Integration HDP CVD oxide sputtering effect for metal void defect solution

Metal discolor defect was observed by in-line visual inspection after HDP oxide deposition. The defect can easily be detected on metal line side-wall which is located on an isolated or open area. The focused ion beam (FIB) cross-section analysis showed the defect was metal void. The metal void was about 1/4∼1/2 of metal line width which had serious reliability concern (electron migration). However, CP yield and WAT testing data could not isolate this problem. The results studied show that the metal void defect has a strong correlation with the thermal effect of the deposition process. A stronger thermal effect on wafer would cause a more serious metal void problem. The improvement strategy was to reduce the thermal effect during the oxide deposition process. A multi-steps oxide deposition recipe was developed to solve the metal void problem. Investigation results show that the HDP multi-steps recipe is very effective to eliminate the metal void defect.