Characterization of buried SiO2 layers formed by ion implantation of oxygen

Oxygen has been ion implanted (200 keV) into silicon at doses ranging from 2E17/cm² to 2E18/cm². The peak oxygen concentration occurs at a depth of 0.5 μm. These doses produce peak oxygen concentrations which are below and above the concentrations necessary to form stoichiometric SiO₂. If the oxygen concentration exceeds stoichiometry, a buried SiO₂ layer is formed with a thin superficial silicon layer on the surface. This superficial silicon layer has been used as a seed for growing single crystal silicon epi. The resulting Silicon on Insulator (SOI) structure has been characterized by Rutherford backscattering, cross-sectional TEM, AES, optical microscopy, spreading resistance probe, Hall effect and infrared transmission measurements. The effects of dose, substrate temperature during the implant, and subsequent anneal conditions have been examined.     

Formation of buried oxide layers by high dose implantation of oxygen ions in silicon

Buried implanted oxide layers have been formed by high dose implantation of oxygen ions of the order of 1 × l0¹⁸−2 in silicon. The effects of dose at a given energy, and energy for a given peak concentration, on the distribution profile of oxygen have been studied. An approximately Gaussian distribution is observed at doses contributing less than the stoichiometric requirement of oxygen for the formation of silicon dioxide. A saturation in the oxygen peak concentration is reached when the stoichiometric requirement is exceeded. The excess implanted oxygen results in a broadening of the stoichiometric implanted oxide layer. A consequent reduction in the interface damage is observed. Other parameters being equal, at higher substrate temperatures the interface damage is decreased. For a given peak concentration, the implanted oxide is buried more deeply with increasing ion energy. Infra-red absorption characteristics of the implanted oxide are almost identical to those of thermal oxide layers grown in a dry oxygen ambient. The implanted oxide layer exhibits also an extremely high resistivity compared to the substrate material. Department of Electronics, University of Kent,Canterbury,Kent,U.K.     

Electric-field-shielding layers formed by oxygen implantation into silicon

The electric-field-shielding effect was found in a layer consisting of a mixture of polycrystalline silicon and silicon oxide formed by oxygen ion implanatation. The layer was formed between the buried SiO2 and the upper Si layer, which improved characteristics for MOSFETs fabricated using SIMOX (separation by implanted oxygen) technology. By forming this layer, the threshold voltages for the MOSFETs were almost independent of substrate bias. Drain-to-source breakdown voltages for the p-MOSFETs and n-MOSFETs were raised to 250 V and 180 V, respectively.     

Characteristics of MOSFETs fabricated in silicon-on-insulator material formed by high-dose oxygen ion implantation

By implanting a dose of 6×1017 cm?2 of 32O at 300 keV into a silicon wafer, a buried oxide layer is formed. Crystallinity of the silicon layer above the buried oxide layer is maintained by applying a high (>200°C) substrate temperature during the ion implantation process. A two-step anneal cycle is found to be adequate to form the insulating buried oxide layer and to repair the implantation damage in the silicon layer on top of the buried oxide. A surface electron mobility as high as 710 cm2/Vs has been measured in n-channel MOSFETs fabricated in a 0.5 ?m-thick epitaxial layer grown on the buried oxide wafer. A minimum subthreshold current of about 10 pA per micron of channel width at VDS=2 V has been measured.     

Regrowth of amorphous layers in silicon-on-insulator structures formed by the implantation of oxygen

Synthesised silicon-on-insulator structures have been formed and implanted with 1×1016 As+ cm?2 at 40 keV. The regrowth kinetics of the amorphised layer, which also contains lattice defects and excess oxygen, has been studied by Rutherford backscattering. The regrowth of the layer occurs at a mean rate of 13 ? min?1 at 500°C with an activation energy of 2.7±0.2 eV. This experiment further demonstrates the suitability of these synthesised structures as a direct replacement for bulk silicon in VLSI technology.     

C.M.O.S. devices fabricated on buried SiO2 layers formed by oxygen implantation into silicon

Buried SiO2, layers were formed by oxygen-ion (14O+) implantation into silicon. The impurity distribution of the oxygen-implanted silicon substrate was analysed by auger spectroscopy. The epitaxially-grown silicon layer on this substrate showed a good monocrystalline structure, and a 19-stage c.m.o.s. ring oscillator exhibited high performance in operation.     

Buried nanoscale damaged layers formed in Si and SiC crystals as a result of high-dose proton implantation

Buried nanoscale damaged layers formed in Si and SiC crystals via 50-and 100-keV proton implantation were studied. It is shown that the sensitivity of atomic-force microscopy is sufficiently high to detect the initial stages of the development of hydrogen-containing voids and microcracks in subsurface layers of irradiated crystals and to study exfoliation of the crystals in the plane of microcracks. As a result, quantitative criteria for the formation of buried damaged layers in the studied crystals were derived; also, the conditions for blistering and for implementation of the “Smart-Cut” technology were determined.     

蜂窝车联网技术架构与关键技术研究

本文从车联网的定义、应用场景和两种无线通信技术的比较切入,首先介绍蜂窝车联网的技术架构和主要功能实体,其次介绍了该网络的两项关键技术,最后对关键技术的网络部署提出了建议。     

p-CZT的钝化处理和C-V特性研究

采用NH4F/H2O2作为p-CZT晶片的表面钝化剂,对未钝化与钝化表面处理的p-CZT晶片的C-V特性进行了对比研究.用XPS分析了钝化前后CZT晶体表面成分,发现钝化后CZT晶片表面形成厚度为3.1 nm的TeO2氧化层.用Agilent 4294A高精度阻抗分析仪,在1 MHz下对未钝化的和钝化的CZT晶片进行C-V测试.对测试结果的计算表明,钝化提高了Au与CZT接触的势垒高度(∮)b.未钝化的(∮)b为1.393 V,钝化后(∮)b变为1.512 V.     

利用高频C-V特性评价CMOS工艺

MOS结构电容由于其结构简单并且和CMOS工艺兼容,是进行实时工艺监控和测试工艺参数的重要测试结构。采用通过对相同工艺不同厂家生产的两批电容样品进行高频C-V测试,编程计算提取器件相关参数。通过对比同一厂家样品中相同面积MOS电容和不同面积电容参数的分布特性,以及不同厂家样品各个参数的差异,对CMOS相关工艺进行评价。为工艺过程以及相关设计的改进提供参考依据。     

Redistribution of ytterbium and oxygen in annealing of silicon layers amorphized by implantation

The redistribution of ytterbium and oxygen was studied in silicon layers that were implanted with 1-MeV Yb⁺ ions at a dose of 1×10¹⁴ cm^?2, which exceeds the amorphization threshold, and 135-keV O⁺ ions at a dose of 1×10¹⁵ cm^?2 and that were subsequently annealed at 620 and 900°C. The redistribution of Yb is due to segregation at the interface between the amorphous and single-crystal layers in solid-phase recrystallization of the buried amorphized layer. The redistribution of oxygen and its accumulation in regions with the highest concentration of Yb is associated with oxygen diffusion and the formation of YbO_n complexes with n varying from 1 to 6. The parameters characterizing the dependence of the Yb segregation coefficient on the thickness of the recrystallized layer and the formation of YbO_n complexes were determined.     

溶胶-凝胶法制备Bi2O3-ZnO-Nb2O5薄膜及GaNMIS结构C-V特性

采用溶胶-凝胶法制备出高介电常数的Bi2O3-ZnO-Nb2Os(BZN)薄膜.总结出适合作为GaN金属-绝缘层-半导体场效应晶体管(MIS FET)栅介质的BZN薄膜的原料配比、烧结温度和保温时间等工艺参数,解决了原料溶解、粘稠度、浸润度等工艺问题.同时,结合半导体工艺制造出以BZN薄膜为绝缘介质的GaN MIS结构,通过测量到的高频C-V特性曲线,得到薄膜的相对介电常数为91,MIS结构的强反型电压为-3.4V,平带电压为-1.9V.     

溶胶-凝胶法制备Bi2O3-ZnO-Nb2O5薄膜及GaNMIS结构C-V特性

采用溶胶-凝胶法制备出高介电常数的Bi2O3-ZnO-Nb2Os(BZN)薄膜.总结出适合作为GaN金属-绝缘层-半导体场效应晶体管(MIS FET)栅介质的BZN薄膜的原料配比、烧结温度和保温时间等工艺参数,解决了原料溶解、粘稠度、浸润度等工艺问题.同时,结合半导体工艺制造出以BZN薄膜为绝缘介质的GaN MIS结构,通过测量到的高频C-V特性曲线,得到薄膜的相对介电常数为91,MIS结构的强反型电压为-3.4V,平带电压为-1.9V.     

Thermal donor and new donor generation in SOI material formed by oxygen implantation

The oxygen content of silicon-on-insulator films, formed by oxygen implantation, is shown to be responsible for the generation of high-density free carriers: thermal donors at 450°C and new donors at 750°C. The variation of sheet resistance and spreading resistance profiles is measured after successive isochronal and isothermal anneals. The initial generation rate of new donors greatly exceeds that of thermal donors, suggesting a surface-states-related mechanism.     

InP基异质结界面暗电流C-V测试分析

采用电化学C-V测试方法,测量分析了InP/InGaAs/InP外延结构的I-V特性,对异质结界面的电学性质进行了表征和分析.采用LP-MOCVD生长技术,对不同界面生长条件的三种样品进行了I-V和XRD测试,得到了InP向InGaAs界面转换采用中断生长、InGaAs向InP界面转换采用As/P直接切换的优化生长方式.用逐层化学腐蚀的方法,对比分析了I-V特性与XRD测试结果的关系,论证了I-V测试结果的有效性,指出了表征异质结界面电学质量的简洁方法.     

基于改进型C-V模型的红外图像自动分割

将C-V模型引入到红外图像分割中,同时提出了一种改进的模型。该模型通过增加偏离能量项,避免了标准C-V模型的重新初始问题。模型允许选取较大的时间步长,可以用简单的有限差分格式实现。实验证明,改进的模型在分割效果不变的情况下可以有效加速演化过程,提高分割效率。     

X-ray-emission study of the structure of Si:H layers formed by low-energy hydrogen-ion implantation

Amorphous silicon layers formed by implantation of 24-keV hydrogen ions into SiO₂/Si and Si with doses of 2.7×10¹⁷ and 2.1×10¹⁷ cm^?2, respectively, were studied using ultrasoft X-ray emission spectroscopy with variations in the energy of excitation electrons. It is ascertained that the surface silicon layer with a thickness as large as 150–200 nm is amorphized as a result of implantation. Implantation of hydrogen ions into silicon coated with an oxide layer brings about the formation of a hydrogenated silicon layer, which is highly stable thermally.     

基于C-V模型的红外图像自动分割方法研究

为解决红外图像分割中背景噪声及边界轮廓的影响,引入了基于曲线演化理论、水平集方法和M-S分割函数的C-V模型。通过将图像表达为分段常量函数来建立适当的能量函数模型,引入水平集的表示方法,在整个图像域中依据最小化分割寻找全局极小值,可令活动轮廓最终到达目标边缘。由MATLAB实现的仿真结果表明采用C-V模型对红外图像进行自动分割不受边界轮廓线连续性限制,对初始轮廓线位置不敏感,对图像噪声具有很强的鲁棒性,对均匀灰度目标分割效果良好。     

基于改进C-V模型的肾脏CT图像分割方法

生物组织的自动分割是计算机辅助诊断和病变 检测的关键步骤。在腹腔CT图像中,肾脏组织本身的灰度不均匀性使得传统C-T模型无法准 确实现肾脏的分割。为了解决上述问题,本文结合图像全局和 局部统计信息改进了传统的C-V模型。 基于先验知识,提出了描述肾脏组织皮质 特征的数学表达式。选择感兴趣区域,在预处理阶段获得了CT图像中肾脏的大致初始轮廓。 随后,应用C-V模型进行轮廓演化时引入局域信息,提高了C-V模型的局部适应性。实验结 果表明,与现有方法相比,本文的方法的结果更接近于人工分割结果,其肾脏分割结果的Di ce系数平均值为94.0%。     

On the behaviour of buried oxygen implanted layers in highly doped GaAs

Highly doped GaAs substrate material (doping level 10¹⁸ cm⁻³) has been implanted with 350 keV O⁺ ions with doses of 10¹⁴ – 10¹⁶ cm⁻² to produce high resistivity layers which are stable at high temperatures. LPE growth of flat GaAs epilayers onto the implanted wafers was achieved up to doses of about 1 × 10¹⁵ O⁺/cm² and 5 × 10¹⁵O⁺/cm² for RT and 200°C implants, respectively. N-o-n and p-o-n structures (o: oxygen implanted) were fabricated in which breakdown voltages of up to 15 V were obtained. Examples for application of this isolation technique are shown.