Metastable Electron Traps in Modified Silicon-on-Insulator Wafer

We perform the total ionizing radiation and electrical stress experiments to investigate the electrical characteristics of the modified silicon-on-insulator(SOI) wafers under different Si ion implantation conditions. It is confirmed that Si implantation into the buried oxide can create deep electron traps with large capture cross section to effectively improve the antiradiation capability of the SOI device. It is first proposed that the metastable electron traps accompanied with Si implantation can be avoided by adjusting the peak location of the Si implantation reasonably.     

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/SiO 2 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.     

Radiation induced inter-device leakage degradation

The evolution of inter-device leakage current with total ionizing dose in transistors in 180 nm generation technologies is studied with an N-type 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, the two-dimensional technology computer-aided design simulation is used to understand the bias dependence.     

Enhanced radiation-induced narrow channel effects in 0.13-μm PDSOI nMOSFETs with shallow trench isolation

Total ionizing dose responses of different transistor geometries after being irradiated by ~(60)Co γ-rays, in 0.13-μm partially-depleted silicon-on-insulator(PD SOI) technology are investigated. The negative threshold voltage shift in an n-type metal-oxide semiconductor field effect transistor(nMOSFET) is inversely proportional to the channel width due to radiation-induced charges trapped in trench oxide, which is called the radiation-induced narrow channel effect(RINCE).The analysis based on a charge sharing model and three-dimensional technology computer aided design(TCAD) simulations demonstrate that phenomenon. The radiation-induced leakage currents under different drain biases are also discussed in detail.     

Radiation response of pseudo-MOS transistors fabricated in hardenedfully-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.     

0.18 μm MOSFET器件的总剂量辐照效应

对0.18 μm 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. 关键词： 总剂量效应 浅沟槽隔离 氧化层陷阱正电荷 MOSFET     

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.     

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.     

Utilizing a shallow trench isolation parasitic transistor to characterize the total ionizing dose effect of partially-depleted silicon-on-insulator input/output n-MOSFETs

We investigate the effects of 60 Co γ-ray irradiation on the 130 nm partially-depleted silicon-on-isolator(PDSOI)input/output(I/O) n-MOSFETs. A shallow trench isolation(STI) parasitic transistor is responsible for the observed hump in the back-gate transfer characteristic curve. The STI parasitic transistor, in which the trench oxide acts as the gate oxide,is sensitive to the radiation, and it introduces a new way to characterize the total ionizing dose(TID) responses in the STI oxide. A radiation enhanced drain induced barrier lower(DIBL) effect is observed in the STI parasitic transistor. It is manifested as the drain bias dependence of the radiation-induced off-state leakage and the increase of the DIBL parameter in the STI parasitic transistor after irradiation. Increasing the doping concentration in the whole body region or just near the STI sidewall can increase the threshold voltage of the STI parasitic transistor, and further reduce the radiation-induced off-state leakage. Moreover, we find that the radiation-induced trapped charge in the buried oxide leads to an obvious front-gate threshold voltage shift through the coupling effect. The high doping concentration in the body can effectively suppress the radiation-induced coupling effect.     

Research on the radiation hardened SOI devices with single-step Si ion implantation

Silicon-on-insulator(SOI) devices are sensitive to the total ionizing dose effect due to the existence of buried oxide.In this paper,an extra single-step Si ion implantation into buried oxide layer prior to the normal complementary metal–oxide–semiconductor transistor(CMOS) process is used to harden the SOI wafer.The top-Si quality of the hardened SOI wafer is confirmed to be good enough for device manufacturing through various characterization methods.The radiation experiments show that the total ionizing dose tolerance of the Si implanted SOI device is improved significantly.The metastable electron traps introduced by Si implantation is also investigated by electrical stress.The results show that these traps are very instable,and electrons will tunnel into or out of the metastable electron traps quickly after hot-electroninjection or hot-hole-injection.