neutrons cm 2 sec 3838 barns 10 24 cm 2 barn 1 11 u00d7 10 17 atoms bpsg alpha flux compared to the u03b1 flux emitted from uranium and thorium impurities in materials bpsg alpha flux from 10 b n u03b1 7 li impurities and their daughter products in dram materials u02dc 0 031 u03b1 hr cm 2 based on 1 cm 2 die size the removal of 10 b from boron compounds is thus necessary to significantly reduce the package level alpha flux bpsg is the primary target and since separated 11 b is relatively inexpensive the formation of bpsg free of 10 b is inexpensive and reduces alpha flux by more than 1000 times to verify the theory an experiment was performed in which two samples a wafer with borophosphosilicate glass bpsg and a wafer with phosphosilicate glass psg were exposed to a neutron flux the bpsg wafer was fabricated in the normal fashion e g the boron contained both 10 b and 11 b and the psg wafer obviously had no boron both films were 5800 u00e5 thick the geometry of the experiment is depicted in fig3 in fig3 a source 300 of neutrons such as a nuclear reactor.