The reconstruction of surface topography based on the detection of backscattered or secondary electrons in SEM has found increasing interest during long time [1-5].

For more accurate reconstruction one should know angular dependecies of secondary electron emission (SE) coefficient δ and backscattered electron (BSE) coefficient η, which, in general, are quite well investigated and defined [6]. But for increasing sensitivity in determination of local surface slopes it is offered to detect BSE and SE not integrally, as in previous works, but differentially by energy, i. e. by value of signal detected in narrow energy range of emitted electrons. As it was shown in our experiments, sensitivity increases in times in such formulation of experiment. Experiments were carried out in LEO-1455VP (Zeiss) equipped with a two-channel toroidal electron spectrometer [7]. We measured energy spectra of SE and BSE for various angles of incidence α (Fig. 1). SE spectra are slightly deformed because of applying negative bias V_s=-33 V to stage (electrons leave surface nonisotropically). Comparison of integral and differential coefficients is depicted on Fig. 2. Values of integral coefficients δ and η were calculated by formulas from [8] (by substituting R to Rcosα [9]) and [10] respectively. Values of integral coefficient at fixed angle of detection θ were obtained by simple integration of measured spectra. LineScans of Ti-ball, obtained as difference signal between two symetrically mounted detectors at fixed energy of electrons, are depicted on Fig. 3.

Obtained results allow us to conclude that secondary electrons are best suited for proplem of surface relief reconstruction than backscattered electrons.

This work was funded thanks to the support of RFBR

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EMC Abstracts - https://emc-proceedings.com/abstract/3-d-reconstruction-of-surface-topography-in-sem-by-means-of-energy-filtered-se-and-bse/