Browsing by Author "Liu, PT"

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A distributed charge storage with GeO2 nanodots
(2004-04-05)
Chang, TC
;
Yan, ST
;
Hsu, CH
;
Tang, MT
;
Lee, JF
In this study, a distributed charge storage with GeO2 nanodots is demonstrated. The mean size and aerial density of the nanodots embedded in SiO2 are estimated to be about 5.5 nm and 4.3x10(11) cm(-2), respectively. The composition of the dots is also confirmed to be GeO2 by x-ray absorption near-edge structure analyses. A significant memory effect is observed through the electrical measurements. Under the low voltage operation of 5 V, the memory window is estimated to similar to0.45 V. Also, a physical model is proposed to demonstrate the charge storage effect through the interfacial traps of GeO2 nanodots. (C) 2004 American Institute of Physics.
A method for fabricating a superior oxide/nitride/oxide gate stack
(2004)
Chang, TC
;
Yan, ST
;
Liu, PT
;
Wang, MC
;
Sze, SM
A superior oxide/nitride/oxide (ONO) gate stack was demonstrated. High density plasma chemical vapor deposition was used to deposit the silicon nitride layer instead of the conventional low-pressure chemical vapor deposition for silicon/oxide/nitride/oxide/silicon technology. The densified nitride layer was performed by high-temperature dry oxidation to form a thermally grown blocking oxide layer on the silicon nitride rather than a deposited oxide layer. The ONO gate stack shows large memory window, high breakdown voltage, and reliable endurance characteristics, which is a potential candidate for future nonvolatile memory technology. (C) 2004 The Electrochemical Society.
A novel approach of fabricating germanium nanocrystals for nonvolatile memory application
(2004-01-01)
Chang, TC
;
Yan, ST
;
Liu, PT
;
Chen, CW
;
Lin, SH
A nonvolatile memory device embedded with Ge nanocrystal dots is fabricated by the thermal oxidation of Si0.8Ge0.2 combined with a rapid thermal annealing at 950degreesC in N-2 gas. The tunnel oxide in the nonvolatile memory is controlled to be 4.5 nm thick and embedded with 5.5 nm Ge nanocrystals. A low operating voltage, 5 V, is implemented and a significant threshold-voltage shift, 0.42 V, is observed. When the electrons are trapped in the Ge nanocrystals, the effect of Coulomb blockade prevents the injection and storage of more electrons and decreases the leakage current. Also, the retention characteristics are tested to be robust. (C) 2003 The Electrochemical Society.
A novel distributed charge storage element fabricated by the oxidation of amorphous silicon carbide
(2004)
Chang, TC
;
Yan, ST
;
Chen, YT
;
Liu, PT
;
Sze, SM
A novel distributed charge storage element fabricated by the oxidation of amorphous silicon carbide is proposed. For low-temperature oxidation processes, the oxidized SiCO gate stack shows a larger memory window due to the retainable dangling bonds with more Si-C bonding types and less Si-O bonds. Under 5 V write operation of the low-temperature oxidized SiCO stack, a 1.5 V threshold voltage shift is exhibited, which is sufficient for a memory device to define "0'' and "1.'' Also, the low-temperature oxidation process of the SiCO layer saves the thermal budget for the manufacturing processes of nonvolatile memory devices. (C) 2004 The Electrochemical Society.
A novel method for growing polycrystalline Ge layer by using UHVCVD
(2006-02-24)
Tu, CH
;
Chang, TC
;
Liu, PT
;
Yang, TH
;
Zan, HW
Poly-Ge grown on SiO2 substrates by using one-step ultra-high vacuum chemical vapor deposition (UHVCVD) process with thin Si nucleation layers at very low deposition temperature (350 degrees C) was demonstrated. The results demonstrated that the polycrystalline silicon (poly-Si) nucleation layer is needed for the growth of polycrystalline germanium (poly-Ge) on SiO2 substrates at low growth temperature. SEM image presents the films with uniform rain size and uniform thickness occurring in the samples. The grain size of poly-Ge is about 100 nm. The Raman shift spectrum and XRD spectrum also identified that films are high quality poly-Ge by using this method. (c) 2005 Elsevier B.V. All rights reserved.
A novel SiGe raised source/drain polycrystalline silicon thin-film transistor with improved on-current and larger breakdown voltage
(2003-03-01)
Peng, DZ
;
Chang, TC
;
Liu, CF
;
Yeh, PH
;
Liu, PT
A novel poly-Si thin-film transistor with a self-aligned SiGe raised source/drain (SiGe-RSD TFT) has been proposed and fabricated. The SiGe-RSD regions were grown selectively by the ultra-high vacuum chemical vapor deposition (UHVCVD) process designed by us at 550degreesC. The resultant transistor structure features an ultra-thin active channel region (20 nm) and a self-aligned thick source/drain region (120 nm), and is ideally suited for optimum performance. Significant improvements in electrical characteristics, such as higher turn-on current, lower leakage current and higher drain breakdown voltage have been observed in the SiGe RSD TFT, compared to its conventional TFT counterpart. Moreover, the process is simple and no additional masks are necessary, which is consistent with conventional fabrication processes.
A study of parasitic resistance effects in thin-channel polycrystalline silicon TFTs with tungsten-clad source/drain
(2003-08-01)
Zan, HW
;
Chang, TC
;
Shih, PS
;
Peng, DZ
;
Kuo, PY
With selectively-deposited tungsten film grown on source/drain regions, the parasitic source/drain resistance of thin-channel polycrystalline silicon (poly-Si) thin film transistors can be greatly reduced, leading to the improvement of device driving ability. After extracting the parasitic resistance from characteristics of devices with different channel length, the influences of parasitic resistance on device performances were discussed. A physically-based equation containing the parasitic resistance effects was derived to explain the behavior of linear transconductance under high gate voltage. Good agreements were found between calculated and measured data for both the thin-channel devices with or without tungsten-clad source/drain structure.
A W-spacer GOLD TFT with high performance and high reliability
(2002-09-26)
Zan, HW
;
Peng, DZ
;
Shih, PS
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Chang, TC
;
Liu, PT
In this paper, we successfully fabricated Gate-Overlapped Lightly-doped Drain (GOLD) polycrystalline silicon thin-film transistors (poly-Si TFTs) with selectively deposited spacers. Under appropriate deposition conditions, tungsten (W) films can be selectively deposited on poly-Si gate electrodes to form spacers without any additional etching process. Compared to the conventional poly-Si TFTs without LDD structures, our devices effectively suppress the kink effect and the punch-through phenomenon in short-channel devices. The hot-carrier reliability of our devices is also improved due to the reduced electric field on the drain side. In addition, the transconductance of our devices is compatible to that of conventional devices. This is because the W-spacer acts as a part of gate electrode to induce channel when the device is operated under ON state. (C) 2002 Elsevier Science Ltd. All rights reserved.
Activation of carbon nanotube emitters by using supercritical carbon dioxide fluids with propyl alcohol
(2006)
Liu, PT
;
Tsai, CT
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Chang, TC
;
Kin, KT
;
Chang, PL
This paper explores the application of supercritical carbon dioxide fluids on the field emission enhancement for vertically aligned carbon nanotubes. The typical heating process cannot effectively activate the deionized-water-rinsed carbon nanotube emitters, exhibiting poorer field emission performance, due to residual moisture uptake in the carbon nanotubes. In contrast, the field emission enhancement can be achieved significantly by applying the supercritical carbon dioxide fluids associated with 3 to 9 vol % propyl alcohol. It is found the cosolvent propyl alcohol plays a critical role in the activation efficiency of supercritical carbon dioxide fluids. A physical model is also deduced to clarify the observation. (c) 2006 The Electrochemical Society.
An interfacial investigation of high-dielectric constant material hafnium oxide on Si substrate
(2005-09-22)
Chen, SC
;
Lou, JC
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Chien, CH
;
Liu, PT
;
Chang, TC
In this study, the hump in the capacitance-voltage (C-V) curves, variation of leakage current, interfacial layer increase, and electron trapping in non-surface treated hafnium oxide (HfO2) samples were observed and investigated. From the results of the investigation, it was found that both rapid thermal oxidation and NH3 surface treatments improved the C-V curves. In addition, it was observed that samples treated with ammonia exhibited a lower leakage current when compared with the others. From the results of the dielectric, leakage current study, a severe electron trapping effect was exhibited under higher electric field stress. Finally, the conduction mechanism in the HfO2 thin film was dominated by Frenkel-Poole emission in a high electric field. (c) 2005 Elsevier B.V All rights reserved.
Characteristics and stress-induced degradation of laser-activated low temperature polycrystalline silicon thin-film transistors
(2003-02-15)
Peng, DZ
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Chang, TC
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Chang, CY
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Tsai, ML
;
Tu, CH
The characteristics and reliability of laser-activated polycrystalline silicon thin-film transistors (poly-Si TFTs) under the stress condition of drain voltage (V-d)=12 V and gate voltage (V-g)=15 V have been investigated. In spite of reducing the source/drain resistivity by using laser activation method, the leakage current (V-g<0) is larger for laser-activated poly-Si TFTs in comparison with traditional furnace-activated counterparts. It is also found that the post-stress leakage and on/off current ratio degrade much faster for laser-activated poly-Si TFTs, while the degradation rates of threshold voltage and subthreshold swing are comparable to those of traditional furnace-activated TFTs. The laser activation modifies the grain structure between drain and channel region and causes grain discontinuity extending from the drain side to the channel region. The grain discontinuity near drain side in the polysilicon film has been investigated by transmission electron microscopy analysis. The effective trap state density calculated from typical I-V curve has been compared for laser-activated and furnace-activated TFTs. As a result, an inferior reliability with extra trap state density and larger leakage current was observed in the laser-activated poly-Si TFTs. (C) 2003 American Institute of Physics.
Characterization of porous silicate for ultra-low k dielectric application
(2002-07-01)
Liu, PT
;
Chang, TC
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Hsu, KC
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Tseng, TY
;
Chen, LM
Thermal stability of a porous low-k film is a critical issue for application consideration in the back-end-of-line. In this study, thermal stability of the porous silicate has been investigated by changing the thermal processing temperatures. Experimental results have shown that the dielectric constant of the porous silicate still remains below 2.0 after thermal processing at 500 degreesC for I h. A series of material analysis techniques and electrical characteristics have been used to verify the physical and chemical characteristics of the porous silicate film. (C) 2002 Elsevier Science B.V. All rights reserved.
CMP of low-k methylsilsesquiazane with oxygen plasma treatment for multilevel interconnect applications
(2004)
Chang, TC
;
Tsai, TM
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Liu, PT
;
Chen, CW
;
Yan, ST
The effect of oxygen plasma treatment on methylsilsesquiazane (MSZ) dielectric was investigated for chemical mechanical planarization (CMP) process. Oxygen plasma treatment was implemented before CMP. Experimental results have shown that the polishing rate of MSZ film with O-2 plasma pretreatment is increased as much as two order of magnitude more than that of MSZ without O-2 plasma pretreatment. Moreover, the electrical properties of post-CMP MSZ are close to those of an as-cured MSZ. These results indicate that the modified surfaces resulting from O-2 plasma treatment increase the polishing rate of MSZ. After polishing, the MSZ film still maintains a low-k quality. (C) 2004 The Electrochemical Society.
CMP of ultra low-k material porous-polysilazane (PPSZ) for interconnect applications
(2004-01-30)
Chang, TC
;
Tsai, TM
;
Liu, PT
;
Chen, CW
;
Yan, ST
In this article, we investigated the impact of chemical mechanical polishing (CMP) on an ultra low dielectric constant (ultra low-k) material Porous-Polysilazane (PPSZ) with slurries of metal polishing during interconnect manufacture process. Since the CMP processing of metals such as TaN and Cu are inevitable steps for interconnect fabrication, we have utilized two types of slurries (marked as TaN and Cu slurries) to evaluate their effects on the dielectric properties of PPSZ films. Electrical and material analyses have shown surface planarity and dielectric properties of PPSZ films will not be degraded during these metal CMP processes. This indicates that the ultra low-k PPSZ films are promising for inter-level dielectric (ILD) applications in ultra large-scale integrated circuits (ULSI) technology. (C) 2003 Elsevier B.V. All rights reserved.
Cu-penetration induced breakdown mechanism for a-SiCN
(2004-12-22)
Chen, CW
;
Liu, PT
;
Chang, TC
;
Yang, JH
;
Tsai, TM
We have investigated the leakage mechanism of amorphous SiCN (a-SiCN) films after bias-temperature-stress (BTS) with Cu electrode. The leakage current became very large and breakdown due to the Cu ions penetration after strict BTS condition. The distribution profile of Cu penetration was depicted by SIMS spectrum. It is apparent that Cu ions penetrated into the a-SiCN film and even reached to the interface between a-SiCN/Si due to BTS. The Cu ions existing in a-SiCN would be taken as trap states and could enhance the carriers to transport. The main characteristics of post-breakdown a-SiCN followed the space-charge-limited current (SCLC) mechanism at 298 K. With decreasing the temperature to 100 K, the Fowler-Nordheim tunneling dominated the conduction in medium fields. However, electrons obeyed the SCLC again in high fields (>3.3 MV/cm) at 100 K. We purpose a physical model to interpret the leakage mechanism of breakdown a-SiCN films due to Cu ions. (C) 2004 Elsevier B.V. All rights reserved.
Damage effect of fluorine implantation on PECVD alpha-SiOC barrier dielectric
(2005-08-01)
Yang, FM
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Chang, TC
;
Liu, PT
;
Chen, CW
;
Tai, YH
in this work the dielectric properties of plasma enhanced chemical vapor deposited (PECVD) amorphous SiOC (alpha-SiOC) films with various concentrations of oxygen are investigated for the barrier dielectric application. Experimental results show after fluorine (F) ion implanted into alpha-SiOC film, the leakage current in carbide film is increased due to the generation of trap centers. Afterwards, the traps can be effectively repaired after thermal annealing, leading to the decrease of leakage current further. From the extraction of the current-voltage (J-E) characteristics, the conducting mechanism of the leakage current obeys the Poole-Frenkel type behavior for intrinsic, F-implanted and thermally annealed samples. Also, the barrier height of the F-implanted and thermally annealed samples are extracted and exhibits a higher value than that of the intrinsic sample. (c) 2005 Elsevier B.V. All rights reserved.
Dielectric characteristics of low-permittivity silicate using electron beam direct patterning for intermetal dielectric applications
(2003-11-17)
Liu, PT
;
Chang, TC
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Tsai, TM
;
Lin, ZW
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Chen, CW
A direct patterning technology of low-permittivity silicate-based polymer is investigated with electron-beam lithography for multilevel interconnections. The smallest feature size of 60 nm for damascene lines can be directly patterned in the silicate film. In this direct patterning, dielectric regions exposed by electron beam are crosslinked and form desirable patterns, while the others are dissolvable in an aqueous solution containing 2.38% tetramethylammonium hydroxide. With an optimum condition of electron-beam lithography, the electron-beam-irradiated silicate exhibits superior dielectric properties than that of the furnace-cured silicate film, due to minimizing the break of Si-H bonds and moisture uptake. The explanation is in agreement with the analyses of Fourier transform infrared spectroscopy and thermal desorption spectroscopy. (C) 2003 American Institute of Physics.
Direct Patterning of low-k hydrogen silsesquioxane using X-ray exposure technology
(2003-05-01)
Chang, TC
;
Tsai, TM
;
Liu, PT
;
Mor, YS
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Chen, CW
An inorganic low-k material, hydrogen silsesquioxane (HSQ), patterned directly using X-ray exposure technology was investigated. In conventional integrated circuit integration processes, photoresist (PR) stripping with O-2 plasma and wet chemical stripper are inevitable steps. However, dielectric degradation often occurs when low-k dielectrics undergo PR stripping processes. To overcome the integration issue X-ray direct patterning is proposed. In this technology, the dielectric regions illuminated by X-ray are cross-linked and form desired patterns, while the regions without X-ray illumination are dissolvable in the solvent of HSQ solution. An optical microscope image of an HSQ linear pattern was demonstrated for the first time to verify process feasibility. (C) 2003 The Electrochemical Society.
Direct Patterning of low-k hydrogen silsesquioxane using X-ray exposure technology (vol 6, pg G69, 2003)
(2003-07-01)
Chang, TC
;
Tsai, TM
;
Liu, PT
;
Mor, YS
;
Chen, CW
Effect of carrier gas on the structure and electrical properties of low dielectric constant SiCOH film using trimethylsilane prepared by plasma enhanced chemical vapor deposition
(2004-12-22)
Cheng, YL
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Wang, Y
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Lan, JK
;
Chen, HC
;
Lin, JH
For a low dielectric constant inter-metal dielectric application, the low-k SiCOH film with a dielectric constant of 2.8-3.2 has been deposited by plasma-enhanced chemical vapor deposition (PE-CVD) with trimethylsilane (3MS), oxygen, and the carrier gas. In this work, we present the effects of the carrier gas on the characterizations of the low-k films, including reaction mechanism, the deposition rate, and the mechanical and electrical properties. According to the experimental results, the low-k film in Ar carrier gas exhibits the improvement in deposition rate, nonuniformity, leakage current, and hardness. In addition, the dielectric constant of the deposited low-k film is slightly sacrificed due to the decrease of micropores in the deposited films. (C) 2004 Elsevier B.V. All rights reserved.