Double Laser Crystallization (DLC) of 50 Nanometer and 20 Nanometer Amorphous Silicon Film for Thin Film Transistors (TFTS) Application

2005 ◽  
Author(s):  
Li Xu ◽  
Costas P. Griogoropoulos
Keyword(s):  
Electron Microscope ◽  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Silicon Film ◽  
Solidification Process ◽  
Grain Structure ◽  
Laser Crystallization ◽  
Surface Reflection ◽  
Microscope Images ◽  
20 Nm

Ultra-large grain poly-crystalline silicon has been formed in 20 nm and 50 nm amorphous silicon films by the double laser crystallization (DLC) method. Surface reflection properties of such thin films upon laser irradiation were calculated. In-situ images were captured to monitor the transient melting and solidification process of 50 nm silicon film in order to understand the crystallization induced by steep laser intensity gradients. SEM (scanning electron microscope) images of crystallized 50 nm film after Secco etch revealed grain size up to 10 m while plane-view TEM (transmission electron microscope) images of 50 nm film also showed perfect crystalline structure inside the grains. AFM (atomic force microscope) images were also taken to show the topology of the grain structure and RMS of 20 nm film.

Ni-Induced Selective Nucleation and Solid Phase Epitaxy of Large-Grained Poly-Si on Glass

1999 ◽  
Vol 587 ◽  
Author(s):  
Rosaria A. Puglisi ◽  
Hiroshi Tanabe ◽  
Claudine M. Chen ◽  
Harry A. Atwater ◽  
Emanuele Rimini
Keyword(s):  
Amorphous Silicon ◽  
Polycrystalline Silicon ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Silicon Film ◽  
Crystallization Rate ◽  
Silicon Films ◽  
Solid Phase Epitaxy ◽  
Tem Analysis ◽  
Glass Substrates

AbstractWe investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since use of glass substrates constrains process temperatures, our approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created on undoped, 75 nm thick, amorphous silicon films, by masked implantation of Ni islands, followed by annealing at temperatures below 600 °. At this temperature, the Ni precipitates into NiSi2 particles that catalyze the transition from the amorphous to the crystalline Si phase. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns in one hour. We have studied the dependence of the crystallization rate on the Ni-implanted dose in the seed, in the 5×1015/cm3 - 1016/cm3range. The large grained polycrystalline Si films were then used as a substrate for molecular beam epitaxy (MBE) depositions of 1 [.proportional]m thick Si layers. Transmission electron microscopy (TEM) analysis showed a strong correlation between the substrate morphology and the deposited layer. The layer presented a large grain morphology, with sizes of about 4 [.proportional]m.

Laser Doping and Recrystallization for Amorphous Silicon Films by Plasma-Enhanced Chemical Vapor Deposition

2005 ◽  
Vol 475-479 ◽  
pp. 3791-3794
Author(s):  
Dong Sing Wuu ◽  
Shui Yang Lien ◽  
Jui Hao Wang ◽  
Hsin-Yuan Mao ◽  
In-Cha Hsieh ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Polycrystalline Silicon ◽  
Laser Annealing ◽  
Crystalline Silicon ◽  
Low Cost ◽  
Sol Gel ◽  
Silicon Film ◽  
Chemical Vapor ◽  
Silicon Thin Film ◽  
Laser Doping

One of the most challenging problems to develop polycrystalline silicon thin-film solar cells is the growth of crystalline silicon on foreign, low-cost and low-temperature substrates. In this paper, a laser doping technique was developed for the plasma-deposited amorphous silicon film. A process combination of recrystallization and dopant diffusion (phosphorous or boron) was achieved simultaneously by the laser annealing process. The doping precursor was synthesized by a sol-gel method and was spin-coated on the sample. After laser irradiation, the grain size of the doped polycrystalline silicon was examined to be about 0.5~1.0 µm. The concentrations of 2×1019 and 5× 1018 cm-3 with Hall mobilities of 92.6 and 37.5 cm²/V-s were achieved for the laser-diffused phosphorous- and boron-type polysilicon films, respectively.

Seed-Induced Crystallization of Amorphous Silicon for the Formation of Large-Grain Poly-Crystalline Silicon

2010 ◽  
Author(s):  
Jason Trask ◽  
Lin Cui ◽  
Andrew J. Wagner ◽  
K. Andre Mkhoyan ◽  
Uwe Kortshagen
Keyword(s):  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Amorphous Film ◽  
Average Crystallite Size ◽  
Dark Conductivity ◽  
Film Deposition ◽  
Grain Structure ◽  
Crystallization Time ◽  
Silicon Thin Films ◽  
Initial Seed

A new method for reducing crystallization time of hydrogenated amorphous silicon thin films and more successfully controlling grain structure has been studied through seeding of the bulk matrix with nanocrystallites during film deposition. Films were deposited by a system in which crystallites and amorphous film were synthesized in separate RF-powered plasmas. Average crystallite size was confirmed to be 20 to 50 nm via TEM imaging. Several films with various initial crystallite population densities were produced, and their crystallization kinetics were studied via Raman spectroscopy throughout a staged annealing process. Seeded films consistently displayed a characteristic crystallization time less than the incubation time of unseeded control films. Furthermore, films with larger initial seed densities exhibited earlier crystallization onset. A separate study also was performed in which the dark conductivity was compared between films re-crystallized from various initial seed densities.

High Performance Thin Film Transistors (TFTs) of Polycrystalline Silicon Crystallized by the Double Laser Crystallization (DLC) Technique

2005 ◽  
Author(s):  
Li Xu ◽  
Costas P. Grigoropoulos
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
High Performance ◽  
Crystalline Silicon ◽  
Solidification Process ◽  
Electrical Performance ◽  
Laser Crystallization ◽  
Definition Of ◽  
Melting And Solidification

Ultra-large grain poly-crystalline silicon has been formed by the double laser crystallization (DLC) method. In-situ images were captured to monitor the transient melting and solidification process in order to understand the crystallization induced by steep laser intensity gradients. SEM (scanning electron microscope) images of crystallized film after Secco etch revealed grain size up to 10μm. High performance thin film transistors (TFTs) were fabricated on the DLC-made poly-crystalline material. The highly localized crystal growth and well-defined orientation allowed precise definition of channels on large grains. The electrical performance of the fabricated devices was studied, indicating a field-effect mobility in the saturation range of undoped channel of 124 cm2/V.sec, threshold voltage of 0.2V and on-off current ratio of 1E8 for n-type devices.

A Simple Lateral Grain Growth of Poly-Si by Single Excimer Laser Crystallization of Amorphous Silicon Film Deposited on Polygon Shaped Trench

2003 ◽  
Vol 762 ◽  
Author(s):  
Sang-Hoon Jung ◽  
Su-Hyuk Kang ◽  
Hee-Sun Shin ◽  
Min-Koo Han
Keyword(s):  
Amorphous Silicon ◽  
Grain Growth ◽  
Excimer Laser ◽  
Silicon Film ◽  
Acute Angle ◽  
Molten Silicon ◽  
Laser Crystallization ◽  
Amorphous Silicon Film ◽  
Excimer Laser Irradiation ◽  
Excimer Laser Crystallization

AbstractA simple lateral grain growth of polysilicon employing single excimer laser irradiation is proposed. In order to increase the size of silicon grain and to control the location of the large lateral grain, the oxide trench is employed under the amorphous silicon film in the proposed method. The proposed oxide trench, which is shaped like a triangle or a polygon with an acute angle, induces temperature gradient on the molten silicon film during the solidification. It was verified by SEM that about 2 μm-long silicon grains are successfully achieved near the oxide trench edge and the locations of lateral grains are controlled by the angular points of the diagram.

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