Recovered Scan Failure Investigation and Failure Mechanism Determination

The success of the electrical fault isolation will assist in narrowing down to the most possible fault location with confidence, and thus increase the success rate in determining the failure mechanism during physical failure analysis. However, any form of recovery from the failure could result in inability to determine the root cause. For example, they are either the sample unable to send to FA since the device is passing, or unable to continue the fault isolation since recovery occurred during analysis. This technical paper will discuss on the investigation of recovery symptom in scan related failure for 55nm wafer technology devices. Through study and investigation, recovery avoidance is implemented during testing, and a new stress flow is identified to reactivate the failure mode. Thus, recoverable failure mechanism like passivation crack and metal defects are identified. The learning from the recovery characteristics also help to forecast possible failure mechanism based on the scan diagnostics and electrical fault isolation findings.