Quantitative two-dimensional dopant profiles obtained directly from secondary electron images

Abstract

Articles you may be interested inHigh resolution quantitative two-dimensional dopant mapping using energy-filtered secondary electron imaging Doping-dependent contrast in secondary electron images of p/n junctions in silicon obtained in a field-emission scanning electron microscope was observed and characterized. The optimum experimental conditions for observing this ''electronic'' contrast were established by investigating the effect of microscope and material parameters on the magnitude of the contrast. The contrast between the bright p-type areas and the darker n-type areas was maximized at an accelerating voltage of ϳ1 kV, and when a through-the-lens detector configuration was employed. Secondary electron contrast profiles of boron doped p ϩ /n junctions in silicon showed a good correlation with secondary ion mass spectroscopy depth profiles of the atomic concentration down to the 10 17 cm Ϫ3 level. However, similar results were not obtainable for n ϩ /p junctions. It is demonstrated that this contrast effect may be exploited for obtaining two-dimensional dopant profiles directly from secondary electron images of p ϩ /n junctions provided that the technique is empirically calibrated against a one-dimensional dopant profiling method.

Ion beams in silicon processing and characterization

“…40, 41, and 42 demonstrate the weakness of the selective-etch/TEM approach, i.e., its lack of contrast at doping concentrations of less than 10 19 atoms cm Ϫ3 . Another electron microscopy based approach uses scanning electron microscopy 139 in which the variation of secondary electron yield with dopant concentration is used to give a dopantdependent image of the area of interest, again prepared in cross section.…”

The injected-charge contrast mechanism in scanned imaging of doped semiconductors by very slow electrons

“…The contrast between the p-and n-type semiconductor (mostly silicon) was found to reach as much as 10%. Its existence has been proven throughout the electron energy range usual for SEM, and some authors detected maximum contrast at low energies such as 1 keV [8].…”

“…Over the last decade attention has been devoted to direct secondary electron (SE) imaging of dopants [2][3][4][5][6][7][8][9][10][11][12][13]. The contrast between the p-and n-type semiconductor (mostly silicon) was found to reach as much as 10%.…”

Secondary emission of strain-induced dopant contrast in the source/drain regions of metal-oxide-semiconductor devices

“…In fact, whereas the contrast of the p-type region is significantly larger, that of the n-type region is significantly smaller than what has been reported for similar concentrations. 11,15 It seems that dopant contrast has been shifted sideways and SE emission is enhanced for both pand n-type regions in real MOS devices. This intriguing phenomena must therefore be related to the different structures involved, either the heterostructures of STI or the Co silicide at the junctions between the blank wafers and MOS devices.…”