UC Irvine

The nanometer-range Indium Arsenide Composite Channel (IACC) High Electron Mobility Transistors (HEMTs) are fabricated on 100 mm Indium Phosphide (InP) substrates. This technology offers the best performance for low-noise and high-frequency, space and military applications. Typical failure mechanisms are observed in III-V HEMT technologies, including gate sinking and oxidation. Experiments were conducted to determine if these failure mechanisms degrade the IACC HEMTs after updating the new HEMT. The experiments conducted were life tests completed at accelerated temperatures and biases with a thin Si3N4 passivation layer; the devices’ electrical characteristics were measured at each stress interval. The failure mechanisms examined within this dissertation include: gate sinking, which is the interdiffusion of the metal gate into the semiconductor. Therefore, a temperature stress was done to initiate the mechanism; oxidation is the migration of oxygen atoms into materials are induced by a high electric field and high temperature. The Si3N4 passivation thickness was then increased to determine if the degradation of the electrical parameters could be decreased. Four HEMTs were placed on a Low-Noise Amplifier (LNA) circuit, therefore, an additional LNA assessment was completed to determine which device degraded and where the defect might be located; the Low-Noise Amplifier (LNA) Circuit assessment determines the limiting HEMT in the LNA circuit. Since many of the known III-V semiconductor failure mechanisms physically degrade or damage HEMTs, cross-sections are important to prepare to detect these mechanisms. Advanced microscopy techniques, with sub-nanometer resolutions, examined physical characteristics of the HEMT at the atomic scale. Each device was cross-sectioned with a Focused Ion Beam/Scanning Electron Microscope (FIB/SEM) and polished with a Nanomill to about 100 nm thickness at the gate fingers to look for the failure mechanisms. The Scanning Transmission Electron Microscope (STEM) along with Energy Dispersive Spectroscopy (EDS) was then used to see the oxygen in the titanium gate layer and no gate sinking. TCAD modeling simulations were used to verify these results and show that the Schottky barrier height changes and the oxygen diffuses faster through the titanium gate layer due to the electric-field increase.