Metal ion reduction in novolak resins solution in PGMEA by chelating ion exchange resin

摘要

The present invention provides methods for producing water insoluble, aqueous alkali soluble novolak resins having a very low level of metal ions, utilizing treated chelated ion exchange resins to make the neutral ammonium salt or acid form. A method is also provided for producing photoresist composition having a very low level of metal ions from such novolak resins and for producing semiconductor devices using such photoresist compositions.