AVS 49th International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS-WeM

Paper AS-WeM8
Accurate SIMS analysis of SiON Films

Wednesday, November 6, 2002, 10:40 am, Room C-106

Session: Optical Methods and High-k Dielectrics Characterization
Presenter: S. Miwa, SONY Corp., Japan
Authors: S. Miwa, SONY Corp., Japan
H. Kobayashi, SONY Corp., Japan
K. Nakajima, Kyoto University, Japan
K. Kimura, Kyoto University, Japan
Correspondent: Click to Email
Oxynitride (SiON) films are generally used in advanced CMOS LSIs as gate dielectrics instead of SiO@sub 2@ films. The nitrogen distribution in the SiON films strongly affects the performance of the transistors, so it is important to analyze exact nitrogen profiles. Secondary Ion Mass spectrometry is the most frequently used method for the analysis of SiON films. In the analysis, low-energy Cs primary ions and the very high incidence angle (about 80 degrees from the normal incidence) are recommended to avoid knock-on, atomic mixing, and matrix effect over the SiON/Si structure. On the other hands, secondary ion yield is sensitive for the surface concentration of primary ion species. In this case, the surface coverage of Cs is dramatically varied depending on the slight change of the incidence angle because the incidence angle of primary ions is very high. We have carefully investigated that the angle dependence of relative sensitive factors (RSF) and the sputtering rate around this very high incidence angle. We have found that RSF is varied about 10% when the angle changed by 0.3 degrees and that sputtering rate is varied about 10% when the angle changed by 0.5 degrees. In conclusion, the incidence angle of primary ions must be controlled within only 0.1 degree in order to keep the quantification errors within 5%. We can control the angles well reproducibly by means of monitoring the ratio of the intensities of two secondary ions (SiCs@super +@ and Cs@sub 2@@super +@). We have also compared the N concentration obtained by SIMS with that obtained by High-resolution Rutherford Backscattering Spectrometry.