A NOVEL APPROACH TO ESTIMATE ELECTRON BEAM SIZE

摘要

An electron microscope (EM) uses a beam of accelerated electrons to illuminate samples and produce images. As the wavelength of an electron beam is much shorter than that of a visible light source, an EM is able to provide a much higher resolving power than a conventional light microscope and can thus reveal sub-nanometre structures. Such an excellent resolution makes EMs a widely used inspection tool for many different industries, in particular photolithography. For example, in photolithography (especially extreme ultra-violet (EUV) lithography), product wafers with nanometre (nm) scale critical dimensions (CDs) are inspected after production by using scanning electron microscopes (SEMs), a type of EM, to ensure a satisfactory quality is achieved. Different from SEMs, where image signals are carried by the reflected electron beam, a transmission electron microscope (TEMs) generates images by collecting the transmitted electron beam through a sample. TEMs are widely used for inspecting the internal structure of a sample.