A case study of backside failure analysis is performed on failed
MMIC ASIC devices sealed in SOP packages. The use of
Benzocyclobutene (BCB) as a dielectric material, which is etched
during wet etch front-side decapsulation, motivated the proposed
backside approach. Due to the transparency of the GaAs substrate
to near infrared wavelengths, innovative optical defect
localization techniques can be used. In this paper we present the
successful application of Thermal Laser Stimulation (OBIRCH, TIVA)
to rapidly, non-destructively and precisely localize the defects
through the GaAs substrate. Backside delayering allowing defect
observation and revelation is also discussed. Finally, an
electrical interpretation of the failure and the corrective actions
are presented.