Ck. Yang et al., CHARACTERISTICS OF TOP-GATE POLYSILICON THIN-FILM TRANSISTORS FABRICATED ON FLUORINE-IMPLANTED AND CRYSTALLIZED AMORPHOUS-SILICON FILMS, Journal of the Electrochemical Society, 143(10), 1996, pp. 3302-3307
This paper presents a comprehensive study on the characteristics of n-
and p-channel polycrystalline-silicon (polysilicon) thin-film transis
tors (TFTs) fabricated on fluorine-implanted-then-crystallized amorpho
us silicon films. Amorphous silicon films of two thicknesses were impl
anted with different energies and various dosages of fluorine, and stu
died using transmission electron microscopy (TEM) and secondary-ion ma
ss spectrometry (SIMS). The electrical characteristics of TFTs fabrica
ted on the films were correlated with the results of TEM and SIMS, It
was found that field-effect mobilities of both n- and p-channel device
s were improved by the fluorine implantation thanks to the enhanced gr
ain size and tile fluorine passivation effect. For the p-channel devic
e, the fluorine implantation did not improve the subthreshold swing an
d even degraded it after hydrogenation. This result was thought to be
caused by the fluorine-induced negative charges in oxides. However, a
thin active layer and a deep implantation reduced this degradation.