This work outlines a case study of charge-induced damage to SOI wafers that caused gate leakage in discrete transistors and static leakage in packaged integrated circuits (ICs). The consequential yield fallout occurred primarily at wafer center. Electrical, optical, and laser-based failure analysis techniques were used to characterize the damage and determine root cause of electrical failure. The failure mechanism was localized to a rinse step during chemical mechanical planarization (CMP). Furthermore, both current-voltage (IV) sweeps and characteristic spatial patterns generated by thermally-induced voltage alteration (TIVA) were used to capture the trends on both packaged ICs and SOI wafers for this type of charge-induced damage; this led to quick identification of another source of charge-induced damage that affected the post-fab yield.

Visible light laser voltage probing (LVP) for improved backside optical spatial resolution is demonstrated on ultra-thinned samples. A prototype system for data acquisition, a method to produce ultrathinned SOI samples, and LVP signal, imaging, and waveform acquisition are described on early and advanced SOI technology nodes. Spatial resolution and signal comparison with conventional, infrared LVP analysis is discussed.

This paper presents two different case studies that highlight the use of reflected light imaging in laser scanning microscopy. In the first case study, the exact location of defects in metal comb test structures were much easier to detect with reflected light imaging than with thermally-induced voltage alteration (TIVA). This case study also shows visible-wavelength TIVA defect localization using a 532-nm laser. A comparison between 532-nm TIVA and conventional 1320-nm TIVA is made to show the resolution improvement with the visible laser. In the second case study, the cause of a linear string of bit failures was localized easily with backside reflected light imaging. It is observed that the indicated sites matched the light-induced voltage alteration signals and the failing cells in the bit map. In both of the case studies, the reflected light images have proved very helpful in the localization and characterization of failing devices or test structures.