Latch-Up in CMOS Integrated Circuits

The parasitic transistors and pnpn paths present on junction-isolated CMOS circuits have been identified and studied quantitatively. Active SCR structures exist which can be triggered electrically or by a radiation pulse. Detailed studies of SCR paths have been performed on two circuits, the CD4007A and the CD4041A, to relate geometrical and materials parameters to latch-up sensitivity. Both normal bias conditions and bias optimum for obtaining SCR action are employed. Several techniques are proposed to eliminate radiation-induced latchup in future CMOS designs.