双极晶体管的低剂量率辐射损伤增强效应

在辐射的剂量率范围内,无论是国产还是进1:21的双极晶体管,都有明显的低剂量率辐照损伤增强现象,且纵向NPN管比PNP管严重.本文对引起双极器件辐照损伤差异的机理进行了探讨,并讨论了双极器件的抗辐射加固技术.     

掺杂浓度对重掺硼直拉<111>单晶硅小角晶界的影响

小角晶界是重掺硼直拉111单晶硅生产制造过程中出现的严重缺陷,生产中需要避免。主要研究掺杂浓度对小角晶界的影响,通过实验发现当前工艺下小角晶界产生的临界掺杂浓度为9.05×1019cm-3。分析研究小角晶界的宏观分布及形态特征,其宏观分布与晶体各项异性具有一致性,并随掺杂浓度变化而规律性变化。利用位错模型计算小角晶界两侧晶向差为0.6″~12.76″,其晶向差随掺杂浓度增加而逐步变大。根据位错模型计算并分析自由能与掺杂浓度的关系,得到样品中宏观长度下小角晶界自由能为5.037×10-10~7 200.421×10-10J,并随着掺杂浓度增加而逐步变大。此外结合生长工艺和晶格补偿原理,提出高掺杂浓度下避免小角晶界的方法,并得到无小角晶界的重掺硼单晶硅,对实际生产有重要意义。     

掺杂浓度对重掺硼直拉<111>单晶硅小角晶界的影响北大核心CSCD

小角晶界是重掺硼直拉〈111〉单晶硅生产制造过程中出现的严重缺陷,生产中需要避免。主要研究掺杂浓度对小角晶界的影响,通过实验发现当前工艺下小角晶界产生的临界掺杂浓度为9．05×10^19 cm-3。分析研究小角晶界的宏观分布及形态特征,其宏观分布与晶体各项异性具有一致性,并随掺杂浓度变化而规律性变化。利用位错模型计算小角晶界两侧晶向差为0．6”～12．76”,其晶向差随掺杂浓度增加而逐步变大。根据位错模型计算并分析自由能与掺杂浓度的关系,得到样品中宏观长度下小角晶界自由能为5．037×10^-10～7200．421×10^-10 J,并随着掺杂浓度增加而逐步变大。此外结合生长工艺和晶格补偿原理,提出高掺杂浓度下避免小角晶界的方法,并得到无小角晶界的重掺硼单晶硅,对实际生产有重要意义。     

基区重掺杂对SiGe HBT热学性能的影响

相对于同质结晶体管,异质结双极晶体管(HBT)由于异质结的存在,电流增益不再主要由发射区和基区掺杂浓度比来决定,因此可以通过增加基区掺杂浓度来降低基区电阻,提高频率响应,降低噪声系数,但基区掺杂浓度对器件热特性影响的研究却很少。以多指SiGeHBT的热电反馈模型为基础,利用自洽迭代法分析了基区重掺杂对器件集电极电流密度和发射极指温度的影响。通过研究发现,随着基区浓度的增加,SiGe HBT将发生禁带宽度变窄,基区反向注入发射区的空穴电流增大;同时,基区少子俄歇复合增强,这些都将减小集电极电流密度,降低发射极指温度,从而抑制发射极指热电正反馈,提高器件的热稳定性。     

场终止型IGBT基区掺杂浓度计算的新方法

基于场终止型IGBT的结构特点与工作机理,提出了一种通过提取IGBT拖尾电流计算基区掺杂浓度新方法,该方法针对已有商用器件只需测试端口电气参数而无需破坏性实验,具有易操作、准确性高的特点.最后分析了一般硬开关和附加吸收电路对IGBT关断拖尾电流测试的影响,提出一种新的测试电路并进行了拖尾电流提取实验,同时也验证了该方法的准确性.     

POCl3掺杂对PNP管特性的影响研究

PNP管的结构是由P型发射区、N型基区、P型集电区组成的三层两结。PNP管的基区宽度和基区掺杂对PNP管电特性的影响很大。在常规IC工艺中,通常采用先做试片的方式来确定基区的磷掺杂扩散时间,工艺加工效率低。为了解决这个问题,从磷源POCl₃的温度、扩散时间两方面入手,对PNP管的电流增益β进行了实验研究。结果表明,在POCl₃温度为(20±1) ℃、预扩散时间为(46±2) min、β不小于80的条件下,PNP管的β变化量小于50%。该研究用于实际PNP管的制造工艺中,工艺加工效率提高了100%。     

掺杂浓度和无序对柔性有机发光二极管载流子迁移率的影响

基于电荷分布的泊松方程和载流子输运方程,考虑最低能量非占据态和最高能量占据态的载流子态密度服从双高斯分布的模型,自洽地研究了掺杂浓度和无序对Alq3柔性有机发光二极管载流子迁移率的影响.发现掺杂浓度低于1×1020cm-3时,掺杂浓度对迁移率影响很小,迁移率几乎保持不变;当掺杂浓度大于1×1020cm-3时,载流子迁移...     

掺杂浓度和无序对柔性有机发光二极管载流子迁移率的影响

基于电荷分布的泊松方程和载流子输运方程,考虑最低能量非占据态和最高能量占据态的载流子态密度服从双高斯分布的模型,自洽地研究了掺杂浓度和无序对Alq3柔性有机发光二极管载流子迁移率的影响.发现掺杂浓度低于1×1020cm-3时,掺杂浓度对迁移率影响很小,迁移率几乎保持不变;当掺杂浓度大于1×1020cm-3时,载流子迁移率非线性增加,与实验结果很好一致.考虑不同无序度时,发现无序度的增加,相应的迁移率下降;低掺杂浓度下迁移率与无序度的大小关系不大,当掺杂浓度较高的时,无序度较小的材料迁移率增加较快.最终给出了柔性发光二极管器件的发光功率密度与电压关系,表明载流子浓度和无序相关的迁移率结果对制备高性能的柔性有机发光二极管具有指导意义.     

聚乙烯醇掺杂对二维MoS2晶体管电学性能的影响

采用机械剥离法得到二维MoS2材料并将其转移到SiO2/Si衬底上,采用光刻、剥离工艺制备出二维MoS2晶体管.将二维MoS2晶体管浸泡在不同质量浓度的聚乙烯醇(PVA)溶液中,然后旋涂成膜并退火实现掺杂.对掺杂前后二维MoS2晶体管的电学性能进行测试.测试结果显示,当PVA溶液质量浓度为0.5％、1％和2％时,掺杂后的二维MoS2晶体管开态电流提高到3倍、3.6倍和10倍,有效电子迁移率提高到1.7倍、2.8倍和4.3倍,开态电阻降低了一个数量级以上.由于掺杂层的覆盖,二维MoS2晶体管的稳定性有了显著提高,暴露在空气中30 d后未观察到电学性能有明显退化.研究结果表明,可以通过控制PVA溶液的质量浓度对二维MoS2晶体管的掺杂浓度进行调控,从而影响其电学性能.     

沟道掺杂浓度对恒流二极管电学特性的影响

设计了一种基于N－JFET结构的恒流二极管,分析了其沟道掺杂浓度与恒流值、开启电压、击穿电压以及温度特性之间的关系。利用SILVACO仿真软件对恒流二极管沟道掺杂分布进行优化设计,最终得到一个开启电压为2 V,击穿电压大于90 V,恒流值为40 mA,温度系数为－0．33%/K的恒流二极管。     

Impact of doped boron concentration in emitter on high- and low-dose-rate damage in lateral PNP transistors

The characteristics of radiation damage under a high or low dose rate in lateral PNP transistors with a heavily or lightly doped emitter is investigated. Experimental results show that as the total dose increases, the base current of transistors would increase and the current gain decreases. Furthermore, more degradation has been found in lightly-doped PNP transistors, and an abnormal effect is observed in heavily doped transistors. The role of radiation defects, especially the double effects of oxide trapped charge, is discussed in heavily or lightly doped transistors. Finally,through comparison between the high- and low-dose-rate response of the collector current in heavily doped lateral PNP transistors, the abnormal effect can be attributed to the annealing of the oxide trapped charge. The response of the collector current, in heavily doped PNP transistors under high- and low-dose-rate irradiation is described in detail.     

Effects of combined x-ray Irradiation and hot-electron injection on NMOS transistors

Changes of NMOS transistor parameters after combined stress of x-ray irradiation and hot-electron injection were studied. We found that, in general, the resultant effects depended strongly on the order of the stress sequence. Of the parameters studied, oxide charge trapping depends more significantly on the stress sequence than the generation of interface traps. Interface trap transformation process and nonuniform defect distribution along the channel have been observed under certain stress conditions. Consequences of the above effects on the transistor dc parameters are discussed.     

Comparison of modulation doped effect in negative differential resistance field effect transistors (NDRFETs)

N-shaped negative differential resistance field effect transistors (NDRFETs) have been fabricated and demonstrated. The interesting N-shaped NDRs are three terminal controlled phenomena. This N-shaped NDR behavior is found in the higher drain-to-source voltage (V_DS) regime and is obtained both at positive and negative gate-to-source bias (V_GS). We believe that the NDR phenomena are attributed to the real space transfer (RST) effect. Due to the modulation doped effect and different barrier height, the NDR behavior can easily be controlled. The influence of V_GS bias on the NDR characteristics is also investigated.     

Annealing behavior of radiation damage in JFET-input operational amplifiers

The elevated and room temperature annealing behavior of radiation damage in JFET-input operational amplifiers (op-amps) were investigated. High-and low-dose-rate irradiation results show that one of the JFET-input op-amps studied in this paper exhibits enhanced low-dose-rate sensitivity and the other shows time-dependent effect. The offset voltage of both op-amps increases during long-term annealing at room temperature. However, the offset voltage decreases at elevated temperature. The dramatic difference in annealing behavior at room and elevated temperatures indicates the migration behavior of radiation-induced species at elevated and room temperatures. This provides useful information to understand the degradation and annealing mechanisms in JFET-input op-amps under total ionizing radiation. Moreover, the annealing of oxide trapped charges should be taken into consideration, when using elevated temperature methods to evaluate low-dose-rate damage.     

JFET输入运算放大器辐射损伤的退火行为

The elevated and room temperature annealing behavior of radiation damage in JFET-input operational amplifiers （op-amps） were investigated. High- and low-dose-rate irradiation results show that one of the JFET-input op-amps studied in this paper exhibits enhanced low-dose-rate sensitivity and the other shows time-dependent effect. The offset voltage of both op-amps increases during long-term annealing at room temperature. However, the offset voltage decreases at elevated temperature. The dramatic difference in annealing behavior at room and elevated temperatures indicates the migration behavior of radiation-induced species at elevated and room temperatures. This provides useful information to understand the degradation and annealing mechanisms in JFET-input op-amps under total ionizing radiation. Moreover, the annealing of oxide trapped charges should be taken into consideration, when using elevated temperature methods to evaluate low-dose-rate damage.     

Radiation damage effects on bipolar and MOS devices in X-Ray lithography

Radiation damage effects of bipolar and MOS transistors have been investigated using the vacuum ultraviolet (VUV) storage ring of the national synchrotron light source (NSLS). The devices under investigation were exposed to x-ray radiation and electrical measurements were performed to determine the radiation effects on device parameters. It was found for bipolar devices that the current gain is the parameter that is most sensitive to x-ray irradiation. The current gain decreases as the dose increases and the degradation reaches saturation at 1000 mJ/cm². Upon annealing in forming gas at 400° C for 30 min, the current gain recovered its pre-irradiation value and stress test did not show any reliability problem. Bothn-channel andp-channel MOS devices with polysilicon gates were investigated. Host of the relevant device parameters were measured before and after irradiation and after annealing. Upon irradiation the threshold voltage shows the most obvious shift, which was more negative in both cases. However, thep- channel devices experienced a much larger shift than then-channel ones. The transconductance of the devices also experienced a shift.     

Impact of Layer Configuration and Doping on Electron Transport and Bias Stability in Heterojunction and Superlattice Metal Oxide Transistors

The astonishing recent progress in the field of metal oxide thin‐film transistors (TFTs) and their debut in commercial displays is accomplished using vacuum‐processed multicomponent oxide semiconductors. However, emulating this success with their solution‐processable counterparts poses numerous scientific challenges. Here, the development of high mobility n‐channel TFTs based on ultrathin (<10 nm) alternating layers of In₂O₃ and ZnO that are sequentially deposited to form heterojunction and superlattice channels is reported. The resulting TFTs exhibit high electron saturation mobility (13 cm² V^?1 s^?1), excellent current on/off ratios (>10⁸) with nearly zero onset voltages and hysteresis‐free operation despite the low temperature processing (≤200 °C). The enhanced performance is attributed to the formation of a quasi‐2D electron gas‐like system at the In₂O₃/ZnO heterointerface due to the conduction band offset. It is shown that altering the oxide deposition sequence has an adverse effect on electron transport due to formation of trap states. Optimized multilayer TFTs are shown to exhibit improved bias‐stress stability compared to single‐layer TFTs. Modulating the electron concentration within the superlattice channel via selective n‐doping of the ZnO interlayers leads to almost 100% saturation mobility increase (≈25 cm² V^?1 s^?1) even when the TFTs are fabricated on flexible plastic substrates.     

锗硅异质结双极晶体管空间辐射效应研究进展

异质结带隙渐变使锗硅异质结双极晶体管(SiGe HBT)具有良好的温度特性,可承受-180~+200 ℃的极端温度,在空间极端环境领域具有诱人的应用前景。然而,SiGe HBT器件由于材料和工艺结构的新特征,其空间辐射效应表现出不同于体硅器件的复杂特征。本文详述了SiGe HBT的空间辐射效应研究现状,重点介绍了国产工艺SiGe HBT的单粒子效应、总剂量效应、低剂量率辐射损伤增强效应以及辐射协同效应的研究进展。研究表明,SiGe HBT作为双极晶体管的重要类型,普遍具有较好的抗总剂量和位移损伤效应的能力,但单粒子效应是制约其空间应用的瓶颈问题。由于工艺的不同,国产SiGe HBT还表现出显著的低剂量率辐射损伤增强效应响应和辐射协同效应。     

总剂量辐射对硅双极和MOS器件性能的影响

对比研究了总剂量辐射对硅微波功率双极器件、LDMOS器件、VDMOS器件以及常规功率VDMOS和抗辐射加固功率VDMOS器件电性能的影响,并分析了辐射后器件性能变化的原因,为抗辐射加固方法的改进和优化提供了基础。     

NMOSFET器件不同源、不同γ剂量率辐射损伤比较

利用不同剂量率γ射线、低能(小于9MeV)质子和1MeV电子对CC4007RH、CC4011、LC54HC04RH NMOSFET进行了辐照实验,结果表明,在＋5V偏置条件下,9MeV以下质子造成的损伤总是小于⁶⁰Co,而且质子能量越低,损伤越小;对于同等的吸收剂量,1MeV电子和⁶⁰Co造成的损伤差别不大;在高剂量率γ射线辐射下,氧化物陷阱电荷是导致器件失效的主要原因,在接近空间低剂量率辐射环境下,LC54HC04RH电路失效的主要原因是辐射感生界面态陷阱电荷,而CC4007RH器件则是氧化物陷阱电荷.