Do SE sub(II) Electrons Really Degrade SEM Image Quality?

Summary Generally, in scanning electron microscopy ( SEM ) imaging, it is desirable that a high-resolution image be composed mainly of those secondary electrons ( SE s) generated by the primary electron beam, denoted SE sub(I). However, in conventional SEM imaging, other, often unwanted, signal components consisting of backscattered electrons ( BSE s), and their associated SE s, denoted SE sub(II), are present; these signal components contribute a random background signal that degrades contrast, and therefore signal-to-noise ratio and resolution. Ideally, the highest resolution SEM image would consist only of the SE sub(I) component. In SEM s that use conventional pinhole lenses and their associated E verhart- T hornley detectors, the image is composed of several components, including SE sub(I), SE sub(II), and some BSE , depending on the geometry of the detector. Modern snorkel lens systems eliminate the BSE s, but not the SE sub(II)s. We present a microfabricated diaphragm for minimizing the unwanted SE sub(II) signal components. We present evidence of improved imaging using a microlithographically generated pattern of A u, about 500 nm thick, that blocks most of the undesired signal components, leaving an image composed mostly of SE sub(I)s. We refer to this structure as a "spatial backscatter diaphragm." SCANNING 35:1-6, 2013. [copy 2012 Wiley Periodicals, Inc.