Abstract
There is a continuing need to prepare PACs with less ionic impurities. In a typical synthesis, a Diazonaphthoquinone (DNQ) sulfonyl chloride is added to a phenolic compound with an amine catalyst. The photoactive compound (PAC) and an amine salt are formed. After the synthesis, the PAC is washed well with water or mixture of solvents to remove the ionic impurities (the amine salts). However, resist specifications are now at the ppb levels. Residual ionic impurities influence photospeed, particle formation, corrosion, dark film loss, etc. The process to remove the unwanted ionic impurities is costly and time consuming. A new method has been developed in our laboratory to prepare DNQ PACs using ion exchange resins. About a 20 fold decrease in ionic contamination has been observed with this method. The procedure is cost effective and can be applied to PACs with different backbones.
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