A Description of the Bell Laboratories Scanned Acoustic Microscope

Scanning reflection acoustic microscopy uses the amplitude of reflected high-frequency sound waves as a contrast mechanism to generate micrographs with submicrometer resolution. This method was first reported in 1974 by R. A. Lemons and C. F. Quate.1 Since that time, much progress has been made in the field, including a steady improvement in the resolution of the instrument.2 To date, acoustic microscopy has been used to study integrated circuits, biological specimens, and various materials with much success.2 Although acoustic micrographs appear quite similar to their optical counterparts, the source of the acoustic contrast lies in the mechanical properties of the sample. Hence, acoustic micrographs provide information that is fundamentally different from that of optical micrographs. Since the acoustic reflectivity at a surface is a strong function of the layering structure beneath,3 much effort has been directed toward nondestructive analysis and characterization of integrated circuit defects using acoustic microscopy. In our research, it is hoped that variations in stress and crystal orientation near dislocations in crystals * Princeton University. 2167