Design-for-debug routing for FIB probing

To observe internal signals, physical probing is an important step in post-silicon debug. Focused ion beam (FIB) is one of most popular probing technologies. However, an unsuitable layout significantly decreases the percentage of nets which can be observed through FIB probing for advanced process technologies. This paper presents the first design-for-debug routing to increase the FIB observable rate. The proposed algorithm, which adopts three FIB states and costs to enhance the maze routing, keeps at least one FIB candidate for each net while routing. Experimental results demonstrate that the proposed method can significantly increase the FIB observable rate under 100% routability.