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.     

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.     

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.     

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.     

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.     

Properties of buried SiC layers produced by carbon ion implantation in (100) bulk silicon and silicon-on-sapphire

Buried layers of SiC were formed in (100) single-crystal bulk silicon and silicon-on-sapphire by ion implantation of 125–180 keV, (0.56-1.00) × 10¹⁸ C/cm² at 30–40 μA/ cm² into samples held at 450-650° C. The as-implanted and 950° C annealed samples were characterized by differential infra-red absorbance and reflectance, Rutherford backscattering and channeling spectrometry, x-ray diffraction, four-point probe measurements, Dektak profilometry, I-V measurements, spreading resistance measurements and secondary ion mass spectrometry. Work done while affiliated with Rockwell International Corporation, Microelectronics Research & Development Center, 3370 Miraloma Avenue, Anaheim, CA 92803 and a Visiting Associate at the California Institute of Technology, Department of Applied Physics, Mail Code 116-81, Pasadena, CA 91125.     

C-V characteristics of ion implanted depletion IGFETs and buried channel CCDs

Capacitance voltage measurements of ion implanted devices for several circuit connections are presented and interpreted in terms of a simple constant profile approximation. Based on this model the device capacitance is described quantitatively in terms of the series combination of a p?n junction capacitance and a conventional MOS capacitance. It is shown that shallow and deep implants reveal characteristically distinctive C-V curves which provide an immediate rough estimate of the implant depth. Analysis of the model yields directly, important parameters for first order design purposes. It is also shown that the measurements provide a simple diagnostic technique to examine the physics of the implanted structure. The use of the simplified model is justified by the agreement between experimental and calculated values.     

6H-SiC埋沟MOSFET的C-V解析模型研究

研究了6H-SiC埋沟MOSFET器件的电容-电压特性,建立了解析模型.具体分析了埋沟MOSFET各种工作模式下的电容与栅电压之间的关系,考虑了SiO2/SiC界面态及pn结对电容-电压特性的影响.对模型进行了仿真分析验证,结果表明:在假设界面态密度分布均匀条件下,由于对界面态做了简化处理,因而在耗尽模式及夹断模式下的C-V特性计算结果与实验结果有所差异.     

用C—V法测试Cd在InSb中扩散层的杂质浓度及其分布

在光伏型红外探测器的生产中,扩散层的杂质浓度及其分布是十分重要的。及时了解杂质浓度及其分布,将有助于获得最佳性能的器件。本文研究了 C-V 法测试 Cd 在 InSb 中扩散层的杂质浓度及其分布,为浅结杂质分布的确定提供了一个新的方法。     

Compositional disordering and the formation of semi-insulating layers in AlAs-GaAs superlattices by MeV oxygen implantation

Data are presented demonstrating the use of MeV oxygen ion implantation and subsequent annealing procedures to induce compositional disordering and to create a semiinsulating region simultaneously within an AlAs-GaAs superlattice. High dose oxygen implantation yields a compositionally disordered region 3500? wide centered 1.25 μm below the surface of the superlattice, as determined by secondary ion mass spectrometry (SIMS) analysis. More extensive disordering of the superlattice occurs at lower implantation temperatures. Current-voltage measurements indicate the formation of a semiinsulating layer which is thermally stable to at least 850° C. The semi-insulating properties of the implanted superlattice are assigned to the disorder-enhanced formation of Al-O pairs and the substitutional introduction of deep level states.     

准静态C-V法测量硅表面态密度分布及数据处理

表面态问题的研究是半导体材料、器件以及集成电路工艺等研究中的一个重要议题,对表面态在禁带中的分布规律进行了研究.采用微波电子回旋共振等离子体化学气相沉积(ECR-CVD)方法在p型硅衬底上沉积了低介电常数绝缘介质的MOS结构;对该样品进行了高频和准静态C-V测试;在给出表面态分析计算的原理基础上,用C语言编写数值积分程序对所采集数据进行了数据处理分析,计算得到了表面态密度分布情况,给出了分布曲线.结果表明,该样品p-Si材料的禁带中表面态存在比较广的连续分布,在靠近价带一侧呈现两个峰值.