New Latchup Mechanism in Complementary Bipolar Power ICs Triggered by Backside Die Attach Glue

It is shown that in complementary bipolar power ICs latchup can be caused by a thyristor formed by the V-PNP power transistor at the frontside of the die and a Ag-filled glue die attach at the backside of the die (used to provide a good thermal contact between the die and the Cu-heatsink. The thyristor is triggered by saturation of the V-PNP power transistors or by forward biasing the backside diode between Ag-filled glue and p-type silicon. The effect is strongly temperature dependent. It can be eliminated by either leaving the backside floating or by applying backside metallization. Consequences for latchup qualification testing are discussed.(C) 1999 Elsevier Science Ltd. All rights reserved.