Contoured device sample preparation technique for ±5 μm remaining silicon thicknesses that meets solid immersion lens requirements

Electrical failure analysis toolsets continue to develop at a pace significantly faster than sample preparation techniques. New solid immersion lenses (SIL) have been developed that require tighter requirements in remaining silicon thickness (RST) variation. Due to the SIL requirements, well established sample preparation techniques are quickly becoming ineffective, and new techniques/tools are required. In this paper, we will present a new methodology for preparing contoured devices by utilizing a contour capable milling system with an incorporated spectral reflectance measurement tool to enable contour correction milling based on remaining silicon thickness. This technique has demonstrated the capability of meeting 50 μm (or other desired target thickness) ±5 μm remaining silicon thickness requirement as requested by the SIL manufacturers.