Jaroslav Jiruse

High Spatial Resolution Time-of-Flight Secondary Ion Mass Spectrometry for the Masses: A Novel Orthogonal ToF FIB-SIMS Instrument with In Situ AFM

We describe the design and performance of an orthogonal time-of-flight (TOF) secondary ion mass spectrometer that can be retrofitted to existing focused ion beam (FIB) instruments. In particular, a simple interface has been developed for FIB/SEM instruments from the manufacturer Tescan. Orthogonal extraction to the mass analyser obviates the need to pulse the primary ion beam and does not require the use of monoisotopic gallium to preserve mass resolution. The high-duty cycle and reasonable collection efficiency of the new instrument combined with the high spatial resolution of a gallium liquid metal ion source allow chemical observation of features smaller than 50 nm. We have also demonstrated the integration of a scanning probe microscope (SPM) operated as an atomic force microscope (AFM) within the FIB/SEM-SIMS chamber. This provides roughness information, and will also allow true three dimensional chemical images to be reconstructed from SIMS measurements.

FIB-SEM Instrument with Integrated Raman Spectroscopy for Correlative Microscopy

Confocal Raman Microscope (CRM) is integrated with Scanning Electron Microscope (SEM) and its standard analyzers such as Energy Dispersive X-ray spectroscope (EDX), that can be further equipped with Focused Ion Beam (FIB). This yields valuable chemical information about molecular composition and chemical bonds in the sample on top of the high resolution SEM image, elemental composition map by EDX, nano-prototyping capability by FIB, etc. In presented system, confocal setup of the Raman Microscope provides lateral resolution of 360 nm (with the 532 nm excitation laser). This is a high standard in the world of light microscopy, however, electron microscopy offers resolution more than 2 orders of magnitude better. Combining the CRM spectral image and high resolution SEM image acquired in-situ is therefore of great benefit. State-of-the-art Raman analyzers inside SEM use parabolic mirror for focusing the primary laser beam on the sample and collecting the Raman-scattered light. The lateral resolution of these systems typically does not exceed 2-5 μm. We achieve the resolution comparable with stand-alone instruments by integrating a full confocal light microscope with SEM. The integrated system is capable of Raman imaging which is an important property. When just a single spectrum is acquired, one can never be sure, whether the position calibration is off. Besides lateral scanning, vertical movement is also supported, which allows non-destructive 3D tomography of laser transparent samples. Combination of CRM chemical analysis and SEM high resolution imaging makes this tool ideal for use in chemistry, medicine, biology, geology, forensic science and many other fields. The integration is feasible with two types of electron columns: conventional (LYRA) and immersion (GAIA). The immersion column [1] is recommended for non-conductive or fragile samples, because it offers better resolution at low acceleration voltages (1 nm at 15 kV and 1.4 nm at 1 kV). Its three-lens design is equipped with a Schottky field-emission gun and it offers multiple display modes (for ultrahigh resolution, large field of view or increased depth of focus) as well as a field-free mode for investigating magnetic samples.

Integrating focused ion beam–scanning electron microscope with confocal Raman microscope into a single instrument

The authors have developed a new method to integrate a scanning electron microscope (SEM) with a confocal Raman microscope (CRM) that uses full optical microscopy inside the vacuum chamber of the SEM, and thus bring the capabilities of a stand-alone CRM instrument into the combined tool. A focused ion beam is also integrated into the system, thereby equipping a single instrument with electron, ion, and photon beams. Chemical imaging with the CRM is done by objective lens scanning. The confocal arrangement of the instrument is also capable of nondestructive three-dimensional Raman tomography on transparent samples.

Design of an Ultra-High Resolution SEM for Enhanced Analysis

The column is equipped with a well-known single-pol e bjective lens [2] that creates a strong magnetic field around the sample, thus dramatically decreasi ng optical aberrations. Design optimization and combining the magnetic immersion field with the ele ctrostatic field [3] further improves the resolutio n to less than 1.1 nm at 1 kV. For analytical purpose s (EDS or EBSD) or for use with a FIB column however, the immersion magnetic field becomes a com plication due either to curvature of signal electron trajectories or beam splitting of ion-isot opes.

Novel field emission SEM column with beam deceleration technology.

A novel field-emission SEM column has been developed that features Beam Deceleration Mode, high-probe current and ultra-fast scanning. New detection system in the column is introduced to detect true secondary electron signal. The resolution power at low energy was doubled for conventional SEM optics and moderately improved for immersion optics. Application examples at low landing energies include change of contrast, imaging of non-conductive samples and thin layers.

A New SEM Column Combining Ultra-High Resolution and Flexible Scanning

The critical parts of the scanning electron microscope optical system are the technology of the objective lens (that determines the resolving power) and the configuration of the deflecting elements used for scanning. However, requirements for high resolution, high beam deflection and analytical compatibility are usually in conflict with each other because of design limitations. A significant advance towards the optimal design was the introduction of Wide Field Optics technology incorporating two objective lenses located below and above the double-stage scanning deflectors. This configuration provides several display modes which delivers both high resolution imaging and a large field of view using optimization of the scanning pivot-point position and an advanced engine for correction of optical distortion. The technology further allows a mode with controlled depth of focus and a rocking beam mode with the pivot point on the sample [1]. Another technology uses ultra-high resolving power with immersion optics, but the resolution in magnetic-field-free mode is lower [2].

Xe Plasma FIB-SEM with Improved Resolution of Both Ion and Electron Columns

Combined plasma Xe ion source FIB (Focused Ion Beam) with SEM (Scanning Electron Microscope) was introduced three years ago [1]. It proved to be an important tool for ultra-fast milling, especially for the semiconductor industry. Besides 50-times higher milling rate compared to traditional Ga ion FIB, it eliminates the conductive contamination of integrated circuits and it is useful for processing of compounds such as SiGe, (In)GaAs and (In, Al)GaN. We demonstrated its utilization also for other fields, for example preparation of large TEM lamella [2] or the first large-scale FIB tomography [3].

A Detection System with Controlled Surface Sensitivity for a New UHR SEM

Control of the surface sensitivity of the detected signal electrons is beneficial for modern scanning electron microscopy. We present our initial results obtained on the new ultra-high resolution SEM with an extended detection system that allows the filtering of secondary electrons (SE), energy filtering of back-scattered electrons (BSE) and angular BSE selection. All three filtering possibilities lead to enhanced surface sensitivity. The tested SEM combines a high-potential tube with magnetic-electrostatic objective lens delivering ultra-high resolving power in the field-free mode and two-stage flexible scanning with extra wide field of view. It can also be combined with a focused ion beam column.

In-Depth Sample Analysis with a Signal-Selective SEM Detection System

Recent trends in analysing the image contrast obtai ned using sophisticated detection systems in scanni ng electron microscopes (SEM) show that it is valuable not only to capture the vast majority of signal electrons, but also to allow the selection of parti cular signal electrons according to the information they carry [1]. This complies with the need to enhance t he subtler changes in contrast, in which case just high detection efficiency is no longer sufficient and en ergy[2] and/or angular[3] filtration of signal electrons becomes necessary.

Low Energy BSE Imaging with a New Scintillation Detector

More and more applications of the scanning electron microscope (SEM) rely on a low electron energy because it decreases the depth of specimen radiation damage. It also enables a clear visualization of nonconductive samples, surface structures are better resolved, and new types of contrast can be observed [1, 2]. In the case of backscattered electron (BSE) imaging, working at low primary beam energies (and currents) puts high demands on the actual detector design because of the weak signal intensities. The sensitivity of the most commonly used scintillation detectors drops rapidly in the region of energies under 3 keV.