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Analysis of common application scenarios for FIB focused ion beams


System & Principle

A dual beam focused ion beam system can be simply understood as a coupling between a single beam focused ion beam and an ordinary SEM. The single-beam focused ion beam system consists of five major parts: ion source, ion optical column, beam tracing system, signal acquisition system, and sample stage. The ion source is at the top of the ion beam barrel, and a strong electric field is applied to the ion source to extract positively charged ions, which are focused and deflected by electrostatic lenses and deflection devices to achieve controlled scanning of the sample. Sample processing is carried out by accelerated ion bombardment of atoms on the sputtered surface of the specimen, while the generated secondary electrons and secondary ions are collected and imaged by the corresponding detectors.

A common dual-beam device is one in which the electron beam is mounted vertically and the ion beam is mounted at an angle to the electron beam, as shown in the figure. The intersection of the electron beam and the ion beam in the focal plane is often referred to as the concentric height position. When using the specimen is located in the concentric height position can achieve both electron beam imaging and ion beam processing, and can be tilted through the specimen table will be perpendicular to the specimen surface of the electron beam or ion beam.

Typical ion beam microscope mainly consists of a liquid metal ion source with ion elicitation pole, pre-focusing pole, focusing pole using a high-voltage power supply, electrical alignment, dispersive electron lens, scanning coils, secondary particle detector, movable sample base, vacuum system, anti-vibration and magnetic field devices, circuit control boards, computers, and other hardware equipment, the application of an electric field in the liquid metal ion source, which can make the formation of liquid gallium fine tip, plus a negative electric field to pull the tip of gallium, and derive a gallium ion beam. Negative electric field traction tip of the gallium, and export gallium ion beam. In the general operating voltage, the tip current density of about 10-4A/cm2, to electric lens focusing, through the variable aperture diaphragm, to determine the size of the ion beam, and then after the second focusing to a very small beam spot bombardment of the sample surface, the use of physical collision to achieve the purpose of cutting, the ion beam to reach the surface of the sample beam spot diameter of up to 7 nanometres.

Semiconductor thin film materials

These samples are mostly thin film materials grown on flat substrates, most of which are multilayers (with different materials in each layer) and very few are monolayers. Most range in thickness from a few nanometres to a few hundred nanometres. The samples are formulated for a wide choice of locations without fixed limitations.

Figure 1: Semiconductor thin film materials

Semiconductor device materials

These samples are mostly shaped materials grown on flat substrates with patterned surfaces, and there are limitations to the range of sampling.

Figure 2: Semiconductor device materials

Metal materials

These samples are mostly shaped materials grown on flat substrates with patterned surfaces, and there are limitations to the range of sampling.

Figure 3: Metal materials

Battery Materials

Battery material is mostly powder, each large particle will be composed of many small particles, the shape is mostly spherical, due to the small atomic number of the elements of the battery material, pt atoms into the TEM will be more obvious, it is recommended that the protective layer using C protection.

Figure 4: Battery Materials

Geological and ceramic materials

Such samples have poor electrical conductivity, some of them will be hollow, the preparation of samples before the need for gold spraying treatment, the material is hard, the preparation time is long.

Figure 5: Geological and ceramic materials

Cross-sectional analysis

The FIB sputter etch function allows you to cut a sample at a fixed point and observe the cross-section to characterise the cross-section size, and it can also be equipped with a system that combines elemental analysis (EDS) to analyse the cross-section composition. Commonly used in chips, LEDs and other failure analysis, common IC chips in the processing of the problem, the use of FIB can be quickly pinpointed to analyse the causes of defects and improve the process, the FIB system has become an essential equipment for the contemporary IC process line.

Figure 6: Cross-sectional analysis

Chip patching and circuit editing

When ICs are designed, design changes must be verified, optimised and debugged on the resulting ICs. After problems are detected, the defective parts need to be repaired. Existing IC processes are shrinking. The number of layers is increasing. The use of FIB sputtering function can be cut off somewhere connected to the line, you can also use its deposition function can be connected to a place that was not originally connected to the place to connect together, so that you can change the direction of the line line can be found, diagnosed in the line of the error, and can be directly on the chip to correct the error, reduce R & D costs and speed up the development process, because it can be free of the original form of the preparation and the mask to change the time and cost required. It reduces R&D costs and speeds up the development process, as it eliminates the time and cost required for prototyping and mask changes.

Figure 7: Chip patching and circuit editing

Preparation of micro- and nanostructures

The FIB system does not need a mask plate, and can directly engrave or deposit the required graphics under the GIS system. Using the FIB system, it has been possible to prepare complex functional structures at the micro- and nanoscale, including nano-quantum electronic devices, sub-wavelength optical structures, surface equipartitioned excitation devices, and photonic crystal structures. Through reasonable methods, not only two-dimensional planar graphic structures, but also complex three-dimensional structures can be prepared.

Figure 8: Preparation of micro- and nanostructures

3D reconstruction analysis

3D imaging analysis using FIB for 3D reconstruction of materials is also an area that has grown at a rapid rate in recent years. This method is mostly used in material science, geology, life science and other disciplines. The purpose of 3D reconstruction analysis is to rely on software control FIB layer-by-layer cutting and SEM imaging alternately, and finally through the software for 3D reconstruction. the effective combination of FIB 3D reconstruction technology and EDS allows researchers to characterise the structure, morphology and composition of the material in the three-dimensional space; and the combination of EBSD can be used to characterise the polycrystalline material in the spatial state of the structure, orientation, grain size, distribution and other information. The combination with EBSD allows the characterisation of polycrystalline materials in space with respect to structure, orientation, grain shape, size and distribution.

Figure 9: 3D reconstruction analysis

Atomic Probe Sample Preparation

Atom Probe ( AP) can be used for three-dimensional imaging ( Atom Probe Tomography, APT) and also to quantitatively analyse the chemical composition of samples at the nanoscale. An important requirement for this application is the preparation of a sharp probe with a large aspect ratio and a tip size of about 100 nm. The requirements for the preparation of atom probe samples are very close to those for TEM thin film samples and the methodology is similar. Firstly, the sampling location of interest is selected, V-grooves are dug on both sides, the bottom is cut, and the sample is removed by a nano-manipulator. Transferred to a fixed sample holder, the sample was Pt-welded and cut from the bulk. The peripheral part was successively excised from outside to inside to form a sharp tip. The sample was finally subjected to final polishing with an ion beam at low voltage to eliminate the amorphous layer, and areas of high ion injection.

Figure 10:Atomic Probe Sample Preparation

Photolithography mask version repair

In ordinary optical lithography, the mask plate is the origin of the graphics, but after a long time of use, the graphics on the mask plate will be damaged, resulting in graphic defects after lithography, the cost of the mask plate is high, and if a small graphic defect on the mask plate results in the failure of the whole mask plate, the cost of re-preparing the mask plate is high. Using FIB system can realise the fixed-point repair of the defects of the mask plate, and the method is simple and fast. Ion deposition can be used to repair defects in the light-transparent area and C deposition can be chosen as the repair material for the mask plate, while ion sputtering is used to repair defects in the light-shielding area and etching of the light-shielding defects. However, the use of FIB to repair the mask version of the biggest problem is that it will lead to Ga ion contamination and changes in glass transmittance resulting in residual defects, which can be combined with RIE and cleaning methods to etch off the glass with Ga ion injection surface, so that its transmittance is restored.