High Voltage Temperature Humidity Bias Test (THB) customized system and methodologies for reliability assessment of power semiconductor devices

High Volt­age Tem­per­a­ture Hu­mid­ity Bias Test (THB-HV) is cur­rently the state of the art test method for re­li­a­bil­ity eval­u­a­tion of power de­vices in high hu­mid­ity en­vi­ron­ments at high volt­age. These con­di­tions have be­come es­pe­cially sig­nif­i­cant in the case of power mod­ules for the au­to­mo­tive in­dus­try and other ap­pli­ca­tions in harsh en­vi­ron­ments. In this re­search work, a cus­tom sys­tem for ac­tive mon­i­tor­ing of THB-HV test­ing is de­vel­oped and cus­tomized, in or­der to eval­u­ate dif­fer­ent test­ing method­olo­gies, in­ter­cept de­vice degra­da­tion in real time, and al­low for a con­trolled and more ac­cu­rate fail­ure analy­sis of the DUTs

Multilayer film passivation for enhanced reliability of power semiconductor devices

Automotive requirements are becoming ever more severe in terms of device operation under high stress and in harsh working conditions. In this context, passivation layers play a fundamental role in determining electrical performance and reliability. This study focuses on the primary and secondary passivation layers applied to the state-of-the-art power devices and their influence on reliability. Power diodes assembled in standard module packages are used as test vehicles, and high-voltage temperature humidity bias tests are performed to stress the structures. A complete failure mode analysis highlights the phenomena behind the degradation of the passivation layers. Different passivation schemes are evaluated through the application of specific inorganic and organic combinations of layers. Finally, a summary of the typical degradation mechanisms and interactions is presented

Novel Cathode Design to Improve the ESD Capability of 600 V Fast Recovery Epitaxial Diodes

Silicon power diodes are used to design different types of electrical energy systems. Their performance has been improved substantially, as a result of a concentrated research efforts that have taken place in the last two decades. They are considered immune to electrostatic discharge (ESD) failures, since usually they withstand an avalanche energy one order of magnitude higher than that of the ESD. Consequently, few works consider this aspect. However, it was observed that during the mounting of power diodes in automotive systems (e.g., with operators touching and handling the devices), ESD events occur and devices fail. In this paper the ESD capability of 600 V fast recovery epitaxial diode (FRED) is analyzed by means of Technology Computer-Aided Design (TCAD) simulations, theoretical analyses and experimental characterization. Two doping profiles are investigated in order to improve the ESD robustness of a standard device and an optimized doping profile is proposed. The proposed design exhibits a higher ESD robustness and this is due to its superior capability in keeping the current distribution uniform in the structure in a critical condition such as the impact ionization avalanche effect. Both experimental and numerical results validate the proposed design