High resolution quantitative two-dimensional dopant mapping using energy-filtered secondary electron imaging

Abstract

We have quantified two-dimensional dopant profiles in Si with high accuracy using a commercial field emission gun scanning electron microscope with added secondary electron energy-filtering capabilities. Quantification was achieved for dopant concentrations of 2.8ϫ 10 17 -7.5ϫ 10 19 cm −3 with an accuracy of ±8.5%. Using energy filtering, we have measured the surface potential difference ⌬⌽ s across a 3 nm wide p-doped Si layer with respect to the n-doped substrate of a test structure to be 0.72± 0.15 V. Spatial resolution limits are discussed and are shown to be limited by the secondary electron escape depth. A technique for the rapid collection of calibrated energy-filtered images is also proposed.

Doping profile of InP nanowires directly imaged by photoemission electron microscopy

“…While no previous quantitative estimation exists for differently doped InP, we note that generally for semiconductor materials where this degree of contrast has been observed by SE emission, the doping levels differed by at least a factor of 1.5. 17 To make a rough quantitative estimate, we use the measure previously obtained for Si by Elliott and co-workers 18 indicating that there is a nonnegligible change in charge carrier concentration, of a factor 2-3 between the top and bottom segments. We propose that different diffusion lengths of dopant atoms or H 2 S molecules on the intrinsic segment as compared to the n-doped segments could lead to a different abundance of dopants atoms available for the growth of the two segments although gas pressures were the same.…”

Secondary electron dopant contrast imaging of compound semiconductor junctions

“…Enhanced dopant contrast using a through-the-lens system at a low extraction voltage was reported and attributed to the different angular distributions of SEs emitted from different doping regions. 6,7 In addition, efforts for quantitative analysis include energy-filtered SE imaging 8,9 and Monte Carlo simulations. 10,11 However, limited studies have been done for heterostructures, 12,13 in spite of their importance for device applications including photovoltaics, light-emitting diodes (LEDs), and high electron mobility transistors.…”

Profiling N-Type Dopants in Silicon

“…1) Among the dopant profiling techniques the scanning electron microscopy (SEM) has become a well established method exhibiting high spatial resolution as well as high sensitivity to the dopant concentration. [2][3][4] Quantitative two-dimensional dopant mapping using energy-filtered secondary electron (SE) imaging has been demonstrated with the SEM. When measuring the shift in the SE energy spectra across the p-n junction, more accurate data are obtained than what mere SE yields from selected areas provide.…”

“…When measuring the shift in the SE energy spectra across the p-n junction, more accurate data are obtained than what mere SE yields from selected areas provide. 3) There are still some open questions as regards the origin of the contrast between the doped structures, which complicates employing the SEM as a quantitative tool in the dopant profiling. The presence of hydrocarbons and oxide contamination layers on the sample surface influences the contrast behaviour significantly.…”