Applying a high-energy electron beam during photomask observations has been studied for improving resolution and reducing measurement uncertainty. Photomasks can be observed and measured by using an electron beam of 50 keV or higher in combination with a conductive coating over the photomask surfaces. Though image brightness and contrast vary with electron-beam exposure time, the effects of brightness and contrast on images are not significant and not essentially different from the effects with conventional low-energy electron beams. Therefore, a high-energy electron beam has the possibility of providing a higher measurement certainty than a conventional low-energy electron beam. (C) 2003 American Vacuum Society.