Optical induce tungsten plug corrosion in CMP process

Optically induced tungsten plug (W-plug) corrosion defects on wafers stored in a water tank waiting for a cleaning treatment during post tungsten chemical mechanical planarization (WCMP) were verified using KLA scan, queue-time (Q-time) splits, layout tracing, SEM/FIB inspection and electric measurement. Reliability tests on an out of control limitation lot also found W-plug corrosion interconnect failures as Q-time went overdue with the defects experiencing a layout dependency. The W-plug corrosion mechanism is being proposed in this article. The installation of yellow lights in the WCMP environment could make Q-time longer but does not completely solve the issue.