High resolution SIMS and neutron depth profiling of boron through oxide–silicon interfaces

Abstract

SIMS and neutron depth profiling (NDP) have been used to study the distribution 10B+ implanted into silicon through thermal oxide, and its segregation at the oxide–silicon interface on annealing. Using the reaction 10B (n,∝)7 Li, and a grazing exit geometry, the depth resolution in the ∝- particle spectrum in NDP is ∼10 nm. Better depth resolution is obtained in the calibrated SIMS profiles. For a wafer implanted with 70 keV 10B+ through 194 nm SiO2 to a dose of 1×1016 cm−2, the segregation coefficient after annealing at 1000 °C for 30 min was ∼3 from NDP. The segregated B was resolved better by SIMS and segregation coefficient of 10 was indicated from the SIMS depth profile. Analysis of the B profile in the Si surface after chemically stripping the SiO2 indicated a value ≥50. Higher depth resolution with NDP should be achievable by using a more grazing exit geometry, but higher flux neutron sources are required to maintain reasonable counting times.