Accelerate SAT-based ATPG via Preprocessing and New Conflict Management Heuristics

Due to the continuous advancement of semicon-ductor technologies, there are more defects than ever widely distributed in manufactured chips. In order to meet the high product quality and low defective-parts-per-million (DPPM) goals, Boolean Satisfiability (SAT) technique has been shown to be a robust alternative to conventional APTG techniques, especially for hard-to-detect faults. However, the SAT-based ATPG still confronts two challenges. The first one is to reduce extra computational overhead of SAT modeling, i.e. to transform a circuit testing problem to a Conjunctive Normal Form (CNF) which is the foundation of modern SAT solvers. The second one lies in the SAT solver's efficiency which is brought by the loss of structural information during CNF transformation. In this work, we propose a new SAT-based ATPG approach to address the two challenges mentioned above: (1) To reduce CNF transformation overhead, we utilize a simulation-driven pre-processing for narrowing down the fault propagation and activation logic cones, leading to an improvement in CNF transformation and reduction in runtime. (2) To further improve the solving efficiency, We propose new ranking-based heuristics to build more effective conflict database, enabling the direct solving for small scale instance and a looking-head method for large scale ones. Extensive experimental results on industrial circuits demonstrate that on average the proposed approach could cover 89.67% of the faults failed by a commercial ATPG tool with a comparable runtime.