Local Lifetime Control Research Articles

Localized Lifetime Control of 10 kV 4H-SiC PiN Diodes by MeV Proton Implantation

In this paper, proton implantation with different combinations of MeV energies and doses from 2×109 to 1×1011 cm-2 is used to create defects in the drift region of 10 kV 4H-SiC PiN diodes to obtain a localized drop in the SRH lifetime. On-state and reverse recovery behaviors are measured to observe how MeV proton implantation influences these devices and values of reverse recovery charge Qrr are extracted. These measurements are carried out under different temperatures, showing that the reverse recovery behavior is sensitive to temperature due to the activation of incompletely ionized p-type acceptors. The results also show that increasing proton implantation energies and fluencies can have a strong effect on diodes and cause lower Qrr and switching losses, but also higher on-state voltage drop and forward conduction losses. The trade-off between static and dynamic performance is evaluated using Qrr and forward voltage drop. Higher fluencies, or energies, help to improve the turn-off performance, but at a cost of the static performance.

Improvement of Q rr –I DSS and dynamic avalanche of field-plate MOSFET by local lifetime control on the cathode side

Reducing the reverse recovery charge (Q rr) is effective for reducing switching loss in field plate (FP)-MOSFETs. A lifetime killer is utilized to reduce Q rr while increasing the leakage current in the off-state. Device simulation shows that a local lifetime killer on the cathode side successfully improves the trade-off between Q rr and I DSS in comparison with that of a uniform lifetime killer. A known issue of cathode lifetime killers is overshoot voltage by hard recovery. However, the overshoot voltage of FP-MOSFET decreases with a cathode lifetime killer owing to an internal snubber, which is a feature of FP-MOSFETs. An internal snubber with a large series resistance causes a dynamic avalanche by both the increase of FP potential and excess carriers in high-speed operation. The cathode lifetime killer also improves dynamic avalanche by excess carriers. Consequently, the cathode lifetime killer is preferable for high-speed FP-MOSFETs because the Q rr–I DSS trade-off and the trade-off between dynamic avalanche and I DSS are effectively improved.

Single Event Burnout Hardening Technique for High-Voltage p-i-n Diodes With Field Limiting Rings Termination Structure

High-voltage p-i-n diodes for space applications are sensitive to single event burnout (SEB), which may cause the failure of the entire electronic system. This article describes the SEB failure mechanism of high-voltage p-i-n diodes with field limiting rings (FLRs) termination structure, based on the electro-thermal coupled transient simulation model in the Sentaurus TCAD simulator. The simulation results show that the catastrophic failures result from the intense local heating at the edge of the main junction, because the high electric field strength at this region induces strong impact ionization of the charge carriers. The strike at the edge of the main junction shows the strongest sensitivity to SEB since the energetic particle-induced carriers are deposited exactly at the high electric field region. Then, a novel SEB hardening technique of localized carrier lifetime control at the edge of the main junction region is proposed based on the analysis on the failure mechanism. Our simulation results demonstrate that the reduction of the localized carrier lifetime can alleviate the peak electric field and reduce the local heat accumulation, thereby improving the SEB performance of high-voltage p-i-n diodes.

Local Lifetime Control in 4H-SiC by Proton Irradiation

The effect of local lifetime control by proton irradiation on the OCVD response of a 10 kV SiC PiN diode was investigated. Carrier lifetime was reduced locally by irradiation with 800 keV protons at fluences up to 1x1011 cm-2. Radiation defects were characterized by DLTS and C-V profiling; excess carrier dynamics were measured by the OCVD and analyzed using the calibrated device simulator ATLAS from Silvaco, Inc. Results show that proton implantation followed by low temperature annealing can be used for controllable local lifetime reduction in SiC devices. The dominant recombination centre is the Z1/2 defect, whose distribution can be set by irradiation energy and fluence. The local lifetime reduction, which improves diode recovery, can be monitored by OCVD response and simulated using the SRH model accounting for the Z1/2 defect.

Accurate SPICE Modeling of Reverse-Conducting IGBTs Including Self-Heating Effects

In this paper, a temperature-dependent compact SPICE model of reverse-conducting IGBTs (RC-IGBTs) is presented. The proposed solution is based on a quasi-two-dimensional (2-D) approach, with the use of IGBT and p-i-n diode subcircuits suitably connected to take into account the inner interactions among the two devices. The resulting device model is derived through physical considerations on the RC-IGBT internal behavior, carried out by means of wide area TCAD 2-D simulations. Transversal current path, localized lifetime control effects, and turn-on dynamics are also included into the model. The model shows good robustness properties, even in demanding numerical conditions. Validation of the SPICE model with experiments performed on a 1.2-kV 30-A commercial device, in both static and dynamic conditions, demonstrates its remarkable correctness and accuracy. To further confirm the applicability of the proposed model in real-operating conditions, a quasi-resonant converter has been realized and the measurements on the realized circuit have been successfully compared with the results obtained with the proposed model.

Comprehensive physics-based compact model for fast p-i-n diode using MATLAB and Simulink

In this study, a physics-based model for the fast p-i-n diode is proposed. The model is based on the 1-D Fourier-based solution of ambipolar diffusion equation (ADE) implemented in MATLAB and Simulink. The physical characteristics of fast diode design concepts such as local lifetime control (LLC), emitter control (EMCON) and deep field stop are taken into account. Based on these fast diode design concepts, the ADE is solved for all injection levels instead of high-level injection only as usually done. The variation of high-level lifetime due to local lifetime control is also included in the solution. With the deep field stop layer taken into consideration, the depletion behavior in the N-base during reverse recovery is redescribed. Some physical effects such as avalanche generation and carrier recombination in the depletion region are also taken into account. To be self contained, a parameter extraction method is proposed to extract all the parameters of the model. In the end, the static and reverse recovery experiments for a commercial EMCON diode and a LLC diode are used to validate the proposed model. The simulation results are compared with experiment results and good agreement is obtained.

Research of Single-Event Burnout in Power Planar VDMOSFETs by Localized Carrier Lifetime Control

This paper presents 2-D numerical simulation results of single-event burnout (SEB) in power planar vertical double-diffused MOSFET (VDMOSFET) with localized carrier lifetime control. A low carrier lifetime control region (LCLCR) is introduced to accelerate the recombination rate of the generated holes caused by an ion's impact. The optimal localized range with LCLCR in epitaxial layer has been investigated. The SEB inhibition mechanism with LCLCR is analyzed and discussed. A VDMOSFET with localized LCLCR can operate like a normal VDMOSFET and can have improved SEB performance effectively. In addition, the leakage current density in breakdown characteristics of VDMOSFET is studied based on the variation of carrier lifetime.

A New Method to Increase the Doping Efficiency of Proton Implantation in a High-Dose Regime

Besides the application of local lifetime control, proton implantations can be used to create deep donor profiles in crystalline silicon. At a certain annealing temperature, the maximum hydrogen-related donor (HD) concentration is limited to a few 1015 cm-3 in the end-of-range depth of the radiation damage profile. This behavior is explained with a passivation of the shallow donors due to an excess supply of hydrogen at high proton doses. The impact of hydrogen remaining in the substrate from prior processing steps is investigated. As a countermeasure to the over-decoration effect, a pre-annealing step at elevated temperatures is investigated. This procedure is fully applicable in a commercial manufacturing environment. Experimental results from spreading resistance measurements are shown that clearly show the beneficial effect of the pre-conditioning. DLTS results of pre-conditioned samples are reported, that show a dominant deep defect level that was previously assigned to be vacancy related.

Suppression of reverse recovery surge voltage of silicon power diode by adjusting trap energy levels through local lifetime control

To suppress the reverse recovery surge voltage of silicon power diodes, the effects of adjusting trap energy levels through local lifetime control were investigated by device simulation and theoretical analysis of the Shockley–Read–Hall (SRH) model. In general, local lifetime control techniques localize carrier traps at the anode side of a diode and optimize the carrier lifetime profile to suppress surge voltage. However, the suppression effect of a certain localized trap density distribution on surge voltage varies with a change in trap energy level, even if the trap density distribution is the same. It became clear that deep trap energy levels suppress surge voltage more than shallow trap energy levels at 1000 A/cm2 or less. Thus, deep trap energy levels such as Et − Ei = 0.0–0.2 eV are favorable for suppressing surge voltage in almost all power devices.

High-Power Silicon p-i-n Diode With the Radiation Enhanced Diffusion of Gold

Fast recovery p-i-n diode with anode p-n junction modified by the radiation-enhanced diffusion (RED) of gold is presented. The RED of gold is shown to provide the local lifetime control of excess carriers, the compensation of n-base doping profile from n-type to p-type, and the enhancement of concentration of two gold-related deep levels. The deep level Au <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-/0</sup> (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> -0.549 eV) controls the low-level lifetime, whereas the gold-hydrogen pair (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> -0.215 eV) the high-level lifetime. This feature eliminates the drawback of negative temperature coefficient of forward voltage drop of the RED with palladium and platinum, where only a single deep level, which controls the high-level lifetime, is enhanced. The RED of gold provides the maximal reverse bias safe operation area at the annealing temperature of 600°C, whereas the RED of palladium at 650°C.

Experimental Detection and Numerical Validation of Different Failure Mechanisms in IGBTs During Unclamped Inductive Switching

The physics of the different failure modes that limit the maximum avalanche capability during unclamped inductive switching (UIS) in punchthrough (PT) and not PT (NPT) insulated-gate bipolar transistor (IGBT) structures is analyzed in this paper. Both 3-D electrothermal numerical simulations and experimental evaluations support the theoretical analysis. Experimental results for UIS test show that, at low time duration (or inductance value) of the test, the UIS limit moves from energy limitation to current limitation. While the energy limitation is well known, the current-limited failures are less studied. In this paper, the current limit for UIS test is analyzed in detail, and the cause is attributed to a filamentary current conduction due to the presence of a negative differential resistance (NDR) region in the IC- VCE curve in breakdown. The filamentary current conduction locally increases the current density causing early device latch-up and possible device failure at a current much lower than the one dictated by energy limitations. The physical parameters that affect both the onset of NDR region and the failure current are discussed for both an NPT trench IGBT structure with a local lifetime control and a PT trench IGBT structure with a field-stop layer.

Compact model of the IGBTs with localized lifetime control dedicated to power circuit simulations

Abstract The physics-based IGBT sub-circuit compact model which can successfully include the effects of the localized lifetime control (LLC) on device electrical performance has been described in this paper. The model of non-punch trough IGBTs with different locations of LLC region is developed and its accuracy is verified based on the agreement with the results of two-dimensional numerical simulations of LLC effects in IGBTs. The models have been implemented in SPICE for investigation of the total power losses in the single phase Pulse Width Modulated (PWM) inverters.

Neon implantation and the radiation enhanced diffusion of platinum for the local lifetime control in high-power silicon diodes

About 10 MeV helium and 120 MeV neon implantations were used for the local lifetime control of silicon power diodes with subsequent annealing at 200 °C. DLTS measurements show that the concentration ratio between VO (–/0) pairs and divacancies V 2 ( – / 0 ) after the implantation of neon is close to one in agreement with the data published for other heavy ions. The implantation dose to achieve the same point at the technology curve of the diodes under test was found about 10 times lower for the neon compared to helium. The radiation enhanced diffusion (RED) of platinum at 725 °C was evaluated both for the enhancement by implantation of helium and neon. The electrical parameters of silicon diodes (carrier lifetime, voltage drop, leakage current and reverse recovery) were compared. One order lower implantation dose of the neon compared to that of the helium was found necessary to obtain the same improvement of electrical parameters. The RED of Pt using the neon implantation was found functional in a similar way to that of the helium. The reduction of carrier lifetime, which would be normally sufficient for robust diodes, was found for the doses of neon at about 1 × 10 13 cm −2. However, the simultaneous increase of background doping concentration at the end of range of neon, which increases electric field, was found responsible for the decreased static breakdown voltage, decreased turn-off ruggedness and increased leakage current.

Physical Modeling of Fast p-i-n Diodes With Carrier Lifetime Zoning, Part II: Parameter Extraction

In this paper, a parameter extraction procedure for high-voltage diodes with local lifetime control is proposed. It is designed for use with the physics-based diode model described in Part I, which is capable of simulating diodes with local lifetime control. The parameter extraction procedure described requires a forward characteristic and a reverse recovery measurement. The parameter extraction procedure is illustrated using finite-element simulations. The physics-based model using the parameters extracted is then compared with experimental results.

Exploration of Power Device Reliability Using Compact Device Models and Fast Electrothermal Simulation

This paper presents the application of compact insulated gate bipolar transistor and p-i-n diode models, including features such as local lifetime control and field-stop technology, to the full electrothermal system simulation of a hybrid electric vehicle converter using a lookup table of device losses. The vehicle converter is simulated with an urban driving cycle (the federal urban driving schedule), which is used to generate transient device temperature profiles. A methodology is also described to explore the converter reliability using the temperature profile, with rainflow cycle counting techniques from material fatigue analysis. The effects of ambient temperature, driving style, and converter design on converter reliability are also investigated.

Physical Modeling of Fast p-i-n Diodes With Carrier Lifetime Zoning, Part I: Device Model

This paper presents the development and implementation of a physics-based diode model which can simulate aspects of high-voltage diodes such as snappy recovery during punch-through and the modified carrier density profile due to local lifetime control. It uses a Fourier series solution for the ambipolar diffusion equation in the lightly doped base region. The model is compared with finite-element device simulations. A parameter extraction procedure for the diode with lifetime control is proposed in Part II.

Dynamic avalanche in diodes with local lifetime control by means of palladium

The increase of the static breakdown voltage and the reduction of dynamic avalanche in a fast recovery 2.5kV/150A P-i-N diode subjected to the radiation enhanced diffusion of a palladium are discussed. The in-diffusing palladium compensates the doping profile in a lightly doped N-base close to the anode junction. Using a device simulation, the increase of the breakdown voltage and the reduction of the dynamic avalanche are explained by the reduction of peak electric field in the additional low-doped P-type layer created by the compensation effect. This is presented for both a dc and transient device operation and confirmed experimentally as well. An improved technology curve for the static versus recovery losses at a high line voltage has been obtained. A high thermal budget of deep levels and a low leakage current are additional benefits of the method.

Local lifetime control in silicon power diode by ion irradiation: introduction and stability of shallow donors

Enhanced formation of shallow donors (SDs) in hydrogen or helium-irradiated and subsequently annealed float‐zone n-type silicon is investigated. Ion energies, irradiation fluences and annealing temperatures were chosen in ranges typically used for local lifetime control in silicon power devices. Introduced radiation defects and SDs were investigated by deep-level transient spectroscopy and C–V profiling. Results show that radiation damage produced by helium ions remarkably enhances formation of thermal donors (TDs) when the annealing temperature exceeds 375°C, i.e. when the majority of vacancy-related recombination centres anneal out. Proton irradiation introduces hydrogen donors (HDs) which form a Gaussian peak at the proton end-of-range. Their concentration linearly increases with proton fluence and changes dramatically during post-irradiation annealing between 100 and 200°C since HD constituents are reacting with radiation damage. Their annealing in this temperature range is influenced by the electric field. If annealing temperature exceeds 400°C, HDs disappear and the excessive shallow doping is caused, as in the case of helium irradiation, by TDs enhanced by radiation damage. Shallow doping introduced by both hydrogen and helium can have a detrimental influence on blocking voltage of power diodes if high irradiation fluences or wrong annealing conditions are chosen.

Radiation-Enhanced Diffusion of Palladium for a Local Lifetime Control in Power Devices

Palladium (Pd) diffusion from a surface layer enhanced by defects from a helium (He) irradiation is shown to provide a local lifetime control in a power p-i-n diode annealed between 350degC and 700degC. An open-circuit voltage decay lifetime measurement is used to identify temperature ranges in which one of two lifetime control mechanisms takes part. Spreading resistance measurements show the doping compensation at the anode junction caused by defects after the Pd diffusion below 725degC. Locally modified doping profiles by introduced defects cause significantly lowered dynamic avalanche (DA) during fast reverse recovery compared to the standard He irradiation as confirmed also by device simulation. Advanced shaping of a shallow doping profile, reducing avalanche generation in the area of peaking electric field under a reverse bias, is suggested as an additional method to suppress the DA in power devices. The diffusion at 650degC gives the best static and dynamic parameters. Breakdown voltage and leakage current are those of untreated diode. Turn-off losses close to the SOA limit are also much lower than in the standard He irradiation, and thermal characteristics are better than after the traditional high-temperature diffusion.

Improvement of 4H-SiC Power p-i-n Diode Switching Performance Through Local Lifetime Control Using Boron Diffusion

A comparison is carried out of the switching characteristics of 4H-SiC conventional p-i-n rectifiers, where the p-layer is formed by aluminum doping during epitaxial growth, with that of p-i-n diodes, where the p-layer is formed by codiffusion of aluminum and boron. It is demonstrated that p-i-n diodes that are produced by high-temperature diffusion exhibit better switching capability as compared to epigrown p-i-n diodes. The improved behavior is attributed to the reduced lifetime region that is created by the diffused boron layer. Also, the reduced lifetime region was implemented in a SiC conventional epitaxial p-i-n structure by boron diffusion through the epitaxial aluminum-doped p+ layer; the switching behavior of such a hybrid p-i-n diode is identical to that of the diffused one. The improvement of reverse-recovery characteristic is attributed to the effect of localized lifetime control by recombination centers that are created by diffused boron