Monitor and eliminate the circular defects in HDP–STI deposition through oxynitride/oxide composite liner

Abstract

This paper investigates the monitor and elimination methods for the circular defects in high-density-plasma shallow trench isolation (HDP–STI) deposition process. The optical measurement method can monitor the circular defects in early stage. When the thickness of silane-burst film exceeds 7.8 nm, the fit-error can alert the circular defects. The oxynitride/oxide composite liner can eliminate the circular defects. Besides this, the oxynitride/oxide composite liner can also improve the breakdown strength of the STI oxide. The breakdown strength of the STI oxide increases, respectively, 375 and 30% in the wafer center and edge. The uniformity of the STI breakdown strength was reduced from greater than 200% to less than 10% using the composite liner. The traditional N 2O plasma treatment for stabilizing the oxynitride film is harmful in the HDP-STI process. The N 2O plasma treatment shows the worst circular defect performance.