NECESSITY OF HYDROGEN FOR ACTIVATION OF IMPLANTED FLUORINE IN SI/SIO2 STRUCTURES

The elimination of trapping centers in Al/SiO2/Si structures by means of fluorine ion implantation was studied in oxides with various contents of hydrogen. It was shown that significant reduction in the density of electron and hole traps in the bulk of oxide may be achieved only in the presence of hydrogen in the system (wet oxide, or post-metallization anneal in a hydrogen containing ambient). Similarly, suppression of the generation of Si/SiO2 interface states by radiation is also observed only in hydrogen containing systems. The results suggest that defect precursors such as weakly bonded hydrogen and strained Si-O bonds are eliminated by the fluorine and that hydrogen is necessary for this elimination. It is proposed that H facilitates the F transport by formation of HF molecules.