Laser-SQUID microscopy: novel nondestructive and non-electrical-contact tool for inspection, monitoring and analysis of LSI-chip-electrical-defects

We propose a new technique that can detect electrical defects nondestructively without any electrical contact with the outside. It is, therefore, applicable not only to the failure analysis but also to the in-line inspection and monitoring. The basic idea of the technique is detection of a magnetic field produced by a laser-beam-induced current by using a HTS (high-temperature-superconducting) DC-SQUID (superconducting quantum interference device) magnetometer. The intensity of magnetic flux detected by the SQUID magnetometer is imaged, while scanning a laser beam and a sample relatively. The spatial resolution of this scanning laser-SQUID microscopy ("laser-SQUID" for short) is expected to be much better than conventional SQUID microscopy because it is limited by the laser beam diameter: that of the conventional SQUID microscopy, on the other hand, is limited by the size of the detector and the distance between the detector and a sample. An experiment using a prototype system has showed that the spatial resolution is about one um. Other experiments have demonstrated the application of the laser-SQUID to LSI inspection and analysis.