Bias dependence of a deep submicron NMOSFET response to total dose irradiation

Deep submicron n-channel metal-oxide-semiconductor field-effect transistors （NMOSFETs） with shallow trench isolation （STI） are exposed to ionizing dose radiation under different bias conditions. The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case （ON bias） for the transistors are discussed. The high electric fields at the corners are partly responsible for the subthreshold hump effect. Charge trapped in the isolation oxide, particularly at the Si/SiO2 interface along the sidewalls of the trench oxide creates a leakage path, which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET. Non-uniform charge distribution is introduced into a threedimensional （3D） simulation. Good agreement between experimental and simulation results is demonstrated. We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.

Total ionizing dose effect in an input/output device for flash memory

Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.

SOI射频开关测试结构特性参数分析

以0.2μm SOI RF工艺平台为基础,对射频开关测试结构基本特性参数进行分析研究。研究内容包括:a)栅极和衬底通过反向二极管连接;b)浮体器件;c)衬底通过大电阻接地(HR GND);d)衬底通过大电阻连接到栅极控制端(HR,Vsub=Vg)等四种结构。比较分析了其插入损耗、隔离度及谐波特性,并阐明产生差异的机制。研究结果可以为射频开关器件结构和电路设计做参考。

0.13μm部分耗尽薄膜SOI MOSFETs击穿特性研究

以0.13μm部分耗尽薄膜SOI器件为研究对象,简要分析了体接触器件和浮体器件基本特性,指出两类器件击穿特性的差异性,并重点讨论了栅长、栅端偏压和衬底偏压等对器件击穿特性的影响,阐明了击穿特性的失效机理,为器件优化和电路设计提供参考。

不同设计参数对SOI射频开关小信号的影响

基于0.2μm SOI RF工艺平台,设计了串联支路、并联支路、单刀单掷、单刀双掷等电路结构,分析研究了单级宽度、级联数目、偏置电阻、偏置电压等设计参数对射频开关小信号特性的影响。通过实验数据,讨论各参数对射频开关小信号特性,主要包括射频开关的插入损耗和隔离度的影响,为射频开关设计提供参考。

Impact of substrate bias on radiation-induced edge effects in MOSFETs

This paper investigates the effects of gamma-ray irradiation on the Shallow-Trench Isolation （STI） leakage currents in 180-nm complementary metal oxide semiconductor technology. No hump effect in the subthreshold region is observed after irradiation, which is considered to be due to the thin STI corner oxide thickness. A negative substrate bias could effectively suppress the STI leakage, but it also impairs the device characteristics. The three-dimensional simulation is introduced to understand the impact of substrate bias, Moreover, we propose a simple method for extracting the best substrate bias value, which not only eliminates the STI leakage but also has the least impact on the device characteristics.

Enhanced Total Ionizing Dose Susceptibility in Narrow Channel Devices

Total ionizing dose effects of different transistor sizes in a 0.18µm technology are studied by 60Coγ-ray irradiation.Significant threshold voltage shift is observed for the narrow channel devices,which is called the radiation induced narrow channel effect(RINCE).A charge sharing model is introduced to understand the phenomenon.The devices'characteristic degradations after irradiation,such as threshold voltage shift,increase in on-state current under different drain biases and substrate biases,are discussed in detail.Radiation induced oxide trapped charge at the edges of shallow trench isolation plays an important role in the RINCE.Narrow channel devices are susceptible to the total ionizing dose effect.

0.18μm MOSFET器件的总剂量辐照效应

对0.18μm metal-oxide-semiconductor field-effect-transistor(MOSFET)器件进行γ射线辐照实验,讨论分析器件辐照前后关态漏电流、阈值电压、跨导、栅电流、亚阈值斜率等特性参数的变化,研究深亚微米器件的总剂量效应.通过在隔离氧化物中引入等效陷阱电荷,三维模拟结果与实验结果符合很好.深亚微米器件栅氧化层对总剂量辐照不敏感,浅沟槽隔离氧化物是导致器件性能退化的主要因素.

浮栅存储器的单粒子辐射效应研究进展

综述了浮栅存储器的单粒子效应国外研究进展,对浮栅存储器控制电路及存储单元的单粒子效应进行详细分析和讨论。指出控制电路是浮栅存储器单粒子效应的关键部件以及重离子轰击使浮栅存储器数据保持特性退化;阐述了浮栅存储单元辐射后可能的电荷损失机制。最后指出纳米晶浮栅存储器具有好的抗辐射能力。

硅离子注入引入纳米晶对SIMOX材料进行总剂量辐射加固

本研究工作采用硅离子注入和高温退火工艺对SIMOX材料的BOX层进行总剂量辐射加固。辐射实验结果证明了该加固方法的有效性。PL谱和HRTEM图像显示了硅离子注入及退火工艺在材料的BOX层中引入了Si纳米晶,形成电子陷阱能级,有效俘获电子,从而提高了材料BOX层的抗总剂量辐射能力。

深亚微米器件沟道长度对总剂量辐照效应的影响

研究了180 nm互补金属氧化物半导体技术下的器件沟道长度对总剂量辐照效应的影响.在其他条件如辐照偏置、器件结构等不变的情况下,氧化层中的陷阱电荷决定了辐照响应.浅沟槽隔离氧化层中的陷阱电荷使得寄生的侧壁沟道反型,从而形成大的关态泄漏电流.这个电流与沟道长度存在一定的关系,沟道长度越短,泄漏电流越大.首次发现辐照会增强这个电流的沟道长度调制效应,从而使得器件进一步退化.

Gate length dependence of the shallow trench isolation leakage current in an irradiated deep submicron NMOSFET

The effects of gamma irradiation on the shallow trench isolation（STI）leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold voltage shift is negligible in all of the devices due to the very thin oxide thickness.However,an increase in the off-state leakage current is observed for all of the devices.We believe that the leakage is induced by the drain-to-source leakage path along the STI sidewall,which is formed by the positive trapped charge in the STI oxide.Also, we found that the leakage is dependent on the device＇s gate length.The three-transistor model（one main transistor with two parasitic transistors）can provide us with a brief understanding of the dependence on gate length.

Radiation response of pseudo-MOS transistors fabricated in hardened fully-depleted SIMOX SOI wafers

The total dose radiation response of pseudo-MOS transistors fabricated in hardened and unhardened FD （fully-depleted） SIMOX （Separation by Implanted Oxygen） SOI （Silicon-on-insulator） wafers is presented. At 1 Mrad（Si） radiation dose, the threshold voltage shift of the pseudo-MOS transistor is reduced from -115.5 to -1.9 V by the hardening procedure. The centroid location of the net positive charge trapped in BOX, the hole-trap density and the hole capture fraction of BOX are also shown. The results suggest that hardened FD SIMOX SOI wafers can perform well in a radiation environment.

Effects of Si implantation on the total dose hardness of fully-depleted SIMOX wafers

Total dose hardened fully-depleted SOI materials are fabricated on separation by implanted oxygen （SIMOX） materials by silicon ion implantation and annealing. The ID-VG characteristics of pseudo-MOS transistors pre- and post-irradiation are tested with ^60Co gamma rays. The chemical bonds and the structure of Si in the buried oxide are also studied by X-ray photoelectron spectroscopy and cross-sectional high-resolution transmission electron microscopy, respectively. The results show that Si nanocrystals in the buried oxide produced by ion implantation are efficient deep electron traps, which can significantly compensate positive charge buildup during irradiation. Si implantation can enhance the total-dose radiation tolerance of the fully-depleted SOI materials.

Influence of drain and substrate bias on the TID effect for deep submicron technology devices

This paper presents a study of the total ionization effects of a 0.18 #m technology. The electrical para meters of NMOSFETs were monitored before and after irradiation with 6~Co at several dose levels under different drain and substrate biases. Key parameters such as offstate leakage current and threshold voltage shift were studied to reflect the ionizing radiation tolerance, and explained using a parasitic transistors model. 3D device simulation was conducted to provide a better understanding of the dependence of device characteristics on drain and substrate biases.

Radiation induced inter-device leakage degradation

The evolution of inter-device leakage generation technologies is studied with an N-type current with total ionizing dose in transistors in 180 nm poly-gate field device （PFD） that uses the shallow trench isolation as an effective gate oxide. The overall radiation response of these structures is determined by the trapped charge in the oxide. The impacts of different bias conditions during irradiation on the inter-device leakage current are studied for the first time in this work, which demonstrates that the worst condition is the same as traditional NMOS transistors. Moreover simulation is used to understand the bias dependence the two-dimensional technology computer-aided design