Diagnosis of Defects on Scan Enable and Clock Trees

In this paper, we propose a different software based method that does not require any extra effort manipulating test parameters. First, we assume the defects are on scan chains and use previously published chain diagnosis algorithms presented in Y. Huang et al. (2005) to identify the suspect scan cells. Secondly, if there is at least one faulty chain that is modeled with stuck-at-X fault, we attempt to diagnose with stuck-at-0 fault model at scan enable. As we mentioned earlier that the shift operation is incorrect when the scan cell value is obtained from the system logic for each shift cycle, it is very likely we see both stuck-at-1 and stuck-at-0 at scan cells. So stuck-at-X fault model at scan cells is a sign of the stuck-at-0 fault model for scan enable defects