A Non-Contact, Non-Destructive Next Generation Imaging tool for the Semiconductor Industry's complex devices, advanced packages, and full assemblies

How magnetic-field imaging works

Source currents in electronic devices can be calculated from magnetic-field images. By mapping the current in an IC, stacked die, or package, short-circuit defects can be localized and designs can be verified to determine if electricity is flowing where expected. HR defects can be found by identifying differences in the magnetic field. Unlike thermal, optical, ion, or electron-beam techniques, magnetic-field detection is not affected by materials in ICs or the package. Therefore, current imaging can be performed from both the front and backside of a device through many layers of metal, the die, or packaging materials. The only difficulty in this approach is that the strength of the magnetic field decreases with current magnitude and the increase in separation between the sensor and source currents. The rate of decrease depends upon the nature of the current source, but the magnetic-field strength for ICs is typically inversely proportional to the distance between the sensor and the source.

The Magma C20, has been developed for failure analysis in ICs, stacked-die components, chip packages, and board assemblies using a high-temperature SQUID with a sensitivity of 20 picotesla (two million times lower than Earth’s magnetic field). The scanning SQUID microscope (SSM) has been designed to keep the SQUID cold and in vacuum while the DUT is at room temperature and in air. The design of the magnetic-field microscope also facilitates positioning of the SQUID as close as 70µm from the DUT. The system can run samples requiring high-resolution current images (at the die level and for wafers) as well as samples requiring high sensitivity (low current and HR). The instrument’s sensitivity is high enough to detect currents as small as 10nA at a 100µm working distance with 1-sec averaging but low enough to enable the instrument to function in an unshielded environment.

With the use of a high-resolution sensor, the Magma C20 is capable of resolving 0.3µm (300nm) features with a potential to reach 0.01µm (10nm) resolution. The sensor is held stationary while the DUT is raster-scanned under the magnetic sensor to acquire the magnetic-field image. The current supplied to the DUT typically alternates at a frequency <100kHz. A lock-in technique enables the instrument to capture only the image of the applied current, while ignoring magnetic fields generated by currents at other frequencies or static background fields.