Focused Ion Beam Processing for 3D Chiral Photonics Nanostructures.

Picocyanobacteria were found to play an important role in calcite precipitation in oligotrophic lakes. In this study, investigations on the interface between cyanobacteria and attached biogenic calcite crystals have been performed to gain further insights into the mechanisms of nucleation of these precipitates. Ultramicrotomy, the conventional preparation technique of thin sections for Transmission Electron Microscopy (TEM) investigations, often fails when working on heterogeneous samples containing soft organic material and hard minerals. Thus, in this study the thin sections were prepared using Focused Ion Beam (FIB) milling. This approach is usually applied in material sciences but until recently was not very common in environmental research. Different analytical TEM methods like Electron Spectroscopic Imaging (ESI) and Electron Energy Loss Spectrometry (EELS) were used to test the suitability of FIB-milling for the preparation of organic/inorganic interface specimens. With this approach we were able to analyze both organic and the inorganic phases of the same sample. Elemental maps of the samples were also calculated. By analyzing the structure of the C K -absorption edge, the different bonding forms of the organic carbon cell and the inorganic carbon of the crystal could be clearly distinguished.

In recent years, nanomachining has attracted increasing attention in advanced manufacturing science and technologies as a value-added processes to control material structures, components, devices, and nanoscale systems. To make sub-micro patterns on these products, micro/nanoscale single-crystal diamond cutting tools are essential. Popular non-contact methods for the macro/micro processing of diamond composites are pulsed laser ablation (PLA) and electric discharge machining (EDM). However, for manufacturing nanoscale diamond tools, these machining methods are not appropriate. Despite diamond’s extreme physical properties, diamond can be micro/nano machined relatively easily using a focused ion beam (FIB) technique. In the FIB milling process, the surface properties of the diamond cutting tool is affected by the amorphous damage layer caused by the FIB gallium ion collision and implantation and these influence the diamond cutting tool edge sharpness and increase the processing procedures. To protect the diamond substrate, a protection layer—platinum (Pt) coating is essential in diamond FIB milling. In this study, the depth of Pt coating layer which could decrease process-induced damage during FIB fabrication is investigated, along with methods for removing the Pt coating layer on diamond tools. The optimum Pt coating depth has been confirmed, which is very important for maintaining cutting tool edge sharpness and decreasing processing procedures. The ultra-precision grinding method and etching with aqua regia method have been investigated for removing the Pt coating layer. Experimental results show that when the diamond cutting tool width is bigger than 500 nm, ultra-precision grinding method is appropriate for removing Pt coating layer on diamond tool. However, the ultra-precision grinding method is not recommended for removing the Pt coating layer when the cutting tool width is smaller than 500 nm, because the possibility that the diamond cutting tool is damaged by the grinding process will be increased. Despite the etching method requiring more procedures to remove the Pt coating layer after FIB milling, it is a feasible method for diamond tools with under 500 nm width.

Optical fibers have been the basis of the modern information technology since Kao and Hockham proposed glass waveguides as a practical medium for communication in 1965. A lot of different optical fiber active/passive devices including couplers, interferometers, gratings, resonators and amplifiers have been widely employed for applications on telecommunications and sensing networks (Agrawal, 2002). For a number of applications, it is important to reduce the device’s size. Small size is often attractive for particular sensing applications because of some benefits such as fast response to detecting small objection with little perturbation on the object being measured. There are two steps to obtain fiber devices as small as possible. First, it is to taper or etch the fiber and reduce its diameter. A subwavelength-scale microfiber is the basic element of miniature fiber devices and subsystems (Tong et al., 2003; Brambilla et al., 2004, 2005, 2010). The second is to engineer the microfiber to realize miniature version of conventional fiber devices. There are various fabrication methods to engineer the microfiber, such as CO2 laser, femtosecond (fs) laser, HF acid etching, arc splicing and focused ion beam (FIB). Most of these techniques have the difficulties in carving the microfiber freely because of the resolution. The latest progress in FIB technique has opened a new widow for ultra-small size fiber devices. So far, FIB is the most flexible and powerful tool for patterning, cross-sectioning or functionalizing a subwavelength circular microfiber due to its small and controllable spot size and high beam current density. FIB systems have been produced commercially for approximately thirty years, primarily for large semiconductor manufacturers. FIB systems operate in a similar fashion to a scanning electron microscope (SEM) except, rather than a beam of electrons and as the name implies, FIB systems use a finely focused beam of ions that can be operated at low beam currents for imaging or high beam currents for site specific sputtering or milling (http://en.wikipedia.org/wiki/Focused_ion_beam). The fine and controllable ion spot size and high beam current density are perfect for microand nano-fabrications with high spatial resolution (~ 10 nm). As a result, FIB has recently become a popular candidate for fabricating high-quality micro-devices or high-precision microstructures. Originally, FIB processing was used for mask repair (Liang et al., 2000), integrated circuit chip repair/modification (Liu et al., 2006), cross-sectional imaging of critical parts of

Examination of fracture surfaces using focused ion beam milling

Focused ion beam (FIB) milling through carbon nanotube (CNT) yarns and bucky-papers followed by scanning electron microscopy has recently emerged as a powerful tool for eliciting details of their internal structure. The internal arrangement of CNTs in bucky-papers and yarns directly affects their performance and characteristics. Consequently this information is critical for further optimisation of these structures and to tailor their properties for specific applications. This chapter describes in detail FIB milling of CNT yarns and bucky-papers and gives a range of examples where FIB milling has enabled a better understanding of how processing conditions and treatments affect the internal structure. Emphasis is placed on how FIB milling elucidates the influence of fabrication conditions on the internal arrangement of CNTs and how this influences the material’s macroscopic properties.

Focused ion beam milling and scanning electron microscopy characterization of polymer + metal hybrids

A dual beam FIB (Focused Ion Beam) system which provides the ion beam (i-beam) and electron beam (e-beam) function are widely used in semiconductor manufacture for construction analysis and failure cause identification. Although FIB is useful for defect or structure inspection, sometimes, it is still difficult to diagnose the root cause via FIB e-beam image due to resolution limitation especially in products using nano meter scale processes. This restriction will deeply impact the FA analysts for worst site or real failure site judgment. The insufficient e-beam resolution can be overcome by advanced TEM (Transmission Electron Microscope) technology, but how can we know if this suspected failure site is a real killer or not when looking at the insufficient e-beam images inside a dual beam tool? Therefore, a novel technique of device measurement by using C-AFM (Conductive Atomic Force Microscope) or Nano-Probing system after cross-sectional (X-S) FIB inspection has been developed based on this requirement. This newly developed technology provides a good chance for the FA analysts to have a device characteristic study before TEM sample preparation. If there is any device characteristic shift by electrical measurement, the following TEM image should show a solid process abnormality with very high confidence. Oppositely, if no device characteristic shift can be measured, FIB milling is suggested to find the real fail site instead of trying TEM inspection directly.

Electrical characterization of FIB processed metal layers for reliable conductive-AFM on ZnO microstructures

We present the results of a DARPA sponsored study on the application of Focused Ion Beam (FIB) systems to metrology in advanced lithography for production and process development. Data on top-down measurements, on the effects of FIB imaging, and on milling strategies for cross-sectional preparation are presented for fine-line resist structures. In addition, some preliminary aspects of Ga contamination are addressed in the context of the residual dose and concentration leftover from FIB processing. A standard deviation of 8 nm for the measured line width was observed, which makes FIB metrology competitive with the more established technique of CD SEM analysis.

In modern photolithography mask repair, shorter exposure wavelengths, smaller dimensions, and tighter process latitudes pose new challenges. We have systematically investigated focused ion beam (FIB) gas assisted etching (GAE) of chrome and mask transmission at 193 nm ultraviolet (UV) irradiation for various FIB parameters. The gases, used either alone or in binary combinations, include XeF2, Cl2, NH3, CO, CO2, Br2, H2O, and O2. While the bromine GAE appears to be the most effective among single gases in etching chrome, the quartz transmission after chrome removal remains ∼50% compared with unexposed material, and residue is present. The gas mixtures NH3/Br2 and CO2/Br2 were found to reduce the amount of residue and to enhance the chromium mask etching rate compared to Br2-only etching. This enhancement occurs in a narrow range of gas partial pressures, and the FIB process may need to be optimized further. The best transmission at 193 nm UV irradiation of the FIB GAE repaired regions achieved to date with no postprocessing is ∼95% of the transmission of a blank mask. We also applied laser power to heat the area where the ion beam is incident. No increase in Cr removal rate was seen for the Br based chemistries. Some increase in removal rate was seen for Cl2+O2 and XeF2 but the overall rate with both gas and laser power was barely higher than sputtering alone.

We have investigated the Ga+ ion-damage effect induced by focused ion beam (FIB) milling in a [001] single crystal of a 316 L stainless steel by the electron channelling contrast imaging (ECCI) technique. The influence of FIB milling on the characteristic electron channelling contrast of surface dislocations was analysed. The ECCI approach provides sound estimation of the damage depth produced by FIB milling. For comparison purposes, we have also studied the same milled surface by a conventional electron backscatter diffraction (EBSD) approach. We observe that the ECCI approach provides further insight into the Ga+ ion-damage phenomenon than the EBSD technique by direct imaging of FIB artefacts in the scanning electron microscope. We envisage that the ECCI technique may be a convenient tool to optimize the FIB milling settings in applications where the surface crystal defect content is relevant.

The focused ion beam technique: A useful tool for pharmaceutical characterization

A focused ion beam (FIB) has been used to trim write heads for perpendicular magnetic recording using untrimmed HGA-level longitudinal heads. The ion-beam imaging of the write head during FIB processing was minimized to limit exposure of the active magnetic material at the ABS to a 30 keV Ga+ ion dose of less than 1014 Ga+/cm2 (≈10−13 C/μm2) (the GMR reader was never exposed), which is significantly below levels where magnetic properties have been observed to degrade [W. M. Kaminsky et al., Appl. Phys. Lett. 78, 1589 (2001)]. The corresponding recording characteristics and spatial profiles of written tracks have been measured on a spin stand and a magnetic force microscope (MFM). Recording performance, such as SNR, and pulse shape of transitions, for example, as a function of head design and FIB processing is discussed, which compares very favorably to the performance of untrimmed heads. The MFM images reveal curvature in the magnetic transitions (transition smile) when writing with a single-pole writer with a straight trailing edge. Conversely, we demonstrate straight transitions using a single-pole writer with a curved trailing edge. Our results demonstrate the robustness of FIB-trimmed heads down to sub-100-nm length scales.

Atomistic simulations of focused ion beam machining of strained silicon

Fresnel zone plates (FZPs) are significant optical objects for extreme ultraviolet and x-ray microscopy, both of which are powerful tools due to their high spatial resolution and large penetration depth. Fabrication of FZPs is challenging as it requires high accuracy to achieve the narrow outmost zone and large aspect ratio. The focused ion beam (FIB) has been practically demonstrated as a potential alternative to electron beam lithography for its precision, rapidness, and mask-free essence. However, the common redeposition effect in the FIB process is a major obstacle to distort actual patterns from designed ones, especially for FZPs with outmost zone width of 100 nm and simultaneously aspect ratio beyond 2. We proposed an efficient method noted as single-pixel line-assisted sputtering (SLAS) to eliminate redeposition in situ during FZP fabrication. Through systematically optimizing parameters predominating ion dosages and, particularly, the positions of SLAS, we successfully obtained high-quality FZPs with outmost zone width down to 100 nm, perpendicular side walls, aspect ratio of up to 3 and diameter of 38 μm in 1.5 h. The application of SLAS also provides instructive guidance for other FIB processes to finely modulate the nanostructures.