浮栅晶体管不同射线剂量响应特性研究

针对浮栅晶体管在不同射线下的响应差异问题,进行了⁶⁰Co-γ射线、25 MeV质子和1 MeV电子的辐照试验,研究了不同射线下浮栅晶体管的剂量响应差异。采用蒙特卡罗方法对器件灵敏区的吸收剂量进行了修正。通过中带电压分离出界面陷阱电荷,分析了不同射线下电离辐射响应差异的微观机理。研究结果表明,在等效剂量下,质子辐照后电离响应特性与⁶⁰Co-γ射线较为接近,电子辐照后响应程度略低于质子和⁶⁰Co-γ射线。对器件灵敏区的吸收剂量进行修正后,三种射线下的剂量响应特性差异降低。质子辐照后界面陷阱电荷数量多于⁶⁰Co-γ射线和电子射线。试验研究为浮栅晶体管辐照传感器的研制提供参考。     

偏置对PMOS剂量计辐照响应的影响

研究了不同偏置条件对PMOS探头样品辐照响应的影响.在－1～1MV/cm的电场范围内,获得了偏置对PMOS剂量计辐照响应灵敏度和线性度的影响规律.利用“空穴陷阱薄层(Hole Traps Sheet)”模型,结合辐射感生界面电荷的栅偏置电场相关性,分析了实验结果.     

PMOS剂量计的稳定性研究

在室温条件下 ,研究了辐照偏置、总剂量和剂量率对 PMOS剂量计辐照剂量记录 -阈电压的稳定性影响 ,观察了辐照后阈电压在不同栅偏条件下的变化趋势和幅度。分析认为慢界面陷阱中电荷的“充放电”是造成不稳定的首要原因。结果表明 ,该种由慢界面态造成的阈电压变化在每次开机测量下具有重复性。讨论了在 PMOS剂量计中提高稳定性的办法。     

偏置条件对NMOS器件X射线总剂量效应的影响

采用10 keV X射线,对NMOSFET在不同偏置条件下进行总剂量辐射,分析了辐照前后辐射感生的氧化物陷阱电荷与界面态电荷对MOS器件阈值电压的影响以及辐射导致漏电现象.实验结果表明,对于NMOSFET,On偏置条件是最劣偏置条件,Off偏置条件是最优偏置条件.     

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。     

MOS栅氧的界面特性和辐照特性研究

通过交流电导法,对经过不同时间N₂O快速热处理(RTP)的MOS电容进行界面特性和辐照特性研究。通过电导电压曲线,分析N₂O RTP对Si-SiO₂界面陷阱电荷和氧化物陷阱电荷造成的影响。结论表明,MOS电容的Si-SiO₂界面陷阱密度随N₂O快速热处理时间先增加再降低;零偏压总剂量辐照使氧化层陷阱电荷显著增加,而Si-SiO₂界面陷阱电荷轻微减少。     

SOI器件X射线与60Co γ射线总剂量效应比较

为进行10 keV X射线和60Co γ射线总剂量辐射效应的比较,采用这两种辐射源对SOI (Silicon-on-Insulator) n-MOSFET在不同偏置条件下进行总剂量辐照试验,分析了SOI NMOS器件在两种辐射源下辐照前后的阈值电压的漂移值并进行比较.实验结果表明,SOI NMOS器件的前栅特性中X射线与60Co γ射线辐照感生阈值电压漂移值的比值α随总剂量增加而增大,而背栅特性中α值在不同偏置条件下变化趋势是不同的;在总剂量为1×106 rad(Si)时,前栅器件α值为0.6～0.75,背栅器件α值为0.76～1.0.     

nMOSFET低能X射线辐照特性研究

讨论了MOSFET的辐照损伤机理,通过低能（10keV）X射线辐照试验,分析了不同X射线辐照总剂量、不同剂量率对nMOSFET单管的转移特性以及阈值电压的影响。结果表明X射线辐照对nMOSFET的阈值电压变化的影响与^60Co辐照影响的规律基本一致。     

双极晶体管ELDRS实验及数值模拟

对典型双极晶体管的低剂量率辐射损伤增强效应进行了实验和数值模拟研究。选取了两种类型的双极晶体管,利用⁶⁰Co放射源开展了不同剂量率下的辐照实验,分析了双极晶体管基极电流等参数的变化规律;建立了衬底型NPN晶体管理论模型,利用半导体模拟软件模拟了载流子在氧化层中的输运、捕获及释放等物理过程,得到了NPN晶体管基极电流随总剂量和剂量率的变化规律。结果表明,双极晶体管在不同剂量率下表现出低剂量率辐射损伤增强效应,主要是因为高剂量率和低剂量率下晶体管基区氧化层内产生的氧化物陷阱电荷所形成的空间电场不同。     

MNOS电容辐照吸收剂量计的研究

从理论上给出了具有存储特性的 MNOS电容在存储电荷后经受γ射线辐照的响应规律 ,并利用这一特性制作电子辐照吸收剂量计。采用 L PCVD工艺制作了具有存储特性的 MNOS电容 ,经自行研制对存储电荷干扰极小的 MNOS电容辐照实验测试系统 ,对样品进行了 60 Co辐照响应规律的研究。结果表明 :MNOS电容电子辐照剂量计适用于 10 3 ～ 10 5Gy范围内的累计剂量的测量。这种新型剂量计的优点是 :一次性校准可重复多次使用并可直接读数的电子测量方式 ,便于测量自动化 ,非常适用于太空飞行器和核技术应用中累计剂量的测量。     

MOS器件的X射线辐照效应

研究了在10keVX射线辐照情况下，MOS器件的阈值电压随总剂量和剂量率的改变而变化的趋势。实验结果表明，辐照后，与用Co^60作为辐射源辐照所做实验结果明显不同的是，NMOS器件的阈值电压漂移幅度远大于PMOS器件的漂移幅度。文中对这种现象进行了讨论。     

Neutron irradiation of insulated gate field effect transistors

Insulated gate field effect transistors and polysilicon-gated capacitors were irradiated with fast (10 keV <E < 2 MeV) neutrons. As expected, damage to the bulk silicon was detected as a degradation in the minority carrier lifetime. Optically assisted electron injection was employed for the first time to examine neutral electron trap and fixed positive charge generation in the gate insulator of the devices. While fixed positive charge densities of ≤6 x 10¹⁰ cm⁻² were detected, little or no neutral electron trap generation was observed. The small density of coulombic defects observed in the insulator could be accounted for fully by the known flux of gamma rays associated with the neutron irradiation process. This indicates that fast neutrons passing through a thin gate oxide do not produce significant amounts of damage in the oxide. Somewhat surprisingly, it was found that 1.5 keV X-rays created similar lifetime degradation effects in the bulk silicon, as did fast neutrons, even though this photon energy is not believed to be capable of producing bulk damage in the form of atom displacement in either the semiconductor or the insulator. The minority carrier lifetime of the silicon could be restored to initial values following either neutron or x-ray exposure by annealing in H₂ for 30 min at 400° C.     

Radiation-stimulated relaxation of internal stresses in homoepitaxial gallium phosphide films

The electroreflection method is used to study the E ₀ and E ₀ + Δ₀ electron transitions in homoepitaxial n-GaP (111) films with the electron concentration of 5.7 × 10²³ m^?3 before and after irradiation with ⁶⁰Co γ-ray photons with the dose range from 10⁵ to 10⁶ rad at room temperature using the electrolythic method. Splitting of the low-energy extremum is observed after irradiation. A decrease in the internal stresses in the film as a result of irradiation with γ-ray photons is estimated from the variations in the electron-transition energy and collisional parameter of broadening. An increase in the time of energy relaxation of charge carriers after irradiation is also estimated.     

深亚微米CMOS管总剂量辐照特性的对比研究

对深亚微米NMOS和PMOS管进行了⁶⁰Coγ总剂量辐射实验。实验结果表明,PMOS管在转移特性、噪声、匹配特性方面比NMOS管的抗辐照能力更强。对NMOS管和PMOS管的辐照损伤机理进行了理论分析。分析结果表明,不同的衬底类型导致了PMOS管和NMOS管的辐照效应的差异。基于实验与分析结果,提出了一些深亚微米模拟IC的抗辐照设计方案。     

Non-equilibrium carrier capture, recombination and annealing in thick insulators and their impact on radiation hardness

This paper describes an approach to prediction of the thick insulators'' radiation response based on modeling of the charge yield, which is dependent on irradiation temperature, dose rate, and electric field magnitudes. Temperature behavior of the charge yield and degradation saturation due to the interface precursor depletion has been modeled and simulated. Competition between the time-dependent and true dose rate (ELDRS) effects has been simulated and discussed within a framework of the rate-equation-based mathematical model. It was shown that the precursor trap in the thick insulating oxides can be important at high dose rates. It was also shown that full filling of the shallow hole traps in the insulating oxide bulk can cause suppression of dose-rate sensitivity at relatively high dose rates, especially in thick insulators.     

Intensification of electroluminescence of ZnSe:(Te,O) crystals as a result of irradiation with γ-ray photons

The effects of irradiation with γ-ray photons of the ⁶⁰Co isotope and of treatment in zinc vapors on the electroluminescence of ZnSe:(Te, O) crystals were studied with the aim of revealing the potential for fabrication of light-emitting structures. The broadband electroluminescence with a peak at 600 nm is excited in the initial samples at voltages higher than 70 V. The threshold voltage is decreased to several volts irrespective of polarity after treatment of the crystals in zinc vapors. A similar effect is observed after irradiation. The position of the peak in the electroluminescence band does not depend on the magnitude of voltage or on irradiation. This position is related to the recombination of charge carriers at the centers of interstitial zinc according to the mechanism of excitation of the prebreakdown type. Treatment in zinc vapors and irradiation with γ-ray photons of ZnSe:(Te, O) bring about an increase in the electroluminescence intensity at both polarities of applied voltage.     

Ionizing-Radiation Response of the GaAs/(Al, Ga)As PHEMT: A Comparison of Gamma- and X-ray Results

An experiment is reported on the effect of ⁶⁰Co gamma rays or 45-keV x-ray photons on the GaAs/(Al, Ga)As PHEMT. It is shown that x-ray treatment can improve the dc performance of the device in some cases. This finding is attributed in part to the annealing or modification of DX centers.     

Investigation on X-ray irradiation on nanoscale nitride based charge trapping flash memory devices

Charge trapping flash memory devices are susceptible to charge loss mechanisms induced by high energy irradiation such as thermal neutrons, X-rays, and gamma ray. The loss of trapped charges due to charge loss mechanism has resulted in the degradation in data retention performance and unwanted read failures in field applications. In this work, charge loss mechanisms of nanoscale nitride based charge trapping flash memory devices due to irradiation of high energy X-rays were carefully studied and examined. Nitride based charge trapping flash memory device stored charges in the nitride storage layer of an Oxide-Nitride-Oxide stack. Threshold voltage of the nitride based charge trapping flash memory cells were collected before and after X-ray irradiation done onto the memory devices. Threshold voltage distributions have shown that significant number of cells at the lower end of the program distribution had perturbed from the overall distribution that was caused by X-ray irradiation induced charge loss mechanism. In this study, the effect of the use of 300 μm Zn filter and its proximity to the device under study to mitigate the X-ray irradiation induced charge loss was also thoroughly elucidated. The results have demonstrated that 300 μm Zn filter has significantly improved the immunity of nitride based charge trap flash memory device up to 6.446 times. However, the proximity of the Zn filter to the flash memory device exacerbated up to 7.4280 times due to the impact of secondary effect in X-ray fluorescence to the device under study. Hence, this investigation concluded that X-ray irradiation is a genuine reliability concern for nanoscale nitride based charge trapping flash memory devices. Furthermore, it is recommended to place Zn filter close to X-ray source to significantly mitigate the Vt distribution drift induced by X-ray irradiation.