SYNCHROTRON X-RAY TOPOGRAPHIC ANALYSIS OF THE IMPACT OF PROCESSING STEPS ON THE FABRICATION OF ALGAAS INGAAS P-HEMTS/

Synchrotron X-Ray Topography (SXRT) has been uniquely applied to nonde structively reveal and evaluate the damage throughout the depth of the wafer, caused by the deposition of source/gate/drain metallization an d of so-called ''passivation'' dielectric layers on power Al0.22Ga0.78 As/In0.21Ga0.79 As pseudomorphic HEMT's. Device metallization is visib le due to the stress imposed on the underlying substrate and is detect ed as a strain field by SXRT. Experimental results are in good agreeme nt with simulation. The quality and detail of the initial control topo graphs disappear when the Si3N4 dielectric layer is deposited. This is believed due to the passivating layer introducing such strain into th e crystal that it overwhelms the metallization strain, in addition to producing a significant amount of stress-induced defect and dislocatio n generation.