栅控横向PNP双极晶体管辐照感生电荷的定量分离

设计并制作了一种栅控横向PNP双极晶体管测试结构,在常规横向PNP双极晶体管基区表面氧化层上制作了一栅电极,利用栅扫描法,通过扫描栅极所加电压,获得了基极电流随栅极电压的变化特性.理论推导和数学计算获得了氧化物陷阱电荷和界面陷阱电荷的定量变化,分离出栅控横向PNP双极晶体管在辐照及其室温退火过程中感生的缺陷.对设计的晶体管测试结构和采用的测试方法做了具体介绍.     

MOSFET 辐照诱生界面陷阱形成过程的1/f噪声研究

基于界面陷阱形成的氢离子运动两步模型和反应过程的热力学平衡假设，推导了金属-氧化物-半导体-场效应晶体管(MOSFET)经历电离辐照后氧化层空穴俘获与界面陷阱形成间关系的表达式.利用初始1/f噪声功率谱幅值与氧化层空穴俘获之间的联系，建立了辐照前的1/f噪声幅值与辐照诱生界面陷阱数量之间的半经验公式，并通过实验予以验证.研究结果表明，由于辐照诱生的氧化层内陷阱通过与分子氢作用而直接参与到界面陷阱的建立过程中，从而使界面陷阱生成数量正比于这种陷阱增加的数量，因此辐照前的1/f噪声功率谱幅值正比于辐照诱生的界面陷阱数量.研究结果为1/f噪声用作MOSFET辐照损伤机理研究的新工具，对其抗辐照性能进行无损评估提供了理论依据与数学模型. 关键词： 辐照效应 界面陷阱 1/f噪声 氧化层空穴俘获     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管辐照退化模型

基于金属-氧化物-半导体场效应晶体管(MOSFET)噪声的载流子数涨落和迁移率涨落理论,建立了MOSFET辐照前1/f噪声参量与辐照后分别由氧化层陷阱和界面陷阱诱使阈值电压漂移之间的定量数学模型,并通过实验予以验证.研究结果表明,辐照诱生的氧化层陷阱通过俘获和发射过程与沟道交换载流子,在引起载流子数涨落的同时也通过库仑散射导致沟道迁移率的涨落,因此辐照前的1/f噪声幅值正比于辐照诱生的氧化层陷阱数.利用该模型对MOSFET辐照前1/f噪声与辐照退化的相关性从理论上进行了解释,同时也为MOSFET抗辐照能力预测提供理论依据.     

MOSFET辐照诱生界面陷阱形成过程的1/f噪声研究

基于界面陷阱形成的氢离子运动两步模型和反应过程的热力学平衡假设,推导了金属-氧化物-半导体-场效应晶体管(MOSFET)经历电离辐照后氧化层空穴俘获与界面陷阱形成间关系的表达式.利用初始1/f噪声功率谱幅值与氧化层空穴俘获之间的联系,建立了辐照前的1/f噪声幅值与辐照诱生界面陷阱数量之间的半经验公式,并通过实验予以验证.研究结果表明,由于辐照诱生的氧化层内陷阱通过与分子氢作用而直接参与到界面陷阱的建立过程中,从而使界面陷阱生成数量正比于这种陷阱增加的数量,因此辐照前的1/f噪声功率谱幅值正比于辐照诱生的界面陷阱数量.研究结果为1/f噪声用作MOSFET辐照损伤机理研究的新工具,对其抗辐照性能进行无损评估提供了理论依据与数学模型.     

中带电压法分离栅控横向pnp双极晶体管辐照感生缺

设计并制作了一种新型双极测试结构,即在常规横向pnp双极晶体管基区表面氧化层上淀积一栅电极,通过扫描栅极所加电压,获得漏极(集电极)电流随栅极电压的变化特性,利用中带电压法分离栅控横向pnp双极晶体管 在辐照过程中感生的氧化物陷阱电荷和界面陷阱电荷.本文对设计的晶体管测试结构和采用 的测试方法做了具体介绍.     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管辐照退化模型

基于金属-氧化物-半导体场效应晶体管(MOSFET)噪声的载流子数涨落和迁移率涨落理论,建立了MOSFET辐照前1/f噪声参量与辐照后分别由氧化层陷阱和界面陷阱诱使阈值电压漂移之间的定量数学模型,并通过实验予以验证.研究结果表明,辐照诱生的氧化层陷阱通过俘获和发射过程与沟道交换载流子,在引起载流子数涨落的同时也通过库仑散射导致沟道迁移率的涨落,因此辐照前的1/f噪声幅值正比于辐照诱生的氧化层陷阱数.利用该模型对MOSFET辐照前1/f噪声与辐照退化的相关性从理论上 关键词： f噪声')" href="#">1/f噪声 辐照 金属-氧化物-半导体场效应晶体管 陷阱     

AlGaN/GaN高电子迁移率晶体管器件电离辐照损伤机理及偏置相关性研究

本文利用~(60)Coγ射线,针对AlGaN/GaN高电子迁移率晶体管(high-electron mobility transistors,HEMT)器件,开展了在不同偏置下器件电离辐照总剂量效应实验研究.采用1/f噪声结合直流电学特性参数对实验结果进行测量分析,分析结果表明,受到辐照诱生氧化物缺陷电荷与界面态的影响,当辐照总剂量达到1 Mrad(Si)时,零偏条件下AlGaN/GaN HEMT器件的电学参数退化得最大,其中,饱和漏电流减小36.28%,最高跨导降低52.94%;基于McWhorter模型提取了AlGaN/GaN HEMT器件辐照前后的缺陷密度,零偏条件下辐照前后缺陷密度变化最大,分别为4.080×10~(17)和6.621×10~(17)cm~(-3)·eV~(-1).其损伤机理是在氧化物层内诱生缺陷电荷和界面态,使AlGaN/GaN HEMT器件的平带电压噪声功率谱密度增加.     

60Coγ射线辐照对肖特基二极管1/f噪声的影响

在肖特基二极管(schottky barrier diode,SBD)辐照损伤机理和总剂量效应分析的基础上,利用1/f噪声的迁移率涨落和载流子数涨落模型,深入研究辐照损伤对器件1/f噪声的影响.研究结果表明,辐照诱生新的界面态,改变界面态密度分布,进而调制了肖特基势垒高度,增大表面复合速度是引起器件性能退化主要原因,也是1/f噪声剧烈增加的主要原因.正因为如此,噪声与器件退化存在相关性,即噪声拟合参数B越大,偏离标准值越多,器件可靠性越差,抗辐照能力越低,在辐照环境下工作越容易失效.由此可知,1/f噪声特性可以用作SBD辐照损伤机理的研究工具,并有可能用于SBD抗辐射加固的无损评估.     

部分耗尽结构绝缘体上硅器件的低频噪声特性

针对部分耗尽结构绝缘体上硅(silicon-on-insulator, SOI)器件低频噪声特性展开实验与理论研究. 实验结果表明, 器件低频噪声主要来源于SiO₂-Si界面附近缺陷态对载流子的俘获与释放过程; 基于此理论可提取前栅和背栅氧化层界面附近缺陷态密度分别为8×10¹⁷ eV^-1·cm^-3和2.76×10¹⁷ eV^-1·cm^-3. 基于电荷隧穿机理, 在考虑隧穿削弱因子、隧穿距离与时间常数之间关系的基础上, 提取了前、背栅氧化层内缺陷态密度随空间的分布情况. 此外, SOI器件沟道电流归一化噪声功率谱密度随沟道长度的增加而线性减小, 这表明器件低频噪声主要来源于沟道的闪烁噪声. 最后, 基于电荷耦合效应, 分析了背栅电压对前栅阈值电压、沟道电流以及沟道电流噪声功率谱密度的影响.     

双极型晶体管总剂量效应的统计特性

双极型晶体管的总电离剂量辐照效应主要体现在基极电流(I_B)的退化,其作用机理是电离辐射在SiO_2中及Si/SiO_2界面作用导致的氧化物陷阱电荷面密度(N_(ot))和界面陷阱电荷面密度(N_(it))的增长.本文基于定制设计的栅控横向PNP晶体管,开展了大样本、多剂量点的电离总剂量效应实验,获得了双极型晶体管I_B, N_(ot), N_(it)的分散性及其随总剂量变化的统计特性,初步建立了晶体管损伤分散性与N_(ot)分散性的关联.该研究成果可以有效支撑双极型电路辐射可靠性的机理研究与定量评估.     

Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co~(60) source up to a total dose of 700 Gy(Si). The low dose rate was 0.001 Gy(Si)/s and the high dose rate was 0.1 Gy(Si)/s. The model accords well with the experimental results.     

Si_3N_4钝化层对横向PNP双极晶体管电离辐射损伤的影响机理

航天器中电子器件在轨服役期间,会遭受到空间带电粒子及各种射线的辐射环境的显著影响,易于造成电离辐射损伤.本文采用60Coγ射线辐照源,针对有/无Si_3N_4钝化层结构的横向PNP型(LPNP)双极晶体管,开展了电离辐射损伤效应及机理研究.利用KEITHLEY 4200-SCS半导体参数测试仪测试了LPNP晶体管电性能参数(包括Gummel特性曲线和电流增益等).采用深能级瞬态谱分析仪(DLTS),对辐照前后有/无Si_3N_4钝化层结构的LPNP晶体管的电离缺陷进行测试.研究结果表明,在相同吸收剂量条件下,与无Si_3N_4钝化层的晶体管相比,具有Si_3N_4钝化层的LPNP晶体管基极电流退化程度大,并且随吸收剂量的增加,电流增益退化更为显著.通过DLTS分析表明,与无Si_3N_4钝化层的晶体管相比,有Si_3N_4钝化层的晶体管辐射诱导的界面态能级位置更接近于禁带中心.这是由于制备Si_3N_4钝化层时引入了大量的氢所导致,而氢的存在会促使辐射诱导的界面态能级位置更接近于禁带中心,复合率增大,从而加剧了晶体管性能的退化.     

Effects of orientation of substrate on the enhanced low-dose-rate sensitivity （ELDRS） in NPN transistors

The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with <111> orientation was more sensitive to ionizing radiation than that with <100> orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.     

ELDRS and dose-rate dependence of vertical NPN transistor

The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article.The results show that the vertical NPN transistors exhibit more degradation at low dose rate,and that this degradation is attributed to the increase on base current.The oxide trapped positive charge near the SiO2-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results.     

60Co γ-ray induced gain degradation in bipolar junction transistors

Commercial indigenously made npn and pnp bipolar junction switching transistors used for space applications are investigated for ⁶⁰Co γ-ray induced effects. The on-line as well as off-line measurements indicate that the forward current gain of the transistors decreases significantly as the accumulated dose increases. Excess base current model is employed to account for the current gain degradation. The pnp transistor undergoes as much degradation as the npn type. It is found that bulk degradation by displacement damage is the dominant mechanism leading to reduction in forward current gain of npn transistors. On the other hand it appears that, in addition to bulk damage, surface degradation due to accumulation of interface states at the silicon-silicon dioxide interface also contributes significantly to gain degradation in pnp transistor as evident from thermal annealing studies. Further, estimation reveals that the transistor with larger base width has higher displacement damage factor.     

Effects of orientation of substrate on the enhanced low-dose-rate sensitivity (ELDRS) in NPN transistors

The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with (111) orientation was more sensitive to ionizing radiation than that with (100) orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.     

ELDRS and dose-rate dependence of vertical NPN transistor

The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article. The results show that the vertical NPN transistors exhibit more degradation at low dose rate, and that this degradation is attributed to the increase on base current. The oxide trapped positive charge near the SiO₂-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results.     

Effect of bias condition on heavy ion radiation in bipolar junction transistors

The characteristic degradations in a silicon NPN bipolar junction transistor(BJT) of 3DG142 type are examined under irradiation with 40-MeV chlorine(Cl) ions under forward,grounded,and reverse bias conditions,respectively.Different electrical parameters are in-situ measured during the exposure under each bias condition.From the experimental data,a larger variation of base current(I B) is observed after irradiation at a given value of base-emitter voltage(V BE),while the collector current is slightly affected by irradiation at a given V BE.The gain degradation is affected mostly by the behaviour of the base current.From the experimental data,the variation of current gain in the case of forward bias is much smaller than that in the other conditions.Moreover,for 3DG142 BJT,the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence,while at high fluence,the gain degradation in the reverse bias case becomes smaller than that in the grounded case.     

偏置条件对NPN及PNP双极晶体管电离辐射损伤的影响研究

本文采用低能电子辐照源对NPN及PNP晶体管进行辐照试验. 在辐照试验过程中, 针对NPN及PNP晶体管发射结施加不同的偏置条件, 研究偏置条件对NPN及PNP晶体管辐射损伤的影响. 使用Keithley 4200-SCS半导体特性测试仪在原位条件下测试了双极晶体管电性能参数随低能电子辐照注量的变化关系. 测试结果表明, 在相同的辐照注量条件下, 发射结反向偏置时双极晶体管的辐照损伤程度最大; 发射结正向偏置时双极晶体管的辐照损伤程度最小; 发射结零偏时双极晶体管的辐照损伤程度居于上述情况之间. 关键词： 双极晶体管 低能电子 电离辐射     

Degradation mechanisms of current gain in NPN transistors

An investigation of ionization and displacement damage in silicon NPN bipolar junction transistors (BJTs) is presented. The transistors were irradiated separately with 90-keV electrons, 3-MeV protons and 40-MeV Br ions. Key parameters were measured {\em in-situ} and the change in current gain of the NPN BJTS was obtained at a fixed collector current (I_{\rm c}=1~mA). To characterise the radiation damage of NPN BJTs, the ionizing dose D_{\i} and displacement dose D_{\d} as functions of chip depth in the NPN BJTs were calculated using the SRIM and Geant4 code for protons, electrons and Br ions, respectively. Based on the discussion of the radiation damage equation for current gain, it is clear that the current gain degradation of the NPN BJTs is sensitive to both ionization and displacement damage. The degradation mechanism of the current gain is related to the ratio of D_{\rm d}/(D_{\rm d}+D_{\rm i}) in the sensitive region given by charged particles. The irradiation particles leading to lower D_{\rm d}/(D_{\rm d}+D_{\rm i}) within the same chip depth at a given total dose would mainly produce ionization damage to the NPN BJTs. On the other hand, the charged particles causing larger D_{\rm d}/(D_{\rm d}+D_{\rm i}) at a given total dose would tend to generate displacement damage to the NPN BJTs. The Messenger--Spratt equation could be used to describe the experimental data for the latter case.