回折パターンによる極微細溝形状の測定評価に関する研究 矩形溝形状の測定評価

Abstract

This paper describes a measuring method based on Fraunhofer diffraction which can estimate quantitatively the size parameters of fine grooves, for example the LSI pattern, the grating and the tracking pre-groove of optical memory disks. Theoretical analysis of the relation between a rectangular groove model and diffraction intensity pattern is performed. Equations which can estimate the size parameters of grooves such as pitch, width and depth from diffraction intensity patterns are derived. From the equations, the duty ratio (width/pitch) in the range of 0.1 to maximum 0.8 and depth 1 nm to maximum 150 nm are determined within 10% errors. In order to verify the validity of the proposed method, computer simulations and fundamental experiments are carried out. It is shown by the computer simulations that this method is useful for measuring the size parameters of the fine grooves without the influences of noise on diffraction intensity and random roughness on the surface of the groove. From the measurement of the size parameters of the grooves of a high precision grating plate with pitch of 2.0 μm, width of 1.0 μm and depth of 100 nm, it is found that this method makes it possible to measure pitch, width and depth of a fine groove with consistency.