Abstract

Magnetic current imaging (MCI) is an effective method for the isolation of individual integrated circuit (IC) current paths [1]. MCI is therefore useful in localizing open/short defects. In the case of a short, the failure current must be large enough to enable the detection of the magnetic field; however, in the case of the open failure, the current is very weak and detection can be limited by the wiring capacitance and modulation frequency. Often, magnetic sensor sensitivity is a function of the sensor size. Superconducting Quantum Interference Device (SQUID) sensors can detect weak current in an open failure, but the resolution is limited by the sensor size and can be difficult to utilize for IC applications. A Giant Magnetic Resistance (GMR) sensor has enough resolution [2], but cannot achieve enough sensitivity till now. This paper will present the use of Magneto-Optical Frequency Mapping (MOFM) using a 532nm light source. In addition, this paper will describe a specific IC application for an open failure measurement. For this technique, the MO crystal (sensor material) is placed directly on the DUT (a wiring test sample). This paper will demonstrate that the magnetic field modulation from AC current in open wirings can be detected. In addition, the details of the AC current path can be visualized using a Magneto-Optical based MCI measurement. Finally, the open point in the failing circuit will be shown to be isolated with an accuracy of a few tens of micrometers.

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