Researchers at Advanced MicroDevices, Singapore, and Zeiss, Pleasanton, Calif., have developed a failure analysis technique for chip-to-chip micro-bump interconnects based on high-resolution 3D X-ray microscopy. 3D integration and packaging has challenged failure analysis (FA) techniques and workflows due to the high complexity of multichip architectures, the large variety of materials, and small form factors in highly miniaturized devices.
In a 3D imaging system, a series of 2D X-ray images are captured at different angles while a sample rotates. These 2D images are used to reconstruct 3D X-ray tomographic slices using mathematic models and algorithms. The spatial resolution of the imaging technique can be improved through the integration of an optical microscopy system. This improved technology is called 3D X-ray microscopy (XRM).
The image shows an example 3D XRM image for a stacked die. The image clearly shows the internal structures – including the TSV, C4 bumps, and μbump of the electronic components – without physically damaging or altering the sample. The high resolution and quality shown here are essential to inspect small structural defects inside electronic devices. With its non-destructive nature, 3D XRM has been useful for non-destructive FA for IC packaging devices.
The integration of XRM into the FA flow can help to overcome the limitations of the various analysis techniques to isolate the failure. It is a great advantage to image small structures and failures with the high spatial resolution and contrast provided by XRM and without destroying the sample.
For failures in stacked die, XRM can be integrated into the FA flow for further fault isolation with high accuracy. The visualization of defects and failed material prior to destructive analysis increases FA success rates. However, the trade-off for imaging small defects at high resolution is time. For stacked die failures, C-SAM and TDR can first be performed to isolate the region of failure. With a known smaller region of interest to focus on, the time taken for XRM to visualize the area at high resolution is significantly reduced.
