A scanning electron microscope using an electron beam with energy more than several tens of keV enables us to observe features that are concealed under the specimen surface. By use of this method, nondestructive and in-line stress estimation of patterned films on a production wafer can be made. This method has been applied to a photoresist pattern, and the results showed mechanical properties of the patterned resist film. (C) 2004 American Vacuum Society.