Optical diagnosis of excess I_DDQ in low power CMOS circuits

Abstract

Picosecond Imaging Circuit Analysis (PICA) was used to diagnose the cause of excess quiescence current, IDDQ in a low power CMOS circuit. Optical inspection immediately showed a very uniform emission pattern over the entire circuit, thus ruling out design and mask defects. The comparison of the luminescence emitted by low and high threshold transistors demonstrated that the high power consumption was due to current leakage through low Vf devices. In particular, it was possible to point out that the abnormally high leakage was mainly due to transistors with minimum channel length (0.18μm). Aside from simply locating defects and failures, static acquisitions of luminescence emission was effectively used to probe the supply voltage levels inside the operating Integrated Circuit (IC), where direct measurement access is not available. © 2002 Elsevier Science Ltd. All rights reserved.