Browsing by Author "WANG, FS"

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CHARACTERIZATION OF H-2/N-2 PLASMA PASSIVATION PROCESS FOR POLY-SI THIN-FILM TRANSISTORS (TFTS)
(1995-06-01)
TSAI, MJ
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WANG, FS
;
CHENG, KL
;
WANG, SY
;
FENG, MS
The effects of nitrogen additives on the plasma hydrogenation of polycrystalline silicon thin film transistors (poly-Si TFTs) have been investigated with various radio-frequency (RF) power densities, substrate heating temperature, gas flow rates, as well as chamber pressures. The nitrogen-containing hydrogen (H-2/N-2) plasma treatments show better passivation effects on the electrical characteristics of the poly-Si TFTs than the pure H-2 hydrogenation. It is attributed to the passivation effect of the nitrogen radicals themselves and the promotion of the hydrogen plasma generation due to the radical collision. The passivation effects have been enhanced by properly chosen RF power density, gas flow rate and chamber pressure. Furthermore, the H-2/N-2 plasma were also utilized to passivate the poly-Si TFTs with different grain structures.
ENERGY-DEPENDENCE OF THE ELECTRON-CAPTURE CROSS-SECTION OF GAP STATES IN UNDOPED A-SI-H FILMS
(1995-02-15)
CHEN, YE
;
WANG, FS
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TSAI, JW
;
CHENG, HC
;
電子工程學系及電子研究所
Isothermal capacitance transient spectroscopy (ICTS) has been employed to measure the energy dependence of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film for the first time, via the proposed novel structure. For undoped a-Si:H films! experimental results show that the electron-capture cross section of defect levels initially decreases exponentially, reaches a minimum, and then increases exponentially with energy depth measured from the mobility edge of the conduction band. This v-shaped distribution of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film is different from that in phosphorous-doped a-Si:H film. This means that mechanisms other than multiphonon emission can be dominant in the electron-capture process in the gap states in undoped a-Si:H film.
LOW-TEMPERATURE ACTIVATION AND RECRYSTALLIZATION OF B+-IMPLANTED AND BF2+-IMPLANTED LPCVD AMORPHOUS-SI FILMS
(1995-10-01)
CHENG, HC
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WANG, FS
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HUANG, YF
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HUANG, CY
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TSAI, MJ
Low-temperature (600 degrees C) activation and recrystallization of the low-pressure chemical vapor deposition (LPCVD) amorphous-Si films B+- and BF2+-implanted with different implantation dosages and projection ranges have been investigated. The boron dopant in the amorphous-Si layer can enhance the recrystallization, resulting in the shorter incubation time and smaller grain size then the undoped specimens. For the BF2+-implanted specimens, the existence of fluorine atoms could postpone the grain nucleation, leading to the longer incubation time and slower nucleation rate for the heavily doped specimens than the undoped ones. For the BF2+-implanted specimens, as the implantation peak reaches to the alpha-Si/SiO2 interface, the recoiled oxygen atoms from the oxide substrate would retard the grain nucleation and exhibit a significantly large grain size after a long time annealing. However, the recoiled oxygen atoms and the microdefects in the poly-Si layers would offset the improvement in hole mobility. Higher hole mobilities and lower trap state densities were also observed for the BF2+-implanted specimens with respect to the B+-implanted ones. It is attributed to the passivation effect of fluorine atoms within the poly-Si layers.
NOVEL STRUCTURE FOR MEASURING THE DENSITY-OF-STATE DISTRIBUTION OF HIGH-RESISTIVITY SEMICONDUCTOR-FILMS BY ISOTHERMAL CAPACITANCE TRANSIENT SPECTROSCOPY
(1994-12-01)
CHEN, YE
;
WANG, FS
;
TSAI, JW
;
CHENG, HC
;
電子工程學系及電子研究所
A novel structure, metal/high-resistivity semiconductor (HRS)/n-type c-Si substrate with the space charge region (SCR) entirely covering the HRS film and penetrating into the c-Si substrate, has been proposed for determining the density-of-state distribution g(E) of the HRS films via the isothermal capacitance transient spectroscopy (ICTS) method. The structure has been tested and applied to the measurement of g(E) of the undoped hydrogenated amorphous silicon (a-Si:H) film. For undoped a-Si:H film with optical gap E(o) = 1.72 eV, a peak in g(E) is observed at 0.66 eV below the conduction band mobility edge E(c), with the attempt-to-escape frequency of u(n) = 1.61 x 10(13) s(-1). These midgap states are surmised to be correlated with the doubly occupied dangling bond D-.
REVERSE ANNEALING OF ARSENIC-IMPLANTED LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION (LPCVD) AMORPHOUS-SILICON FILMS
(1994-09-01)
TSAI, MJ
;
WANG, FS
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The reverse annealing of arsenic-implanted amorphous-silicon films has been observed. The dose dependence of this phenomenon is also investigated. For the specimens implanted with the dosage of 4 x 10(14) ion/cm(2), the sheet resistances show an increase in the annealing temperature range from 700 to 850 degrees C, which is attributed to the segregation of the activated dopants to the grain boundaries. This reverse annealing phenomenon is less prominent and the turnaround temperature is lower for the implantation dosage of 2 x 10(15) ion/cm(2), which is attributed to the effects of dopant segregation which decreases with increasing implantation dosage. Consequently, this reverse annealing phenomenon was not observed for the case of dosage of 1x10(16) ion/cm(2).
THE EFFECTS OF NH3 PLASMA PASSIVATION ON POLYSILICON THIN-FILM TRANSISTORS
(1995-11-01)
WANG, FS
;
TSAI, MJ
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The NH3 plasma passivation has been performed for the first time on the polycrystalline silicon (poly-Si) thin-film transistors (TFT's). It is found that the TFT's after the NH3 plasma passivation achieve better device performances, including the off-current below 0.1 pA/mu m and the on/off current ratio higher than 10(8), and also better hot-carrier reliability as well as thermal stability than the H-2-plasma ones, These improvements were attributed to not only the hydrogen passivation of the grain-boundary dangling bonds, but also the nitrogen pile-up at SiO2/poly-Si interface and the strong Si-N bond formation to terminate the dangling bonds at the grain boundaries of the polysilicon films.