Phase shifting SEM moire method

A new phase shifting scanning electron microscope (SEM) moire method is proposed in this paper. The phase shifting technique is realized in four steps from 0 to 2pi by shifting electron beam in the y-axis direction controlled by the SEM system. It is successfully applied to determine the residual strain of a deformed holographic grating with a frequency of 1200 lines/mm in an electronic package. As a further application, it is used to measure the virtual strain of a MEMS structure with a 5000-line/mm grating and to determine the phase distribution of a SEM moire formed with a 6000-line/mm grating fabricated by electron beam lithography. The experiments show the feasibility of this method. It provides a new way for disposal of fringes pattern in sub-micro moire method. (C) 2003 Elsevier Ltd. All rights reserved.