András E. Vladár, K. P. Purushotham and Michael T. Postek, NIST, Gaithersburg, MD
Presented at SPIE Advanced Microlithograpy Feb 2008, San Jose, CA
Electron beam-induced contamination is becoming one of the most bothersome problems of the scanning electron microscopes. 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 changes the size and shape of the small structures of current and future state-of-the art ICs. This greatly disturbs the measurement process and the erroneous results can lead to wrong process control decisions. NIST has developed cleaning procedures and a viable contamination specification that offer an effective solution for this problem.