New developments concerning lock-in phase detection and spectral analysis techniques applied to accessible IC signals are introduced in detail. These techniques combine the thermal laser stimulation (TLS) with the high sensitivity of lock-in to phase variation or the selectable frequency detection in spectrum analyzer. The difference to normal lock-in techniques utilizing pulsed lasers is exemplary pointed out. Moreover the applications to phase related soft-defects and to a design related jitter problem are shown. The power of such techniques for direct mapping a signal path is shown. Further benefits of lock-in phase methodology and spectral analysis technique applied to 65 nm and 90 nm technology is presented and illustrated using different case studies.