INTERFEROMETRIC ROUGHNESS MEASUREMENT OF OHMIC CONTACT III-V SEMICONDUCTOR INTERFACES

The nondestructive measurement of the internal roughness of Ohmic cont acts on GaAs and InP using near-infrared interferometry through the re ar of the wafer is investigated. The main difficulties were found to b e associated with the thick high refractive index viewing window leadi ng to conflicting requirements in the position of the interface along the optical axis for forming the image and the fringes. Two solutions are proposed: the first using a low numerical aperture objective, and the second using a rear surface reflecting GaAs reference mirror, givi ng an axial resolution of approximately 8 nm. (C) 1997 American Instit ute of Physics.