ATOMIC-FORCE MICROSCOPY FOR CROSS-SECTION INSPECTION AND METROLOGY

Images of integrated circuit cross sections may be acquired with the a tomic force microscope (AFM) by introducing material-dependent topogra phy through a series of selective etches. AFM images of a fully proces sed complementary metal-oxide-semiconductor inverter structure show ex cellent qualitative agreement with high resolution scanning electron m icroscope (SEM) images. Measurements of layer thicknesses and lateral dimensions, however, do not precisely correlate. These discrepancies a re attributed to tip-sample convolution due to the finite cone angle a nd rounding of the probe. We describe a one-dimensional computer simul ator that models the nonlinear geometrical interaction between a tip a nd sample. Simulation results are used to determine the tip shape from an AFM image of a feature of known dimensions. The tip influence can be subsequently deconvolved from a cross section AFM image, generating a more faithful reflection of the surface topography. We demonstrate that this scheme yields measurements that correlate well with those ma de by the SEM and suggest that AFM imaging may be a viable alternative for the inspection and metrology of IC cross sections. (C) 1996 Ameri can Vacuum Society.