Patterning of amorphous and polycrystalline Ni78B14Si8 with a focused-ion-beam

The machining response of amorphous and crystalline Ni₇₈B₁₄Si₈ was investigated when structuring substrates using focused-ion-beam (FIB) milling. In particular, the sputtering yield as a function of the scan speed, and the effects of ion fluence and scan speed on the milled depth were studied. The ion fluence dependent evolution of the cross-sectional profiles of trenches was examined by atomic force microscopy (AFM). When milling amorphous Ni₇₈B₁₄Si₈, it was found that the sputtering yield first decreased with increasing the beam scan speed, then kept constant within the scan speed range, up to 710 nm/s, investigated in this work; it was also found that the milled depth was almost proportional to the ion beam fluence. The patterning of polycrystalline Ni₇₈B₁₄Si₈ resulted in anisotropic milling-rates due to the varying orientation of the grains in the material. The analysis of the profile evolution in both materials indicated that the surface finish of trenches was scan speed, ion beam fluence and scan strategy dependent. The study demonstrated that direct patterning by FIB could be used for producing masters in amorphous Ni-based alloys for injection moulding and hot embossing.     

Ordering of Ge nanocrystals using FIB nanolithography

Formation and ordering of Ge nanocrystals (NC) are studied on Si(0 0 1) and SiO₂/Si(0 0 1) substrates patterned by focused ion beam (FIB). In both cases we use a three step process consisting of FIB milling of hole patterns with various periodicities, ex-situ substrate cleaning to remove Ga contamination and Ge NC growth by molecular beam epitaxy (MBE). We show that Ge NC can be ordered between or inside the holes on patterned Si(0 0 1) substrates and inside the holes on patterned SiO₂/Si(0 0 1) substrates.     

Development of the Technique for Fabricating Submicron Moire Gratings on Metal Materials Using Focused Ion Beam Milling

A focused gallium ion （Ga＋） beam is used to fabricate micro/submicron spacing gratings on the surface of porous NiTi shape memory alloy （SMA ）. The crossing type of gratings with double-frequency （25001/mm and 50001/mm） using the focused ion beam （FIB） milling are successfully produced in a combination mode or superposition mode. Based on the double-frequency gratings, high-quality scanning electron microscopy （SEM） Moird patterns are obtained to study the micro-scale deformation of porous NiTi SMA. The grating fabrication technique is discussed in detail. The experimental results verify the feasibility of fabricating high frequency grating on metal surface using FIB milling.     

Etched facet and semiconductor/air DBR facet of a AlGaInP laser diode prepared by focused ion beam milling

The study of focused ion beam (FIB) milling for making etched facet and semiconductor/air distributed Bragg reflector (DBR) facets of AlGaInP-based red laser diodes (LD) is presented in this letter. For the Ga ion beam current of 100 pA at fixed accelerated voltage 30 kV, FIB milling rate of GaAs was found to be 0.46 μm³/nC. As a trade-off between high reflectivity and enough technical tolerance, the combination of third Bragg orders of semiconductor wall and air gap was chosen. The deeply etched mirror and distributed Bragg reflector facet consisting of pairs of semiconductor wall/air gap on laser diodes (LD) cavity facets with vertical sidewall on AlGaInP LDs were fabricated by focused Ga ion beam milling. Comparison of the AlGaInP LD with the mirrors between cleaved and FIB made facet was given and discussed.     

The application of FIB milling for specimen preparation from crystalline germanium

The effectiveness of focused ion beam (FIB) for preparation of crystalline germanium specimens has been studied. FIB milling results in strong cellular relief of the germanium surfaces on bulk specimens. This cellular relief, associated with the generation of high densities of point defects during interaction of the specimen with the high-energy gallium beam, can be reduced by using either a lower ion beam currents or a lower beam energy. Even under these milling conditions the cellular relief is, however, still evident on the surface of the TEM specimens as evidenced by so-called 'curtaining' relief. Nevertheless good quality specimens for both conventional and high-resolution imaging may be prepared using FIB milling if low currents are employed for final milling.     

Redeposition effects in transmission electron microscope specimens of FeAl-WC composites prepared using a focused ion beam

Artifacts associated with transmission electron microscope (TEM) specimens prepared using a focused ion beam (FIB) are not well understood, especially those in non-semiconductor materials. In this paper the extent and origins of artifacts associated with redeposition of milled material in TEM specimens of a FeAl--WC metal matrix composite prepared by FIB were investigated. Cross-sections were prepared normal to an initial FIB cut that allowed direct observation of any damage layers, which are believed to be associated with both redeposition of sputtered material and amorphisation of the surface of the specimen by the ion beam. Techniques for the minimisation of redeposition using either final cleaning mills at low accelerating voltages or plasma cleaning were also investigated and found to be ineffective in removing or reducing these damaged layers. TEM cross-sections of specimens treated using low energy mills and plasma cleaning, further confirmed that these techniques did little to reduce any redeposited or amorphous material.     

Focused ion beam induced swelling in MgO(0 0 1)

The interplay between swelling and milling phenomena in determining the morphology of Focused Ion Beam (FIB) -processed MgO(0 0 1) was investigated by atomic force microscopy. At the early stages of ion irradiation, before milling erosion is observed, MgO shows a relevant swelling behaviour with protrusion of the bombarded areas up to 6 nm for a dose of 5 × 10¹⁶ ions cm⁻². The effect is mainly ascribed to subsurface defect accumulation, while the low Ga ions concentration, as measured by in-depth Auger analysis, seems to exclude a contribution from ion implantation. In order to explain and control the morphology of Fe/NiO FIB patterned sub-micron structures on MgO substrates, we have also investigated FIB effects on Fe(0 0 1) and NiO(0 0 1) single crystals. Absent or negligible swelling has been observed on these materials.     

Optimized FIB silicon samples suitable for lattice parameters measurements by convergent beam electron diffraction

The aim of this paper is to check the effect of artefacts introduced by focused ion beam (FIB) milling on the strain measurement by convergent beam electron diffraction (CBED). We show that on optimized silicon FIB samples, the strain measurement can be performed with a sensitivity of about 2.5 × 10⁻⁴ which is very close to the theoretical one and we conclude that FIB preparation can be suitable for such measurements in microelectronic devices.

To achieve this, we first used CBED and electron energy loss spectroscopy (EELS) which provide a procedure permitting an exact knowledge of the sample geometry, i.e. the thickness of both amorphous and crystalline layers. This procedure was used in order to measure the FIB-amorphized sidewall layer. It was found that if the FIB preparation is optimized one can reduce this amorphous layer down to around 7 nm on each side. Secondly different preparation techniques (cleavage, Tripod™ and FIB) permit to check if the surface damaged layer introduced by FIB influences the strain state of the sample. Finally, it was found that the damaged layer does not introduce measurable strain in pure silicon but reduces appreciably the quality of the CBED patterns.     

Integration of correlative Raman microscopy in a dualbeam FIB SEM

We present an integrated confocal Raman microscope in a focused ion beam scanning electron microscope (FIB SEM). The integrated system enables correlative Raman and electron microscopic analysis combined with focused ion beam sample modification on the same sample location. This provides new opportunities, for example the combination of nanometer resolution with Raman advances the analysis of sub‐diffraction‐sized particles. Further direct Raman analysis of FIB engineered samples enables in situ investigation of sample changes. The Raman microscope is an add‐on module to the electron microscope. The optical objective is brought into the sample chamber, and the laser source, and spectrometer are placed in a module attached onto and outside the chamber. We demonstrate the integrated Raman FIB SEM function with several experiments. First, correlative Raman and electron microscopy is used for the investigation of (sub‐)micrometer‐sized crystals. Different crystals are identified with Raman, and in combination with SEM the spectral information is combined with structurally visible polymorphs and particle sizes. Analysis of sample changes made with the ion beam is performed on (1) structures milled in a silicon substrate and (2) after milling with the FIB on an organic polymer. Experiments demonstrate the new capabilities of an integrated correlative Raman–FIB–SEM. Copyright © 2016 John Wiley & Sons, Ltd.     

Long-life bismuth liquid metal ion source for focussed ion beam micromachining application

Liquid metal ion sources (LMISs) with Ga as ion species are widely used in focused ion beam (FIB) technology for micromachining and surface treatment on the sub-micron and nano-scale. Key features of a LMIS for investigating mechanical properties and 3D-microfabrication of materials are long life-time, high brightness, stable ion current and a highly effective milling ability for the material to be modified. In order to increase the material removal rate, heavier ions than Ga and their clusters should be applied. Bismuth (Bi) is the heaviest, non-radio-active element in the periodic table, is non-toxic and exhibits a low melting point. We have thus produced a long-life (about 1000 h) Bi LMIS with a good beam performance, applicable in any FIB system. Since Bi is the only element in this source, it is not necessary to separate it from other ions by a mass filter. Investigation of the sputtering rate of NiTi shape memory alloys using Ga and Bi LMIS showed that, for the same experimental conditions, the material removal rate with using of Bi_n^k+ ions in a standard FIB machine without a mass separator is about five times larger compared to Ga⁺ ions. This use of Bi as LMIS-species is the ultimate breakthrough in sputtering applications.