Study of Topographic Features, Shape, and Mechanical Stresses in Microelectronic Structures Using Geomorphometric Techniques

We describe the use of geomorphometric methods for studying thin-film structures in microelectronics. In particular, we developed a method for processing data from measuring equipment (optical profilometer and spectral ellipsometer) to calculate maps of mechanical stress distribution considering a complex (i.e., nonspherical) shape of structures (that is, nonuniform deformation) and nonuniform film thickness. The results of calculations for SiO2/Si and GaN/Al2O3 structures are presented. The calculated value of mechanical stresses for SiO2: σ ≤ 300 MPa. A relationship was obtained between the highest values of mechanical stress and volumetric defects for GaN. Geomorphometric methods are effective for (1) preparation of initial experimental data for the purpose of subsequent calculation of second partial derivatives (which are necessary for computation of mechanical stresses from the topographic data of structures); (2) direct calculation of curvature maps for subsequent determination of mechanical stresses; and (3) qualitative assessment of local topographic features poorly manifested on the initial topographic maps, which are directly related to the areas of the highest mechanical stresses.