Effect of alignment mark depth on alignment signal behavior in advanced lithography
Date
2008Author
Normah, Ahmad
Uda, Hashim
Mohd Jeffery, Manaf
Kader Ibrahim, Abdul Wahab
Metadata
Show full item recordAbstract
Finding a robust alignment strategy is one of the key evaluations in defining
photolithography process. Alignment is a process to determine how the current pattern is
placed on the wafer. Alignment is done by an optical system, which means that it is
dependable on the quality of the alignment signal to determine the correct orientation.
Alignment signal is generated by alignment mark, a diffraction grating structure (trench
and line structure) printed on wafer. Hence, the processing steps can possibly affect the
properties of alignment mark. The alignment mark depth (trench depth) can be varied due
to the nature of processing. According optics, a light optical path variation may lead to a
destructive interference, which is not good.