背栅偏置对不同沟道长度PDSOI晶体管总剂量损伤规律及机理研究

为研究辐照过程中施加背栅偏置对不同沟道长度部分耗尽绝缘体上硅金属氧化物半导体场效应晶体管（Partily Depleted Silicon-On-Insulator Metal Oxide Semiconductor Field Effect Transistors,PD SOI MOSFETs）电参数影响规律,及对隐埋氧化层（Buried Oxide,BOX）辐射感生陷阱电荷的调控规律及机理。基于晶体管转移特性曲线,通过提取辐射诱导晶体管阈值电压变化量,对比了不同沟道长度PD SOI在不同背栅偏置条件下的辐射损伤数据,试验结果显示：辐照过程中施加背栅偏置可以显著增强长沟晶体管的损伤。通过提取辐射在BOX层中引入陷阱电荷密度,结合TCAD(Technology Computer Aided Design)器件模拟仿真进行了机理研究,研究结果表明：短沟道晶体管在施加背栅偏置时会受到源漏电压的影响,从而使BOX层中电场分布及强度不同于长沟道晶体管,而长沟道晶体管受源漏电压的影响可以忽略。     

JFET区宽度对SiC MOSFET单粒子效应的影响

SiC MOSFET(金属-氧化物半导体场效应晶体管)关键参数——结型场效应晶体管(JFET)区宽度一直被认为是SiC MOSFET单粒子效应的主要影响因素。针对这一影响因素,以同一结构不同JFET区宽度的1.2 kV SiC MOSFET器件为对象进行单粒子效应实验,探究JFET区宽度对器件单粒子烧毁阈值电压、漏电退化阈值电压以及负栅压条件下器件性能的影响。结果表明：随着JFET区宽度的减小,漏电退化阈值电压增大;减小器件JFET区宽度可有效改善器件的抗单粒子效应能力;在负栅压条件下对器件单粒子效应也会有此效果。采用Sentaurus TCAD进行模拟仿真,模拟结果证实,JFET区宽度以及负栅压的变化会影响氧化层下JFET区内空穴的积累,随之影响氧化层电场强度,从而影响器件单粒子漏电退化,与实验结果相符。以上结果为SiC MOSFET抗单粒子效应加固提供了理论基础。     

基于SOI结构的辐照传感器的辐照响应特性研究

绝缘体上硅埋氧层(Silicon-On-Insulator Buried Oxide,SOI BOX)P型金属氧化物半导体场效应晶体管(Positive channel Metal Oxide Semiconductor,PMOS)是用于新型高灵敏度辐射探测仪的一种关键器件。通过试验研究了SOI BOX PMOS的辐照响应特性,包括辐照偏置对SOI BOX PMOS的辐射响应灵敏度的影响、不同辐射剂量率环境下的SOI BOX PMOS的灵敏度响应差异、辐照后的SOI BOX PMOS的退火特性及其对辐射响应敏感度影响,以及SOI BOX PMOS沟道宽长比与其灵敏度的关系等,并对试验结果进行了必要的理论分析。实验结果表明:正偏置辐照的器件对电荷的收集响应灵敏度明显高于零偏置辐照的器件;阈值电压的辐照变化几乎不受退火效应影响;相比于宽沟道器件,窄沟道器件的阈值电压漂移更为明显。实验研究为新型辐射剂量探测仪的研制打下了基础。     

应用于空间系统的Power MOSFET辐射响应特性

为给金属氧化物半导体场效应功率管（Power MOSFET）在航天系统中的应用提供辐照数据基础和依据。用60^Co源对将应用于空间系统的两种Power MOSFET进行了不同总剂量的辐照实验。从微观氧化物陷阱电荷和界面态的辐射感生角度，分析了Power MOSFET器件在60^Co γ，射线辐射下的总剂量和剂量率效应以及辐照后70℃退火特性。试验表明与N沟道Power MOSFET相比，P沟道Power MOSFET可能更适合空间应用。     

MOSFET辐射效应测试装置的研制

为进行金属-氧化物-半导体场效应管(MOSFET)的单粒子翻转、烧毁截面、栅穿、闭锁等辐射效应的研究,研制了MOSFET辐射效应的测试装置.记述了利用该装置在252Cf源、激光辐射效应实验装置及HI-13串列加速器上进行的MOSFET的辐射效应实验.     

功率MOSFET器件单粒子烧毁252Cf源模拟试验研究

本工作涉及利用²⁵²Cf源进行辐射效应试验研究的方法。结合功率MOSFET器件单粒子烧毁测试技术，对功率MOSFET器件辐射效应进行模拟试验研究。研究结果表明：在空间辐射环境下，功率MOSFET器件尽量使用在低电压范围内；在电路设计中附加必要的限流电阻是1种十分有效的抗单粒子烧毁措施。     

动态偏置频率对X射线总剂量效应的影响

辐射偏置条件是影响MOSFET(Metal Oxide Silicon Field Effect Transistor)总剂量辐射效应的主要因素之一,因为辐射时栅氧化层中电荷的产生、传输与俘获都与辐射偏置有关.本文采用10 keV X射线对MOSFET在不同频率的动态偏置条件下进行总剂量辐射,分析了MOSFET辐照前后的阈值电压的漂移量和辐射感生电荷对阈值电压的影响.实验结果表明,动态偏置频率越高,辐射对MOSFET电特性的影响越小,产生的辐射感生电荷越少.     

MOSFET功率管器件单粒子烧毁效应(SEB)截面测量

对MOSFET功率管进行了16^O、35^Cl、79^Br离子及高剥离态^127I离子的单粒子烧毁(SEB)效应截面测量，得到了SEB截面相对于线性能量转移(LET)值的曲线。对两种类型10片MOSFET功率管器件的SEB截面进行了测量。研究了器件在不同工作条件下，如不同的漏源电压VDs和栅源电压KGs条件下的SEB效应。在相同条件下，^127I的SEB截面比^79Br的高近两个量级。     

MOSTET器件单粒子烧毁效应（SEB）截面测量

MOSFET功率管器件是卫星关键器件之一。单粒子烧毁(SEB)效应指由于功率晶体管中的高电流状态致使器件损伤,造成永久性破坏。在本MOSFET功率管烧毁效应截面测量实验装置的探测器室中,DUT为被研究的10片MOSFET功率管器件,连同检测探测器SD2和位置灵敏探测器PPSD一起,固定在可沿焦面移动的小车上。通过92芯真空密封座引出,器件与专用MOSFET功率管测试系     

SiC MOSFET单粒子效应研究现状

伴随核能与空间技术的快速发展,SiC MOSFET等高压大功率器件的应用不断增加,其因环境中的高能粒子辐射所引起的单粒子效应问题（如单粒子烧毁、单粒子栅击穿等）也逐渐凸显。为全面深入认识该问题,首先,论证了SiC MOSFET的优势特性,及其在辐射应用中面临的关键问题。然后,整理了目前国内外关于SiC MOSFET单粒子效应的模拟计算、辐照实验及相应研究成果,总结了在SiC MOSFET单粒子效应研究中的主要关注点,并分析了SiC MOSFET单粒子效应敏感性较高的原因。最后,基于目前SiC MOSFET单粒子效应研究中仍存在的问题,展望了未来可重点关注的研究方向。通过系统总结国内外SiC MOSFET单粒子效应研究进展,希望能为研究SiC MOSFET单粒子效应物理机制以及改进其抗单粒子效应加固技术提供有价值的参考。     

Ionization radiation induced degradation of MOSFET channelfrequency response

A model is presented for the frequency response degradation of metal-oxide-semiconductor field-effect transistors (MOSFETs) exposed to ionizing radiation. It is shown that response degradation can be predicted by monitoring a single parameter, the gate-to-channel time-constant τ_GC, which is highly sensitive to the density of interface traps at the silicon-insulator interface. The value of τ_GC and its degradation with radiation dose are directly obtained by measuring the small signal impedance of a MOSFET. The measurement technique used enables the extraction of effective mobility of the inversion layer. Frequency response characteristics of two types of MOSFETs, fabricated using two different gate-insulator technologies and exposed to a total dose of 1 Mrad (Si), are compared     

Characteristics of delayed neutrons: Systematics and correlation properties

Newly found features of delayed neutron characteristics are used to evaluate total delayed neutron yields, V_d and average half-lives, T, of delayed neutron precursors from fast neutron induced fission. On this basis different sets of time dependent parameters (Y_i, T_i) and V_d values obtained using the summation method are evaluated.     

Effects of total-dose irradiation on gate-all-around (GAA) devices

The response of gate-all-around (GAA) MOS transistors to dose irradiation is quite different from that observed on other types of silicon-on-insulator (SOI) MOSFETs. In regular SOI MOSFETs, edge leakage increases substantially faster than the main transistor leakage upon creation of oxide charges due to the irradiation. The GAA MOSFET behaves in the opposite way; the shift of edge threshold voltage upon creation of charges in the oxide is smaller than that of the main transistor. As a result, a kink develops in the subthreshold characteristics of regular SOI MOSFETs upon irradiation, while the original subthreshold kink of GAA devices disappears when the device is irradiated     

Measurement of the Fermi potential of diamond-like carbon and other materials

The Fermi potential V_f of diamond-like carbon (DLC) coatings produced with laser-controlled vacuum arc deposition and that of diamond, Al, Si, Be, Cu, Fe and Ni was measured using two different methods, (i) transmission of slow neutrons through foils in a time-of-flight experiment and (ii) cold neutron reflectometry (CNR). For diamond-like carbon in transmission we obtain V_f = (249 ± 14) neV. This is approximately the same as for beryllium and consistent with the theoretical expectations for the measured diamond (sp³) content of 45%. For an sp³-content of 67%, we find V_f = (271 ± 13) neV from reflectometry, again in agreement with theory. These findings open new perspectives in using DLC as storage volume and neutron guide coatings for ultracold neutron sources.     

S-wave Neutron Strength Function of Ta-181

A method for correcting leakage currents is described to predict the radiation-induced threshold voltage shift of sub-micron MOSFETs. A practical model for predicting the leakage current generated by irradiation is also given on the basis of experimental results on 0.8-μm process MOSFETs. The constants in the threshold voltage shift model are determined from the “true” I-V characteristic of the MOSFET, which is obtained by correction of leakage currents due to characteristic change of a parasitic transistor. In this way, the threshold voltage shift of the n-channel MOSFET irradiated at a low dose rate of 2 Gy(Si)/h was also calculated by using data from a high dose rate irradiation experiment (100 Gy (Si)/h, 5h). The calculated result well represented the tendency of measured data on threshold voltage shift. The radiation-induced leakage current was considered to decay approximately in two exponential modes. The constants in this leakage current model were determined from the above high dose rate experiment. The response of leakage current predicted at a low dose rate of 2 Gy(Si)/h approximately agreed with that measured during and after irradiation.     

全脑全脊髓放疗中静态调强和容积调强的剂量学对比

回顾性选取2019年在我院放疗中心接受全脑全脊髓照射(CSI)的病人20例,勾画靶区和危及器官(OAR)后,传输至Oncentra 4.1治疗计划系统,对全脑全脊髓放疗采用静态调强(ss-IMRT)和容积调强(VMAT)两种放疗技术进行计划,分别计算两种技术的适形指数(CI)、均匀指数(HI)、107%处方剂量线所包含的靶区体积(V₁₀₇)、靶区内最大剂量点剂量值(D_max)、危及器官受量、正常组织(NT)受量、机器跳数和治疗时间并进行比较,比较两种调强方法的剂量学差异。结果表明,采用VMAT技术,靶区覆盖度、CI、HI、V₁₀₇、D_max、OAR受照量等参数优于ss-IMRT技术,治疗时间和机器跳数也明显减少。但靶区外正常组织(NT)低剂量的辐射区域增大。说明在CSI中,VAMT优于ss-IMRT 具有优势,但接受CSI患者大多是儿童,低剂量的辐射区域是否增加不良反应及其对临床影响有待于进一步研究。     

NAND型Flash存储器总剂量效应实验研究

针对镁光公司的4种NAND型Flash存储器,开展了不同辐照偏置下的总剂量效应实验及不同工艺尺寸器件的静态加电辐照实验。实验结果表明,器件在静态加电和动态辐照偏置下的总剂量效应相似,而与不加电辐照偏置下的总剂量效应不同。不同工艺尺寸器件的敏感参数有相同的变化趋势,由于受其他因素的综合影响,各敏感参数并不随工艺尺寸单调变化。     

Measurements of distribution of self-bias potential on an RF-plane electrode in plasma etching devices

The self-bias potential (V_dc) induced on an RF-powdered electrode (153 mm Ø) in a plasma is measured using electrical probes which are buried in, de-insulated from, and RF-connected to the electrode. The configuration of the probes allows to study the distribution of V_dc discretely on the electrode. The potential is homogeneous in the absence of external magnetic field. In the presence of a homogeneous magnetic field parallel to the electrode, it is reduced and a monotonous gradient takes place in its distribution due to the plasma shift induced by E × B drift. When the magnetic field is rotated along the axis of the RF-electrode at a frequency less than 50 Hz, the distribution, which is almost identical to the one in a static field, rotates with the magnetic field. On the coordinate system rotating with the magnetic field, the probes are regarded to be rotating. The potential distribution is obtained as a continuous function of the azimuthal angle. Thus the rotation of the field provides information for the experimental interpolation.     

Investigation of sensitivity and threshold voltage shift of commercial MOSFETs in gamma irradiation

This article is about the absorbed-dose-dependent threshold voltage shift of the MOSFET transistors.Performance of the MOSFETs has been tested in different gate voltages.Sensitivity of the transistors for 662 ke V gamma ray is studied in 1–5 Gy dose range.It was found that for transistors irradiated in biased mode,significant changes in the threshold voltage occurred,and the sensitivity to gamma rays increased with the bias voltage.