I am going to set an interference lithography (IL) setup to make gratings on the wafer. I have a basic idea regarding how to make a simple setup of IL using laser source and mirror assembly. And using that I can make gratings on wafer.
After this I have some other processes to do and again I need to make the gratings on the same place which I did before using the same setup. But I am not sure about how to do the 2nd level alignment. Do I need to add anything in the IL setup to do alignment or is there any particular steps which I have to follow to get accurate alignment?
This depends on the feature size and the alignment accuracy you need. By using optical setup I think it is hard to get alignment in few microns level.
You may refer to photolithography or EBL technique, where some alignment markers are defined together with the 1st level grating, and then they are used to alignment the 2nd level grating. You may need a microscope lens or other means to find and align the markers.
Dear Chee-Wei Lee,
EBL is an obvious answer for that purpose but I want to write gratings of period at least 500 nm for full 2-inch sample. Using EBL to write those gratings will take too much time and also there will be stitching error.
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