Research On Test Path Selection For Combinational Circuit Considering Degradation Effect

The test of Integrated Circuit(IC) is playing an important role in the design, production and manufacturing of integrated circuit. The test of combinational circuit is always important during the design stage and the test stage when the integrated circuit is in use, because it is necessary to test whether the delay condition meet the requirement for circuit to work in the right logical function. So every researchers need to test the time delay condition of the critical path during the test of Integrated Circuit, and evaluate the timing state through the working state of the critical path.Due to the advanced manufacturing process of integrated circuit, the feature size of Integrated Circuit reduces and the circuit configuration becomes more complicated. The tolerability of circuit to the influence brought by inner degradation is lower and lower. In the combinational circuit, many degradation effects may cause the time delay getting bigger and bigger while the degradation makes the working condition of gates getting worse and worse and changes the time delay of every path. These degradation will bring instability to combinational circuits, and sometimes even cause timing faults. So it’s necessary to discuss the influence of degradation effect on time delay of circuit and choose some appropriate paths to do circuit delay test.This thesis begins with the time delay test and typical degradation effects, and discusses the relationship between the degradation and the delay variation based on the degradation behavior of the basic gate units in combinational circuit. Use the DFS algorithm to search the critical path of time delay test based on the gate delay model, and use the ant colony optimization(ACO) algorithm to improve the efficiency and speed of critical path searching. Then use the critical nodes to improve the efficiency and makes ACO work better. At last, the DFS and ACO algorithms can effectively achieve the research on path selection for combinational circuit considering degradation effect, and the ACO algorithm notably improve the efficiency and speed.