Failure analysis of GaAs microwave devices with plastic encapsulation by electro-optical techniques
Abstract GaAs devices technology used for space applications have failed before the required 1000 h of the temperature humidity bias standard aging test. The results have shown that gate-source reverse bias is the most severe stress condition for transistors and also that capacitors are the most critical parts. This paper establishes an original method to analyze plastic encapsulated devices by combining different electro-optical techniques. Many of the possible faults in ICs are linked with local heat dissipation, such as shorts between lines, oxide or junction breakdowns. Infrared thermography is based on emissivity of a material at a given temperature in relation with Planck’s law. This kind of system generates a temperature map image with a micrometric spatial resolution. Thanks to the transparency property of GaAs to near-infrared wavelengths, we propose a backside failure analysis of encapsulated devices and a precise localization of physical defects, without altering the surface. This methodology enables to make the link between electrical failure signatures and failure mechanisms of GaAs devices during aging tests.