what are the parameters which affect the etching and liftoff when we do patterning in microfabrication?
Some time people prefer etching over liftoff and some time lift off over-etching. when we go small patterns(say less than 10 microns) what should be the best technique?
you can read the following:
1. https://www.inup.cense.iisc.ac.in/static/downloads/Introduction-to-Micro-Nanofabrication.pdf
2. https://www.sciencedirect.com/topics/chemistry/microfabrication
3. https://www.microchemicals.com/technical_information/lift_off_photoresist.pdf
Generally it depends more on used materials and available deposition technique than on pattern critical dimension. Lift-off works best when combined with low-temperature and anisotropic deposition techniques like e-beam or thermal evaporation. In order to achieve clean lift-off at least some undercut of the photoresist pattern is necessary. You are also limited by thickness of PR which should be at least 1.3-1.7x thicker than layer to be deposited, but in case of 10um pattern thickness of the PR does not really matter that much.
In order to achieve good results with etching you need to employ selective etchant to avoid damage to underlying layer and/or mask, ideally with high anisotropy to avoid underetching. Dry etch approach offers better anisotropy, but is far more time consuming and cost intensive than wet approach.
put sample for 15-20 min into acetone or slightly heating can also help, don't dry up until unwanted metal is completely removed. Keep checking using microscope
Dear Inayat, acetone is one of the least efficient solvents for lift-off due to high vapor pressure causing comparatively high redeposition defects and it does not readily dissolve most of the even slightly crosslinked lift-off resits or PMGI. Solvents tailored for lift-off, such as dimethyl sulfoxide are much better choices.
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