Browsing by Author "CHEN, TP"

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CHARACTERISTICS OF BORON-DIFFUSION IN POLYSILICON SILICON SYSTEMS WITH A THIN SI-B LAYER AS DIFFUSION SOURCE
(1995-02-01)
CHEN, TP
;
LEI, TF
;
LIN, HC
;
CHANG, CY
;
電子工程學系及電子研究所
A new material, Si-B layer, as boron diffusion source for polysilicon/silicon systems, has been investigated. The Si-B layer was deposited on polysilicon in an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system at 550 degrees C. The characteristics of boron diffusion in Si-B layer/polysilicon/silicon systems have been investigated by using secondary ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (XTEM). To remove the Si-B layer after the drive-in step, the Si-B layer was oxidized completely during thermal drive-in stage and removed with a diluted hydrofluoric acid. The effects of thermal oxidation of Si-B layer on boron diffusion profiles and polysilicon structures were analyzed. It was found that the boron profiles within the polysilicon are slightly dependent on the oxidation of Si-B layer. Moreover, the polysilicon grain size for Si-B layer source were enlarged, as compared with conventional BF2+-implanted polysilicon source. It is attributed to the effects of the gettering of oxygen impurity by the Si-B layer and secondary grain growth during Si-B layer oxidation. In addition, the boron diffusion profiles in the silicon substrate for Si-B layer source exhibited a more shallow junction depth and less sensitivity to the thermal budget, as compared with BF2+-implanted polysilicon source. This is considered to be the effect of the smaller surface concentration, C-s, in the silicon substrate for Si-B layer source.
INVESTIGATION ON THE DISTRIBUTION OF FLUORINE AND BORON IN POLYCRYSTALLINE SILICON SILICON SYSTEMS
(1995-06-01)
CHEN, TP
;
LEI, TF
;
CHANG, CY
;
HSIEH, WY
;
CHEN, LJ
The behaviors of fluorine in BF2+ implanted polycrystalline silicon (poly-Si) on silicon have been investigated in the annealing temperature range of 850 to 1100 degrees C. The distribution of fluorine atoms as functions of temperature and time have been monitored by the secondary ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (XTEM). The XTEM micrographs revealed that fluorine bubbles are distributed in the poly-Si and at the original poly-Si/Si interface after annealing. The locations of bubbles were found to correspond to the fluorine peaks in the SIMS depth-concentration profiles. The presence of the boron peak at the original poly-Si/Si interface is attributed to the gettering of boron atoms by the fluorine bubbles. Moreover, the boron profiles in the silicon substrates are sensitive to thermal budget due to the pileup of fluorine atoms at the poly-Si/Si interface. The pileup of fluorine at the poly-Si/Si interface leads to an enhancement of epitaxial regrowth of poly-Si films and. the formation of fluorine bubbles. Consequently higher surface dopant concentration and deeper junction depth were obtained.
LOW-TEMPERATURE GROWTH OF SILICON-BORON LAYER AS SOLID DIFFUSION SOURCE FOR POLYSILICON CONTACTED P(+)-N SHALLOW JUNCTION
(1995-12-01)
LEI, TF
;
CHEN, TP
;
LIN, HC
;
CHANG, CY
;
電子工程學系及電子研究所
A new material, Si-B, is proposed as a solid diffusion source for fabrication of poly-Si contacted p(+)-n shallow junctions, The junction depth of the Si-B source diode has been measured and compared with that of a BF2+-implanted poly-Si source diode, It was found that the Si-B source diode had a much shallower junction and was less sensitive to thermal budget than the BF2+ source diode, This was attributed to the smaller surface concentration and diffusivity of boron in the silicon in Si-B source diodes. Regarding electrical characteristics of diodes with a junction depth over 500 Angstrom, a forward ideality factor of better than 1.01 over 8 decades and a reverse-current density lower than 0.5 nA/cm(2) at -5 V were obtained, As the junction depth shrank to 300 Angstrom, the ideality factor and reverse current density of diodes increased slightly to 1.05 and 1.16 nA/cm(2), respectively, These results demonstrated that a uniform ultrashallow p(+)-n junction can be obtained by using a thin Si-B layer as a diffusion source.
LOW-TEMPERATURE GROWTH OF SILICON-BORON LAYER BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-04-04)
CHEN, TP
;
LEI, TF
;
LIN, HC
;
CHANG, CY
;
HSIEH, WY
A polycrystalline silicon-boron (Si-B) layer with a thickness of 180 nm was grown on recrystallized amorphous silicon in an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system using pure SiH4 and B2H6 (1% in H-2). The growth temperature was as low as 550-degrees-C. Auger electron spectroscopy and secondary ion mass spectroscopy showed that the boron concentration is extraordinarily high (2 x 10(22) cm-3). From the analysis of transmission electron diffraction patterns, the phase of silicon hexaboride (SiB6) was found to be present in the as-deposited Si-B layer. After thermal annealing, most of the boron atoms in the Si-B layer were found to be immobile. The presence of SiB6 in the Si-B layer may lead to the reduction of boron diffusivity in the Si-B layer during thermal annealing.