Contamination specification for dimensional metrology SEMs

Electron beam-induced contamination is one of the most bothersome problems encountered in the use of the scanning electron microscope (SEM). Even in "clean-vacuum" instruments it is possible that the image gradually darkens because a polymerized hydrocarbon layer with low secondary electron yield is deposited. This contamination layer can get so thick that it noticeably changes the size and shape of the small structures of current and future state-of-the art integrated circuits (ICs). Contamination greatly disturbs or hinders the measurement process and the erroneous results can lead to wrong process control decisions. NIST has developed cleaning procedures and a contamination specification that offer an effective and viable solution for this problem. By the acceptance, implementation and regular use of these methods it is possible to get rid of electron beam induced contamination.