Case Study of Titanium Nitride defect after Tungsten Etch Back process

This paper is to present on the tiny round shape defect encountered after Tungsten Etch Back (WEB) process. The defect will result in wafer scrap when the defect count is detected at Outgoing Quality Assurance (OQA) inspection. This tiny round shape defect is a result of formation of Titanium Fluoride (TiFx) after WEB process caused by the interaction of Sulfur Hexafluoride (SF6) plasma with the exposed Titanium Nitride (TiN) on wafer surface. The TiFx defect cannot be avoided however the growth rate can be reduced or controlled. Numerous approaches were taken by segregating the process. However the final solution was by inserting an additional scrubbing step and having a Q-time control between WEB process and the subsequent processes.