QUANTIFICATION OF CARBON IN SI1-X-YGEXCY WITH UNIFORM PROFILES

Methods to quantify the carbon concentration of CVD grown Si1-x-yGexCy (0.25 < x < 0.37 and 0.01 < y < 0.12) layers on (100) Si with uniform composition profiles were investigated, Two analysis techniques were used: Rutherford backscattering spectrometry (RES) using a 4.295 MeV H e+2 incident ion and elastic recoil detection (ERD) using a 24 MeV Si5 incident ion. For the RES measurements the C-12(alpha,alpha)C-12 ela stic resonance reaction near 4.265 MeV was used to enhance the scatter ing cross section of carbon. These carbon concentrations were calculat ed by either integrating the resonant scattering cross section across the energy width of the layer or by using a Lorentzian fit to estimate the area. The backscattering data were additionally analyzed with the program RUMP. These different analysis techniques resulted in a large scatter in the RES predictions for the carbon concentrations dependin g on how the resonant cross sectional area was calculated. The appropr iateness of each technique was judged by comparing the predicted conce ntrations to those obtained by ERD. The divergence between the carbon concentration predicted by using the Lorentzian approximation and the ERD values was great enough to deem this method as inappropriate. The values obtained by RUMP were systematically greater than the ERD conce ntrations, however the percent difference was never more than 20. The predicted carbon concentration that had the closest correlation to ERD was found by integrating an appropriate scattering cross section acro ss the energy width of the layer.