Lateral PNP Bipolar Transistors Research Articles

Quantitative comprehension the impact of X-light on current gain of lateral PNP bipolar transistor

Bias emission voltage and dose-dependent current gain are the key parameters to detect the physical performance of bipolar transistors. Firstly, the effect of X-light with energy 22.1 and 25.0 keV from 109Cd on the current gain of lateral PNP bipolar transistors is measured. The substantial difference of current gain with the variation of bias and emission voltage is observed. Then, on basis of the outcomes of the nonlinear curve fitting approach, the relationship between bias voltage and emission-related current gain is successfully explained by using the model of combination Maxwell Boltzmann statistical with Bose-Einstein probability. The simulation results are in good agreement with the observed curves (current gain vs. voltage). The minimal correlation coefficient between experimental data and computed data is 0.998. In all cases considered, the mean relative error between the measured value and the model value is not more than 5.0%. Finally, the mathematical link between the parameters of current gain and voltage and the X-light dose is obtained. Therefore, using only one function, the current gain can be anticipated by the voltage and dose between bias and emission. The influence of X-light on the current gain of transverse PNP bipolar transistors is firstly discussed quantitatively.

Radiation mechanism of gate-controlled lateral PNP bipolar transistors in the hydrogen environment

Hydrogen plays a crucial role in realizing modern silicon devices. Molecular hydrogen may be found in processes of integrated circuit fabrication and packaging, such as wafer cleaning procedure, film depositions, high- and low-temperature anneal and die attachment by forming gas. It has been shown that hydrogen has strong effects on the total dose and dose rate response to bipolar devices. In order to study the relationship between hydrogen and radiation-induced products, we preform two experiments by using gate-lateral PNP transistors. In the first experiment, one set of devices is soaked in 100% hydrogen gas for 60 h and another set is not soaked, they are together irradiated at 5 rad(Si)/s to a total dose of 50 krad(Si). In the second experiment, devices are irradiated at 50 rad(Si)/s to 100 krad(Si), and then one group is annealed in 100% hydrogen gas and the other is annealed in the air for 40 h at the same temperature. The results show that the damage to devices which are soaked in hydrogen before irradiation is stronger than the devices that are not soaked, the anneal characteristics of devices in hydrogen gas are also changed more greatly than in the air. So the hydrogen can enhance the radiation and anneal damage to bipolar transistors. Using the gate-sweep technique, the radiation-induced products are separated and show that the hydrogen that enters into the transistor will cause the interface traps to increase and oxide trapped charge to decrease. The main reason is that the hydrogen can react with the oxide trapped charge to produce protons which can transport to the Si/SiO<sub>2</sub> interface, and then react with H-passivized bond to create interface trap. Based on the reaction mechanism presented in our work, a numerical model of enhanced low dose rate sensitivity including molecular hydrogen reaction and proton generation mechanism is established. The simulation results for the density of interface traps and oxide trapped charge show a trend consistent with the experimental data, which verifies the correctness of the damage mechanism. This research provides not only the basis of the study of damage mechanism of bipolar devices, but also the powerful support for hydrogen soaking irradiation acceleration method.

Quantitative study of the effect of gamma radiation on lateral PNP bipolar transistor

Bias-emission voltage and dose-dependent current gain is a key parameter in detecting the physical properties of the bipolar transistor. The first objective of this work is to measure the influences of gamma radiation on current gain in lateral PNP bipolar transistors. Substantial differences of the current gain as a function of voltage between bias and emission are observed. Then, based on the calculated results from the non-linear curve fitting method, the voltage between bias and emission-dependent current gain is theoretically explained successfully via the asymmetric peak function. The simulations agree very well with the observed curves (current gain versus voltage). The minimum correlation coefficient between the experimental and calculated data is 0.998. The average relative errors between the measured and modeled values do not exceed 9.14% in all considered cases. Finally, the mathematical relationships between the parameters, which serve to link the current gain and voltage together with dose, are obtained. Consequently, the current gain can be predicted by both voltage between bias and emission and dose using only one function. To the best knowledge of the author, the effects of gamma irradiation on the lateral PNP transistors are quantitatively discussed for the first time in current gain.

A high-order curvature compensated voltage reference based on lateral BJT

This paper presents a curvature compensated voltage reference (VR), which is based on lateral PNP bipolar junction transistor (BJT). The proposed VR is fabricated in 0.18 μm CMOS process. The circuit consists of two first-order current-mode band gap references (BGR) and a subtraction circuit. Temperature characteristics of lateral PNP BJT is utilized for temperature curvature compensation. Moreover, in order to reduce the errors introduced by the conventional subtraction circuit, an improved subtraction circuit is proposed for improving performance of curvature compensation. Test results of prototype chips show the proposed VR has an average 2.36 ppm/° C within temperature range of −40 ° C to 120 °C. Power supply rejection ratio (PSRR) of the proposed VR achieves 69.5 dB at 100 Hz.

Effects of pre-irradiated thermal treatment on ideal factor of excess base current in bipolar transistors

<sec>During the service of the spacecraft, it will be disturbed by the energetic particles and rays, and thus induce total ionizing dose (TID), displacement damage (DD) or single event effect (SEE) to generate inside the electronic system, which can seriously affect the service lifetime of the electronic components. The difference in structure and types of electronic components are less sensitive to the radiation effects, but bipolar transistor is strongly sensitive to ionizing radiation effect. As a basic component of bipolar circuits, the in-depth study of bipolar transistor ionization radiation effect is of significance for engineering.</sec><sec>It has been shown that the an amount of hydrogen can inevitably introduced from an external source during the sealing process of the devices. The KOVAR alloy is widely used as a metal cap material of bipolar transistor in the process of encapsulation. The residual gas analysis (RGA) for sealed Kovar lid packages is shown to have 1%–2% of the hydrogen in the cavity. The source of the hydrogen is generally considered to be out-gassing from the gold plating on the KOVAR. So far, the researches have focused on the study of the ionization damage effect of bipolar transistors with different structures under <sup>60</sup>Co gamma ray irradiation. There is lack of systemic study on the comparison of transistors packaged with and without cap.In this paper, we study the influence of sealed KOVAR lid packaged on ionizing radiation damage of lateral PNP bipolar transistor (LPNP) by using <sup>60</sup>Co gamma ray as an irradiation source. The semiconductor parameter analyzer is used to measure the electrical parameters of LPNP transistor during irradiation. The irradiation defects in LPNP transistors packaged with and without cap are characterized by deep level transient spectroscopy (DLTS). Experimental results show that the LPNP transistors packaged with and without cap have similar electrical characteristics. The base current increases with the total dose increasing, while the collector current remains almost constant. The degradation of LPNP transistor packaged with cap is more serious.</sec><sec>According to the excess base current varying with base-emitter voltage for the LPNP transistors packaged with and without cap, the degradation of bipolar transistor packaged with cap is more serious under the same irradiation conditions. According to the analysis of DLTS, comparing with bipolar transistor packaged without cap, the signal peak at about 300 K is shifted to the left for the bipolar transistor packaged with cap. These results indicate that the LPNP transistors packaged with cap can generate more interface states during irradiation, which is attributed to a large amount of hydrogen and water vapor out-gassing from the gold plating on the KOVAR, which is released under the thermal stress. In the sealed environment, hydrogen can only diffuse into the device cavity, and is combined with the metal material in the transistor to form metal hydride. Therefore the degradation of transistor is severe under the same irradiation condition.</sec>

Impact of nitride passivation layer on ionizing irradiation damage on LPNP bipolar transistors

Bipolar junction transistors (BJTs) are generally employed in spacecraft, due to their current drive capability, linearity and excellent matching characteristics. High-energy particles and cosmic rays in space environment remarkably affect electronic devices, especially in BJTs producing total ionizing dose, displacement damage or single event effect. Among them, ionizing irradiation effects on BJTs dominates. For BJTs, ionization damage can induce the oxide trapped charges in SiO2 layer and interface traps in Si/SiO2, resulting in more recombination base current and the degradation of current gain. Consequently, the accumulation of both oxide charges and interface traps causes an increase in the base current.#br#Passivation layer is also an important factor of the irradiation effects of BJTs. Previous works only studied the degradation of electrical properties of the devices with/without passivation layer induced by irradiation, and did not give an influence mechanisms of passivation layer on the irradiation respond of devices. Therefore, the irradiation damage mechanisms of the BJTs with or without nitride passivation layer are not clear so far.#br#In this paper, the impact of Si3N4 passivation layer on ionizing irradiation damage on lateral PNP bipolar transistors (LPNP) was studied by using 60Co gamma irradiation source. The KEITHLEY 4200-SCS semiconductor parameter analyzer was used to measure the relationship between the electrical properties of LPNP transistors and ionization dose, including the Gummel characteristics, the degradation of current gain, etc. The irradiation defects of the LPNP transistors with/without passivation layer structure were analyzed by the deep level transient spectroscopy (DLTS). The experimental results show that the electrical properties of the LPNP transistors with and without passivation layer exhibit similar characteristics. For all samples, the base current increases with increasing the total dose, while the collector current does not almost change. Compared with the LPNP transistors without Si3N4 passivation layer, the degradation of LPNP transistor with Si3N4 passivation layer is severe.#br#Based on the excess base current as a function of base-emitter voltage for the LPNP transistors with/without nitride passivation layer, the degradation of bipolar transistors with nitride passivation layer is severe under the same irradiation conditions. The DLTS analyses show that compared with the bipolar transistors without nitride passivation layer, the signal peak located at about 300 K is shifted to low temperature for the bipolar transistors with nitride passivation layer. The above results show that the LPNP transistors with nitride passivation could produce a large number of interface states with the energy level is closer to the middle of the forbidden band during the irradiation, which is attributed to a large number of hydrogen presence during the processing of fabricated passivation layer.

Dependence on Base Width and Doping Concentration of Current Degradation in Gate-controlled Lateral PNP Bipolar Transistors Exposed to Reactor Neutrons and Gamma Rays

Bipolar devices are widely used in the nuclear reactor control system, and the radiation effects on them are very important to reactor operation. The lateral PNP bipolar transistor is a radiation-sensitive structure in bipolar integrated devices. Its degradation under irradiation is the primary cause for functional failures of bipolar integrated devices. It is useful to understand the radiation response of the transistors to find better design strategies for radiation hardness. Three kinds of gate-controlled lateral PNP bipolar transistors (GCLPNPs) with different base widths and doping concentrations are specially designed to explore base current degradation induced by reactor neutrons and gamma rays. Dependence on base width and doping concentration of the degradation is analyzed in this work and the results are beneficial to radiation-hardening design of the lateral PNP bipolar transistor.

Dependence of Ideality Factor in Lateral PNP Transistors on Surface Carrier Concentration

The influence of surface carrier concentration on the ideality factor of excess base current ( $\Delta I_{B}$ ) in gated lateral PNP (GLPNP) bipolar junction transistors (BJTs) induced by 1-MeV electrons is investigated. $\Delta I_{B}$ in LPNP BJTs is impacted by the surface carrier density and radiation-induced interface traps. In GLPNP BJTs, the surface carrier concentration can be controlled by the voltage applied to a gate over the base region. The ideality factor changes after irradiation, and its dependence on emitter-base voltage ( $V_{\mathrm {EB}}$ ) is a function of gate voltage. For the irradiated devices, as the gate voltage decreases from +20 to −5 V, the ideality factor for excess base current changes from a single slope to two-slope behavior. The majority carrier concentration at the surface of the base, controlled by the gate voltage, impacts the excess base current and its ideality factor.

Ionizing/displacement synergistic effects induced by gamma and neutron irradiation in gate-controlled lateral PNP bipolar transistors

A kind of gate-controlled lateral PNP bipolar transistor has been specially designed to do experimental validations and studies on the ionizing/displacement synergistic effects in the lateral PNP bipolar transistor. The individual and mixed irradiation experiments of gamma rays and neutrons are accomplished on the transistors. The common emitter current gain, gate sweep characteristics and sub-threshold sweep characteristics are measured after each exposure. The results indicate that under the sequential irradiation of gamma rays and neutrons, the response of the gate-controlled lateral PNP bipolar transistor does exhibit ionizing/displacement synergistic effects and base current degradation is more severe than the simple artificial sum of those under the individual gamma and neutron irradiation. Enough attention should be paid to this phenomenon in radiation damage evaluation.

The effects of gamma irradiation on neutron displacement sensitivity of lateral PNP bipolar transistors

The effects of gamma irradiation on neutron displacement sensitivity of four types of lateral PNP bipolar transistors (LPNPs) with different neutral base widths, emitter widths and the doping concentrations of the epitaxial base region are studied. The physical mechanisms of the effects are explored by defect analysis using deep level transient spectroscopy (DLTS) techniques and numerical simulations of recombination process in the base region of the lateral PNP bipolar transistors, and are verified by the experiments on gate-controlled lateral PNP bipolar transistors (GCLPNPs) manufactured in the identical commercial bipolar process with different gate bias voltage. The results indicate that gamma irradiation increases neutron displacement damage sensitivity of lateral PNP bipolar transistors and the mechanism of this phenomenon is that positive charge induced by gamma irradiation enhances the recombination process in the defects induced by neutrons in the base region, leading to larger recombination component of base current and greater gain degradation.

Simulation of synergistic effects on lateral PNP bipolar transistors induced by neutron and gamma irradiation

With semiconductor device simulation software TCAD, numerical simulations of ionizing/displacement synergistic effects on 6 kinds of lateral PNP bipolar transistors induced by the mixed irradiation of neutron and gamma are carried out by means of changing the minority carrier lifetimes, adding charged traps to the oxide layer and increasing the surface recombination velocity in Si/SiO2 interface. The results indicate that ionizing/displacement synergistic effects on the lateral PNP bipolar transistors are not a simple sum of total ionizing dose effects and displacement effects, and total ionizing dose effects can enhance neutron displacement damages, leading to greater gain degradation. The physical mechanisms of ionizing/displacement synergistic effects are analyzed based on the results. The positive charge in the oxide layer and Si/SiO2 interface traps induced by gamma irradiation can enhance the recombination processes of carriers in the bulk defects induced by neutron irradiation, and this is the main cause of ionizing/displacement synergistic effects on the lateral PNP bipolar transistors.

The base current broadening effect and charge separation method of gate-controlled lateral PNP bipolar transistors

In order to study the total dose effect and hardness assurance technology for the bipolar devices, we have designed and fabricated different gate-controlled lateral PNP bipolar transistors by various technologies, and preformed 60Co-γ low-dose rate irradiation. The test results show that: 1) Irradiation characteristics of the gate-controlled bipolar transistor are strongly dependent on the fabrication technology, and the passivation layer has a great influence on the irradiation response of the device. The device with a passivation layer will have more interface traps in ionizing radiation environments, and its resistance to ionizing irradiation is greatly weakened. 2) A domestic gated-controlled lateral PNP transistor exhibited a peak current broadening effect at low-dose rate irradiation. In this paper, we analyze the mechanism of the broadening effect, and put forward a new separation method for reducing the base current broadening effect, which not only provides the basis for the design of hardened devices, but also a powerful tool for the study of the enhanced low-dose rate sensitivity of the bipolar device.

Impact of Low Temperatures $({< 125}~{\rm K})$ on the Total Ionizing Dose Response and ELDRS in Gated Lateral PNP BJTs

<?Pub Dtl=""?> Total ionizing dose characteristics and dose rate dependence are evaluated under low temperature conditions for gated lateral PNP bipolar junction transistors. The results show that the dose rate sensitivity of the examined linear bipolar circuit technology is reduced when irradiations are performed at low temperature. The results are supported by numerical simulations that model low temperature behaviors through the suppression of hole and proton transport in the irradiated oxide. These findings agree well with previous studies of CMOS technologies, which reported on the time and bias dependence of defect buildup in MOS capacitors and transistors. This study of temperature effects on the total dose and dose rate response of PNP BJTs expands upon these works by examining the impact of low temperature on ELDRS in bipolar technologies.

Modeling the Effects of Hydrogen on the Mechanisms of Dose Rate Sensitivity

The effects of hydrogen on dose-rate sensitivity are simulated using a one-dimensional (1-D) model that incorporates the physical mechanisms contributing to dose-rate effects in the metal-oxide-semiconductor (MOS) system of gated lateral pnp (GLPNP) bipolar transistors. Calculations show that molecular hydrogen cracking at positively charged defects may be a key reaction relating hydrogen and dose rate response. Comparison to experimental data on bipolar devices is in good agreement with the dose rate calculations of interface trap buildup.

Use the subthreshold-current technique to separate radiation induced defects in gate controlled lateral pnp bipolar transistors

In this paper, we design and fabricate a new test structure of bipolar device. A gate is deposited on the oxide layer covering the base region of normal lateral pnp bipolar transistor. The characteristic of drain current (collector current) versus the gate voltage is recorded by sweeping the voltage applied to the gate, then the subthreshold-current technique is used to separate the radiation induced oxide trapped charges and interface traps in the gate controlled lateral pnp bipolar transistor during 60Co- irradiation. The test structure and the measurement of the bipolar transistor used in the experiment are introduced in detail in this paper.

Quantitative separation of radiation induced charges for gate controlled later PNP bipolar transistors

A new test structure of gate controlled lateral PNP bipolar transistors designed and fabricated. An independent gate terminal is patterned on the oxide layer above the active base region of normal lateral PNP bipolar transistors. According to the gate sweep technique, by sweeping the voltage applied to the gate terminal, one can obtain the characteristic of base current versus gate voltage. The quantitative variations of oxide trapped charges and interface traps are analytically estimated and numerically calculated, and the radiation induced defects in the gate controlled lateral PNP bipolar transistors during 60Co-γ irradiation and annealing at room temperature are separated independently. The test structures and measurements of the bipolar transistors used in the experiment are introduced in detail in this paper.

Modeling the Dose Rate Response and the Effects of Hydrogen in Bipolar Technologies

A physical model describing the dose rate response and the effect of hydrogen in bipolar technologies is presented. The model uses electron-hole pair recombination and competing hydrogen reactions to explain the behaviors of bipolar devices and circuits at different dose rates. Dose-rate-dependent computer simulations based on the model were performed, and the results provide excellent qualitative agreement with the dose rate data taken on both gated lateral pnp bipolar test transistors and LM193 bipolar dual-voltage comparators. The model presented in this paper can be used to explain a variety of factors that can influence device dose rate response in bipolar technologies.

The Effects of Aging and Hydrogen on the Radiation Response of Gated Lateral PNP Bipolar Transistors

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Complex interplay between hydrogen-related defect formation and passivation is observed in irradiated bipolar transistors. Hydrogen soaking experiments are performed to evaluate the dependence of defect buildup and annealing in gated lateral bipolar transistors on hydrogen exposure. Comparisons of the radiation responses of transistors tested in 2009 to identical devices from the same wafer tested in 2003 show that aging has reduced the amount of radiation-induced interface trap and oxide trapped charge formation in most cases. These results demonstrate that the way in which the radiation response of a hydrogen-sensitive device evolves with age depends on whether hydrogen is diffusing into or out of the device, and whether the initial defect concentration favors passivation or depassivation reactions. These results strongly suggest that hydrogen exposure cannot replace low-dose-rate irradiation in ELDRS tests for bipolar devices and ICs without extensive characterization testing. </para>

Electron Capture, Hydrogen Release, and Enhanced Gain Degradation in Linear Bipolar Devices

We present evidence that enhanced low-dose-rate sensitivity (ELDRS) in lateral and substrate pnp bipolar devices can occur because of the much lower probability for electron capture by protons in SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , as compared to mobile or trapped holes. New experimental results and a critical evaluation of previous work demonstrate that, at high dose rates and/or in oxides with low concentrations of hydrogen, electrons can more easily neutralize slowly diffusing or metastably trapped holes via annihilation (recombination) or compensation (offsetting trapping) before the holes can release H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> . In contrast, at low dose rates and/or in oxides with higher concentrations of hydrogen, which can react with and modify the structure of O-vacancy-related defects, it is more likely that holes can release H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> during transport. This is because the cross section for electron capture by H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> is several orders of magnitude smaller than the electron capture cross section for a slowly moving or metastably trapped hole. This enhanced proton release at low dose rates or in oxides with high hydrogen concentrations can lead to increased interface trap formation, which is the most common source of enhanced gain degradation in lateral and substrate pnp bipolar transistors.

Determination of the origin of failure mechanism involved in the degradation of the threshold voltage of a PMOS FET associated to a lateral PNP bipolar transistor in a I2L test cells.

L'objet de cette étude est de déterminer les mécanismes mis en jeu dans la dégradation de la tension de seuil de transistors PMOS parasites associés aux transistors PNP latéraux des cellules de test d'une technologie I2L. Une nouvelle modélisation de cette dégradation tenant compte de la variation de la tension de bandes plates et de la réduction de la largeur du canal à la fois du côté drain et du côté source est proposée. Ce modèle électrique et l'analyse du procédé de fabrication montrent que cette dégradation est due au piégeage d'électrons dans l'oxyde de grille. Nous démontrons aussi que ces charges proviennent de la gravure plasma du nitrure.The aim of this study is to determinate the origin of failure mechanism involved in the degradation of the threshold voltage of PMOS FET Associated to Lateral PNP Bipolar Transistor in a I2L Test Cells. A new modelling in accordance with the physical phenomena involved in the degradation is proposed. Instead of a more general approach as previously presented, this electrical modelling of the threshold voltage is based on the same assumption, but it takes into account the shortening of the channel length on both drain and source sides and the variation of the flat-band voltage. Both, the analysis of fabrication process and the modelling, show that this degradation is due to negative trapped charges in deposited oxide and induced by nitride plasma etching Keywords:PNP latéraux, modèle électrique, piégeage d'électrons, gravure plasma; Lateral PNP Bipolar Transistor, electrical modelling, trapped charges, plasma etching.. Journal des Sciences Pour l\'Ingénieur. Vol. 8 2007: pp. 9-13