Nondestructive dose determination and depth profiling of arsenic ultrashallow junctions with total reflection X-ray fluorescence analysis compared to dynamic secondary ion mass spectrometry

Secondary ion mass spectrometry (SIMS) has been the most widely used technique for the measurement of dopant distribution in Si because of its ability of determining profile shape, junction depth, and dose with adequate depth resolution and detection limits. In the case of ultrashallow implants though, SIMS is going towards its intrinsic limits; in fact, initial transient width and native oxide-induced matrix effects affect the measurement in the first nanometres where a relevant part of the dopant is confined. Therefore, complementary techniques able to give information on the dose and on the distribution in the first nanometres are required. In this work, total reflection X-ray fluorescence analysis (TXRF) resolved in angle has been evaluated as a candidate, given its high sensitivity in the near surface region, its ability of a quantitative analysis, its multielement capability, and its nondestructiveness. Three arsenic implanted Si samples have been analysed by SIMS and TXRF. The SIMS measurements have been carried out by a magnetic sector instrument of new generation with a Cs+ primary beam and by monitoring negative secondary ions. The TXRF measurements were performed at beamline 6-2 of the Stanford Synchrotron Radiation Laboratory. For the fluorescence measurements, an absolute quantification by fundamental parameters and comparison with the Si fluorescence signal has been adopted. The TXRF dose determination showed good agreement with other techniques. TXRF could also evaluate the accuracy of the SIMS profile in the first nanometres.