The scanning laser-SQUID microscope can detect electrical defects in a chip without requiring electrical contacts to the chip. Using our new system, we can get magnetic flux images of a 300mmɸ wafer in air. Experiments with 256Mbit-DRAM chips showed that IDDS testing results are correlated well with laser-SQUID images, and that the spatial resolution is 0.59 µm in an intensity image, and 0.54 µm in a phase image. We have also succeeded in localizing the open site in a whole chip area of a 90nm-node logic IC chip.

The identification of voids and Si nodules in the Al stripes of integrated-circuit-device chips is a key part of failure analysis and process monitoring in the semiconductor industry. The optical-beam-induced resistance-change-detection (OBIRCH) method has been shown to be more useful in void detection than other methods. In this study, the wavelength of the laser used for heating the Al stripes on the Si chips has been changed from 633 to 1300 nm and the OBIRCH method has been modified to use a near-field (NF) optical probe as the heat source instead of a laser beam. Results showed that NF-OBIRCH method has three advantages over the conventional OBIRCH method: its spatial resolution is higher; the OBIRCH caused by heating can be observed using the metallized probe without interference from the optical beam induced current; and the OBIC can be observed using the apertured probe, in a high spatial resolution.

We can identify various contrasts by scanning an 1.3 um laser beam from the backside of a chip and displaying current changes as brightness changes on a CRT, because the 1.3 um laser beam generates no OBIC signal and can penetrate P- Si substrate with little intensity degradation. The contrasts we have confirmed up to now are: (1) Current pass contrast at Al lines caused by OBIRCH, (2) Defect contrast at Al interconnects caused by OBIRCH, (3) Current pass contrast at a poly Si lines caused by OBIRCH, (4) Parasitic MIM (metal-insulator-metal) contrast caused by temperature dependence of MIM current, (5) Schottky-barrier contrast caused by internal photoemission.