Synchrotron X-ray topographic analysis of the impact of processing steps on the fabrication of AlGaAs/InGaAs p-HEMT's

Abstract

Abstract-Synchrotron X-Ray Topography (SXRT) has been uniquely applied to nondestructively reveal and evaluate the damage throughout the depth of the wafer, caused by the deposition of source/gate/drain metallization and of so-called "passivation" dielectric layers on power Alo.22Gao.78As/Ino.21 Gao,7gAs pseudomorphic HEMT's. Device metallization is visible due to the stress imposed on the underlying substrate and is detected as a strain field by SXRT. Experimental results are in good agreement with simulation. The quality and detail of the initial control topographs disappear when the Si.lN4 dielectric layer is deposited. This is believed due to the passivating layer introducing such strain into the crystal that it overwhelms the metallization strain, in addition to producing a significant amount of stress-induced defect and dislocation generation.