A Novel Technique for Probe Intensity Profile Characterisation in the Environmental Scanning Electron Microscope

Abstract The environmental scanning electron microscope (ESEM) allows imaging and analysis in a gaseous environment at pressures up to 20 torr. Gas phase scattering of primary electrons leads to a loss of useable probe current and produces an electron skirt around the beam that can degrade the spatial resolution in microanalytical studies. Progress in ESEM microanalysis requires accurate modeling and measurement of the beam intensity profile. Previously, x-ray techniques and beam sensitive materials have been used to measure the extent of the skirt. These investigations have yielded inconsistent skirt distances possibly due to dose dependence of the measurement techniques. We present a new, high gain method to measure the useable probe current and skirt profile using the electron beam induced current (EBIC) from a P-N junction. The interface of an N- and a P-type semiconductor contains an electrostatic donor-acceptor dipole (“depletion layer”) created by an electron-hole recombination energy minimization mechanism.