Site-specific dopant profiling in a scanning electron microscope using focused ion beam prepared specimens

Kazemian, P.; Twitchett, A C; Humphreys, C. J.; Rodenburg, Cornelia

doi:10.1063/1.2207552

Cited by 22 publications

(17 citation statements)

References 11 publications

(7 reference statements)

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“…Further studies are required in order to minimize artifacts due to FIB induced contrast degradation resulting from near-surface damage. 28 The agreement between the experimental contrast profile and the energy of the valence bandedge calculated using adjusted ionized dopant densities in Fig. 7 suggests that SEM dopant contrast imaging is a suitable candidate for 2D charge mapping in compound semiconductors, although further studies are necessary in order to quantitatively correlate experimental contrast and charge density.…”

Section: Discussionmentioning

confidence: 53%

Secondary electron dopant contrast imaging of compound semiconductor junctions

Chung

Myers-Ward

Nyakiti

et al. 2011

Journal of Applied Physics

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Secondary electron imaging combined with immersion lens and through-the-lens detection has been used to analyze various semiconductor junctions. Dopant contrast imaging was applied for multi-doped 4H-SiC, growth-interrupted n þ /p and n/n þ homoepitaxial interfaces, and an AlGaAs/ GaAs p-n junction light-emitting diode structure. Dopant contrast was explained by the local variation in secondary electron escape energies resulting from the built-in potential difference. The effect of varying electron affinity on contrast for the heterostructures is also discussed. The contrast profile of the n-doped AlGaAs compared reasonably well to the simulated valence bandedge energy using a previously determined efficiency of dopant ionization.

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Section: Discussionmentioning

confidence: 53%

Secondary electron dopant contrast imaging of compound semiconductor junctions

Chung

Myers-Ward

Nyakiti

et al. 2011

Journal of Applied Physics

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“…FIB milling seems to be an ideal solution, since it is routinely used in device failure analysis and sample preparation for TEM. The drawback of FIB is the formation of an amorphous layer, which contributes to a DC decrease (Kazemian et al, 2006b;Cooper et al, 2009Cooper et al, , 2010Cooper et al, , 2011Chee et al, 2010). It is known that the thickness of this amorphous layer decreases with decreasing ion energy, therefore TEM lamella preparation and FIB nanostructuring is usually done by low-energy ion milling and polishing (Kato et al, 1999;Giannuzzi et al, 2005;Mayer et al, 2007).…”

Section: Resultsmentioning

confidence: 99%

“…Our procedure uses final preparation polishing steps providing minimization of a damaged layer thickness (Giannuzzi et al, 2005), similar to the commonly used technique for preparation of lamellas needed in high-resolution transmission electron microscopy (TEM) experiments. After the initial cross-section milling using 30 keV Ga + FIB (Kazemian et al, 2006 b ), we polished the cross-section surface using an ion beam with energies down to 1 keV. The obtained contrast values from variously doped areas were quantitatively comparable to those achieved by sample cleavage.…”

Section: Introductionmentioning

confidence: 82%

Toward Site-Specific Dopant Contrast in Scanning Electron Microscopy

et al. 2014

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Since semiconductor devices are being scaled down to dimensions of several nanometers there is a growing need for techniques capable of quantitative analysis of dopant concentrations at the nanometer scale in all three dimensions. Imaging dopant contrast by scanning electron microscopy (SEM) is a very promising method, but many unresolved issues hinder its routine application for device analysis, especially in cases of buried layers where site-specific sample preparation is challenging. Here, we report on optimization of site-specific sample preparation by the focused Ga ion beam (FIB) technique that provides improved dopant contrast in SEM. Similar to FIB lamella preparation for transmission electron microscopy, a polishing sequence with decreasing ion energy is necessary to minimize the thickness of the electronically dead layer. We have achieved contrast values comparable to the cleaved sample, being able to detect dopant concentrations down to 1×10(16) cm-3. A theoretical model shows that the electronically dead layer corresponds to an amorphized Si layer formed during ion beam polishing. Our results also demonstrate that contamination issues are significantly suppressed for FIB-treated samples compared with cleaved ones.

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“…By investigating biased junctions, Elliott et al [4] attributed the contrast mechanism to the varying collection efficiency of the SE detector caused by the p-n junction potential. SEM-based contrast mapping of dopants continues to be actively pursued in the current literature [5][6][7], using both SE and backscattered electron emission [8].…”

Section: Introductionmentioning

confidence: 99%

TEM-based phase retrieval of p–n junction wafers using the transport of intensity equation

Petersen

Keast

Johnson

et al. 2007

Philosophical Magazine

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Two cross-sectional specimens of pattered silicon wafers implanted with either arsenic or phosphor are investigated in the transmission electron microscope (TEM). Phase retrieval using the transport of intensity equation (TIE) is suggested as a means for nano-scale sensing of dopants in such p-n junction wafers. Improvements in TIE phase retrieval are proposed and implemented using a through-focus series of large numbers of images. Polynomial fitting to robustly estimate the required intensity defocus-derivative is shown to enhance data quality, resulting in phase maps that portray detail over a broad range of spatialfrequencies in a realistic manner.

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Site-specific dopant profiling in a scanning electron microscope using focused ion beam prepared specimens

Cited by 22 publications

References 11 publications

Secondary electron dopant contrast imaging of compound semiconductor junctions

Secondary electron dopant contrast imaging of compound semiconductor junctions

Toward Site-Specific Dopant Contrast in Scanning Electron Microscopy

TEM-based phase retrieval of p–n junction wafers using the transport of intensity equation

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