The photoemission microscope (PEM) is a powerful and widely used tool for location and identification of failure sites on integrated circuit (IC) chip and wafers. A PEM operating in the infrared (IRPEM) offers several advantages over systems operating in the visible part of the spectrum.. A combined PEM/IRPEM has been built having a cooled (77K) mercury cadmium telluride (MCT) focal plane array (FPA) sensitive in the range 800 to 2500 nm, an intensified charge coupled device (CCD) camera sensitive in the range 350 to 900 nm and a conventional, colour CCD camera. A cooled filter wheel enables the user to select the spectral range of the FPA. Direct comparison of photoemission images obtained in the IR and visible parts of the spectrum is straightforward, while the colour camera permits easy navigation around the device and facilitates probing of wafers. Comparing the sensitivity of the IRPEM with a conventional PEM camera (GEN III intensifier) indicates that for forward bias emission and NMOS emission the IRPEM is approximately 500 times more sensitive. Applications of the system to failure analysis in ICs, sensor devices and electronics packaging are described.
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