7. How can e-beam resist films be removed again?
For the removal of all e-beam resist coatings baked at lower temperatures (softbake), polar solvents may be used such as e.g. the recommended thinner AR 300-12 or AR 600-01, 600-07, and 600-09, as well as remover AR 600-70 (acetone-based). AR 600-70 is the most commonly used remover for this purpose.
For the wet-chemical removal of PMMA coatings baked up to 190 °C, the highly versatile organic remover AR 600-70 is recommended, as well as AR 300-70 and AR 300-72. Remover AR 300-70 and AR 300-72 do not attack aluminium and may be heated to 80 °C to reduce the time for removal. The
time for removal is generally in the range of 2 – 10 min. Copolymer films baked at up to 210 °C may require up to 15 min for removal. Additional plasma etch steps impede the removal even further. In this case, using ultrasound for heated removers AR 300-70 or 300-72 or an oxygen plasma asher may be helpful. For very hard baked layers, stripping with oxidising acids is recommended.
For the wet-chemical removal of baked novolak coatings (AR-P/N 7000) up to 150 °C, the highly versatile organic remover AR 300-70 and AR 300-72 are recommended, which are also employed after moderate plasma etchings. For layers baked at even higher temperatures, only ultrasound treatment (for
heated removers AR 300-70 or 300-72), plasma asher, or oxidising acids are recommended.
In semiconductor industry, removal (stripping) is mostly carried out by ashing in a plasma asher.
Microwave excitation generates an O2-plasma which in most cases reliably removes all PMMA-layers.