A technique to investigate the root cause of Write Recovery Time (tWR) failure

We developed a technique to investigate the root cause of Write Recovery Time (tWR) failure on Circuit Probing for 30nm DRAM. We take Electrical Failure Analysis (EFA) to probe the Drain current (Id) and detected the unbalanced between forward Drain-Source currents (Ids, forward) and reverse Drain-Source currents (Ids, reverse) on device because the shadowing effect from Lightly Doped Drain (LDD) processing induced Id lower. The result of the EFA and Physical Failure Analysis (PFA) are good agreement with the assumption. We also found the Y Center of Gravity (YCOG) parameter vs. Drain current (Id) has highly relation and YCOG parameter raiser will induced Id current lower. We discovered that measuring of forward and reverse Drain-Source currents (Ids) would be useful to quickly and easily detect the unbalance of the implant dose issue.