Correlation of Hot-Carrier and Radiation Effects in MOS Transistors

The effects of processing variations on the hot-carrier susceptibility of radiation-hardened CMOS transistors have been examined. It has been determined that many process variations which enhance radiation hardness also reduce hot-carrier-induced device degradation. The interactions of radiation and hot-carrier effects are demonstrated not to be additive.     

The Effects of Co60 Gamma Radiation on MOS Diodes

MOS diodes were fabricated on silicon substrates and exposed to Co60 gamma radiation. A change in both surface state density and oxide charge density was noted. Non-irradiation annealing studies were carried out to determine the nature of the oxide charge. It was deduced on the basis of annealing data that the oxide charge was due to mobile alkali ions. The radiation was seen to cause a decrease in the oxide charge density. A model attempting to explain this change was fabricated assuming Compton scattering in the oxide. The change in semiconductor surface charge density caused by the gamma irradiation was found producable or reversible by means of elevated temperature, applied bias annealing.     

Geant4在中子辐射效应中的应用

中子辐射效应是半导体器件在辐射环境中损伤的重要因素。本文建立了中子在半导体材料中的电离和非电离能量沉积、原子空位密度的Geant4模拟方法。电离能量沉积可用于分析电离总剂量效应,非电离能量沉积可用于分析位移损伤效应。电离kerma因子的模拟结果定量解释了中子辐照在CMOS工艺单片机中引起的电离增强效应。通过原子空位密度计算了中子引入的附加陷阱密度,分析了位移损伤对电离效应的增强作用。实验和模拟结果表明,中子的电离能量沉积加剧了CMOS工艺单片机的退化。     

Neutron Radiation Effects in Junction Field-Effect Transistors

A theory is formulated for the static properties of silicon junction field-effect transistors which are compensated with defects with deep energy levels. A single effective level of an acceptortype 0.40 eV below the conduction band accounts satisfactorily for the degradation of heavily doped n-channel devices with neutron irradiation. Furthermore, based on the existence of defect levels, a frequency dependence of the transconductance is predicted and observed experimentally. The charging and discharging of the defects in the junction space-charge region can follow only at low frequencies. At higher frequencies (above 10-100 kHz at room temperature) the trapped charge cannot respond to the signal frequency very rapidly and the transconductance may be several times higher than the low frequency value.     

Radiation Effects on MOS Devices: Dosimetry, Annealing, Irradiation Sequence, and Sources

This paper reports on some investigations of dosimetry, annealing, irradiation sequences, and radioactive sources, involved in the determination of radiation effects on MOS devices. Results show that agreement in the experimental and theoretical surface to average doses support the use of thermo-luminescent dosimeters (manganese activated calcium fluoride) in specifying the surface dose delivered to thin gate insulators of MOS devices. Annealing measurements indicate the existence of at least two energy levels, or activation energies, for recovery of soft oxide MOS devices after irradiation by electrons, protons, and gammas. Damage sensitivities of MOS devices were found to be independent of combinations and sequences of radiation type or energies. Comparison of various gamma sources indicated a small dependence of damage sensitivity on the Cobalt facility, but a more significant dependence in the case of the Cesium source. These results were attributed to differences in the spectral content of the several sources.     

A Simple Model for Predicting Radiation Effects in MOS Devices

A mathematical model for the electrical consequence of charge buildup in metal-oxide-semiconductor devices has been investigated and found to be useful. It can be used (a) for comparing experimental data from different sources and (b) for making predictions of the lifetime of MOS circuits exposed to radiation in space or laboratory environments. A wide range of experimental data has been collected together and is presented in the form of a normalised oxide radiation-sensitivity parameter A, representing the probability of hole capture. The results show that the simple model, based upon a thin sheet of hole traps, must be modified when the rate of interface-state creation is commensurate with the trap filling rate but that this does not destroy its usefulness for a wide range of applications.     

超深亚微米SOINMOSFET中子辐照效应数值模拟

考虑3种特征尺寸的超深亚微米SOINMOSFET的中子辐照效应。分析了中子位移辐照损伤机理,数值模拟了3种器件输出特性曲线随能量为1MeV的等效中子在不同辐照注量下的变化关系及中子辐照环境下器件工艺参数对超深亚微米SOINMOSFET的影响。数值模拟部分结果与反应堆中子辐照实验结果一致。     

Radiation and Oxide-Metal Interactions in MOS

Radiation stability of the MOS system is controlled by the oxide-silicon and oxide-metal barriers; oxide-metal interactions and certain dopants appear to affect the radiation sensitivity. It is shown that the OS system behaves differently from the MOS system. The effect of metals have been studied with the use of aluminum, molybdenum and chromium. Chromium appears to be a desirable metal; when this electrode is used other factors also assume importance. The best results obtained with chromium gate p-enhancement transistors are: a shift of only 1.5 V (~1011 charges/cm2) with a Co-60 source depositing 2 x 107 rad(Si) or 1.5 MeV electrons depositing 1014 electrons/cm2. The change in surface mobility is small. Isothermal relaxation experiments show a wide range of activation energies, some of which are characteristic of the metal used. Studies related to the "photocurrent" flowing during irradiation appear to indicate that the prevailing model for radiation "damage" must be altered.     

The Effects of Neutron Radiation on Second Breakdown and Thermal Behavior of Silicon Transistors

A method of measuring and the subsequent analysis of this data has indicated that the "thermal time constant" of silicon diffused transistors decreases with increasing neutron dosage. Emperically, it was noted that thermal time constant degradation constants, K?, can be assigned to all devices examined. For the silicon planar devices studied, degradation constants varied from 2.6 × 10-13cm2/neut for the radiation resistant devices, to 1.4 × 10-12 cm2/neut for other devices examined. By examining previous data for single diffused transistors the thermal time constant degradation factor was 2 × 10-11 cm2/neut. The conclusion of this report is that the "thermal time constant, which is related to second breakdown, effectively degrades upon exposure to neutron radiation, thereby decreasing the safe operating area of the device. However, the extent of degradation per dose may be predictable by data presented in the text.     

辐照偏置影响MOS结构辐射损伤的机制

本文研究了CMOS集成电路在1.5MeV电子辐照下p沟MOS晶体管感生阈电压偏移与辐照期间栅偏条件的关系。在不同器件中导致阈电压负偏最大的辐照偏置,有导通与截止两种。通过研究两种代表性工艺的n型硅MOS电容,在不同偏置辐照后的辐射感生平带电压、开启电压和界面态的变化,揭示了导致p沟MOS晶体管存在两种最劣辐照偏置的机制。     

Permanent Radiation Effects in Hardened Al2O3 MOS Integrated Circuits

Complementary-symmetry metal-oxide semiconductor (COS/MOS) inverter circuits have been fabricated with aluminum oxide as channel insulator. This oxide was formed either by plasma-anodization of Al or by vapor deposition at 450°C using Al-isopropoxide. The RCA CD-4007 circuit configuration was used for these studies. The inverters were subjected to ionizing radiation with the applied gate biases encountered under normal operation (0 and +10 volts). For all units tested, the shifts in the inverter characteristics were due to shifts in the threshold voltages of the individual transistors. No measurable deterioration in gain due to interface state generation was observed. These results confirm the expected radiation hardness measured previously with MOS capacitors. Based on the net voltage shifts in the transfer characteristics of the complementary inverters, plasma-grown A12O3 shows an increase of more than an order of magnitude in hardness over units with SiO2 channel oxide. The hardness of units with deposited A12O3 was found to be intermediate to these. The increased hardness of A12O3 over SiO2 is attributed, at least in part, to the presence of trapping centers for negative charge. This serves to balance the positive trapped oxide charge so that a considerable reduction in the net oxide charge is attained.     

ADS散裂中子源材料不锈钢和钨的辐照效应(英文)

研究了80 MeV碳或85 MeV氟离子辐照在国产改进型316L不锈钢、普通不锈钢和钨中产生的辐照效应。实验结果表明,不锈钢的抗辐照性能比钨的好;它们中,国产改进型316L不锈钢具有最好的抗辐照性能。选用不锈钢做ADS散裂中子源的束窗等材料是较好的选择,采用国产改进型316L不锈钢是最佳的选择。     

中子辐射损伤等效性研究进展

为建立不同辐射源损伤评价的统一标准,制定武器抗中子辐射性能考核及验收的依据,国内外确定了中子辐射损伤等效标准源,开展了大量的等效性研究工作。本文从位移损伤函数、辐射源能谱以及二者的结合关系方面梳理了理论研究进展。从基本实验方法、效应参数及场量参数的控制趋势方面总结了实验研究进展。探讨了降低实验不确定度的方法,展望了辐射损伤等效性研究工作的方向。     

Neutron radiation effects on metal oxide semiconductor (MOS) devices

The main purpose of this study is to provide the knowledge and data on Deuterium-Tritium (D-T) fusion neutron induced damage in MOS devices. Silicon metal oxide semiconductor (MOS) devices are currently the cornerstone of the modern microelectronics industry. However, when a MOS device is exposed to a flux of energetic radiation or particles, the resulting effects from this radiation can cause several degradation of the device performance and of its operating life. The part of MOS structure (metal oxide semiconductor) most sensitive to neutron radiation is the oxide insulating layer (SiO₂). When ionizing radiation passes through the oxide, the energy deposited creates electron-hole pairs. These electron-hole pairs have been seriously hazardous to the performance of these electronic components. The degradation of the current gain of the dual n-channel depletion mode MOS caused by neutron displacement defects, was measured using in situ method during neutron irradiation. The average degradation of the gain of the current is about 35 mA, and the change in channel current gain increased proportionally with neutron fluence. The total fusion neutron displacement damage was found to be 4.8 × 10⁻²¹ dpa per n/cm², while the average fraction of damage in the crystal of silicon was found to be 1.24 × 10⁻¹². All the MOS devices tested were found to be controllable after neutron irradiation and no permanent damage was caused by neutron fluence irradiation below 10¹⁰n/cm². The calculation results shows that (n,α) reaction induced soft-error cross-section about 8.7 × 10⁻¹⁴ cm², and for recoil atoms about 2.9 × 10⁻¹⁵ cm², respectively.     

Si3N4／SiO2叠层栅MOS电容抗辐照总剂量研究

本论文主要分析了SiN4/SiO2叠层栅MOS电容总剂量效应,叠层栅MOS电容中SiO2为20nm,Si3N4厚度分别为40nm和110nm,通过辐照前后电容CV曲线的对比分析,发现CV曲线的正方向漂移主要是由于界面态电荷的作用,同时氧化物俘获电荷也起到一定的作用.同时也发现叠层栅中Si3N4越厚,将产生越多的界面态电荷和氧化物俘获电荷.     

基于中子多重性方法的~(252)Cf中子强度测量算法及实验研究

252 Cf中子发射强度的获取在核技术应用中具有重要意义,为测量其绝对发射强度,分析了一种可能的替代测量算法,该算法基于252 Cf自发裂变的中子多重性分布,并结合中子在测量系统内的衰减时间行为,在不依赖测量系统探测效率和被测样品任何信息的条件下,可给出其中子强度测量值。利用5个252 Cf镀膜中子源在中子多重性测量装置上进行了实验测量,通过测量算法获取的中子强度值与账面记录值最大相对偏差为1.41%,其结果初步验证了该算法的正确性。     

砷化镓体效应二极管中子辐照效应

本文研究了C、X和KQ等波段体效应二极管的中子辐照损伤效应。实验观察到中子辐照环境中体效应二极管低场电阻变大,工作电流和射频输出下降,VI特性变化,甚至使负阻特性消失。实验认为,器件性能退化是由中子辐照砷化镓材料的载流子去除效应引起的。