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Transmission Electron Microscopy with EDS Elemental Color Mapping Technology

With the rapid development of semiconductor chip design, crystal manufacturing, and advanced packaging technology, failure analysis plays an increasingly important role. In failure analysis, we not only need to provide fast and accurate failure analysis results but more importantly, must provide information about the semiconductor chip's internal nano-scale structure and materials/elemental color distribution (Elemental Color Mapping). Using transmission electron microscopy analysis, we can achieve and satisfy these requirements. Particularly, the latest Talos series field emission/transmission electron microscope can provide rapid, accurate nano-material analysis and quantitative evidence.

Using the Talos F200E field emission/transmission electron microscope as an example, the new design has over 150 patents, equipped with high-brightness electron sources and 4 high-efficiency EDS signal detectors. It can achieve rapid EDS signal collection and obtain precise quantitative and qualitative EDS component analysis results, particularly for chip nano-structure, material, and surface elemental color distribution information. The new full-field 16M CMOS camera can quickly capture high-resolution transmission electron microscope images (HR-TEM) and electron diffraction patterns. The Talos series transmission electron microscope's automated design simplifies material analysis procedures, enabling engineers to achieve highly automated sample analysis reports through computer control.

Figure 1 shows the new Talos series high-resolution field emission/transmission electron microscope and EDS system installed in the Victory Nano laboratory. The instrument uses a fully-enclosed control system design, allowing engineers to achieve highly automated sample analysis and generate analysis reports through computer control.

Figure 1:The new generation of S/TEM-EDS analyzers - Talos high-resolution scanning/transmission electron microscopy and energy spectroscopy systems.

Discussion of TEM analysis follows, focusing on how conventional TEM can achieve high-magnification images like the FinFET structure shown in Figure 2 at 1.05M× magnification. However, the new Talos series provides additional capabilities beyond just high-magnification imaging.

The EDS elemental color mapping analysis technology operates under STEM mode. During analysis, electrons gather in a convergent area to scan the sample. When the electron beam hits the sample, it generates characteristic X-ray signals. Using the EDS detector to collect these X-ray signals and analyzing software to process the collected characteristic X-ray signals, we can display different elemental regions in different colors to obtain the elemental color distribution image. As shown in Figure 3, we obtained an extremely clear image of a semiconductor microstructure using this technology. From the image, we can not only see the structural morphology near the chip's Gate/Oxide circuit but also clearly see the elemental composition distribution information on the structure. This information is extremely important for semiconductor chip development and failure analysis. Using this technology, we can obtain high spatial resolution, accurate elemental composition and quantitative color distribution information in an extremely short time.

Figure 2:High-resolution TEM image of a FinFET structure with TEM magnification up to 1.05 M×. The arrangement of the silicon atoms can be clearly seen in the figure.

Figure 3:A photograph of a semiconductor microstructure obtained by the technique of color surface distribution analysis of elements in the energy spectrum in transmission electron microscopy. The image shows the structure and morphology of the chip near the Gate Oxide circuit, as well as a clear distribution of the elemental composition on the corresponding structure.

Applications of New-Generation Transmission Electron Microscopy EDS Elemental Color Mapping Analysis in Semiconductor Chip Failure Analysis

To better compare traditional EDS technology with the new-generation EDS technology, we first demonstrate the differences between them through comparative results. Figures 4(a) and 4(b) show the elemental color distribution mapping results obtained using traditional EDS technology and new-generation EDS technology respectively. From the information shown in the images, traditional EDS technology has limitations in signal collection, image signal ratio, interface resolution, and other aspects of performance. Particularly for light elements like O, N in semiconductor components, the signal collection amount is obviously insufficient. Meanwhile, compared to new-generation EDS technology, traditional technology's data collection time is several times longer.

Figure 4:Comparison of the results of color surface distribution energy spectral images of colored elements obtained by applying (a) traditional EDS spectral analysis technique and (b) new generation EDS spectral analysis technique.

The significant differences in analysis results are mainly due to the detection materials. For traditional EDS technology, the detection material is silicon (lithium) - Si(Li) detector, as shown in Figure 5. This detector typically uses liquid nitrogen cooling and can maintain good energy resolution at low count rates. However, as the count rate increases, the energy resolution will decrease, leading to differences in elemental detection capability. The new-generation Si drift detector (SDD detector) can maintain extremely high energy resolution at high count rates. Additionally, compared to the new-generation SDD detector, the electron-space transfer rate of traditional Si(Li) detectors is relatively low, so the Si(Li) detector's signal resolution effect is lower than the SDD detector. Furthermore, the traditional Si(Li) detector's active area is generally smaller than the SDD detector's surface area. To obtain high-resolution EDS elemental color distribution maps with high signal-to-noise ratio, using traditional Si(Li) detectors requires several times longer collection time than SDD detectors.

Figure 5:Conventional liquid nitrogen cooled Si(Li)-Si(Li) spectroscopy probes. The efficiency of signal acquisition is low due to the limited material and area of the probe.

As EDS collection time extends, other problems will inevitably arise. For example, in semiconductor component manufacturing, some low-k (low-k) materials are introduced that are typically not resistant to electron beam radiation. Long-term electron exposure can cause material deformation or even structural changes. Due to STEM-EDS technology requiring repeated scanning of the sample surface, material changes may lead to some analysis areas becoming unanalyzable, and edge effects appearing. At the same time, this can cause semiconductor samples to develop structural and composition changes, making it impossible to continue subsequent analysis work. This makes such challenging failure analysis cases particularly difficult to address. Additionally, long-term scanning requires sample drift correction work, which may affect the final analysis results on one hand, and further extend the measurement analysis time on the other hand.

Figure 6 shows the geometric design of the Super-X SDD detector head mounted on the latest Talos F200E. It consists of 4 independent SDD detector heads, distributed symmetrically in TEM's objective lens area. The detector head's total area reaches 120 mm², with an effective collection angle reaching 0.9 srad. Compared to traditional Si(Li) single detector design, Super-X SDD's multi-detector design can collect excited X-ray signals from samples at multiple angles simultaneously. The large-area detector design can greatly improve EDS signal collection efficiency, reducing the original hours-long EDS spectrum collection time to about 10 minutes, essentially enabling researchers to conduct atomic-level EDS energy analysis. The symmetrical detector design ensures that regardless of sample tilt angle, the detector head can collect maximum X-ray signals, making three-dimensional compositional analysis work possible. Therefore, the new EDS energy technology not only improves image contrast ratio, signal detection sensitivity, and signal collection efficiency but also greatly expands application areas including atomic-level EDS analysis and three-dimensional chemical composition analysis.

Figure 6:Schematic of the geospatial design of the new Super-X SDD EDS spectroscopy probe for the Talos F200 series of field emission scanning/transmission electron microscopes.

Three-dimensional Semiconductor Structure Representation

For complex semiconductor structures, obtaining the three-dimensional structure of semiconductor components and analyzing their actual defect structure or elemental distribution is becoming increasingly important. Currently, transmission electron microscopes mainly use electron beam layer-by-layer technology to gradually observe semiconductor samples from different angles, thereby reconstructing the semiconductor component's three-dimensional structure.

The new Super-X detector head uses a symmetrical design, so the EDS signal collection is not affected by sample tilt angle. In different angles, it can always collect sufficient EDS signal information, thus realizing the electron beam layer technology's ability to simultaneously collect electron microscope images and elemental microregion data.

Benefiting from the development and innovative applications of new transmission electron microscope detector heads, EDS signal collection efficiency has been greatly improved. Therefore, the electron beam layer technology's signal collection time has also been significantly reduced, improving signal contrast ratio and achieving high-sensitivity elemental color surface distribution collection, while also avoiding the damage to samples during long-time signal collection.

Figure 7 shows the three-dimensional elemental structure results of a logic device, where different elements are shown in different colors, directly displaying the device's structural details. Taking the M0 metal layer as an example, we can observe the copper conductor structure's completeness, including external layer barrier structure defects. We can also clearly observe details like device gate electrode copper electrode structure completeness, which can directly observe the device's defect generation mechanism, helping to solve failure analysis problems.

Figure 7:Three-dimensional structure diagrams of the energy spectrum elements of the logic device, with different elements in different colors to show the structural details of the device visually.

Conclusion

In this paper, we have further researched and applied transmission electron microscope analysis technology, particularly investigating EDS elemental color mapping analysis technology. Using the Talos F200E field emission/transmission electron microscope as an example, we discussed the differences between this new detection technology and traditional detection methods, as well as the reasons why this new technology can obtain element color distribution images with both high spatial resolution and sensitivity. We discussed and demonstrated several practical application examples of EDS elemental color mapping analysis technology. Using EDS elemental color mapping analysis technology, we conducted successful analysis and characterization of nano-sized defects in crystal manufacturing. In the Via failure analysis case study, we also successfully demonstrated three-dimensional semiconductor structure representation, providing great assistance for advanced semiconductor component production manufacturing, yield improvement, and research development.

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