A dielectric breakdown model based on the phenomenological description of the nucleation and growth of filaments is proposed. This description involves different characteristic times according to the interfacial or bulk nature of the growth processes. The resulting time to breakdown distribution presents Weibull or bimodal shape according to the relative values of those characteristic times. In particular, the variation in the Weibull slope with thickness is observable when the interfacial process characteristic time is the larger. Bimodal shapes are observable when the characteristics times are in the same range and the surface scaling of the distributions influences the apparent Weibull slopes. The model is compared to experimental constant voltage stress and linear ramp voltage stress measurements made on metal insulator metal and metal oxide semiconductors structures. The physical parameters extracted are discussed. Breakdown electric fields are derived as functions of temperature, dielectric thicknes...

Dielectrical properties of metal-insulator-metal aluminum nitride structures: Measurement and modeling

The electrical properties of polycrystalline aluminum nitride (AlN) films grown by reactive dc magnetron sputtering are investigated in the transient and the steady-state regimes through metal-insulator-metal (MIM) structures with molybdenum (Mo) as metal electrodes. Measurements of current-time, current-voltage, and current-temperature characteristics are performed on AlN MIM structures. The extracted dielectric constant is 9.9. The transient current is observed to follow the empirical Curie–Von Schweidler law and its dependence on the applied field and the operating temperature is modeled. The time approach result is compared with the frequency-approach result by measuring the permittivity dispersion for low frequencies. Also, all the leakage mechanisms in AlN are identified in the steady-state regime depending on the applied field range. For a low electric field, the conduction mechanism is the Ohmic regime and the AlN resistivity is estimated to be 2.1×1015 Ω cm at room temperature. For higher electri...

Frequency Effect on Voltage Linearity of

This letter deals with the electrical and wideband frequency characterizations of metal-insulator-metal capacitors integrating medium-¿ material, ZrO2. In particular, this letter focuses on the frequency effect on the voltage linearity of these capacitors and material. The dependence of the voltage-capacitance coefficient (VCC) ¿ is, for the first time, studied from 1 kHz to 1 GHz. Intrinsic or extrinsic material origin of the VCC are discussed.

\hbox{ZrO}_{2}

Abstract The time to breakdown distribution of bilayer gate stack dielectrics is measured at nanometric scale using an atomic force microscope in conduction mode under ultra-high vacuum. The bilayer consists of a SiON interfacial layer and a HfSiON High-K layer. Thanks to the small tip/sample contact area the time to breakdown distribution of the single interfacial layer is measured separately. It is found that the Weibull parameters of the Interfacial layer distribution are the same as those of the high percentile part of the bilayer bimodal distribution. This experimentally confirms the validity of former dielectric breakdown model assumptions. Considering the fields in each layer an accurate evaluation of acceleration factors and voltage scaling of the bimodal distribution are given.

-Based RF Metal–Insulator–Metal Capacitors

For the first time, we present a Phase Change Memory (PCM) device with an optimized Ge-rich GeSbTe (GST) alloy integrated on a 12Mb test vehicle. We confirm that PCM can guarantee high data retention in extended temperature range and we provide the understanding of the high thermal stability of the two programmed states. We show how the elemental distribution reaches an equilibrium at the core of the storage element after the electrical activation of the cell, which relates to the strong opposition against crystallization of the RESET state. We also highlight the low number of grain boundaries along the conductive path of the optimized SET state, thus explaining the low drift of the resistance. Simulation results account for the experimental observations, showing how the segregation phenomena and the localization of the electronic switching impact the elemental distribution and the formation of the crystalline structure during programming.

Impact of bilayer character on High K gate stack dielectrics breakdown obtained by conductive atomic force microscopy

Hf-family compounds have been widely studied as high k gate dielectric materials, they can be elaborated in a wide range of deposition techniques but ALD and MOCVD are the most advanced. In this contribution, the deposition of pure HfO 2 is performed by Atomic Vapour Deposition, which is a sort of pulsed-mode MOCVD. The precursor, diluted into a solvent, is pulsed through specific injectors (TriJet®), micro-droplets are vaporised and distributed to the substrate through a showerhead. ATR-FTIR and Hg-probe measurements have been extensively used to evaluate the materials. The advantage of this specific MOCVD system is that it allows working within a wide range of liquid injection frequencies. Thus, we have been able to show that the frequency of injection has a huge impact on the structural and electrical properties of the material. It has been evidence that working at low frequencies is crucial in order to get good electrical behaviour. Higher temperature deposition shows also a clear benefit. An EOT of 1.15 nm with 6.10 −2 A/cm 2 at |Vfb| + 1 V, that is to say about 3 orders of magnitude below what is obtained with SiO 2 has been obtained on capacitors with TiN gate. This is a very good achievement fore pure HfO 2 deposited by MOCVD. This work has been made in the frame of MEDEA + T207 European project with the help of Air Liquide and Epichem.