Semiconductor Test Site structures were analyzed using an EBIRCH (Electron Beam Induced Resistance CHange) system. Localization of a RX (active area) to PC (gate) short was achieved with resolution that surpassed that of OBIRCH (Optical Beam Induced Resistance CHange). A voltage breakdown test structure at Metal 1 was stressed in the system, giving isolation to the specific contact. A five-fin diode macro was examined, and it is believed that the electrically active diffusions were imaged as individual fins from Metal 1. A series of ring oscillator devices were examined in steady state condition, and careful consideration of the image supports a hypothesis that Seebeck effect, from heating material interfaces in an EBIRCH system, is the reason for the “dipoles” reported in earlier literature.

Applications of MpOBIC (Multi-photon Optical Beam Induced Current) are discussed for use in defect localization. The MpOBIC signals in a ring oscillator under static conditions are examined and demonstrate the superior optical resolution of the system over traditional OBIRCH. A 5-fin diode test structure is examined under passive conditions, demonstrating that true multi-photon OBIC has occurred from the backside. The same diode is examined in forward bias, and the resulting discussion concludes that both OBIC and OBIRCH signals are present in the sample. Thus, we claim that both OBIC and OBIRCH signals can provide device characterization information from an MpOBIC system.

The ring oscillator is an important tool for inline monitoring during technology development, as it contains the most important front end of line technology features, is testable at first metal, and generally shows a good correlation to SRAM yield. This work explores various failure analysis techniques for the ring oscillator, during the development of 14 nm FinFET technology. OBIRCH, which is typically a DC technique, was operated with voltages as low as 0.15 V to find multiple defect mechanisms affecting the yield of ring oscillators, which operate at a frequencies in the GHz range. In contrast to typical photon emission analysis of ring oscillators, examines the devices which are flipping on, it is here proposed that the OBIRCH spots which are generated are indications of the Ioff, or the leakage of devices in the inverter stages across the ring. The results from this failure analysis approach enabled a rapid improvement in yield not only of the ring oscillator itself but of the SRAM.