Browsing by Author "TSAI, MJ"

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A NEW PORTRAYAL OF OXIDATION OF UNDOPED POLYCRYSTALLINE SILICON FILMS IN A SHORT-DURATION
(1994-01-01)
WANG, PW
;
SU, HP
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TSAI, MJ
;
HONG, G
;
FENG, MS
Both polysilicon films low-pressure chemical-vapor-deposited (LPCVD) at 625 degrees C and amorphous films deposited at 550 degrees C with subsequent annealing at 600 degrees C for 24 h to form polysilicon films were used to grow polyoxides at 850 degrees C in wet or dry oxygen. Detailed high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) studies have been performed to determine the microstructures of the polyoxide/polysilicon interface and the crystallinity of the polysilicon films. It is found that the oxidation phenomena of these two films are very different. For the recrystallized amorphous silicon specimens, the polyoxide/polysilicon interface is very flat because of the poor crystallinity and low-angle grain boundaries between the grains. On the other hand, the polyoxide/polysilicon interface is rough for the as-deposited polysilicon samples due to the distinct grain characteristics and the high-angle grain boundaries between these grains.
CHARACTERIZATION OF H-2/N-2 PLASMA PASSIVATION PROCESS FOR POLY-SI THIN-FILM TRANSISTORS (TFTS)
(1995-06-01)
TSAI, MJ
;
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.
EFFECTS OF ZRO2 ON THE TEXTURING AND PROPERTIES OF MELT-PROCESSED Y1BA2CU3O7-DELTA
(1994-04-25)
JUANG, JY
;
WU, CL
;
WANG, SJ
;
CHU, ML
;
WU, KH
The addition of ZrO2 is found to be very effective as the nucleation sites to promote the oriented growth of Y1Ba2Cu3O7-delta (YBCO) during peritectic solidification. Extended regions of well-textured YBCO grains with superior superconducting properties of the YBCO bulk are readily obtained by a single-step melt process at much lower process temperatures. At 77 K, the platelike Josephson weak-link behaviors observed in pure melt-processed YBCO have been effectively eliminated, indicating that the coherency between the spherulitic superconducting YBCO grains may have been greatly improved by ZrO2 additions.
ELECTRICAL CHARACTERISTICS OF THIN-FILM TRANSISTORS WITH DOUBLE-ACTIVE-LAYER STRUCTURE
(1995-02-01)
TSAI, MJ
;
WANG, PW
;
SU, HP
;
CHENG, HC
;
電子工程學系及電子研究所
Thin-film transistors (TFTs) with a doubie-active-layer (DAL) structure have been proposed and found to exhibit two kinds of special electrical characteristics. One is the improvement of current drivability and transconductance as compared to the traditional structure. The other is the double-switching characteristics caused by the bi-transistor action. By means of a buried oxide separating the conduction channel into two parts, carrier transport could be enhanced due to the reduction of the vertical electric Field. In addition, the weak avalanche breakdown for the top channel results in hole accumulation in the top poly-Si/buried oxide interface, further promoting the conduction of the bottom active layer, leading to the novel double-switching properties.
GRAIN-GROWTH OF LASER-RECRYSTALLIZED POLYCRYSTALLINE AND AMORPHOUS-SILICON FILMS
(1994-09-15)
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 grain growth mechanisms of polycrystalline and amorphous silicon films on SiO2 have been studied using continuous wave (CW) CO2 laser system under different laser powers. A solid-phase grain growth mechanism was observed at laser powers ranging from 5 W to 15 W. In this power region, the grain growth of the amorphous silicon specimens was more significant than that of the polycrystalline silicon ones. Dramatic grain growth was obtained as the laser power increased from 17.5 W to 22.5 W for both specimens. The liquid-phase grain growth mechanism could be used to explain this phenomenon. In the solid-phase grain growth regime, the [110] texture was dominant for the polycrystalline silicon samples and a stronger [100] texture was observed for the amorphous specimens. However, X-ray diffraction revealed a [100] preferred orientation for both the laser-recrystallized polycrystalline and amorphous silicon films in liquid-phase growth regime. Furthermore, thin film transistors fabricated with these recrystallized films were also demonstrated. TFTs with an on/off current ratio of 1.58 x 10(8) and an effective mobility as large as 200 cm(2) V-1 s(-1) could be achieved for silicon films laser-recrystallized in the liquid-phase growth regime due to the large grain size.
LOW-TEMPERATURE ACTIVATION AND RECRYSTALLIZATION OF B+-IMPLANTED AND BF2+-IMPLANTED LPCVD AMORPHOUS-SI FILMS
(1995-10-01)
CHENG, HC
;
WANG, FS
;
HUANG, YF
;
HUANG, CY
;
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.
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.