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Post silicon validation techniques require backside sample preparation by silicon thinning techniques. The conventional fixture to this preparation on large die packages causes silicon to crack. A new “4-point bending” fixture was developed to reduce silicon bending strain during thinning to eliminate silicon cracking. This new fixture and technique improved remaining silicon thickness uniformity as well as process time.

Post silicon validation techniques specifically Focused Ion Beam (FIB) circuit editing and Failure Analysis (FA) require sample preparation on Integrated Circuits (IC). Although these preparation techniques are typically done globally across the encapsulated and silicon packaging materials, in some scenarios with tight mechanical or thermal boundary conditions, only a local approach can be attempted for the analysis. This local approach to access the underlying features, such as circuits, solder bumps, and electrical traces can be divided into two modification approaches. The back side approach is typically done for die level analysis by de-processing through encapsulated mold compound and silicon gaining access to the silicon transistor level. On the other hand, the front side approach is typically used for package level analysis by de-processing the ball grid array (BGA) and package substrate layers. Both of these local de-processing approaches can be done by using the conventional Laser Chemical Etching (LCE) platforms. The focus of this paper will be to investigate a front side modification approach to provide substrate material removal solutions. Process details and techniques will be discussed to gain access to metal signals for further failure analysis and debug. A pulse laser will be used at various processing stages to de-process IC package substrate materials.

Post silicon validation techniques specifically Focused Ion Beam (FIB) circuit editing and Failure Analysis (FA) require backside sample preparation on Integrated Circuits (IC). Although these preparation techniques are typically done globally across the encapsulated and silicon packaging materials, in some scenarios with tight boundary conditions, only a local approach can be attempted for the analysis. This local approach to access the underlying features, such as circuits, solder bumps, and electrical traces will typically use conventional Laser Chemical Etching (LCE) platforms. The focus of this analysis will be to investigate and conjoin previously published techniques to this local preparation by using a combination of laser sources. A Continuous Wave (CW) and Pulse laser will be used at various processing stages to de-process IC packaging materials silicon and mold compound encapsulation.