An AFM Encoder Using An Interferometer

Abstract

In this paper, an AFM encoder using an interferometer is proposed. The AFM encoder is a multiple probe AFM. Displacement is measured by the periodicity of the sample used as a displacement standard. Since the AFM realizes atomic scale resolution, the AFM encoder will realize very high resolution. We manufacture the AFM encoder, and the fundamental experiments are carried out. The deflections of the AFM cantilevers are detected by a Michelson interferometer simultaneously. A line-focused red color semconductor laser is used as a light source and a photodiode array is used as a detector. A sample is moved in x and z directions by an AFM stage. The AFM cantilevers detect the surface topography of the sample and the displacement is measured by using the detected signals. In this study, an optical grating, which is 1.2μm periods and 240nm height, is used as a displacement standerd. The periodical signals indicating surface topography of the optical grating are obtained. The resolution of the AFM encoder in x direction is less than 10nm.