PARTIALLY CARBOXYMETHYLATED NOVOLAKS FOR PHOTORESIST SYSTEMS - NEW PHOTORESISTS FOR DEVELOPMENT UNDER MILDLY ALKALINE CONDITIONS

The dissolution behaviour of cresolic novolaks in alkaline developers has been modulated by a modification reaction with chloroacetic acid ( 'carboxymethylation'). This reaction effected a partial etherification of the phenolic OH-groups. The desired solubility has been adjusted b y the degree of conversion in combination with the choice of an approp riate parent novolak. The influence of the carboxymethylation on the d issolution rates of the resins turned out to be strongly dependent on type and concentration of the developer. Moreover, different dissoluti on kinetics have been observed in TMAH and sodium carbonate solution. The lithographic properties of selected carboxymethylated novolaks hav e been investigated. Photoresists have been optimised with respect to environmental and safety aspects ('safer solvents', development in aqu eous sodium carbonate solution). The formulation of negative resists h as been complicated by an unexpected incompatibility of the resin and the photoactive compound. However, first results of positive resist fo rmulations were promising. Resolutions down to 1 mu m l&s have been ac hieved.