The measurement of boron at silicon wafer surfaces by neutron depth profiling

摘要

The thermal neutron reactionn+10Brarr;4He+7Li is utilized to measure the boron concentration on the surface of silicon wafers. This neutron depth profiling measurement technique requires no sample preparation. Boron is determined on the ashyphen;received wafers at a level of 1012to 1013atoms/cm2. A boron level of about 2times;1012atoms/cm2is found at the wafer surface after oxidation or epitaxial or polycrystalline silicon deposition. Ambient air appears to be one source of the boron. Secondaryhyphen;ion mass spectroscopy performed on wafers with polysilicon provides additional support for an atmospheric source of boron.