FIB SEM Micro-Sectioning

Sub-Surface Imaging

Extraction of visual detail from the interior of a solid object requires the systematic destruction of layers in a controlled environment. When performing fib sem micro-sectioning, the operator focuses a beam of gallium ions to mill away a precise rectangular pit in the surface of the sample. This pit exposes the vertical face of the structure, allowing the secondary electron detector to image the internal interfaces at high tilt.

The instrument manages the beam energy to ensure the side wall remains vertical and smooth, providing an undistorted view of individual transistors or interconnects. This allows for the inspection of features that are invisible from the top down, such as the contact quality between a via and its metal line. Practitioners often deposit a thin layer of platinum or tungsten beforehand to protect the very top surface from being rounded off by the ion beam.

The boundary between the protective layer and the sample helps identify the exact surface position during high magnification surveys. Every slice reveals a new plane of information, which can be stacked into a sequence to build a three dimensional reconstruction of the defect.

Defect Analysis

Localizing the root cause of an electrical fail requires seeing the exact morphology of the material inside the trace. During the process of fib sem micro-sectioning, the engineer looks for evidence of atomic migration, cracks in the dielectric or unwanted metal whiskers. Finding an interface that has widened or a grain boundary that shows significant oxidation explains why a device failed during its operational trial.

The mechanism of sectioning avoids the mechanical vibration and local heat that standard grinders introduce, which could otherwise heal or hide subtle thermal cracks. Because the technique is highly localized, it preserves the rest of the chip for further diagnostic tests like laser voltage imaging. This selectivity is the primary advantage for high value samples where only one specific die displays the error.

The results of the section provide the evidence needed to adjust the manufacturing recipe or disqualify a specific chemical vapor deposition source. Without this evidence, companies would rely on guesswork when a yield falls below commercial targets.

Tool Integration

Automated software handles the coordination between the ion source and the electron detector to ensure the image remains centered as more material is removed. Advancements in fib sem micro-sectioning include the use of xenon plasma sources which allow for much faster removal of large volumes compared to traditional gallium. This increases the operational limit to include whole packages or large solder bumps rather than just individual transistors.

Coordination between the beams must stay precise to avoid ion damage on the face intended for imaging, as overspill creates artifacts that look like real features. High resolution imaging requires a low noise environment and ultra stable vacuum conditions to prevent surface charging. If the sample is insulating, the build up of charge will deflect the beams and result in a blurry or distorted view of the cross section.

Modern tools use electron flood guns or gas injection systems to neutralize this effect during the mill phase. Consistency in this process allows labs to process dozens of targeted sites per week, feeding vital data back to the design teams. Reliable cross sections form the empirical foundation for all packaging reliability claims.