Function Of Stress Time Research Articles

Electrical instability in LaLuO3 based metal–oxide–semiconductor capacitors and role of the metal electrodes

Trapping in LaLuO3 MOS capacitors with different metal nitride gates is investigated for the first time. The instability of the flat band voltage during electrical stress is monitored systematically with the pulsed C-V technique as function of stress time and voltage. Ad-hoc experiments aiming to force electron trapping in sites close to the metal/high-k interface are performed, and the role of different metal nitride gates is discussed. Trapping exhibits a power-law dependence on stress time in any investigated condition. Interpolation of the experimental data with an analytical model of trapping allows extraction of the energy level of traps involved in the capture mechanism.

Dielectric Relaxation and Reliability of Al<sub>2</sub>O<sub>3</sub>-HfO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Sandwiched Metal-Insulator-Metal (MIM) Capacitor

. In this paper, dielectric relaxation and reliability of high capacitance density metal-insulator-metal (MIM) capacitor using Al2O3-HfO2-Al2O3 sandwiched structure were analyzed. It is shown that multilayer MIM capacitor provides high capacitance density and low dissipation factor at room temperature. The dielectric relaxation voltage shows little dependence on the capacitor area. The capacitance density (C0) increases and quadratic voltage coefficient (α) decreases as a function of stress time under constant voltage stress (CVS) because of the charge trapping effect in the high-k dielectric.

Voltage and current stress induced variations in TiN/HfSixOy/TiN MIM capacitors

In this paper we have investigated the long-term reliability of TiN/HfSixOy/TiN Metal–Insulator–Metal (MIM) capacitors by using constant voltage stress (CVS) and constant current stress (CCS). No significant increase in leakage current was observed as a function of stress time. On the other hand, stress induced capacitance changes were observed due to change in quadratic and liner coefficients of permittivity nonlinearities. Stress-induced oxygen vacancy related defect formation believed to be the cause of this shift in permittivity.

Comparison of Multilayer Dielectric Thin Films for Future Metal–Insulator–Metal Capacitors: Al2O3/HfO2/Al2O3 versus SiO2/HfO2/SiO2

In this paper, two kinds of multilayered metal–insulator–metal (MIM) capacitors using Al2O3/HfO2/Al2O3 (AHA) and SiO2/HfO2/SiO2 (SHS) were fabricated and characterized for radio frequency (RF) and analog mixed signal (AMS) applications. The experimental results indicate that the AHA MIM capacitor (8.0 fF/µm2) is able to provide a higher capacitance density than the SHS MIM capacitor (5.1 fF/µm2), while maintaining a low leakage current of about 50 nA/cm2 at 1 V. The quadratic voltage coefficient of capacitance, α gradually decreases as a function of stress time under constant voltage stress (CVS). The parameter variation of SHS MIM capacitors is smaller than that of AHA MIM capacitors. The effects of CVS on voltage linearity and time-dependent dielectric breakdown (TDDB) characteristics were also investigated.

Thermal reliability of VCO using InGaP/GaAs HBTs

Degradations of InGaP/GaAs heterojunction bipolar transistor (HBT) collector current and base current subjected to cumulative long-term junction temperature stress are examined experimentally. The aged SPICE model parameters as a function of stress time are extracted from the measurement data. The VCO phase noise, tuning range, and output amplitude are studied in circuit simulation. The phase noise increases, tuning range and output amplitude decrease with increasing junction temperature.

Effects of channel thickness variation on bias stress instability of InGaZnO thin-film transistors

Here, we report on the effects of channel (or active) layer thickness on the bias stress instability of InGaZnO (IGZO) thin-film transistors (TFTs). The investigation on variations of TFT characteristics under the electrical bias stress is very crucial for commercial applications. In this work, the initial electrical characteristics of the tested TFTs with different channel layer thicknesses (40, 50, and 60nm) are performed. Various gate bias (VGS) stresses (10, 20, and 30V) are then applied to the tested TFTs. For all VGS stresses with different channel layer thickness, the experimentally measured threshold voltage shift (ΔVth) as a function of stress time is precisely modeled with stretched-exponential function. It is indicated that the ΔVth is generated by carrier trapping but not defect creation. It is also observed that the ΔVth shows incremental behavior as the channel layer thickness increases. Thus, it is verified that the increase of total trap states (NT) and free carriers resulted in the increase of ΔVth as the channel layer thickness increases.

Conduction Mechanism and Reliability Characteristics of a Metal–Insulator–Metal Capacitor with Single ZrO2Layer

In this paper, the electrical characteristics and reliability of ZrO2-based metal–insulator–metal (MIM) capacitors are investigated. High capacitance density of 15.3 fF/µm2 was achieved for ZrO2 MIM capacitors, which is acceptable for the reported MIM capacitors. Schottky emission at the low field region is not a dominant mechanism, and Frenkel–Poole emission is the dominant mechanism at the high electric field region. The extracted dynamic constant and trap energy level were 4.013 and 0.963 eV, respectively. The reduced trap energy level with increasing electric field is due to a rise in the field-induced barrier-lowering effect. The variation of α as a function of stress time under constant voltage stress (CVS) gradually decreases, while the variation of ΔCstress/C0 under CVS increases because the generation of new dipoles in the high-κ dielectric under CVS may cause charge trapping in the high-κ dielectric.

Conduction Mechanism and Reliability Characteristics of a Metal–Insulator–Metal Capacitor with Single ZrO2 Layer

In this paper, the electrical characteristics and reliability of ZrO2-based metal–insulator–metal (MIM) capacitors are investigated. High capacitance density of 15.3 fF/µm2 was achieved for ZrO2 MIM capacitors, which is acceptable for the reported MIM capacitors. Schottky emission at the low field region is not a dominant mechanism, and Frenkel–Poole emission is the dominant mechanism at the high electric field region. The extracted dynamic constant and trap energy level were 4.013 and 0.963 eV, respectively. The reduced trap energy level with increasing electric field is due to a rise in the field-induced barrier-lowering effect. The variation of α as a function of stress time under constant voltage stress (CVS) gradually decreases, while the variation of ΔCstress/C0 under CVS increases because the generation of new dipoles in the high-κ dielectric under CVS may cause charge trapping in the high-κ dielectric.

Reliability studies on Ta2O5 high-κ dielectric metal-insulator-metal capacitors prepared by wet anodization

The temperature dependence of leakage current for tantalum oxide metal-insulator-metal capacitors has been investigated over the temperature range 20–160 °C. The leakage current shows an increase with temperature and the conduction mechanism at medium to high electric fields is in agreement with the modified Poole–Frenkel model. The activation energy of the dominant deep trapping center in the oxide is calculated using this model. Constant voltage and constant current stress have been applied to the devices and the effect of stress conditions on leakage current, breakdown voltage, and high frequency capacitance-voltage have been investigated. Early oxide breakdown or time-dependent dielectric breakdown was observed during constant voltage and constant current stress, in which the former is a function of stress time and applied voltage or current. There is an increase in leakage current with time during the constant voltage stress, presumably due to generation of positive defect states. This is also apparent from the decrease in voltage with time during constant current stress. Degradation of the oxides by constant current stress and its effect on the oxide leakage current (or stress induced leakage current) at various constant current values and stress times has also been investigated and is discussed in this article.

Nanoscale probing of dielectric breakdown at SiO2/3C-SiC interfaces

Thin (6–7 nm) SiO2 layers were thermally grown onto cubic silicon carbide (3C-SiC) heteroepitaxial layers of different surface roughness and with different types of near-surface epitaxial defects. Localized dielectric breakdown (BD) was studied by electrically stressing the system using conductive atomic force microscopy (C-AFM), which constitutes a means to directly and simultaneously observe localized dielectric failure as a function of stress time and surface morphology with nanoscale lateral resolution. AFM and scanning capacitance microscopy (SCM) were used to monitor defects and the morphological and capacitive uniformities of the SiO2, respectively, while capacitance-voltage (C-V) measurements were used to evaluate the presence of charges and traps in the oxide layers. The BD kinetics was evaluated by fitting the experimental failure ratios as a function of the stress time to the failure probability described by Weibull statistics, in turn allowing a distinction to be made between defect-induced (extrinsic) and intrinsic dielectric BD events. The results give useful information about how morphological features at the 3C-SiC surface as well as trapped charges influence the BD generation in thermally grown oxides on this polytype.

Integration of Damage Differentials (IDD): General presentation and verification results

Integration of Damage Differentials (IDD) is proposed for fatigue life assessment, and such a method is completely different from any other life prediction approach. IDD can be applied under arbitrary loading including the general case of plane stress condition, that is, the stress–time functions σ x ( t), σ y ( t) and τ xy ( t) can be deterministic or random and are not restricted to be cyclic, neither with specified variations, nor the three of them proportional. Then, no reversals and cycles could be distinguished along the loading path in the σ x − σ y − τ xy coordinate space. Hence, any trial to apply again the well-known notions of loading cycles (amplitudes) and damage per cycle would conceptually fail. That is why damage differentials d D are introduced in order to be summed (integrated), where еach damage differential d D is per loading (stressing) differential d s. Two empirical factors of (material’s sensitivity to) multiaxial loading non-proportionality, f c and f τ , are involved in the definition of d D. The IDD method has been implemented in software. Results of IDD verifications under multiaxial non-proportional loadings are shown. Based on them, an empirical data bank developed so far is given for IDD parameters.

A New BSIM3v3 SPICE Model for Reliability of Hot Carrier Injection Effect in MOSFET

This paper reports a new BSIM3v3 SPICE reliability model for describing the reliability of hot carrier injection (HCI) in MOSFET, which can be widely used in traditional process MOSFET. In this work, thousands of BSIM3v3 model parameters are analyzed, seven parameters primarily affected by HCI are extracted and optimized in original BSIM3v3 source code.The I-V simulation results after parameter extraction fits the measured results very well, so an accurate new model of MOSFETs reliability model is achieved. Using the new BSIM3v3 SPICE reliability model, the idvd curves at the stress time from 10 to 50000s of the nMOSFET with 10µm gate length and 0.5µm gate width can be achieved. So the device characters variation with time can be monitored. Besides, the typical Idsat, Vth, Idlin and Gmax degradation as a function of stress time are also plotted and the lifetime of MOSFETs can be evaluated from these functions.

Energetic distribution of oxide traps created under negative bias temperature stress and their relation to hydrogen

By applying an incremental sweep technique to silicon devices subjected to negative bias temperature stress, we identify two significant peaks of recoverable oxide defects located energetically within the silicon band gap. The first peak is near midgap and is almost fully developed after ten seconds of stress while the second peak is found in the upper half of the silicon band gap and develops gradually as a function of stress time. We obtain very similar density-of-state profiles for two samples having vastly different hydrogen concentrations within the gate oxide indicating that the precursor for oxide trap creation is independent of hydrogen.

Impact of Voltage and Current Stress on TiN/HfSixOy/TiN MIM Capacitors

In this paper we have investigated the long-term reliability of TiN/HfSixOy/TiN Metal-Insulator-Metal (MIM) capacitors by using constant voltage stress (CVS) and constant current stress (CCS). No significant increase in leakage current was observed as a function of stress time. On the other hand stress induced capacitance changes were observed due to change in dielectric constant.

$\hbox{HfO}_{2}$ Gate Breakdown and Channel Hot Electron Effect on MOSFET Third-Order Intermodulation

The effect of n-channel hot electron and p-channel gate oxide breakdown (BD) on the third-order intermodulation of HfO2 MOS transistors has been studied. Both reliability physics mechanisms result in a similar shift of the intermodulation intercept point characteristics versus the absolute value of gate-source voltage. However, the device VIP3 in the subthreshold region is sensitive to BD leakage current and BD location effect. The third-order input intercept point as function of stress time was evaluated experimentally and compared with the analytical model predictions. A good agreement between the model predictions and experimental data is obtained.

New aspects for lifetime prediction of bipolar transistors in automotive power wafer technologies by using a power law fitting procedure

Bipolar transistors are part of the design manuals of almost all semiconductor wafer technologies. These design library devices must be qualified and released according to the present qualification standards, e.g. AEC (automotive electronic council) or JEDEC [Automotive Electronic Council. AEC-Q100-Rev-F; 2003; Automotive Electronic Council. AEC-Q101-Rev-C; 2005; JEDEC JP-001. Foundry process qualification guideline; 2002]. Dedicated stress tests (e.g. high temperature electrical operation (HTEO), bias temperature stress (BTS) or emitter base reverse bias (EBRB)) must be performed to check device specific drift and degradation mechanisms. A lifetime prediction must be performed on base of the determined device parameter drifts. The mentioned qualifications tests are arranged at typical device application conditions for electrical operation and temperature. Due to the breakdown behaviour of bipolar transistors the electrical operation parameters are limited to the save-operation-area (SOA). This excludes the possibility of any acceleration during these tests. Based on this fact the final check of the requested device lifetime in customer applications can be performed only by non-accelerated end-of-life tests. The paper shows a review of typical stress tests of dedicated bipolar transistors of an automotive power wafer technology. A presentation of the drift behaviour of the current gain (beta) parameter as function of stress time and qualification test is presented. In order to replace the end-of-life test requirement and to find a new approach to estimate the expected lifetime in the final device application a power law fitting procedure will be introduced. New aspects to discuss these results with respect to the defined lifetime target will be shown.

Role of hydrogen in Ge∕HfO2∕Al gate stacks subjected to negative bias temperature instability

This work investigates the role of hydrogen and nitrogen in a Ge∕HfO2∕Al gate stack by comparing the negative bias temperature instability (NBTI) characteristics with and without the surface nitridation of Ge surface prior to HfO2 deposition. Flatband voltage shift, change in interface state density, and stress induced leakage current were also monitored as a function of stress time. Virtually unchanged interface state density as a function of NBTI indicates no atomic hydrogen release from the dangling bond sites. However, the low n value in power law dependence of flatband voltage shift suggests diffusion of molecular hydrogen absorbed at the interface.

Degradation of magnetic tunnel junctions with thin AlOx barrier

The degradation of magnetic tunnel junctions (MTJs) with AlOx barrier was experimentally investigated. Constant voltage stress (CVS) measurement was carried out to monitor the time evolution of the conductance and tunneling magnetoresistance (TMR) of MTJs. The gradual increase of the stress-induced leakage current (SILC) was observed prior to the breakdown, following a power law function of stress time with an exponent of about 0.2–0.4, which is similar to the case of the ultrathin gate oxide films in MOSFETs. The measured TMR for SILC suggests that the spin-dependent current component would be involved in the early stage of degradation, while spin-independent conduction becomes dominant before the breakdown resulting in a decrease of TMR.

Sixty Thousand Hour Light Output Reliability of AlGaInP Light Emitting Diodes

Both fixed current density and variable current density stress conditions are used to study light output degradation of (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> P light-emitting diodes (LEDs) as functions of LED stress current and LED stress time. Quantification of the resulting data indicates that (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> P LED degradation, D, is a linear function of current density, J, and a logarithmic function of stress time, t, for stress times as long as 60 000 hours in duration. For stress times long enough and current densities high enough to saturate any short-term effects (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> P LED degradation is therefore quantified by the empirical equation D=D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 </sub> +D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> J+(D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> +D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> J)ln(t), where D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 </sub> , D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , and D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> are independent of LED stress current and LED stress time. Within the limits of the data presented here, this equation is shown to accurately describe light output degradation of individual LED lamps, the average degradation behavior of individual LED wafers, and the average degradation behavior of a distribution of multiple LED wafers. The resulting expression may thus provide helpful guidance in quantifying the tradeoff between LED flux and LED degradation, both of which depend linearly on current density

Determination of the contribution of defect creation and charge trapping to the degradation of a-Si:H/SiN TFTs at room temperature and low voltages

In this paper is presented a qualitative investigation upon the mechanisms that cause the shift of the electrical parameters in thin film transistors (TFT). The transistors are made of amorphous hydrogenated silicon (a-Si:H) as active semiconductor layer and substoichiometric silicon nitride (SiN) as gate insulator. The work refers to the degradation at room temperature and low positive and negative gate voltage stresses. The electrical parameters: threshold voltage (Vth), subthreshold swing (S) and flat-band voltage (Vfb) have been determined from the dependence of the drain current on gate voltage (Id–Vg) and the dependence of the capacitance on the gate voltage (C–Vg) measurements as function of stress time and bias.