Hi all,
I am fabricating micro-scale arrays of pillars on silicon wafer with SU8-2025; however, after completing the photolithography process and checking the samples with microscope, I found the pillars are connected to each other from their base, or around each pillar there is some dark area that I am not sure why I got such patterns.
Does anyone know why such results are obtained?
Thanks in advance.
There can be multiple reason for this. Since the linkages are uniform, I suggest that you check the mask patterns properly.
You can try to clean the wafer with piranah and moist bake it for at least an hour at 120deg. Provide an exact UV dosage as suggested in the data sheet. Over exposure can also cause such patterns.
If longer exposure didn't help, it means that your resist is crosslinked in supposedly dark areas. This could be caused by multiple factors such as overexposure, diffraction (due to a too large gap between mask and wafer), or a too high temperature during the PEB. Usually, the first step in setting up the lithography process is dose optimization. Parameters given in the technical data sheet are good starting points, but they can vary widely depending on your pattern and application.
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