Hot-electron damage-resistant Si-gate submicrometer MOSFETs with a fluorinated oxide

It has been reported previously (see E.F. da Silva, Jr. et al., 1987) that, by introducing minute amounts of fluorine in thermal SiO/sub 2/, the reliability of MOS capacitors can be significantly improved. The authors present a new technique to incorporate fluorine into the gate oxide, and the subsequent improvement of the resistance to hot-electron damage of the resulting micrometer-size and submicrometer MOSFETs. This technique utilizes low energy F implantation onto the surface of the polysilicon gate electrode, followed by annealing at 950 degrees C to diffuse F into the gate SiO/sub 2/ toward the SiO/sub 2//Si interface. The MOSFETs investigated covered a wide range of gate lengths (0.6-10 mu m on mask; 0.2-9.6 mu m after processing) and widths (0.8-10 mu m on mask; 0.2-9.4 mu m after processing). Among other findings, it is shown that the incorporation of F causes a reduction of midgap interface trap density and an increase of maximum transconductance in as-processed devices over a wide range of the F-implant doses studied (0-10/sup 16//cm/sup 2/).