Ni-induced Lateral Crystallization Research Articles

Three-Dimensionally Orientation-Controlled Ge Rods on an Insulator Formed by Low-Temperature Ni-Induced Lateral Crystallization

Three-Dimensionally Orientation-Controlled Ge Rods on an Insulator Formed by Low-Temperature Ni-Induced Lateral Crystallization

Asymmetric Low Metal Contamination Ni-Induced Lateral Crystallization Polycrystalline-Silicon Thin-Film Transistors With Low OFF-State Currents for Back-End of Line (BEOL) Compatible Devices Applications

In this work, polycrystalline-silicon thin-film transistors (poly-Si TFTs) with asymmetric low metal contamination Ni-induced lateral crystallization (LC-NILC) poly-Si channel and high- $\kappa $ HfO2 gate insulator (GI) have been successfully fabricated and demonstrated for the first time. The amounts of Ni diffused into the poly-Si film can be effectively reduced by Ni removal processes prior to NILC. The asymmetric LC-NILC poly-Si TFTs exhibit higher field-effect mobility ( $\mu _{\mathrm{ FE}}$ ), steeper ideal subthreshold swing (S.S.), larger ON/OFF currents ratio ( $\text{I}_{\mathrm{ ON}}/\text{I}_{\mathrm{ OFF}}$ ), better uniformity, and improved C-V curves compared to traditional NILC (T-NILC) poly-Si TFTs owing to better crystallization quality and less low metal contamination. These remarkable device characteristics and the matched complementary TFTs (C-TFTs) electrical characteristics with low $\text{I}_{\mathrm{ OFF}}$ and low operation voltages make the asymmetric LC-NILC poly-Si TFTs promising for the future back-end of line (BEOL) compatible devices applications in monolithic three-dimension integrated circuits (3D-ICs).

Ni-Induced Lateral Fast Crystallization of Amorphous Silicon Film by Microwave Annealing

Polycrystalline Si (poly-Si) thin films for application to display devices and solar cell are generally fabricated by crystallizing amorphous Si (a-Si) thin film precursors. In this paper, studies on Ni-induced lateral crystallization of a-Si thin films by microwave annealing at low temperature were reported. The crystallization of a-Si thin films was enhanced by applying microwaves to the films. The poly-Si films were invested by Optical Microscopy, X-ray Diffraction (XRD) , Raman Spectroscopy and Scanning Electron Microscope(SEM). After processing of Ni-induced lateral crystallization by microwave annealing above 500°C, the a-Si has begun to be crystallized with large grains having the main (111) orientation. The rate of crystallization at 550°C is about 0.033μm/min. Compared to Ni-induced lateral crystallization by conventional furnace annealing, Ni-induced lateral crystallization by microwave annealing both lowers the crystallization temperature and reduces the time of crystallization. The crystallization mechanism during microwave annealing was also studied. The technique that combines Ni-induced lateral crystallization with microwave annealing has potential applications in thin-film transistors (TFT’s) and solar cell.

Physical Analysis of Electric Field Effect on Metal-Induced Crystallization of a-Si

Amorphous silicon (a-Si) film crystallized by Ni-induced lateral crystallization under static electric field was analyzed. It has been demonstrated that Ni-induced lateral crystallization of a-Si is directional with electric field. Moreover, there exists a critical value of electric field strength, below which the rate of Ni-induced lateral crystallization of a-Si increases remarkably with the increase of field strength, while above which the rate will decrease instead. This phenomenon can be interpreted well based on electromigration effect.

Effect of Ni Thickness on Off-State Currents of Poly-Si TFTs Using Ni-Induced Lateral Crystallization of Amorphous Silicon

We have studied the effect of metal thickness for the metal-induced lateral crystallization (MILC) of a-Si on the off-state currents of poly-Si thin-film transistors (TFTs). It is found that they decrease with decreasing the Ni thickness for MILC. The Ni-MILC poly-Si TFT with the Ni area density of 1.4 X 10 14 cm -2 exhibited a field-effect mobility of 53.5 cm 2 /Vs and minimum leakage current of 0.44 pA/μm at V ds = -10 V. However, the off-state current is 6.6 pA/μm when the Ni density is 9.2 X 10 15 cm -2 , corresponding to the average Ni thickness of 10 A. It is concluded that the average Ni thickness for MILC should be less than 0.79 A to have low off-state currents from our experimental data.

A very low temperature single crystal germanium growth process on insulating substrate using Ni-induced lateral crystallization for three-dimensional integrated circuits

Metal (Ni)-induced lateral crystallization (MILC) of amorphous (α)-germanium (Ge) films on silicon dioxide (SiO2) is investigated on α-Ge planar films, annealing at 350–380°C in a N2 ambient. MILC is not observed after annealing for 1h at 350°C, and self-nucleation with its small, deleterious microcrystals plagues the process at 380°C. 360°C is determined to be an optimum annealing temperature. These conditions are subsequently applied to a patterned nanowire to obtain a single-crystal Ge wire on SiO2. The method is promising for integrating high quality Ge transistors at low temperatures as required by three-dimensional integrated circuits.

Microstructural Characterization of Polycrystalline Si Films Grown by Vapor-Induced Crystallization of Amorphous Si Using Al ∕ Ni Chloride

A polycrystalline Si film with uniform and large grains can be grown by crystallizing with chloride vapor transport. At the initial stage of crystallization, the poly-Si grains had round-shaped cores with needles at the growth front. It showed that the needles were grown by the Ni-induced lateral crystallization process and the sidewall of the needles was enlarged by the Al-induced crystallization process. The needles were emerged coherently to an extent by the sidewall growth. As a result, a poly-Si film with grains larger than and fewer intragrain defects was obtained. The Ni concentration was constant through out the film thickness with a value of . The Al concentration at the surface was and was reduced below at 25 -nm depth. The thin film transistor utilizing the film showed an electron mobility of at a drain voltage of . But the threshold voltage was that is considered as relatively high due to Al doping.

Effects of oxygen in Ni films on Ni-induced lateral crystallization of amorphous silicon films at various temperatures

Effects of oxygen in Ni films on the Ni-induced lateral crystallization (NILC) of amorphous silicon (a-Si) films at various temperatures have been investigated. It was found that oxygen in Ni films retarded the nucleation of polycrystalline silicon (poly-Si) from a-Si, but had little effect on the growth rate of poly-Si. This is because that needed an incubation period to be reduced to Ni metal for the subsequent mediated crystallization of a-Si.

Performances of Ni-Induced Lateral Crystallization Thin Film Transistors with and Needle Grains

Thin-film transistors (TFTs) fabricated using <111 > and <112 > needle grains have been investigated. They were fabricated by Ni–metal-induced lateral crystallization and Ni–metal imprint-induced crystallization method. It is found that the performance of 112-TFT was far superior to that of 111-TFT. The device transfer characteristics of 112-TFT include 2.6-fold-higher field-effect mobility (µFE), 4-fold-higher on/off current ratio (Ion/Ioff), and 2.4-fold-lower leakage current (Ioff) compared with those of the 111-TFT.

Ge-dot/Si multilayered structures through Ni-induced lateral crystallization

We demonstrate a method for fabricating high-quality Ge-dot/Si multilayered structures. High-density self-assembled Ge dots are grown on amorphous Si layer periodically by low-pressure chemical vapor deposition, and then the amorphous Si are crystallized through Ni-based metal-induced lateral crystallization. Optical microscopy, micro-Raman spectroscopy, and electron microscopy observations reveal that the crystallized Si film has large leaflike grains elongated along the lateral crystallization direction, which shows (110) preference. Furthermore, this preference is found to deliver to different Si layers. The strain shift of Ge dots deduced from Raman spectroscopy reveals a formation of a high-quality interface between the crystallized Si and Ge dot.

Ge‐dots/Si multilayered structures fabricated by Ni‐induced lateral crystallization

AbstractWe report on the fabrication of high‐quality Ge‐dots/Si multilayered structure films by metal‐induced lateral crystallization (MILC). Ge dots are self‐assembled grown on amorphous Si layer using low‐pressure chemical vapor deposition, and then low‐temperature crystallization is carried out by Ni‐based MILC processing. The micro Raman spectroscopy, optical microscopy and electron microscopy observations reveal that the crystallized Si film has large leaf‐like grains elongated along the MILC direction with (110) preference. Moreover, the strain shift of Ge dots reflects the formation of high quality interface between the crystallized Si and Ge dot. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Ni触媒誘起固相成長法を用いた次世代TFT用多結晶Si1-xGex(0≦x≦1)薄膜の低温形成

Development of new semiconductors with high carrier mobility is strongly needed to realize future system-in-displays. To achieve this, we have been investigating low-temperature crystallization of a-Si1-xGex (0≤x≤1) on insulating films. Present paper focuses our recent progress of the Ni-induced lateral crystallization of a-Si1-xGex (0≤x≤1). Effects of the Ge fraction and the electric field on the growth characteristics are discussed.

Effect of Pd Addition on Ni-Induced Lateral Crystallization and Poly-Si TFTs

The effect of Pd addition to a Ni layer on the metal-induced lateral crystallization (MILC) and the performance of poly-Si thin-film transisters (TFTs) were studied. By adding 5 atom % Pd, the growth rate of Ni-ILC was faster two times than that of pure Ni-ILC without the degradation of TFTs. The minimum leakage current of TFTs was reduced from 7.5 X 10 - 1 0 to 3.6 X 10 - 1 0 A at V d - 10 V. But further addition of Pd worsened the properties of TFTs. These results were in accord with the microstructural variation of MILC poly-Si as the concentration of Pd.

Device Characteristics of Polysilicon Thin-Film Transistors Fabricated by Electroless Plating Ni-Induced Crystallization of Amorphous Si

Compared with conventional solid phase crystallized (SPC) thin-film transistors (TFTs), metal-induced laterally crystallized (MILC) TFTs exhibit significantly enhanced performance. Metal films are usually deposited by the physical vapor deposition (PVD) method, which is time-consuming and expensive in terms of equipment cost. In this work, a simpler electroless plating Ni was introduced to replace PVD Ni. It was found that the morphologies and the device characteristics of Ni-induced lateral crystallization TFT were as good as those of PVD Ni-induced lateral crystallization TFT.

Influence of doping concentration on Ni-induced lateral crystallization of amorphous silicon films

Nickel-metal-induced lateral crystallization (MILC) was used to fabricate polycrystalline silicon thin films on glass substrates. Patterned Ni lines were formed on amorphous Si films by a lift-off process using photo resist. The samples were annealed in an N2 atmosphere in a furnace at temperatures ranging from 5501C to 6001C. Both the doping concentration of the Si films and the annealing temperature strongly affected the orientation of the crystals. A p-type poly-Si film with a boron concentration of 5 � 10 19 cm � 3 annealed at 5501C was found to be strongly oriented in the / 22 0S direction. r 2002 Elsevier Science B.V. All rights reserved.

Defined crystallization of amorphous-silicon films using contact printing

Patterned Ni layers are printed on amorphous-silicon (a-Si) films and, during this printing, the metal patterns induce lateral crystallization of the precursor a-Si layer. The printing process consists of simultaneously pressing the Ni printing plate to an a-Si layer and annealing at 550 °C. Printing times of 1 and 3 h are explored. The growth rate of the Ni-induced lateral crystallization is about 8 μm/h in this process. After this printing, Raman spectra show that the resulting polycrystalline-silicon (poly-Si) regions have the characteristic transverse-optical 519 cm−1 phonon peak typical of crystalline silicon. The nonprinted, noncrystallized a-Si areas have the Raman signature of a-Si; i.e., they do not have any peak. The resulting laterally crystallized Si area shows a morphological texture (i.e., a strip-like morphology) originating from the printed Ni area and growing in one direction in transmission electron microscope imaging. In terms of the selective area diffraction pattern (i.e., diffraction spot position and crystal structure), the signature of the area directly contacted by the Ni cannot be distinguished from that of the surrounding laterally crystallized silicon film. This printing approach can be used for channel crystallization/device isolation resulting in a saving of device fabrication steps.