The device did not pass the highly accelerated stress test (HAST), which tests the device performance after long term high humidity high temperature exposure. The side-walls of the device had to be protected against moisture.
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A conformal ALD Al2O3/TiO2 multilayer moisture barrier was deposited on the die-level with the Beneq P400A high-capacity batch ALD system. A low-temperature process was used to enable coating while the die are on tape.