Abstract:Abstract. The role of laser assisted atom probe tomography (APT) in microelectronics is discussed on the basis of various illustrations related to SiGe epitaxial layers, bipolar transistors or MOS nano-devices including gate all around (GAA) devices that were carried out at the Groupe de Physique des Matériaux of Rouen (France). 3D maps as provided by APT reveal the atomic-scale distribution of dopants and nanostructural features that are vital for nanoelectronics. Because of trajectory aberrations, APT images… Show more
“…Varying evaporation field conditions were achieved by altering the laser energy, which was slowly decreased while field-evaporating Layer 3 Si cap. The evaporation field was approximated by the ratio of total counts of the 28 Si 2+ : 28 Si + (Blavette & Duguay, 2014; Estivill et al, 2015; Estivill et al, 2017) with data collected at six different ratios ranging from 0.8:1 up to 270:1. These different Si ratios were achieved while maintaining a constant detection rate by inversely altering the voltage and laser energy.…”
Understanding and resolving discrepancies between atom probe tomography (APT) and secondary ion mass spectrometry (SIMS) measurements of B dopants in Si-based materials has long been a problem for those in the semiconductor community who wish to measure B within the source/drain SiGe of a device. APT data collection of Si-based materials is typically optimized for Si, which is logical, but perhaps not ideal for field evaporation of B. Increasing the evaporation field well beyond the typically used 28Si2+:28Si+ ratio of approximately 10:1 up to a ratio of ~200:1 is demonstrated to improve B detection while retaining well-matched Si and Ge concentrations with respect to those measured by SIMS. A range of evaporation conditions are examined from a very low field with high laser energy to an extremely high field with extremely low laser energy demonstrating problems at both far ends of the spectrum and a sweet spot when the operating conditions used produce a 28Si2+:28Si+ ratio of approximately 200:1 (in terms of total counts of each ionization state), which is more than an order of magnitude higher than normally used conditions and results in nicely matched B, Si, and Ge APT measurements with those of SIMS.
“…Varying evaporation field conditions were achieved by altering the laser energy, which was slowly decreased while field-evaporating Layer 3 Si cap. The evaporation field was approximated by the ratio of total counts of the 28 Si 2+ : 28 Si + (Blavette & Duguay, 2014; Estivill et al, 2015; Estivill et al, 2017) with data collected at six different ratios ranging from 0.8:1 up to 270:1. These different Si ratios were achieved while maintaining a constant detection rate by inversely altering the voltage and laser energy.…”
Understanding and resolving discrepancies between atom probe tomography (APT) and secondary ion mass spectrometry (SIMS) measurements of B dopants in Si-based materials has long been a problem for those in the semiconductor community who wish to measure B within the source/drain SiGe of a device. APT data collection of Si-based materials is typically optimized for Si, which is logical, but perhaps not ideal for field evaporation of B. Increasing the evaporation field well beyond the typically used 28Si2+:28Si+ ratio of approximately 10:1 up to a ratio of ~200:1 is demonstrated to improve B detection while retaining well-matched Si and Ge concentrations with respect to those measured by SIMS. A range of evaporation conditions are examined from a very low field with high laser energy to an extremely high field with extremely low laser energy demonstrating problems at both far ends of the spectrum and a sweet spot when the operating conditions used produce a 28Si2+:28Si+ ratio of approximately 200:1 (in terms of total counts of each ionization state), which is more than an order of magnitude higher than normally used conditions and results in nicely matched B, Si, and Ge APT measurements with those of SIMS.
“…There is a critical need to analyze many material systems in three dimensions (3D), for example to understand the connectivity of phases, porous networks, and complex shapes. Fortunately, there are now several tools available for 3D characterization, for example, X-ray computed tomography (CT) [1], serial section SEM Tomography (SST) [2–4], transmission electron tomography [4], and atom probe tomography [5, 6], each covering different length scales (see Figure 1). Figure 13D imaging methods for materials science.…”
Xenon plasma focused ion beam (FIB) technology has the potential to investigate large volumes, hundreds of micrometers in size whilst retaining the high resolution of SEM imaging. Three different materials, an aluminum alloy, a zirconium-based metallic glass, and a tungsten carbide-cobalt hard metal, were subject to serial sectioning to build up 3D microstructural images. Lastly a sample of human dentine was shaped into a pillar for analysis using nanoscale X-ray CT. The plasma FIB broadens the range of length scales, which can be investigated and holds significant promise for bringing new understanding of complex microstructures.
“…Since the 1990's, the control of field ion evaporation was carried out though voltage pulses, which was inadequate to the analysis of nonmetallic materials due to the propagation delays and to the bleaching of the voltage pulse towards the apex of the tip. The recent development of laser-assisted atom probe tomography (La-APT) [4] has made it possible to analyze a large variety of non-metallic nanostructures [5][6][7]. Among these structures, there are functional materials of particular interest because of their optical properties, such as the quantum dots shown in the 3D reconstructed volumes of Fig.…”
This lecture will introduce and revise recent experimental developments on correlative laser-assisted atom probe tomography and optical spectroscopy, with a particular attention to the domain of semiconductor nanostructures. The main goal of correlative microscopy is to gain a deeper insight in materials science studies. For the materials scientist, indeed, the possibility of establishing a link between optical spectroscopic properties of a given system and the reconstruction of its 3D structure and composition by atom probe tomography yields an unprecedented insight into the complex influence of the structure on the electronic states and on the optical transitions characterizing the system. This lecture will therefore revise the different approaches by which it is possible to correlate optical spectroscopy experiments -in particular micro-photoluminescence with atom probe tomography and, possibly, with transmission electron microscopy. Dedicated sample preparation protocols and recent case studies will be reported. Finally, a perspective approach will be introduced, in which the same femtosecond laser pulse could be exploited not only for triggering ion evaporation, but also photon emission in situ in the atom probe itself.
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