Profiling N-Type Dopants in Silicon

Hovorka, Miloš; Mika, Filip; Mikulı́k, Petr; Frank, L.

doi:10.2320/matertrans.mc200910

Cited by 7 publications

(3 citation statements)

References 16 publications

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“…The photoemission electron microscopy study produced a proposal to explain the observed phenomena with p/n differences in absorption of the hot electrons on their move toward the surface, existing due to a different energy threshold for generation of the e-h pairs [ 48 ]. The first detailed study of the n-type patterns on the p-type substrate [ 49 ] produced data previously not available, which we discuss below.…”

Section: Resultsmentioning

confidence: 99%

Scanning Electron Microscopy with Samples in an Electric Field

et al. 2012

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The high negative bias of a sample in a scanning electron microscope constitutes the “cathode lens” with a strong electric field just above the sample surface. This mode offers a convenient tool for controlling the landing energy of electrons down to units or even fractions of electronvolts with only slight readjustments of the column. Moreover, the field accelerates and collimates the signal electrons to earthed detectors above and below the sample, thereby assuring high collection efficiency and high amplification of the image signal. One important feature is the ability to acquire the complete emission of the backscattered electrons, including those emitted at high angles with respect to the surface normal. The cathode lens aberrations are proportional to the landing energy of electrons so the spot size becomes nearly constant throughout the full energy scale. At low energies and with their complete angular distribution acquired, the backscattered electron images offer enhanced information about crystalline and electronic structures thanks to contrast mechanisms that are otherwise unavailable. Examples from various areas of materials science are presented.

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Section: Resultsmentioning

confidence: 99%

Scanning Electron Microscopy with Samples in an Electric Field

et al. 2012

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“…[17] Similar results can be found in the work presented by Venables et al [50] and Xu et al [20] Hovorka et al employed photo emission electron microscopy (PEEM) as a more sensitive alternative to the SEM and probing the surface energy spectra for Si with different dopant concentrations with its mechanism of hot electron generation. [55] Heath et al applied external bias and varied the bias to calibrate the SE signal. [36] Hovorka et al and Heath et al are the only two cases found to successfully establish a monotonic dependency between the image intensity and the doping levels for Si with an n-type emitter.…”

Section: Semdci Issues With N-type Dopingmentioning

confidence: 99%

Scanning Electron Microscopy Dopant Contrast Imaging of Phosphorus‐Diffused Silicon

Zhang

Scardera

Wang

et al. 2022

Adv Materials Technologies

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Phosphorous dopant diffusion profiles feature in many silicon semiconductor devices, including the vast majority of silicon solar cells. Accurate spatially resolved dopant profiling is crucial for understanding the performance of these diffused regions, however, it is very challenging to obtain such profiles in non‐planar samples. Scanning electron microscopy for dopant contrast imaging (SEMDCI), where the secondary electron (SE) image contrast is used to determine the dopant level of a semiconductor sample, is an ideal candidate for Si dopant profiling, especially for silicon samples with surface nanotexturing or black silicon (BSi) technology. However, in previous SEMDCI studies, the dopant concentration of heavily doped n‐type layers in silicon samples have shown a poor correlation with the SE signal contrast. In this work, 1) good contrast for n‐type diffused silicon without contrast‐enhancing techniques; 2) a new contrast definition to account for imaging non‐uniformities; 3) clear correlations between SE contrast and sample work function for phosphorus‐diffused planar silicon specimens across a wide range of emitter profiles; 4) implementation of an empirical baseline correction to normalize scanning electron microscopy image condition variations, are presented. This SEMDCI method is subsequently used for the first time to obtain 2D electron concentration maps for both planar and BSi samples.

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“…After non-zero diffracted rays emerge, flat surface crystals may be imaged in the diffraction contrast [8]. When varying the landing energy of electrons, we get doped areas in semiconductors revealing either a proportional dopant contrast or a constant brightness [9], [10].…”

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confidence: 99%

Scanning Electron Microscopy With Slow Electrons

Frank¹,

Mikmeková²,

Pokorná³

et al. 2013

Microsc Microanal

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When focusing the primary electron beam in a scanning electron microscope (SEM) using a standard electromagnetic or electrostatic lens with the main aberration coefficients independent of the beam energy, we get a spot size proportional to (energy) -3/4 [1]. However, an immersion electrostatic lens has aberrations proportional to the lower of the electron energies existing on both its sides, so when retarding the primary beam with a bias applied directly to the sample via the cathode lens, we get a spot extending only as (energy) -1/4 at the lowest energies, with the overall spot size remaining within one order of magnitude throughout the full energy scale [1]. The above-sample field not only retards the primary electrons but also accelerates the signal electrons and collimates them towards the optical axis, thereby ensuring excellent collection efficiency for all energies. A below-sample detector enables performance of the transmission mode at any energy [2].Scanning low energy electron microscopy (SLEEM) with a cathode lens provides improved image resolution at low energies, an enhanced signal of secondary electrons, a completely collected signal of backscattered electrons (BSE) including very low energy electrons that are traditionally abandoned, and plenty of contrast mechanisms not available with fast incident electrons. Below a fuzzy threshold at 50 eV, the inelastic scattering phenomena fade away so the BSE signal strongly dominates and the penetration of primary electrons also increases. At and below hundreds of eV, the BSE signal abandons its dependence on the atomic density of the sample and becomes governed by its crystallinic structure, while at tens and units of eV the electronic structure is what reflects the image signal behavior.From the experimental point of view, it is important to have flat samples with surface unevenness not exceeding tens of m at hundreds of eV and units of m at the lowest energies. It is good practice to cover the sample with a flat cap leveling the equipotential surface. With a primary beam energy of several keV we get, using the sample bias, excellent performance at lower energies, i.e. not only better resolution, but also much higher signal-to-noise ratio and enhanced surface sensitivity. When tuning the landing energy of electrons to what is known as the second critical energy, we get nonconductive samples imaged free of charging artifacts [3]. The dynamical theory of electron diffraction indicates [4], and practice confirms [5], that in the 10 2 eV range the grain contrast of polycrystals substantially increases and even the distribution of residual strains inside grains becomes visible [6]. Below 50 eV, the absorption of hot electrons injected into samples is low enough to allow the electron reflectance in the (00) spot to respond to the local density of empty electron states available in the direction of motion, which provides an alternative method of determining the local crystallographic system and its orientation [7]. After non-zero diffracted rays emerge, flat sur...

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Profiling N-Type Dopants in Silicon

Cited by 7 publications

References 16 publications

Scanning Electron Microscopy with Samples in an Electric Field

Scanning Electron Microscopy with Samples in an Electric Field

Scanning Electron Microscopy Dopant Contrast Imaging of Phosphorus‐Diffused Silicon

Scanning Electron Microscopy With Slow Electrons

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