Metal ion reduction in the raw materials and using a Lewis base to control molecular weight of novolak resin to be used in positive photoresists

A method for producing a positive photoresist composition comprising:

• a) washing an acidic ion exchange resin with water, washing said ion exchange resin with a mineral acid solution and thereby reducing the metal ions in the ion exchange resin to less than 500 ppb each;
• b) passing a water/formaldehyde solution through the ion exchange resin and thereby reducing the metal ion level of the solution to less than 500 ppb each;
• c) providing one or more phenolic compounds having a metal ion content of less than 200 ppb each;
• d) providing such admixture with a Lewis base concentration before condensation, of from about 10 to 1000 ppm, condensing the formaldehyde with said one or more phenolic compounds, in the presence of an acid catalyst, and thereby producing a water insoluble, aqueous alkali soluble novolak resin having a desirable and consistent molecular weight, a metal ion level of less than 500 ppb each;
• e) providing an admixture of:
• 1) a photosensitive component in an amount sufficient to photosensitize the photoresist composition, 2) the water insoluble, aqueous alkali soluble novolak resin and 3) a solvent.