In this work, we discussed the fault isolation method for the Thin-Film Transistor (TFT). Many defects in the TFT can be directly observed by optical microscope; however, some defects are not visible in either optical microscope or SEM making the fault isolation effort very challenging. We demonstrated that OBIRCH can be used to find defect locations in TFT failures for leakage and shorts. The TFT is so fragile that the laser power and biasing voltage have to be very carefully controlled to avoid damaging the TFT. After identifying the defect location by OBIRCH hot spot detection, the defect was successfully captured with TEM analysis.