Patent ID: 8612811
Filing Date: 2013-12-17
Classification: G06F,G11C

Abstract:
1. A defective-ratio predicting method in a system having a storage unit for storing an actual defective ratio of each fail bit mode of a memory device and a critical area of each process and each fail bit mode calculated by a layout simulation in which a plurality of foreign substances are virtually dropped at random onto a design layout whose wiring names are previously defined, and a predicting unit for calculating a characteristic defective ratio and a foreign-substance defective ratio by using the actual defective ratio of each fail bit mode and the critical area of each process and each fail bit mode, wherein the predicting unit executes the defective-ratio predicting method comprising: a first step of obtaining the actual defective ratio of each fail bit mode and the critical area of each process and each fail bit mode stored in the storage unit; a second step of selecting a fail bit mode, whose gap between the actual defective ratio of each fail bit mode except for the arbitrary fail bit mode and a foreign-substance defective ratio of each fail bit mode calculated by using the critical area of each process and each fail bit mode and an arbitrary number of foreign substances is the largest; a third step of calculating a fail bit mode, whose gap between the actual defective ratio of each fail bit mode and the foreign-substance defective ratio of each fail bit mode calculated by using a new number of foreign substances calculated by matching the arbitrary number of foreign substances by a first matching of the number of foreign substances based on the largest gap between the foreign-substance defective ratio and the actual defective ratio of the fail bit mode; a fourth step of, after updating the number of foreign substances by a plurality of times of the matching such as a second matching of the number of foreign substances based on the largest gap between the foreign-substance defective ratio and the actual defective ratio of the fail bit mode, calculating the foreign-substance defective ratio of each process and the foreign-substance defective ratio of each fail bit mode by using the number of foreign substances obtained by the number of times of the matching by which the gap between the foreign-substance defective ratio of each fail bit mode and the actual defective ratio of each fail bit mode is the smallest; and a fifth step of calculating a characteristic defective ratio of the arbitrary fail bit mode based on the foreign-substance defective ratio of each fail bit mode and the actual defective ratio of each fail bit mode.