SIMS depth profiling and SRIM simulation to lower energy antimony implantation into silicon

Abstract

There is a notable trend for formation of shallower dopant profiles: i.e. the use of heavier ions, such as Sb and In at relative higher energies (vs. As or 11B) to make shallow dopant profiles. In the work, the 121Sb depth profiles and irradiation damage of Si wafers implanted with low energies Sb ions were studied by secondary ion mass spectrometry (SIMS), cross-sectional transmission electron microscopy (XTEM), and simulation by the program of the stopping and range of ions in matter (SRIM). (100) Si wafers were implanted with 10 to 50keV 121Sb ions to a dose of 1e14 or 1e13 atoms/cm2. For the 10keV Sb implanted wafer, analysis by SIMS shows that an Sb doped layer was built up in Si, with the implanted peak at 9.7nm. The damaged peak simulated by SRIM program is located at a depth of 69% of the implanted Sb peak. By combining the XTEM observation and SRIM simulation it has been found that a dpa (displacement per atom during the irradiation) level of > 0.29 resulted in amorphization of the implanted layer. In other words, the critical dpa level for amorphizing Si by Sb ions is 0.29. Analyses by XTEM show that a lower damage level with a simulated dpa level of <0.065 only resulted in some strain and point defects associated contrast in the implanted layer. XTEM analyses also show that the low irradiation damage to a dpa level of 0.065 can be essentially removed by RTP (Rapid Thermal Processing) annealing at 1050°C for 30 seconds, while the SIMS Sb depth profile showing less obvious change.