MOS器件及电路的总剂量辐射效应测试技术

介绍了半导体器件与电路的总剂量辐射效应及其测试技术,主要分析了MOS器件的效应机理、总剂量效应试验模拟源以及各种模拟源辐射环境的测量方法,最后给出了部分实验结果,并对其进行了讨论。     

高压SOI pLDMOS总剂量辐射致BV退化研究

对高压SOI pLDMOS器件总剂量辐射效应进行了研究。分析了不同偏置条件下器件击穿电压的退化机理,并使用TCAD在不同氧化层界面引入固定陷阱电荷,仿真了电离辐射总剂量效应。结果表明,总剂量辐射在FOX和BOX引入辐射陷阱电荷Q_BOX和Q_FOX。Q_FOX增加了漏极附近横向电场,降低了埋氧层电场,使击穿位置由体内转到表面,导致击穿电压退化。Q_BOX降低了埋氧层电场,降低了埋氧层压降,导致击穿电压退化。     

NMOS晶体管的总剂量辐射效应仿真

分析了MOS晶体管总剂量辐射效应的理论模型,并在此基础上给出了主要作用机理的仿真方法,用Sentaurus TCAD器件仿真软件对不同栅氧厚度的NMOS晶体管辐射前后的电学特性进行了模拟仿真,通过对比研究不同辐射总剂量下NMOS晶体管的I-V特性曲线,得出了NMOS晶体管阈值电压漂移与辐射总剂量的关系。与实验数据进行了对比验证,并准确计算出仿真中理论模型中的修正参数fot和K,使仿真结果和实验结果能够很好地吻合,为CMOS集成电路的总剂量辐射效应的仿真研究提供依据。     

银河飞腾DSP芯片总剂量辐照试验研究

利用60Co产生γ射线辐射场对国产银河飞腾DSP的总剂量效应进行了初步试验.建立了一个辐射环境下银河飞腾DSP芯片功能检测的计算机测量平台,对不同剂量率(2～10 rad(Si)/s)、不同积累剂量情况下,银河飞腾DSP的存储器、数据总线等进行了测试.试验结果表明,银河飞腾DSP在总剂量115.2 k rad(Si)情况下存储器读取和CPU内核运行功能正常.     

大规模集成电路浮栅ROM器件总剂量辐射效应

提出了一种大规模集成电路总剂量效应测试方法:在监测器件和电路功能参数的同时,监测器件功耗电流的变化情况,分析数据错误和器件功耗电流与辐射总剂量的关系.根据该方法利用60Co γ射线进行了浮栅ROM集成电路(AT29C256)总剂量辐照实验,研究了功耗电流和出错数量在不同γ射线剂量率辐照下的总剂量效应,以及参数失效与功能失效时间随辐射剂量率的变化关系,并利用外推实验技术预估了电路在空间低剂量率环境下的失效时间.     

总剂量辐射中偏压对功率管的影响研究

基于漂移扩散方程的理论模型,研究了总剂量辐射效应与偏压条件的关系,逐个分析了功率管中常用偏压条件对总剂量效应的影响。根据辐照过程中SiO₂内部和Si-SiO₂界面处感生的陷阱电荷的积累情况,推测出较恶劣的偏压条件。将40 V耐压的NLDMOS和5 V耐压的NMOS功率管在0.35 μm商用BCD工艺下进行了流片,并在不同偏压条件下进行了Co⁶⁰总剂量辐照实验,对总剂量辐照中的偏压效应进行了测试验证。实验结果证实功率管在开态偏压下的辐射退化更明显。     

星载通信电子侦察设备总剂量辐射效应及结构加固技术

本文分析了星载通信电子侦察设备的空间辐射环境及总剂量辐射效应，阐述了抗总剂量辐射效应的设计流程及设计思路，并提出了一些结构防护与设计方法。     

抗总剂量辐射华夫饼功率管版图设计

功率管在空间辐射环境下会发生沟道边缘漏电,导致功率集成电路性能退化。介绍了一种0.35 μm单片集成(BCD)工艺下基于华夫饼结构的全新功率管版图,并对普通条形栅结构N沟道功率管和新型华夫饼结构N沟道功率管进行了Co-60辐射实验。总剂量辐射使N沟道条形栅功率管发生漏电。辐射实验结果表明,经过无边缘化处理的华夫饼结构可以有效控制总剂量辐射诱发的漏电,能够大幅提升功率管的抗总剂量辐射能力。     

超高总剂量辐射下SOI MOS器件特性研究

在超高总剂量辐射下,界面电荷的改变对MOS器件的阈值电压影响将越来越显著,甚至会引起NMOS的阈值电压增加,即所谓的“反弹”现象。文章研究的SOI NMOS的阈值电压并没有出现文献中所述的“反弹”,原因可能和具体的工艺有关。另外,通过工艺器件仿真和辐射试验验证,SOI器件在超高总剂量辐射后的漏电不仅仅来自于闽值电压漂移所导致的背栅甚至前栅的漏电流,而是主要来自于前栅的界面态的影响。这样,单纯的对埋层SiO2进行加固来减少总剂量辐射后埋层SiO2中的陷阱正电荷,并不能有效提高SOI MOS器件的抗超高总剂量辐射性能。     

不同偏置下铁电存储器总剂量辐射损伤效应

对两款商用铁电存储器进行了钴源辐射试验,研究了不同偏置条件下铁电存储器的总剂量效应。使用了超大规模集成电路测试系统测试了铁电存储器的直流、交流、功能参数,分析了辐射敏感参数在辐射过程中的变化规律,研究了器件功能失效和参数退化的原因。研究表明,将铁电存储器置于不同的偏置条件下,铁电存储器的功能失效阈值不同,原因可能是偏置不同造成了辐射损伤的短板电路模块不同。     

自然操作方式下螺旋天线手机电磁辐射的数值模拟

在建立三维旋转人头模型基础上，模拟计算了真实情形下人体接受螺旋天线手机的电磁辐射剂量，研究了人体对螺旋天线辐射特性的影响，并与垂直使用方式进行了对比分析。     

Poly(3-hexylthiophene-2,5-diyl) based diodes for ionizing radiation dosimetry applications

Accurate measurements of radiation dose are essential prerequisites for the safe and effective use of ionizing radiation in diagnostic and therapeutic medical applications. Recently, dosimeters based on organic polymers have been developed for this purpose. In this work, Poly(3-hexylthiophene-2,5-diyl) (P3HT) based organic diodes were evaluated as potential radiation dosimeters by quantifying the radiation-induced photocurrent under various measurement conditions. Control devices were fabricated in which the P3HT was replaced by polystyrene (PS) for the purpose of quantifying the non-photocurrent contribution to the measured signal. Net photocurrent was determined by subtracting the signal from the PS devices from the signal in the P3HT devices under identical measurement conditions. The responses of these devices were tested in various beam qualities: 100 kVp, 180 kVp, 300 kVp and 6 MV, 18 MV photons. The influences of electric field, film thickness and dose rate on dosimeter sensitivity were investigated. The diodes produced a linear increase in current with increasing dose rate. They demonstrated an increase in sensitivity with increased instantaneous dose rate and an increase in sensitivity at the lowest average dose rates studied here. The sensitivities for different energies were 22.9 nC/Gy, 21.8 nC/Gy and 21.4 nC/Gy for 100 kVp, 180 kVp and 300 kVp, respectively; and 14.5 nC/Gy, 14.7 nC/Gy for 6 MV and 18 MV, respectively for device with P3HT thickness 29 μm.     

An integrated readout circuit for personal dosimetry with phase-shift compensation technique to improve stability

In this paper an integrated CMOS readout circuit for a radiation detector in a personal dosimeter is presented. High counting rate and low power requirements make the stability of the conventional high-pass pulse shaper a big problem. A novel phase-shift compensation method is proposed to improve the phase margin. The principle of the compensation circuit and its influence on noise performance are analyzed theoretically. A readout chip with two channels of conventional structure and one channel of the proposed structure has been implemented in a 0.35 μm CMOS technology. It occupies an area of 2.113×0.81 mm². Measurement results show that the proposed channel can process up to 1 MHz counting rate and provide a conversion gain of about 170 mV/fC at a power dissipation of 330 μW with a 3.3 V power supply. Ac-coupled to a silicon PIN detector, it successfully detects β-rays.     

Circuit related issues due to radiation in hostile environments

Various types of radiation in hostile environments cause transient and permanent changes in the devices used in complex integrated circuits. The failure of a particular IC is a function not only of the basic material and device parameter changes but also of the circuit environment in which the device is located. Circuit techniques have been developed which minimize the detrimental effects of radiation on certain types of circuits. In other cases, circuit techniques are not very effective in minimizing radiation effects. This work discusses selected issues related to the interactions between device radiation effects and circuit performance or circuit failure in a hostile radiation environment. This is not meant to be a comprehensive study of circuit effects but rather several examples are selected to illustrate the issues involved in designing circuits to operate in hostile radiation environments.     

Soft breakdown in irradiated high-κ nanolaminates

In this paper the electrical characteristics of different atomic layer deposited (ALD) high permittivity dielectric films (Al₂O₃ and Al₂O₃/HfO₂ nanolaminates) subjected to ion irradiation (25 MeV oxygen ions and 10 MeV protons) are evaluated. The capacitance-voltage (C-V) and current-voltage (I-V) characterization show that high-κ nanolaminates are more tolerant to radiation than the Al₂O₃ layers, but suffer radiation soft breakdown (RSBD) events. The main variation on the electrical characterization could be interpreted as a gradual decrease of the dielectric constant and/or as an increase of the series resistance of the device.     

Effect of ionizing radiation on MOS capacitors

A numerical model of metal-oxide-semiconductor (MOS) capacitor has been developed to investigate the effect of ionizing radiation on the characteristics of the device during exposure and also in the post-irradiated condition. The model takes into account the effect of radiation-induced changes in silicon-dioxide as well as in silicon substrate of MOS structure. It is found that the total high frequency capacitance of the device during exposure to radiation is different from its value in the post-irradiated condition. The results of the study are expected to be useful in predicting the behavior of MOS based devices operating in radiation environment.     

A study of x-ray damage effects on the short channel behavior of IGFET’s

Ionizing particles and radiation may play an important, albeit undesirable role in the processing of VLSI and ULSI circuits in that they can generate bulk charge in the gate insulator of IGFETs. In this regard, there is conflicting information in the literature on the effects of ionizing radiation on short channel phenomena in IGFETs. For example, Peckeraret al. in 1983 claimed that the effective channel length increases when positive coulombic charge is introduced during irradiation, resulting in a decrease in the short channel effect. Schrankleret al. in 1985 claimed in an experimental study, on the other hand, using 28.0 nm thick gate oxides and 0.9–10 μm channel lengths, that the effect is increased,i.e., the short channel effect begins at longer channel lengths. Wilson and Blue in 1982, in a theoretical study concluded that other than a uniform downward shift in theV _T -channel length curve due to the presence of insulator net fixed positive charge, no effect should be observed. Because of these conflicting reports, it was decided to evaluate this behavior using two different background doping levels inn-channel structures, with physical channel lengths ranging between 1.5 and 10 μm, in 0.1 and 0.5 gWcm (100) Si. To further explore the situation, gate oxide (grown at 1000° C in O₂ containing 4.5% HC1) thicknesses were varied from 17.0–35.0 nm, and the absorbed radiation dose using Al-K_α (1.5 keV) x-rays was varied between 2.4 × 10⁶ rad (SiO₂) and 2.4 × 10⁷ rad (SiO₂). For all conditions studied above, a uniform downward shift in the V_T-Channel length curve was observed, essentially corroborating the theoretical conclusions of Wilson and Blue. In addition to the above, the effects of intentionally doping the gate insulator with boron (1.2 × 10¹² B⁺ cm⁻²) implanted at 8 and 10 keV into 25.0 nm and 31.4 nm oxides, respectively, on short channel effects were evaluated for devices grown onp-type 0.5 Ω.cm substrates. Unlike the devices which did not have excess boron intentionally implanted into the gate insulator, it was found that higher concentrations of boron (2.0 × 10¹⁷ cm⁻³ in the insulator via implantation as compared to 4.2 × 10¹⁶ cm⁻³ incorporated in oxides during the oxide growth on 0.5 Ω.cm type (100) Silicon) leads to smaller short channel effects in unirradiated devices. On the other hand, these heavily doped oxides show a distinct worsening of the short channel effect after exposure to 2.4 × 10⁷ rad (SiO₂) using Al-K_α radiation. Thus, while normal devices exhibit little if any short channel improvement, or degradation following irradiation, intentionally doped insulators show an improvement in short channel characteristics prior to irradiation, and a worsening of the short channel effect following irradiation.     

Considerations for the development of radiation resistant devices and VLSI circuits

The impact of radiation on Very Large Scale Integration (VLSI) silicon technology is discussed with a focus on Complimentary Metal-Oxide Semiconductor (CMOS). Effects of total dose, transient radiation, single event phenomena, and neutron fluence on devices and circuits are presented. General approaches to mitigating radiation effects are put forth. With proper considerations, VLSI CMOS can be enhanced to achieve several orders-of-magnitude increase in radiation tolerance.     

Radiation effects in new materials for nano-devices

Exposure to radiation poses significant challenges for electronic devices, including parametric degradation, loss of data, or catastrophic failure. The challenges and solutions change significantly as new materials are introduced and feature sizes become smaller. This paper reviews the effects of radiation on electronics, with emphasis on the impact of new materials.     

A feedforward excess-phase cancellation technique for integrators

Integrators are useful analogue function blocks. A representative application of integrators is a continuous-time filter on an integrated circuit. Excess phase shift of integrators is one of the most severe problems, because excess phase shift at the unity gain frequency degrades the frequency characteristics of the filters. This paper describes a feedforward excess-phase cancellation technique. The proposed technique is applied to integrators which have feedback with an amplifier. The proposed idea is verified by experiment. It is shown that the excess-phase shift due to the gain-bandwidth product of operational amplifiers is cancelled. The proposed technique is useful for realization of integrated continuous-time filters using integrators because extra capacitors are unnecessary. An integrator with the excess-phase cancellation and a third-order leapfrog filter using the integrator are designed and demonstrated by HSPICE simulation. The integrator has a parasitic pole whose frequency is proportional to the unity gain frequency. The simulation results show that the phase characteristics are improved by the proposed technique over the wide range of the unity gain frequency.