注氟MOSFET电离辐射响应特性

对氢氧合成栅氧化后注F的MOSFET进行了γ射线辐照试验,分析了不同注F剂量的MOSFET电离辐射响应特性。结果表明,在1×10~(15)～1×10~(16)F/cm~2F注量范围内,注F能够明显抑制辐射感生氧化物电荷和界面态的增长,且F注量越高,抑制能力越强,F的注入能减少工艺过程所带来的氧化物电荷和界面态。用Si一F结键替代其它在辐射过程中易成为电荷陷阱的应力键模型对实验结果进行了讨论。可以预测,F在Si/SiO_2界面附近和SiO_2中的行为直接与MOS结构的辐射响应相对应,而F的行为依赖于注F工艺条件。     

薄二氧化硅MOS电容电离辐射陷阱电荷研究

采用高频 C- V曲线方法 ,研究了 5 0 nm及 15 nm MOS电容电离辐射空穴陷阱及界面态的建立过程 .二种样品电离辐射空穴陷阱电荷密度在 1× 10 3Gy(Si)剂量下近乎相同 ,而在大于 3× 10 3Gy(Si)剂量下 ,5 0 nm MOS电容的电荷密度约为 15 nm MOS电容的 2倍 .利用电离辐射后的隧道退火效应 ,计算出二种样品电离辐射陷阱电荷在Si- Si O2 界面附近分布的距离均约为 4nm .     

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.     

不同辐照剂量率下NPN晶体管的电流增益退化模型

电离辐照使NPN晶体管基极电流增加,导致电流增益退化。辐照感生的界面态使表面复合速率,感生的氧化物电荷改变基区表面势,导致表面复合率增加,这两者都引起基极电流增加;基于此,建立了电流增益退化模型。结合感生的界面态和氧化物电荷的产生机制,这个模型能够解释辐照导致的增益退化,以及增益退化的低剂量率增强效应。在Co60 源上进行了γ射线辐照试验,高剂量率为10 rad (Si)/,低剂量率为0.1 rad(Si)/s,总剂量为70krad(Si)。这个模型很好解释实验数据。     

环境温度、电离辐射剂量率对NMOSFET器件特性参数的影响

研究了辐射环境温度、辐射剂量率、退火温度和退火偏置对 CC40 0 7NMOS器件阈值电压的影响 .研究发现 ,低温 (- 30℃ )辐照感生的氧化物陷阱电荷比室温 (2 5℃ )多 ,界面态电荷比室温要少 ;受不同 γ剂量率辐射时 ,阈值电压的漂移程度不一样 ,在总剂量相同情况下 ,辐射剂量率高时 ,阈值电压的漂移量也大 ;辐照后 ,NMOS器件 10 0℃退火速度要大于 2 5℃退火速度 ,+5 V栅偏压退火情况要大于浮空偏置情况 .并对以上现象进行了分析和解释     

深亚微米体硅器件电离辐射及退火与温度的相关性研究

对经过Co60不同剂量剂量率辐照的体硅MOS器件(NMOSFET与PMOSFET)分别进行了室温和高温下的退火实验,并对退火结果进行分析,讨论了退火温度对MOS器件阈值电压及辐射感生的氧化层陷阱电荷与界面态电荷产生的影响.     

环境温度、电离辐射剂量率对NMOSFET器件特性参数的影响

研究了辐射环境温度、辐射剂量率、退火温度和退火偏置对CC4007NMOS器件阈值电压的影响.研究发现,低温(-30℃)辐照感生的氧化物陷阱电荷比室温(25℃)多,界面态电荷比室温要少;受不同γ剂量率辐射时,阈值电压的漂移程度不一样,在总剂量相同情况下,辐射剂量率高时,阈值电压的漂移量也大;辐照后,NMOS器件100℃退火速度要大于25℃退火速度,+5V栅偏压退火情况要大于浮空偏置情况.并对以上现象进行了分析和解释.     

利用MOSFET亚阈I-V特性进行辐射感生界面陷阱的测量

本文利用MOSFET亚阈IV曲线对加固和非加固MOSFET的辐射感生界面陷阱密度进行了测量.分析和讨论了辐射感生的界面陷阱密度依赖于辐射总剂量和辐射剂量率的变化关系     

脉冲γ射线对光纤的辐射感生损耗

研究了光纤受射线辐照响应机制,计算了光纤对射线吸收率、效应截面、Compton电子的能通量及角度分布;提出了瞬态辐射感生损耗的测量方法,采用波长分别为405、660、850、1 310、1 550 nm的模拟宽带光纤传输系统,设计了瞬态辐射感生损耗的实验测量系统。在平均光子能量0.3 MeV、剂量率2.03107 Gy/s和平均光子能量1.0 MeV、剂量率5.32109 Gy/s的两种脉冲射线辐照条件下,获得了4种光纤瞬态辐射感生损耗与剂量的关系、永久性感生损耗的谱分布和折射率变化结果:（1）脉冲射线对光纤的瞬态辐射感生损耗随探测波长在近红外到可见光范围内的减小而增大;（2）在相同辐照条件下,多模光纤的瞬态辐射感生损耗稍大于单模光纤;（3）辐射致光纤折射率降低;（4）在一定剂量范围内,多模光纤瞬态辐射感生损耗和剂量呈近似线性关系。研究表明,射线导致光纤基质原子产生新的色心和光纤折射率降低,色心对传输光子的共振吸收导致光纤吸收损耗增加,折射率降低导致光纤波导损耗增加,感生损耗是两种机制共同作用的结果。     

一种抗辐射加固功率器件──VDMNOSFET

采用 Si3N4- Si O2 双层栅介质及自对准重掺杂浅结 P+区研制出了一种抗辐射加固功率器件—— VDMNOS-FET (垂直双扩散金属 -氮化物 -氧化物 -半导体场效应晶体管 ) .给出了该器件的电离辐射效应及瞬态大剂量辐射的实验数据 ,与常规 VDMOSFET相比获得了良好的抗辐射性能 .对研制的 2 0 0 V VDMNOSFET,在栅偏压 +10 V,γ 总剂量为 1Mrad (Si)时 ,其阈值电压仅漂移了 - 0 .5 V,跨导下降了 10 % .在 γ瞬态剂量率达 1× 10 1 2 rad(Si) /s时 ,器件未发生烧毁失效 .实验结果证明 Si3N4- Si O2 双层栅介质及自对准重掺杂浅结 P+区显著地改善了功率 MOS器件的     

EEPROM和SRAM瞬时剂量率效应比较

对一种256 kb EEPROM电路AT28C256和一种256 kb SRAM电路HM62256开展了"强光一号"瞬时剂量率效应实验,测量了存储器的闩锁效应、翻转效应等。HM62256的翻转阈值为9.0×106 Gy(Si)/s,闩锁阈值高于5.4×107 Gy(Si)/s。AT28C256的闩锁阈值为2×107 Gy(Si)/s,存储单元翻转阈值高于3.0×108 Gy(Si)/s。对于SRAM,其翻转阈值远低于闩锁阈值;而对于EEPROM,在瞬时辐照下,闩锁阈值远低于存储单元的翻转阈值。基于两种存储器的数据存储原理,分析了SRAM和EEPROM瞬时剂量率效应差异的原因。     

The effect of oxide layer thickness on the quantification of 1.5 MeV γ–radiation induced interface traps in the Ag/SiO2/Si MOS devices

This work presents the effect of varied thickness of oxide layer and radiation dose on electrical characteristics of Ag/SiO₂/Si MOS devices irradiated by 1.5 MeV γ–radiations of varied doses. SiO₂ layers of 50, 100, 150 and 200 nm thickness were grown on Si substrates using dry oxidation and exposed to radiation doses of 1, 10 and 100 kGy. The exposure to radiation resulted in generation of fixed charge centers and interface traps in the SiO₂ and at the Si/SiO₂ interface. Capacitance-conductance-voltage (C-G-V) and capacitance-conductance-frequency (C-G-f) measurements were performed at room temperature for all MOS devices to quantify the active traps and their lifetimes. It is shown that accumulation and minimum capacitances decreased as the thickness of SiO₂ layer increased. For the unexposed MOS devices, the flat band voltage V_FB decreased at a rate of −0.12 V/nm, density of active traps increased by 4.5 times and depletion capacitance C_DP, increased by 2.5 times with the increase of oxide layer thickness from 50 to 200 nm. The density of active traps showed strong dependence on the frequency of the applied signal and the thickness of the oxide layer. The MOS device with 200 nm thick oxide layer irradiated with 100 kGy showed density of active interface traps was high at 50 kHz and was 3.6×10¹⁰ eV⁻¹ cm⁻². The relaxation time of the interface traps also increased with the exposure of γ–radiation and reached to 9.8 µs at 32 kHz in 200 nm thick oxide MOS device exposed with a dose of 100 kGy. It was inferred that this was due to formation of continuum energy states within the band gap and activation of these defects depended on the thickness of oxide layer, applied reverse bias and the working frequency. The present study highlighted the role of thickness of oxide layer in radiation hard environments and that only at high frequency, radiation induced traps remain passivated due to long relaxation times.     

硅PIN光电二极管γ电离脉冲辐射的数值模拟

分析了γ电离脉冲辐射诱发硅PIN光电二极管产生光电流的机理.建立了硅PIN光电二极管的器件物理模型以及γ电离脉冲辐射效应模型;运用MEDICI软件,进行了辐射效应数值模拟计算.得出了γ电离脉冲辐射剂量率在10°～109Gy(Si)/s范围内,诱发硅PIN光电二极管光电流变化的初步规律.对比了辐射效应数值模拟结果与国外相关文献给出的辐照实验结果.

Abstract：

The mechanism of photocurrent of Si PIN photodiode induced by γ ionization pulse radiation is analyzed.The device physics and γ ionization pulse radiation models are established to simulate photocurrent of Si PIN photodiode by MEDICI software.The primary regularity of photocurrent of Si PIN photodiode is concluded by γ ionization pulse radiation with the dose rate of 10~0～10~9 Gy (Si)/s.The Simulation results are in agreement with the experimental results given in correlative literatures.     

Optical and electrical characteristics of 17 keV X-rays exposed TiO2 films and Ag/TiO2/p-Si MOS device

This work presents the effect of varied doses of X-rays radiation on the Ag/TiO₂/p-Si MOS device. The device functionality was observed to depend strongly on the formation of an interfacial layer composed of SiO_x and TiO_y, which was confirmed by the spectroscopic ellipsometry. The XRD patterns showed that the as prepared TiO₂ films had an anatase phase and its exposure to varied doses of 17 keV X-rays resulted in the formation of minute rutile phase. In the X-rays exposed films, reduced Ti³⁺ state was not observed; however a fraction of Ti–O bonds disassociated and little oxygen vacancies were created. It was observed that the device performance was mainly influenced by the nature and composition of the interfacial layer formed at the TiO₂/Si interface. The spectroscopic ellipsometry was used to determine the refractive indices of the interfacial layer, which was 2.80 at λ=633 nm lying in between that of Si (3.87) and TiO₂ (2.11). The dc and frequency dependent electrical measurements showed that the interface defects (traps) were for both types of charge carriers. The presence of SiO_x was responsible for the creation of positive charge traps. The interface trap density and relaxation time (τ) were determined and analyzed by dc and frequency dependent (100 Hz–1 MHz) ac-electrical measurements. The appearance of peak in G/ω vs log (f) confirmed the presence of interface traps. The interface traps initially increased up to exposure of 10 kGy and then decreased at high dose due to compensation by the positive charge traps in SiO_x part of the interface layer. It was observed that large number of interface defects was active at low frequencies and reduced to a limiting value at high frequency. The values of relaxation time, τ ranged from 4.3±0.02×10⁻⁴ s at 0 V and 7.6±0.2×10⁻⁵ s at −1.0 V.     

Total ionizing dose radiation effects on NMOS parasitic transistors in advanced bulk CMOS technology devices

In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are examined. The radiation tests are performed at ⁶⁰Co sources at the dose rate of 50 rad (Si)/s. The investigation''s results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation structure is the main total dose problem. The total ionizing dose (TID) radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is established. The I-V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I-V characteristics of 180 nm commercial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device.     

Traps with near-midgap energies at the bonded Si/SiO<Subscript>2</Subscript> interface in silicon-on-insulator structures

Capture centers (traps) are studied in silicon-on-insulator (SOI) structures obtained by bonding and hydrogen-induced stratification. These centers are located at the Si/SiO₂ interface and in the bulk of the split-off Si layer. The parameters of the centers were determined using charge deep-level transient spectroscopy (Q-DLTS) with scanning over the rate window at fixed temperatures. Such a method allows one to study the traps near the Si midgap at temperatures near 295 K. It is shown that the density of traps with a continuous energy spectrum, which are located at the bonded Si/SiO₂ interface, decreases by more than four orders of magnitude at the mid-gap compared with the peak density observed at the activation energy E _a ≈0.2–0.3 eV. The capture centers are also found in the split-off Si layer of the fabricated SOI structures. Their activation energy at room temperature is E _a =0.53 eV, the capture cross section is 10^?19 cm², and the concentration is (0.7–1.7)×10¹³ cm^?3. It is assumed that these capture centers are related to deep bulk levels induced by electrically active impurities (defects) in the split-off Si layer close to the Si/SiO₂ interface.     

MOS结构辐照陷阱消长研究的快速I—V技术

建立了一套用于MOS结构辐照陷阱消长规律研究的快速I－V在线测试系统，用此系统可进行自动加偏和Ids－Vgs亚阈曲线测试，从而可快速定性定量地获得辐照和退火环境中氧化物电荷和Si／SiO_2界面态随辐照剂量、时间、偏置等的依赖关系。快速I－V测试系统最高可以达到1次／秒的Ids－Vgs测量速度。用此系统研究了PMOSFET5×10~3Gy（Si）总剂量辐照后100℃恒温退火下，辐照陷阱的消长规律和机制。     

Charge fluctuations at the bonding interface in the silicon-on-insulator structures

Starting from the data of deep-level transient spectroscopy, the charge fluctuations at the interface between the top Si layer and buried insulator in Si-on-insulator structures are evaluated. The interface was prepared by bonding Si with the thermally oxidized substrate. The magnitude of fluctuations at the interface is found to be equal or exceed (1.5–2.0)×10¹¹ cm^?2 against the charge background of ～5×10¹¹ cm^?2 at this interface. It is shown that the fluctuations are most likely associated with the negative charge at the surface states rather than with the fluctuations of the fixed positive charge within oxide.