COMPARATIVE FILM THICKNESS DETERMINATION BY ATOMIC-FORCE MICROSCOPY AND ELLIPSOMETRY FOR ULTRATHIN POLYMER-FILMS

Ellipsometry and atomic force microscopy (AFM) were used to study the film thickness of continuous and discontinuous polymer films in the 1- 20 nm thickness range on smooth silicon wafers and on structured alumi nium substrates. The methods of exploiting AFM for thickness measureme nts with a high spatial resolution are described. For continuous films , the AFM method is a direct one, i.e. it does not rely on any model. There is excellent agreement between APM and ellipsometry in the 1-10 nm thickness range. Very small systematic deviations occur in this ran ge but big deviations occur above 10 nm, and are discussed. The film p reparation method, spin coating, was characterized to result in prepol ymer films with a very homogeneous thickness. Discontinuous films of 2 -9 nm thick were also evaluated by both methods of thickness determina tion. In this case, for one of the AFM approaches a model has to be us ed too. The agreement between both methods ranged from very good to po or, depending on the kind of sample and on the kind of AFM determinati on method.