Resist deconstruction as a probe for innate material roughness

We developed an atomic force microscopy (AFM)-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, we have deconstructed the resist into component materials and established that the photoacid generator (PAG) is a major material contributor of film roughness and that PAG segregation in the resist is likely responsible for nanoscale dissolution inhomogeneities. Small differences in PAG concentration as a result of standing waves in the resist can lead to large changes in surface roughness due to PAG or PAG-photoproduct segregation and the resultant nonlinear change in nanoscale dissolution rates. The temperature dependence of the PAG segregation suggests that increased mobility of the PAG that occurs may be due to a lowering of the film T g during the deprotection process.