AlGaN/GaN RF Power Amplifier Failure Analysis and Backside Via Etching Process Improvement

This paper mainly introduces the failure analysis and process improvement of a drive-stage power amplifier centralized at 3.5 GHz in the Doherty structure. During the failure positioning process, it is found that the function of the components in some channels can restore at high temperatures or under positive pressure. A four-point probe resistance found that the through-holes of the failure samples were more significant than the control value. The FIB and Scanning Microscope (SEM) were used to analyze the failure units. It was confirmed that the contact between the metal layer of the grounding through-hole and the top-layer metal was abnormal. Metal interface consistency at the edge of the grounding through-hole and residue could not be cleaned within the standard cleaning time. Finally, after optimizing the key parameters such as energy, gas flow rate, and air pressure during the etching process, the contact surface consistency after process improvement is greatly improved. At the end of the paper, defect units with poor metal layers connection were sent to reflow. The result shows that similar defective products can be screened through one-time reflow. This research is helpful for reference to the reversible failure of the AlGaN/GaN HEMT process power amplifier.