Solid Phase Crystallization Method Research Articles

Effect of Sn on crystallinity and electronic property of low temperature grown polycrystalline-Si1−x−yGexSny layers on SiO2

We examined the formation of polycrystalline-Si1−x−yGexSny layers on SiO2 by the solid phase crystallization method. We investigated the impact of Sn incorporation on the polycrystallization, crystallinity, and electrical property of Si1−xGex layers. We found that the polycrystallization time of Si1−x−yGexSny decreases with increasing in the Sn content in the annealing at 500°C. No Sn precipitation is observed after the crystallization of Si1−x−yGexSny layer with an Sn content of 2%, while severe Sn precipitation is found in the sample with an Sn content of 10%. Moreover, larger grains of polycrystal can be obtained by the incorporation of 2%-Sn with comparison to that without Sn. The enlargement of polycrystalline grain of Si1−x−yGexSny improves in the hole mobility to 74cm2/Vs.

Advanced Si solid phase crystallization for vertical channel in vertical NANDs

The advanced solid phase crystallization (SPC) method using the SiGe/Si bi-layer structure is proposed to obtain high-mobility poly-Si thin-film transistors in next generation vertical NAND (VNAND) devices. During the SPC process, the top SiGe thin film acts as a selective nucleation layer to induce surface nucleation and equiaxial microstructure. Subsequently, this SiGe thin film microstructure is propagated to the underlying Si thin film by epitaxy-like growth. The initial nucleation at the SiGe surface was clearly observed by in situ transmission electron microscopy (TEM) when heating up to 600 °C. The equiaxial microstructures of both SiGe nucleation and Si channel layers were shown in the crystallized bi-layer plan-view TEM measurements. Based on these experimental results, the large-grained and less-defective Si microstructure is expected to form near the channel region of each VNAND cell transistor, which may improve the electrical characteristics.

Characterization of polycrystalline silicon-oxide-nitride-oxide-silicon devices on a SiO2 or Si3N4 buffer layer

Silicon-oxide-nitride-oxide-silicon (SONOS) memory devices were fabricated from polycrystalline silicon (poly-Si) using the solid phase crystallization (SPC) method for use in a low-power system-on-panel (SOP) display. In these poly-Si SONOS memories, oxide or nitride was used as a buffer layer. The electrical characteristics, such as the threshold voltage (VT), subthreshold slope (SS) and transconductance (gm), were determined for each SONOS device. To interpret the characteristics of both poly-Si devices, x-ray diffraction (XRD) measurements and flicker noise analysis were conducted. The results show that the poly-Si SONOS on the oxide layer has better electrical, memory characteristics, such as turn-on speed and gm, program/erase, endurance and data retention than that on the nitride layer. From the XRD measurements, it is shown that the grain size of the poly-Si on the oxide layer is larger than that on the nitride layer. From the flicker noise analysis, the poly-Si device on oxide was shown to have less traps or defects in the channel layer than that on nitride.

Characteristics of Schottky-barrier source/drain metal-oxide-polycrystalline thin-film transistors on glass substrates

Polycrystalline-silicon (poly-Si) Schottky-barrier thin-film transistors (SB-TFTs) with Ptsilicided source/drain junctions were fabricated on glass substrates, and the electrical characteristics were examined. The amorphous silicon films on glass substrates were converted into high-quality poly-Si by using excimer laser annealing (ELA) and solid phase crystallization (SPC) methods. The crystallinity of poly-Si was analyzed by using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analysis. The silicidation process was optimized by measuring the electrical characteristics of the Pt-silicided Schottky diodes. The performances of Pt-silicided SB-TFTs using poly-Si films on glass substrates and crystallized by using ELA and SPC were demonstrated. The SB-TFTs using the ELA poly-Si film demonstrated better electrical performances such as higher mobility (22.4 cm2/Vs) and on/off current ratio (3 × 106) and lower subthreshold swing value (120 mV/dec) than the SPC poly-Si films.

Steam Reforming of Glycerol into Hydrogen Over Nano-Size Ni-Based Hydrotalcite-Like Catalysts

Steam reforming (SR) of glycerol for the production of hydrogen was investigated over the nano-sized Ni-based catalysts. The Ni-based catalysts were prepared by solid phase crystallization and impregnation methods, and characterized by N2 physisorption, CO chemisorption, XRD, SEM, and TEM techniques. The Ni/gamma-Al2O3 catalyst showed higher conversion and H2 selectivity. However, it was slowly deactivated due to the carbon formation on the surface of catalyst and the sintering. It was found that the Ni based hydrotalcite-like catalyst (spc-Ni/MgAl) showed higher catalytic activity to prevent carbon formation than Ni/gamma-Al2O3 catalyst in the SR of glycerol.

Studies on the conversion of glycerol to 1,2-propanediol over Ru-based catalyst under mild conditions

The effects of support in Ru-supported catalyst on the conversion of glycerol and selectivity of 1,2-propanediol (1,2-PDO) were investigated in the hydrogenolysis of glycerol. The Ru-based catalysts were prepared by solid phase crystallization and impregnation methods in order to improve 1,2-PDO selectivity. The prepared catalysts were characterized by N 2 physisorption, CO chemisorption, XRD, TPR, NH 3-TPD and TEM techniques. The catalytic hydrogenation of glycerol was investigated at 453 K, initial H 2 pressure of 2.5 MPa and 20 wt% glycerol aqueous solution for 18 h. It was found that the 5 wt% Ru–CaZnMg/Al catalyst prepared by the solid phase crystallization and impregnation methods showed higher catalytic performance than the other catalysts. The glycerol conversion and 1,2-PDO selectivity obtained were 50% and 85%, respectively. It was found that the selectivity of 1,2-PDO increased with the acidity of catalyst.

Boron induced recrystallization of amorphous silicon film by a rapid thermal process

Rapid thermal process (RTP) is to induce boron-doped amorphous silicon into a high degree of crystallization of polycrystalline silicon in 5 min. In addition to the short time characteristic, it also provides a relatively lower temperature route to prepare high percentage of polycrystalline silicon in comparison with solid phase crystallization method. Before RTP, boron is homogeneously doped into the amorphous silicon film by ion implantation technology. After rapid thermal processing, the grain size of the polycrystalline silicon was found about at 0.1–0.5 μm. The degree crystallization of silicon is reached up to 99.1% with a good hole mobility of 138.6 cm²/V s.

Hydrogen-doped In2O3 transparent conducting oxide films prepared by solid-phase crystallization method

We have characterized amorphous to crystalline transformation of hydrogen (H)-doped In2O3 (In2O3:H) films by transmission electron microscopy, thermal desorption spectroscopy, spectroscopic ellipsometry, and Hall measurements. The In2O3:H films that show a mixed-phase structure embedded with small density of crystalline grains in a large volume fraction of amorphous phase have been fabricated at room temperature by the sputtering of an In2O3 ceramic target with introduction of H2O vapor, and the films have been postannealed in vacuum to crystallize the amorphous phase. With increasing annealing temperature up to 200 °C, the film shows a large increase in Hall mobility (μHall) from 42 to 110 cm2/V s and a decrease in carrier density (NHall) from 4.6×1020 to 2.1×1020 cm−3 with slight decrease in resistivity. The change in μHall and NHall with annealing temperature is strongly correlated with the volume fractions of the amorphous and crystalline phases in the films. Analyses of dielectric functions of the films using the Drude model revealed that the high electron mobility in the crystallized films is attributed mainly to longer relaxation time rather than smaller effective mass, as compared with as-deposited films. Temperature-dependent Hall analysis, relationship between NHall and μHall, and comparison between μHall and optical mobility showed that (i) scattering processes inside amorphous and/or crystalline matrices limit the mobility, (ii) doubly charged ionized impurity scattering is reduced by crystallization, and (iii) phonon scattering becomes dominant after crystallization in the In2O3:H films. The above results suggest that H-doping reduces carrier scattering in the crystallized In2O3:H and structural rearrangements during crystallization eliminate oxygen deficiency and generate H+ that acts as a singly charged donor. In this article, we discuss the transport properties with the variation in microscopic and chemical structures in the In2O3:H films.

New Crystallization Method of Amorphous Silicon by Selective Area Heating for Stamp Process

We propose a new crystallization technique called selective area heating. In this study, we investigated a new technique for high-reliability selective area crystallization of a-Si films that does not cause thermal damage to glass substrates. We reduced the crystallization time as compared to the conventional solid phase crystallization method using a stamp-type isolated thin heater. The thin heater was fabricated with a layer of Pt on a quartz substrate via Ta adhesion and capping layers. A crystalline transverse optic phonon peak at about 519 cm−1 was seen in Raman scattering spectra, showing that the films were crystallized. The poly-Si grain size was found to be smaller than 100 nm, and the dendritic structure was found using scanning electron microscopy.

Electrical properties of poly-Ge on glass substrate grown by two-step solid-phase crystallization

The carrier concentration and mobility of intrinsic holes in poly-Ge films grown by solid-phase crystallization (SPC) were investigated. The two-step SPC method, consisting of low-temperature annealing (425 °C) to obtain large grains and subsequent high-temperature annealing (500 °C) to decrease defects, is proposed. The hole concentration remarkably decreased from 1 × 10 18 to 5 × 10 17cm −3 with keeping a high-mobility (140 cm 2/Vs) after post-annealing.

플레티늄-실리사이드를 이용한 쇼트키 장벽 다결정 박막 트랜지스터

Schottky barrier thin film transistors (SB-TFT) on polycrystalline silicon(poly-Si) are fabricated by platinum silicided source/drain for p-type SB-TFT. High quality poly-Si film were obtained by crystallizing the amorphous Si film with excimer laser annealing (ELA) or solid phase crystallization (SPC) method, The fabricated poly-Si SB-TFTs showed low leakage current level and a large on/off current ratio larger than 10), Significant improvement of electrical characteristics were obtained by the additional forming gas annealing in 2% <TEX>$H_2/N_2$</TEX> ambient, which is attributed to the termination of dangling bond at the poly-Si grain boundaries as well as the reduction of interface trap states at gate oxide/poly-Si channel.

Fabrication of n- and p-Channel Schottky Barrier Thin-Film Transistors Crystallized by Excimer Laser Annealing and Solid Phase Crystallization Methods

Schottky barrier thin-film transistors (SB-TFT) based on polycrystalline silicon (poly-Si) films crystallized by solid phase crystallization (SPC) and excimer laser annealing (ELA) methods were fabricated for system-on-glass (SOG) application. The structure of poly-Si films by ELA and SPC methods was analyzed. The formations of platinum silicide and erbium silicide were developed for p- and n-channel metallic junctions, respectively. The fabricated SB-TFTs have a large on/off current ratio with a low leakage current. The effects of forming gas annealing (FGA) in 2% H2/N2 gas ambient were evaluated. As a result of FGA, significant improvements of electrical characteristics were obtained due to reduction of trap states.

9.3: 15‐inch AMOLED Display with SPC TFTs and a Symmetric Driving Method

AbstractWe have developed a new 15.0‐inch AMOLED display. An advanced Solid Phase Crystallization (a‐SPC) method was employed for the increase of uniformity and reliability of TFTs. A new pixel was proposed for the compensation of I×R voltage drop in power line and a symmetric driving scheme was also developed for the reduction of short term image sticking problem.

Excimer Laser Annealing 결정화 방법 및 고유전 게이트 절연막을 사용한 poly-Si TFT의 특성

The electrical characteristics of polycrystalline silicon (poly-Si) thin film transistor (TFT) crystallized by excimer laser annealing (ELA) method were evaluated, The polycrystalline silicon thin-film transistor (poly-Si TFT) has higher electric field-effect-mobility and larger drivability than the amorphous silicon TFT. However, to poly-Si TFT's using conventional processes, the temperature must be very high. For this reason, an amorphous silicon film on a buried oxide was crystallized by annealing with a KrF excimer laser (248 nm)to fabricate a poly-Si film at low temperature. Then, High permittivity <TEX>$HfO_2$</TEX> of 20 nm as the gate-insulator was deposited by atomic layer deposition (ALD) to low temperature process. In addition, the solid phase crystallization (SPC) was compared to the ELA method as a crystallization technique of amorphous-silicon film. As a result, the crystallinity and surface roughness of poly-Si crystallized by ELA method was superior to the SPC method. Also, we obtained excellent device characteristics from the Poly-Si TFT fabricated by the ELA crystallization method.

Application of HfO2 high-k gate insulator for excimer laser annealed poly-Si TFT

The electrical characteristics of polycrystalline silicon (poly-Si) thin film transistor (TFT) crystallized by excimer laser annealing (ELA) method with high-k gate dielectrics were evaluated. Because a high thermal budget is inevitable for conventional fabricating process of poly-Si TFTs, an amorphous silicon film on a buried oxide was crystallized by annealing with a KrF excimer laser (248) to fabricate a poly-Si film at low temperature. Furthermore, the high permittivity HfO2 film with a thickness of 20 nm as the gate-insulator was deposited by atomic layer deposition (ALD) to low temperature process. In addition, the solid phase crystallization (SPC) was compared to the ELA method as a crystallization technique of amorphous-silicon film. As a result, the crystallinity and surface roughness of poly-Si crystallized by ELA method was superior to the SPC method. Also, we obtained excellent device characteristics from the poly-Si TFT fabricated by the ELA crystallization method.

Improved Performance of F-Ions-Implanted Poly-Si Thin-Film Transistors Using Solid Phase Crystallization and Excimer Laser Crystallization

Polycrystalline silicon thin-film transistors (Poly-Si TFTs) with F-ions-implantation were investigated in this study. The electrical characteristics and reliability of the F-ions-implanted poly-Si TFTs were reported for solid phase crystallization (SPC) and excimer laser crystallization (ELC) methods respectively. The thermal annealing causes F-ions to pile up at the poly-Si interface, without the initial pad oxide deposition. With the introduction of fluorine in poly-Si film, the trap state density was effectively reduced. Also, the presence of strong Si-F bonds enhances electrical endurance against hot carrier impact by using F-ions-implantation. These improvements in electrical characteristics are even obvious for the ELC poly-Si TFTs compared to the SPC ones

Investigation of potential and compositional fluctuations in CuGa 3Se 5 crystals using photoluminescence spectroscopy

We studied the photoluminescence (PL) properties of the ordered defect compound CuGa 3Se 5. Different single crystals were grown by the vertical Bridgman method and by the solid phase crystallization method. Their crystal structure and cell parameters were determined by X-ray diffraction. The PL spectra were recorded at T = 10–300 K. Also, laser power dependences were studied. We found an asymmetric PL band at 1.76 eV. PL band shifts towards higher energies with increasing laser power. The shape and properties of this band assure the presence of potential and compositional fluctuations. The influence of both fluctuations on the PL properties of CuGa 3Se 5 is studied and the radiative recombination processes are explained.

Partial oxidation of CH4 to synthesis gas using Ni-catalyst/Au|YSZ|Ag electrochemical membrane reactor

Spc-Ni/MgAl (spc-: solid phase crystallization method) catalyst has been prepared from Mg–Al hydrotalcite-like compounds containing Ni at the Mg site as the precursors and successfully used as a catalyst on an electrochemical membrane reactor for partial oxidation of CH4 at 1173K. The precursors based on [Mg2+A1−xl3+(OH)2x]x+(CO3−)x·mH2O, in which a ratio of Mg/Al varied and a part of Mg2+ ions were replaced by Ni2+ ions, were prepared by co-precipitation method, thermally decomposed, calcined and reduced to spc-Ni/MgAl catalyst. The electrochemical reactor, using yttria-stabilized zirconia (YSZ) as a solid electrolyte, has been employed as an oxygen permeable membrane reactor. The Ni catalyst coupled with Au paste was used as the catalyst-anode, while Ag paste was used as the cathode of the electrochemical cell. The reaction was carried out over the catalyst-anode film under oxygen pumping through the YSZ, and the results were compared with those obtained by various supported Ni catalysts prepared by impregnation (imp-) method. Spc-Ni/MgAl catalysts showed higher activity than imp-Ni catalysts and the best composition of metals in the catalyst was spc-Ni0.5/Mg2.5Al. This catalyst showed the CH4 conversion following the thermodynamic equilibrium between 1023 and 1173K, while the other catalysts of different compositions or imp-Ni catalysts showed a clear decrease in the CH4 conversion with decreasing temperature. Moreover, spc-Ni0.5/Mg2.5Al catalyst showed stable activity during the reaction for 40h. It is concluded that the high and stable activity for the partial oxidation of CH4 is due to highly dispersed and stable Ni metal particles formed on spc-Ni0.5/Mg2.5Al catalyst film.

Autothermal reforming of CH 4 over supported Ni catalysts prepared from Mg–Al hydrotalcite-like anionic clay

spc-Ni/MgAl (spc: solid-phase crystallization method) catalysts have been prepared from Mg–Al hydrotalcite-like compounds containing Ni at the Mg site as the precursors and tested for partial oxidation of CH 4 into synthesis gas. The precursors based on [Mg 2+ 1− x Al 3+ x (OH) 2] x+ (CO 3 − x ) mH 2O, in which a ratio of Mg/Al varied and a part of the Mg 2+ ions were replaced by Ni 2+ ions, were prepared by a coprecipitation method, thermally decomposed, and reduced to form spc-Ni/MgAl catalyst. Surface areas of spc-Ni/MgAl catalysts were around 150 m 2 g cat −1. Ni 2+ ions first substituted a part of the Mg 2+ sites in the Mg–Al hydrotalcite-like compounds and then incorporated in the rock-salt-type Mg–Ni–O solid solutions in the mixed oxide after the decomposition. The dispersion of Ni was thus repeatedly enhanced during the spc preparation, resulting in the highly dispersed Ni metal particles after the reduction. The activity of the spc-Ni/MgAl catalyst was the highest at the ratio of Mg/Al of 1/3. When the catalysts were tested in the partial oxidation of CH 4, spc-Ni 0.5/Mg 2.5Al afforded enough high CH 4 conversion even at the high space velocity (9×10 5 ml h −1 g cat −1), exceeding the value obtained over 1 wt% Rh/MgO. Ni species on spc-Ni 0.5/Mg 2.5Al catalysts were stable even under the presence of O 2, while Ni catalysts prepared by the conventional impregnation quickly lost activity due to the surface oxidation of Ni particles. Moreover, the total heat produced by the reaction was the lowest over the spc-Ni 0.5/Mg 2.5Al catalyst among the catalysts tested. This strongly suggests that the heat of exothermic CH 4 combustion to H 2O and CO 2 could be quickly consumed by the following endothermic CH 4 reforming by H 2O and CO 2 over spc-Ni 0.5/Mg 2.5Al. Thus, the spc-Ni 0.5/Mg 2.5Al catalyst is a hopeful candidate for the autothermal reforming of CH 4 which can be carried out under the copresence of both H 2O and O 2 to feed H 2 to the fuel cell economically. Actually the autothermal reforming of CH 4 has been successfully carried out over spc-Ni 0.5/Mg 2.5Al catalysts.

2-26.ハイドロタルサイトを前駆体とする高分散担持Ni触媒の調製とそのメタン改質反応への応用((8)転換利用I,Session 2 天然ガス・メタンハイドレート等)

2-26.ハイドロタルサイトを前駆体とする高分散担持Ni触媒の調製とそのメタン改質反応への応用((8)転換利用I,Session 2 天然ガス・メタンハイドレート等)