Charge-coupled-device response to electron beam energies of less than 1 keV up to 20 keV

Recent developments of backside treatment for the backside-illuminated scientific charge-coupled device (CCD) imagers have shown near-theoretical efficiency even at the short wavelength region of the spectrum. By using a scanning electron microscope (SEM), we report here, for the first time, performance comparisons of backside-treated and untreated CCDs to an electron flux varying from 1 to 100 pA and beam energy ranging from less than 1 keV up to 20 keV. We describe the theoretical analysis, the SEM testing procedure, and the quantum efficiency measurement results. It is shown, for example, that the average quantum efficiency increases from less than 1% for an untreated CCD to nearly 40% for a backside-treated CCD at a beam energy of 1 keV.