Focused Ion Beam, Dual Beam (Dual Beam FIB)

In a Nutshell

Take Home Point:

In Situ SEM Sample Prep/Analysis of small and/or unique features; TEM Sample Prep

What It Provides:

Provides cross-section for SEM and TEM analyses. Subsequent SEM analysis can be performed within the same instrument providing high quality 3D images as well as elemental data if instrument is equipped with an EDS system.

Brief Description:

Ions and Electrons In/Electrons and X-Rays Out

Dual Beam FIB combines two powerful techniques, SEM and FIB. The SEM portion of the instrument provides high resolution imaging while the FIB performs cross-sectioning. A sample surface is first imaged so that features of interest can be identified. The FIB can then precisely 'cut' into the sample creating cross-sections from specific areas, which are subsequently imaged with the SEM. The instruments are typically equipped with EDS detectors as well allowing for elemental information from both the near surface and bulk regions (via the cross-sections). Dual Beam FIBs are also frequently used to produce high quality samples for TEM and Atom Probe analysis.

What is Detected:

B-U (when equipped with EDS)

Detection Limits:

~0.1-1 Weight % (element dependent)

Information Depth:

Not Applicable

Applications:

Site specific cross-sectioning of small features such as particles, embedded defects and individual transistors
Cross-Sections to determine film thickness of layered structures (e.g. semiconductors)
Cross-Sections of hard materials (e.g. Metals, Glass, Ceramics)
TEM Sample Prep
3D Reconstruction/FIB Tomography

Manufacturers:

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Greater Detail

Overview

The Dual Beam FIB is a unique tool that marries two powerful techniques, SEM and FIB. The SEM portion of the instrument produces high resolution imaging while the FIB portion of the tool provides for site specific cross-sectioning and depth analysis. This allows for the investigation of both the surface and sub-surface of samples. It also is frequently used to produce high quality samples for TEM and Atom Probe analysis.

A typical Dual Beam FIB contains an Electron Gun to produce high energy (typically up to 30keV) electrons and a Focused Ion Beam (FIB) to produce ions for sample imaging and milling. Both the Electron and Ion Beams are configured to look at the same point around a tilt axis allowing the instrument to be used for cross-sectioning and sample prep activities. The instruments also commonly have a Gas Introduction System (GIS) to introduce gases into the system that can form protective layers (e.g. Pt) on the location of the sample that is being cross-sectioned as well as a micromanipulator used to transfer prepared TEM and atom probe samples from the original sample from which the cut was made to respective holders for subsequent analysis. Finally, the tools also typically have a variety of detectors such as secondary electron detectors, back scattered electron detectors, EDS detectors and secondary ion detectors for a variety of imaging and elemental analysis applications.

The ions produced by the FIB traditionally have been Ga formed from Liquid Metal Ion Guns as they have long lifetimes, produce high currents and Ga ions can be tightly focused. However, some modern tools now use plasma guns that emit species such as Xe to minimize sample damage during the milling process.

Sample prep via the Dual Beam FIB is preferable for many types of samples over conventional cutting/polishing methods. These include hard materials (e.g. metals, glass, ceramics), soft metals that can smear when hand cutting/polishing (e.g. Cu, Au), layered structures (e.g. semiconductors) and small features such as surface or embedded particles and defects. Advances in FIB technology are even enabling their use for soft materials such as plastics and biological materials that have commonly only been successfully prepped via microtome.

While Dual Beam FIB systems are commonly used to provide in situ sample prep/analysis without having to remove the sample from the instrument, many systems are dedicated to preparing TEM samples. The process for this is that an area of interest is identified and a metal protective layer is applied via beam induced deposition. Two opposing trenches are then milled away leaving a 1-2um thick section. The bottom and the sides of this section are then removed leaving only the ‘shoulder’ holding it. This thin section (i.e. lamella) is then welded onto a micromanipulator and the shoulder milled away. The lamella is then lifted out and welded onto a TEM grid. Final thinning/polishing down to a thickness of <100nm is then performed using low incident angles and ion currents.

Dual Beam FIBs are also used for Tomography (i.e 3D Reconstruction). In this process the FIB is utilized to create sections from the sample which can then be imaged for secondary or backscattered electrons, EBSD and/or characteristic X-rays for elemental information. The data from each slice is then reconstructed giving 3D rendering of morphology, crystallography and/or chemistry (i.e. elemental information).

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