Effects of indium ion implantation on the total dose hardness of fully depleted SOI NMOSFET

In this work, we investigate the effects of the indium ion implantation towards the back-channel interface on the total dose hardness of the n-channel SOI MOSFET. The results show that the indium implant has slight impact on the normal threshold voltage while preserving low leakage current after irradiation. The advantage is attributed to the narrow as-implanted and postanneal profile of the indium implantation. Two-dimensional simulations have been used to understand the physical mechanisms of the effects.

Silicon-on-insulating multi-layers for total-dose irradiation hardness

Silicon-on-insulating multi-layer (SOIM) materials were fabricated by co-implantation of oxygen and nitrogen ions with different energies and doses. The multilayer microstructure was investigated by cross-sectional transmission electron microscopy. P-channel metal-oxide-semiconductor (PMOS) transistors and metal-semiconductor-insulator-semiconductor (MSIS) capacitors were produced by these materials. After the irradiated total dose reaches 3 x 10(5) rad (Si), the threshold voltage of the SOIM-based PMOS transistor only shifts 0.07 V, while thin silicon-on-insulating buried-oxide SIMOX-based PMOS transistors have a shift of 1.2V, where SIMOX represents the separated by implanted oxygen. The difference of capacitance of the SOIM-based MSIS capacitors before and after irradiation is less than that of the thin-box SIMOX-based MSIS capacitor. The results suggest that the SOIM materials have a more remarkable irradiation tolerance of total dose effect, compared to the thin-buried-oxide SIMOX materials.

Radiation hardness improvement of separation-by-implantation-of-oxygen/silicon-on-insulator material by nitrogen ion implantation

In our work, nitrogen ions were implanted into separation-by-implantation-of-oxygen (SIMOX) wafers to improve the radiation hardness of the SIMOX material. The experiments of secondary ion mass spectroscopy (SIMS) analysis showed that some nitrogen ions were distributed in the buried oxide layers and some others were collected at the Si/SiO2 interface after annealing. The results of electron paramagnetic resonance (EPR) suggested the density of the defects in the nitrided samples changed with different nitrogen ion implantation energies. Semiconductor-insulator-semiconductor (SIS) capacitors were made on the materials, and capacitance-voltage (C-V) measurements were carried out to confirm the results. The super total dose radiation tolerance of the materials was verified by the small increase of the drain leakage current of the metal-oxide-semiconductor field effect transistor with n-channel (NMOSFETs) fabricated on the materials before and after total dose irradiation. The optimum implantation energy was also determined.

Improvement of the radiation hardness of SIMOX buried layers using nitrogen implantation

An investigation of hardening the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers to total-dose irradiation has been made by implanting nitrogen into the BOX layers with a constant dose at different implantation energies. The total-dose radiation hardness of the BOX layers is characterized by the high frequency capacitance-voltage (C-V) technique. The experimental results show that the implantation of nitrogen into the BOX layers can increase the BOX hardness to total-dose irradiation. Particularly, the implantation energy of nitrogen ions plays an important role in improving the radiation hardness of the BOX layers. The optimized implantation energy being used for a nitrogen dose, the hardness of BOX can be considerably improved. In addition, the C-V results show that there are differences between the BOX capacitances due to the different nitrogen implantation energies.

Effect of the technology of implanting nitrogen into buried oxide on the radiation hardness of the top gate oxide for partially depleted SOIPMOSFET

The effect of implanting nitrogen into buried oxide on the top gate oxide hardness against total irradiation does has been investigated with three nitrogen implantation doses (8 x 10(15), 2 x 10(16) and 1 x 10(17) cm(-2)) for partially depleted SOI PMOSFET. The experimental results reveal the trend of negative shift of the threshold voltages of the studied transistors with the increase of nitrogen implantation dose before irradiation. After the irradiation with a total dose of 5 x 10(5) rad(Si) under a positive gate voltage of 2V, the threshold voltage shift of the transistors corresponding to the nitrogen implantation dose 8 x 10(15) cm(-2) is smaller than that of the transistors without implantation. However, when the implantation dose reaches 2 x 10(16) and 1 x 10(17) cm(-2), for the majority of the tested transistors, their top gate oxide was badly damaged due to irradiation. In addition, the radiation also causes damage to the body-drain junctions of the transistors with the gate oxide damaged. All the results can be interpreted by tracing back to the nitrogen implantation damage to the crystal lattices in the top silicon.

Improved neutron radiation hardness for Si detectors: Application of low resistivity starting material and or manipulation of N-eff by selective filling of radiation-induced traps at low temperatures

Radiation-induced electrical changes in both space charge region (SCR) of Si detectors and bulk material (BM) have been studied for samples of diodes and resistors made on Si materials with different initial resistivities. The space charge sign inversion fluence (Phi(inv)) has been found to increase linearly with the initial doping concentration (the reciprocal of the resistivity), which gives improved radiation hardness to Si detectors fabricated from low resistivity material. The resistivity of the BM, on the other hand, has been observed to increase with the neutron fluence and approach a saturation value in the order of hundreds k Omega cm at high fluences, independent of the initial resistivity and material type. However, the fluence (Phi(s)), at which the resistivity saturation starts, increases with the initial doping concentrations and the value of Phi(s) is in the same order of that of Phi(inv) for all resistivity samples. Improved radiation hardness can also be achieved by the manipulation of the space charge concentration (N-eff) in SCR, by selective filling and/or freezing at cryogenic temperatures the charge state of radiation-induced traps, to values that will give a much smaller full depletion voltage. Models have been proposed to explain the experimental data.

NP难问题的算法和实验性研究

NP难是计算机科学中的一个重要概念和核心问题，自从它的提出到现在， 人们已经得到了很多重要的理论结果。直观上讲，一个问题一旦被证明是NP难 的就意味着我们很难找到该问题的一个多项式时间的有效算法。但从实用的角 度讲，对于应用中遇到的问题，单单是证明它很难（是NP难的）是不够的，如何 在合理的时间内求解实际问题也是必须解决的现实问题。本文主要侧重于NP难 问题的算法和实验性研究，研究对象主要是可满足性问题、图的顶点染色、图 的子图匹配等NP难问题，以及可满足性模理论的解空间计算和体积估算等扩展 问题。 围绕几个著名的问题，本文的主要工作如下： 针对图染色问题，日本研究人员提出了一种通过组合小图单元得到大的难 实例的方法。他们通过试错的方式手工找到了7个小图单元。我们提出了一种新 的构造算法来系统地生成这类小图单元，用我们的算法生成的难图染色实例， 主流的图染色工具需要指数时间才能求解；在一些专门求解色数比较小的图的 图染色工具上我们的算法生成的实例更难求解。针对皇后图染色问题，我们利 用模型查找工具SEM来对这类问题进行求解，在求解过程中提出了新的变量选 择策略，发现比简单地使用可满足性问题工具和图染色工具效果要好。 针对语义Web推理中的关键问题RDF蕴含关系的判定问题，我们利用从子 图同构问题到可满足性问题的编码方案，把它转化为命题逻辑公式的可满足性 判定问题，并采用了启发式的方法对编码过程进行必要的化简得到较少的布尔 公式，然后再利用高效的可满足性问题工具来求解。这种转化为可满足性问题 的方法，是跟RDF简单蕴含的模型论语义结合比较自然的一个方法。在小规模 实例上，这种方法的效果也很好。 针对布尔和数值混合约束的公式，即可满足性模理论（线性理论）公式的 体积计算这一新问题，我们首先给出一个直接计算体积的方法，然后提出一个 改进的算法，并研究了如何通过引入可满足性模理论中的技术来尝试对该算法 进一步地改进。我们实现了工具并做了实验。在一个实际的程序实例上，我们 还就“热门路径”问题做了实例研究和探讨。 体积计算是一个有广泛应用背景的经典难题（#P难的），但以前的方法要 么只能处理线性约束，要么只具有理论价值（不够实用）；针对含非线性约束的 体积计算问题我们提出了实用的算法，并设计了相应的工具，在低维实例有很 好的逼近效果。

纯公钥模型下对NP语言的高效并发零知识证明系统

提出了一种从3轮公开掷币的对任何NP语言的诚实验证者零知识证明系统到纯公钥模型下4轮f轮最优）对同一语言的具有并发合理性的并发零知识证明系统．该转化方法有如下优点：1）它只引起D（1）（常数个）额外的模指数运算，相比DiCrescenzo等人在ICALP05上提出的需要qn）个额外的模指数运算的转化方法孩系统在效率上有着本质上的提高，而所需的困难性假设不变；2）在离散对数假设下，该转化方法产生一个完美零知识证明系统．注意到DiCrescenzo等人提出的系统只具有计算零知识性质．该转化方法依赖于一个特殊的对承诺中的离散对数的3轮诚实验证者零知识的证明系统．构造了两个基于不同承诺方案的只需要常数个模指数运算的系统这种系统可能有着独立价值．

Radiation hardness characteristic of N-implanted and F-implanted SIMOX/NMOSFET

Radiation hardness of SIMOX(separation by implanted oxygen)/NMOSFET by implanting N and F ion has been carefully studied in this paper.Both N and F ion implantation can reduce hole traps in the buried oxide and the interfacial regions,which consequently improves the radiation hardness,especially under high dose radiation conditions.Moreover,experimental data show that the higher dose of the N and F ion implantation is,the better radiation hardness is achieved.In order to minimize the influence on the threshold voltage of devices,it is important to choose suitable implantation dose and energy of N or F implantation that have smaller impact on the preradiation device performance.

Sensitivity of Total-Dose Radiation Hardness of SIMOX Buried Oxides to Doses of Nitrogen Implantation into Buried Oxides

In order to improve the total-dose radiation hardness of the buried oxides(BOX) in the structure of separa tion-by-implanted-oxygen(SIMOX) silicon-on-insulator(SOI), nitrogen ions are implanted into the buried oxides with two different doses,2 × 1015 and 3 × 1015 cm-2 , respectively. The experimental results show that the radiation hardness of the buried oxides is very sensitive to the doses of nitrogen implantation for a lower dose of irradiation with a Co-60 source. Despite the small difference between the doses of nitrogen implantation, the nitrogen-implanted 2 × 1015 cm-2 BOX has a much higher hardness than the control sample (i. e. the buried oxide without receiving nitrogen implantation) for a total-dose irradiation of 5 × 104rad(Si), whereas the nitrogen-implanted 3 × 1015 cm-2 BOX has a lower hardness than the control sample. However,this sensitivity of radiation hardness to the doses of nitrogen implantation reduces with the increasing total-dose of irradiation (from 5 × 104 to 5 × 105 rad (Si)). The radiation hardness of BOX is characterized by MOS high-frequency (HF) capacitance-voltage (C-V) technique after the top silicon layers are removed. In addition, the abnormal HF C-V curve of the metal-silicon-BOX-silicon(MSOS) structure is observed and explained.

Improved neutron radiation hardness for Si detectors: Application of low resistivity starting material and or manipulation of N-eff by selective filling of radiation-induced traps at low temperatures

Radiation-induced electrical changes in both space charge region (SCR) of Si detectors and bulk material (BM) have been studied for samples of diodes and resistors made on Si materials with different initial resistivities. The space charge sign inversion fluence (Phi(inv)) has been found to increase linearly with the initial doping concentration (the reciprocal of the resistivity), which gives improved radiation hardness to Si detectors fabricated from low resistivity material. The resistivity of the BM, on the other hand, has been observed to increase with the neutron fluence and approach a saturation value in the order of hundreds k Omega cm at high fluences, independent of the initial resistivity and material type. However, the fluence (Phi(s)), at which the resistivity saturation starts, increases with the initial doping concentrations and the value of Phi(s) is in the same order of that of Phi(inv) for all resistivity samples. Improved radiation hardness can also be achieved by the manipulation of the space charge concentration (N-eff) in SCR, by selective filling and/or freezing at cryogenic temperatures the charge state of radiation-induced traps, to values that will give a much smaller full depletion voltage. Models have been proposed to explain the experimental data.