Robustness Assessment Through 77GHz Operating Life Test of Power Amplifier for Radar Applications in 28nm FD-SOI CMOS

RF reliability of a power amplifier is analyzed for automotive applications. Autonomous driving detection based on radar sensors require a high level of reliability to perform the mission during the operative lifetime. The robustness of power amplifier under RF stress is presented in the paper. After introduction of the receiver/transmitter components and phase modulation scheme used in radar sensor, a first analysis is performed at device level to figure out the reliability capability to sustain aggressive voltage profile. Using a 77GHz vectorial load-pull tester, several stresses are carried out to exacerbate the degradation of a LVT NMOS in 28nm FD-SOI technology, used as a power stage. With special tuning of the biasing point, input and output matching networks and input power, is it possible to generate voltage profile that mimics a load-line of class-AB power amplifier, or a RF voltage profile centered in the worst-case hot carrier DC condition, i.e. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VDS</tex> close to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VGS</tex> . Results show small degradation for these two RF profiles. Then, in the second part, Operating Life Test is performed at 77GHz with a dedicated test chip where RF signal is build-in and output amplified power is measured with a power meter. Characterization of the output power is performed both in the on-wafer and the on-board version. The result of 1500h burn-in for several parts is presented. The degradation magnitude during the stress is in agreement with simulation.