Latch-up in a BiCMOS technology

The presence of active bipolar transistors in a BiCMOS technology increases the latchup susceptibility compared to pure CMOS processes, due to the injection of carriers in the substrate when the device is switched into saturation. The firing of the parasitic thyristor due to transient forward signals on a diode and the influence of the active bipolar transistors on this firing are examined. It is shown that the use of a buried layer in the well, which is also the highly doped part of the collector of the active transistor, results in a strong increase of the latchup hardness. both transient and DC latchup have been investigated, and a good agreement between measured and simulated values is obtained by the use of a lumped model.<>