The ‘resist’ is a masking material used in the lithographic process that forms semiconductor circuits on a chip substrate. Once the circuit is etched, the resist must be removed by using peroxymonosulphuric acid, which is produced by mixing sulphuric acid with hydrogen peroxide.
The new technology reduces the volume of sulphuric acid used in the resist stripping process by 70 per cent and totally eliminates the use of hydrogen peroxide. With the new technology, peroxymonosulphuric acid can be produced without hydrogen peroxide but by electrolysing the sulphuric acid.
As a result, the new technology is more eco-friendly as well as more efficient. The electrolysed sulphuric acid can also be recycled, which was not possible with the old technology. The process also reduces the resist stripping time by up to 20 per cent.
Toshiba, Shibaura and Chlorine have already developed a single-wafer resist stripping system that will be integrated into the resist stripping process at Toshiba’s