In a recent study published in the Journal of Applied Physics, a group of researchers from the company GLOBALFOUNDRIES utilized 3D EDS electron tomography for the analysis of semiconductor materials. While various different analytical techniques are currently used to analyze the presence of defects and the functionality of semiconductors, these methods are limited in fully elucidating the extent and origin of these defects. The researchers in this study found that 3D EDS electron tomography is not only capable of providing information on both the chemical composition and microstructure of the semiconductor, but is also able to illustrate the full origin and pathway of defects.
Transmission Electron Microscopy (TEM) for Semiconductor Devices
Transmission Electron Microscopy (TEM)
TEM is a well-known analytical technique that is commonly used to assess both the microstructure and chemical information of materials at the nanoscale. For semiconductor device analysis, TEM is capable of detecting the presence of small variations within the structure of the device, such as line width roughness and material composition, both of which can have a significant effect on the semiconductor’s electrical properties. While useful, the information provided by two dimensional (2D) TEM analysis does not provide a full depth of information on the semiconductor device.
Three Dimensional (3D) Analysis of Semiconductor Devices
The need to provide manufacturers with more in-depth information on semiconductor devices has pushed researchers into looking towards 3D analysis techniques. For example, 3D serial sectioning by SEM-FIB dual beam has been utilized for this purpose, however, the lack of this technique to provide chemical information limits its applicability for novel semiconductor devices. Additionally, 3D atom probe tomography has been postulated as a possible analytical technique that provides chemical information at the atomic scale, however, its limited field of view prevents this technique from being a viable option for semiconductor analysis.
3D EDS Elemental Tomography
While there are various methods available to improve the contrast of electron tomography, such as energy-filtered transmission electron microscopy (EFTEM) tomography, EELS tomography and EDS tomography, EDS tomography is typically preferred over these other options. EDS tomography can be applied to almost all semiconductors as it is an easy to use technology that can generate X-ray images of almost any given element. In fact, this analytical method allows results to be completed in less than half a day, which is particularly advantageous compared to other tomography techniques.
In a recent study published in the Journal of Applied Physics, the researchers utilized 3D EDS Elemental tomography to analyze a nickel silicon (NiSi) semiconductor and compared their results to traditional TEM analysis. They found that they were able to acquire additional depth information on the presence and significance of defects present within the semiconductor compared to when they used the TEM technique. In their results, the researchers were able to not only discover the presence of the defect, but also its origin as a silicon oxide particle that it blocked the formation of NiSi and was eventually covered with silicon nitride during later processing. The covering of this article limited its detection in TEM, however, the 3D EDS electron tomography technique was capable of measuring its complete lifespan within the material.
While the benefits of this analytical technique are evident, there remain certain limitations to utilizing 3D EDS electron tomography for studying semiconductors. Such limitations include the “missing wedge” artifact, which results from an inability to tilt the sample past a 180-degree range, which is typically required for semiconductor samples. Additionally, the EDS detector in this tomography technique may also be blocked by the sample during stage tilting, which can also limit the configuration of the detector during analysis.
In summary, the results of this study demonstrated that the application of 3D EDS elemental tomography in analyzing semiconductor materials provides useful information on the geometry of various detectors.
1. “3D analysis of semiconductor devices: A combination of 3D imaging and 3D elemental analysis” B. Fu & M. Gribelyuk. Journal of Applied Physics. (2018). DOI: 10.1063/1.5010186.
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