Surface tension and adhesion of photo- and electron-beam resists

In order to reduce the defect density of resist structures, a general optimization of surface tension was developed and successfully applied, using Si, SiO 2 , Si 3 N 4 , AlCu, WTi and Cr as substrates, modified by priming. We demonstrate that the contact angle water (Theta) w can be used to reach the optimal conditions for adhesion of resists. We use models based on the Young and Dupre equations and the model of interaction of molecules by Wu to determine the surface tension and work of adhesion. Good resist adhesion results if the work of adhesion is greater than 5 dyn/cm. We outline preferred process windows for the contact angle for certain combinations of different types of resist and developer.