Mechanism of high density plasma chemical vapor deposition phosphosilicate glass process without in-situ plasma chamber clean

Abstract

Plasma chamber dry clean after chemical vapor deposition (CVD) was widely used in the plasma enhanced CVD processes. The effects of the plasma clean periodicity on the deposited film qualities were explored in this research. The variations of the film qualities of high-density plasma phosphosilicate glass (HDP-PSG) were found for consecutive film deposition. The comparisons in the film qualities such as phosphorous concentration, stress, thickness and wet etch rate for successively depositing wafers after plasma chamber dry clean were studied. The phosphorous concentrations were measured using X-ray fluorescence (XRF) method. The consecutively depositing wafers exhibited comparable phosphorous concentrations from the XRF results. The stress of the first three wafers had 10% difference. The first wafer had the most compressive stress. The film thickness of the first wafer was 30–40 nm thicker than that of the third wafer. The film wet etch rate also showed a decreasing trend. The first wafer had 10% higher wet etch rate than the third wafer. The secondary ion mass spectrometry (SIMS) analysis displayed that the first wafer had more uniform phosphorous distribution. The different phosphorus depth profile generated the different wet etch rate performance for the consecutive deposition wafers. These differences in the film qualities were caused by the chamber out-gassing. The residual gas analysis (RGA) was used to monitor the chamber out-gassing. The oxygen and moisture from the chamber out-gassing impacted the HDP-PSG film qualities for no in situ plasma chamber clean.