Is Low Accelerating Voltage Always the Best for Semiconductor Inspection and Metrology?

• Published in: Microscopy today 2004-01, Vol.12 (1), p.46-47
• Main Authors: Postek, M. T., Vladár, A. E.
• Format: Magazinearticle
• Language: English
• ISSN: 1551-9295; 2150-3583
• DOI: 10.1017/S1551929500051865

Low accelerating voltage operation is an excellent mode of scanning electron microscopy and it is extensively used for measurements in semiconductor production. The beam penetration is small, and if properly applied, the specimen charging is kept at acceptable levels. But, is this always enough? Today, the scanning electron microscope (SEM) is being used in photomask metrology and imaging where charging is excessive. Charging is difficult to quantify and control as it varies greatly with instruments, operating conditions and sample. Therefore, it is also very difficult to model accurately. For accurate metrology charging must be overcome because the dynamic charging of the sample deflects the electron beam from its intended position and the intensity of the induced signal may vary uncontrollably. Deflection of the electron beam of even a few nanometers potentially results in a measurement error that is significant to modern semiconductor production.