Two-dimensional Dopant Profiling and Imaging of 4H Silicon Carbide Devices by Secondary Electron Potential Contrast

Characterization of photonic devices by secondary electron potential contrast

“…On the contrary, the normalized SEPC signal (Figure 2) evidences the staircase with contrast differences of the adjacent layers in the 2% range. This contrast level between two adjacent regions corresponds to a doping difference of about one decade, as predicted by the theory for the unipolar junctions [1]. …”

“…Secondary Electron Potential Contrast (SEPC) recently emerged as a quantitative tool for the characterization of SiC based devices, capable to acquire two-dimensional maps of the dopant distribution, and to delineate accurately electrical junctions [1]. The mechanism leading to the contrast formation is based on the effect of local surface potentials on the secondary electrons (SE) emitted from the valence band when a semiconductor sample is scanned by a Scanning Electron Microscope (SEM).…”

Towards quantification of doping in gallium arsenide nanostructures by low‐energy scanning electron microscopy and conductive atomic force microscopy

“…Type‐2 SEs (so‐called SE2s that are produced by BSEs rather than directly by the primary electrons) have been used in (4) to image highly doped layers but generally reduce image contrast. The angular collection range of the SE detector, 3 trapped surface charges 9 and various surface effects, such as carbonaceous overlayers, 8,15 surface oxides, 9 subsurface damage due to mechanical tripod polishing, 5,14 chemical etching 11 and ion beam damage due to argon ion milling 16 or focused Ga + ion beam milling, 13 have all been identified previously to reduce the contrast relative to the best surface preparation available, which is by cleavage. So doping mapping will only become fully quantitative and reproducible in different laboratories once one uses calibrated test structures and also defines standard operation procedures for specimen handling, where cleavage is the preferred option for sphalerite semiconductors as it yields the highest contrast.…”

“…Doping is the intentional local change of the conductivity in semiconductors by adding impurity atoms and as such this bandgap engineering forms the basis for all pnjunctions found in diodes and many field-effect transistors. There have been numerous studies of secondary electron (SE) imaging in scanning electron microscopy (SEM) of doped semiconductor layers, mostly in Si [1][2][3][4][5][6][7][8][9][10][11][12][13] but also a few for SiC, 14 InP, [15][16][17] GaAs [18][19][20] and, most recently, GaN. 21 The central problem here has always been to predict and interpret correctly the image contrast, though it was recognised right from the beginning 22 that under most imaging conditions p-type layers appear bright 18 and n-type dark, 19 for which the origin of the secondary electron emission from doped regions needed to be understood.…”

High-Resolution Two-Dimensional Imaging of the 4H-SiC MOSFET Channel by Scanning Capacitance Microscopy

“…Usually, scanning electron microscopy (SEM) analyses on cross-sectioned samples are routinely used to obtain information on the extension of the n + - and p ‒ -implanted regions in 4H-SiC power devices, by exploiting the sensitivity of secondary electrons’ contrast to potential variations in this wide-bandgap semiconductor [ 13 ]. However, this technique suffers from a certain degree of uncertainness in the determination of the electrical junction position, as it is sensitive only to high concentrations.…”