Specimen preparation for high-resolution transmission electron microscopy using focused ion beam and Ar ion milling

We have developed a focused ion beam (FIB)-Ar ion-milling technique for high-resolution transmission electron microscopy. A micrometresized specimen was mounted on a cross section of metal foil of a few micrometres thick, using FIB microsampling. Following this, a 2 degrees wedgeshaped part was made in the specimen using FIB. Finally, the specimen was milled using an Ar ion beam to remove the FIB-damaged layers. We applied the FIB-Ar ion milling technique to a CeO(2)/Gd(2)Zr(2)O(7) multilayer specimen, resulting in the crystal lattice fringes of both layers being clearly observable in comparison to a specimen finished using a Ga ion beam at an accelerating voltage of 10 kV.     

Electron backscattering diffraction investigation of focused ion beam surfaces

A focused ion beam (FIB) instrument has been used to mill surfaces in single-crystal Si and single-crystal Cu for subsequent electron backscattering diffraction (EBSD) analysis. The FIB cuts were performed using a 30 keV and a 5 keV Ga⁺ ion beam at a stage tilt of 20° to provide a readily obtainable 70° surface for direct EBSD investigation in a scanning electron microscope (SEM). The quality of the patterns is related to the amount of FIB damage induced in the Cu and Si. These or similar methods should be directly transferable to a FIB/SEM dual beam instrument equipped with an EBSD detector.     

Improvements in performance of focused ion beam cross-sectioning: aspects of ion-sample interaction

A gallium (Ga) focused ion beam (FIB) has been applied increasingly to 'site-specific' preparation of cross-sectional samples for transmission electron microscopy (TEM), scanning TEM, scanning electron microscopy and scanning ion microscopy. It is absolutely required for FIB cross-sectioning to prepare higher-quality samples in a shorter time without sacrificing the site specificity. The present paper clarifies the parameters that impose limitation on the following performances of the FIB cross-sectioning: milling rate, cross-sectioning at a right angle with respect to the sample surface, curtain structures formed on the cross sections, ion implantation and ion damage. All of these are discussed from the viewpoint of ion-sample interaction. Improvements for these performances achieved by diminishing their limiting origins or by correcting the resultants are described. Especially, the FIB scanning speed is significantly utilizable to improve the milling rate. A microsampling method, which allows the FIB incidence in a sidewards or upwards direction as well as downwards with respect to the microsample surface, is very effective to minimize the curtain structures.     

聚焦离子束在光纤探针制备技术中的应用

本文概述了利用聚焦离子束制备用于近场光学显微镜光纤探针的方法,讨论了探针的锥型刻蚀、孔径控制和特殊结构加工等;论述了聚焦离子束的工作原理和在光纤探针高精度加工方面的优势。利用此技术制备的光纤探针的锥型和针尖孔径精确可控,并具有高光洁度,高通光效率等特点。     

聚焦离子束系统原理、应用及进展

聚焦离子束纳米加工系统,具有传统加工工具无可比拟的优势而逐渐成为新一代微纳分析、加工的工具在微纳米加工、操纵以及器件的研制等方面具有重要应用.本文介绍了聚焦离子束系统的内部结构和工作原理,探讨了该系统的扩展功能、应用及发展前景.     

基于聚焦离子束注入的微纳加工技术研究

提出了聚焦离子束注入（focused ion beam implantation,FIBI）和聚焦离子束XeF2气体辅助刻蚀（gas assisted etching,GAE）相结合的微纳加工技术。通过扫描电镜观察FIBI横截面研究了聚焦离子束加工参数与离子注入深度的关系。当镓离子剂量大于1.4×1017ion/cm2时,聚焦离子束注入层中观察到均匀分布、直径10～15nm的纳米颗粒层。以此作为XeF2气体反应的掩膜,利用聚焦离子束XeF2气体辅助刻蚀（FIB-GAE）技术实现了多种微纳米级结构和器件加工,如纳米光栅、纳米电极和微正弦结构等。结果表明该方法灵活高效,很有发展前途。     

Reducing focused ion beam damage to transmission electron microscopy samples

One of the most important applications of focused ion beam (FIB) systems is sample preparation for transmission electron microscopy (TEM). However, the use of the FIB inherently involves changing and damaging the sample, and thereby degrades the TEM resolution. This paper addresses the beam-induced damage and artifacts, particularly in applications involving silicon semiconductors. The damage appears in the form of amorphization on the surface of the TEM foil. The characteristics of this amorphous damage were studied by making TEM observations of cross sections of the affected foil. The damage is typically 20 to 30 nm thick for a 30 keV FIB, which is generally overly thick for modern silicon devices with feature sizes less than 250 nm. This paper reviews the reported damage depths of FIB-prepared samples, which are determined by experiments and calculations. Several damage reduction techniques, such as the use of gas-assisted etching, low energy FIB, cleaning the FIBfabricated cross section by wet or dry etching and cleaning by broad ion beam (BIB) milling have also been reviewed, with emphasis on applicability to silicon devices. We conclude that the use of low energy FIB and cleaning by argon BIB are particularly efficient techniques.     

Focused ion beam contact to non-volatile memory cells

Electrical characterization of non-volatile memory cells has been performed. A focused ion beam (FIB) contact procedure is presented that allows to contact the floating gate.Calculations and measurement results on an exemplary floating gate memory cell show intact cell structure with limited retention time after FIB modification. The presented procedure allows the measurement and control of the previously unavailable floating gate current and voltage.     

A review of focused ion beam technology and its applications in transmission electron microscopy

The role of focused ion beam (FIB) fabrication in the development of sample preparation techniques for transmission electron microscopy (TEM) has been described in this paper. Since the repeatability of FIB sampling and TEM observations has become important, the microsampling and in situ lift-out methods are currently in wide use. Furthermore, artifacts induced during FIB milling and the consequent difficulties with energy dispersive X-ray spectroscopy are detailed. The remarkably increased capability of scanning ion microscopy and its applications are also discussed.     

Focused ion beam microsurgery for electronics

Methods of making and breaking connections on an Al conductor test pattern using a focused ion beam (FIB) are demonstrated. Submicrometer dimension connections between crossing conductors separated by oxide were fabricated in 7 s. Resistances of the connections were measured to be 3 Ω and were tested up to 50 mA. Milled cuts in 0.65- µm-thick 10-µm-wide conductors produced open-circuit resistances > 20 MΩ in 300 s. The combined imaging, restructuring, and verification capability of FIB microsurgery is shown.     

Electrical characterization of platinum deposited by focused ion beam

Focused ion beam (FIB) systems are commonly used to image, repair and modify integrated circuits by cutting holes in passivation to create vias or to selectively break metal tracks. The ion beam can also be used to deposit a metal, such as platinum, to create new connections. These techniques are very useful tools for debugging designs and testing possible changes to the circuit without the expense of new mask sets or silicon. This paper presents test structures which can be used to characterize a FIB induced platinum deposition process. Sheet resistance test structures have been fabricated using a FIB tool and the results of testing these structures are presented. The sheet resistance data has been used to fabricate platinum straps with a known resistance. This extends the capability of the focused ion beam system beyond the deposition of simple conducting straps. The design of the test structures has been improved through the use of current flow simulation to investigate the effects of geometry and misalignment on the measurement accuracy. The results of these simulations are also presented.     

Prediction of nanopattern topography using two-dimensional focused ion beam milling with beam irradiation intervals

Beam irradiation intervals are a critical parameter in the fabrication of nanopatterns via focused ion beam (FIB) milling. The beam irradiation intervals are defined in terms of the overlap. In this paper, the nanopattern height on a silicon surface is predicted using a mathematical FIB milling model that varies the overlap. The proposed model takes into account the angle dependence of the sputtering yield and redeposition effect, together with the superposition of a bi-Gaussian beam. The model was verified by comparing the results of a nanopattern machining experiment to those of a simulation based on the model. The simulation calculated the final two-dimensional geometry from ion milling parameters. The results of the simulation indicate that the proposed model is more precise than one that only considers the superposition of a Gaussian beam.     

聚焦离子束加工中的缺陷及成因

聚焦离子束技术作为一种直接加工微纳米结构的工具,在很多领域有着重要的应用。但在实际应用中,它并不能总是如人所愿,加工出的结构有时会产生缺陷。如在切割截面时会形成倾斜侧壁、窗帘结构;在刻蚀平面结构时形成非均匀的底面;在利用气体注入系统诱导沉积生长结构后残留污染物等。本文将剖析聚焦离子束加工中这些常见缺陷产生的根源,探讨减轻或消除这些缺陷的方法。     

Focused ion beam lithography and its application to submicron devices

Applications of focused ion beam (FIB) technology to lithography in the sub-half-micron region will be discussed. First, the special characteristics of FIB sputtering are studied, and the fabrication of a GaAs FET by the use of a bilayer structure is mentioned. Next, resist patterning using light ions, Be and Si, is investigated. This process has the advantage of high throughout due to the high rate of energy deposition into the resist. The last application is the dry development of a gallium-implanted resist. This process will be effective for use in nanometer-range lithography because it is free from pattern swelling normally resulting from wet treatments. These three processes are applied to the fabrication of submicron devices, and the results demonstrate the practical feasibility of FIB lithography.     

Side-milling technique of preparing device cross-sections for electron holography based on a focused ion beam micro-sampling system

A new milling technique based on a focused ion beam (FIB) microsampling system is proposed to avoid the curtaining effect, commonly occurring in other FIB milling methods, in order to obtain a crosssectional device specimen with uniform thickness can be obtained for electron holographic observation.     

Hollow cathode metal ion lasers

A new class of metal ion lasers with significant CW output power in the UV (220-320 nm) and near IR (800-2000 nm) spectral regions is described. In a hollow cathode discharge the upper laser levels are excited via charge transfer collisions between ground state buffer gas ions and ground state metal atoms. At the present stage of development, hollow cathode metal ion lasers are shown to be comparable in UV output power to rare-gas ion lasers but with lower threshold currents by a factor of more than twenty. Visible output powers are lower than rare-gas ion lasers. In the text we present device progress to date, measurements of important plasma parameters, and an outline of potential applications of hollow cathode metal ion lasers.     

Dual-beam focused ion beam (FIB): A prototyping tool for micro and nanofabrication

Focused ion beam (FIB) is a powerful and versatile tool for the maskless fabrication of structures and devices in the micro and nanometre scales. This can be performed by the milling and deposition capabilities of a focused ion beam, the latter being achieved by the ion beam-assisted decomposition of a metalorganic gas precursor of the specific material that has to be deposited. The combination of the FIB and a SEM in the same machine, giving rise to the so-called dual-beam or cross-beam machines, further expands the capabilities of the technique by the possibility of performing electron-beam assisted deposition and inspection, which is less harmful than using the ion beam. In this work three examples of the various capabilities of dual-beam systems for the fabrication of prototypes of different types of devices will be presented. The devices fabricated are a microinductor made in copper, the fine trimming of silicon mechanical resonators and the fabrication of nanocontacts to nanowires for the extraction of electrical parameters and for the fabrication of gas sensors from them.     

Integration of microdiffractive lens with continuous relief withvertical-cavity surface-emitting lasers using focused ion beam directmilling

A novel one-step integration of bottom-emitting vertical-cavity surface-emitting laser (VCSEL) (operation wavelength of 980 nm) with microdiffractive lens by means of focused ion beam (FIB) technology is described. A diffractive lens with continuous relief, diameter of 140 μm, and six annulus was designed and fabricated using FIB direct milling on the backside of VCSEL with GaAs substrate for beam collimation. The divergence angle (half angle) of the VCSEL was reduced from 12° before integration of the VCSEL/diffractive optical elements (DOEs) to 0.6° after FIB integration, allowing for an interconnect length of ~4 mm. It was proven by device testing that there is little influence upon the VCSEL performance after FIB processing     

Electron beam testing of VLSI circuits assisted by focused ion beam etching

Electron beam testing assisted by focused ion beam etching was examined. Before electron beam testing (EB testing), a small window was made in the passivation film by focused ion beam etching (FIB etching). EB testing was performed through this window. This method was useful because charge buildup on the passivation film is avoided during EB testing. The threshold voltage shift caused by FIB etching was permitted until the residual film thickness on the gate electrode became 0.5μm. This technique was applied to measure the internal voltage waveform of the 256K bit dynamic RAM and confirmed that it was effective for functional testing and failure analysis of VLSI circuits.     

Crystallographic orientation contrast associated with Ga+ ion channelling for Fe and Cu in focused ion beam method

In this study, Cu and Fe single crystals are used to examine the change in secondary electron intensity associated with Ga(+) ion channelling in a focused ion beam (FIB) system. The single crystals having three different orientations are tilted with respect to the beam incidence and the resulting variation in the secondary electron intensity is measured through the variation in brightness of the crystals. It is shown that intensity minima appear at the beam directions normal to the lower indices of the crystal orientations. The appearance of the intensity minima including the magnitude of the minima is consistent with the prediction based on the event of ion channelling in the crystal and is affected by the crystal structure. The effect of background on the intensity minima is discussed in this study. It is suggested that the presence of the intensity minima may be used to identify a crystal orientation including a crystal structure.