A new low temperature crystallization method for poly-Si TFTs was developed: Metal-Induced Lateral Crystallization (MILC). The a-Si film in the channel area of a TFT was laterally crystallized from the source/drain area, on which an ultrathin nickel layer was deposited before annealing. The a-channel poly-Si TFTs fabricated at 500/spl deg/C by MILC showed a mobility of 121 cm/sup 2//V/spl middot/s, a threshold voltage of 1.2 V, and an on/off current ratio of higher than 10/sup 6/. These electrical properties are much better than TFTs fabricated by conventional crystallization at 600/spl deg/C.

Low temperature poly-Si thin-film transistor fabrication by metal-induced lateral crystallization

An active matrix display device having a pixel structure in which pixel electrodes, gate wirings and source wirings are suitably arranged in the pixel portions to realize a high numerical aperture without increasing the number of masks or the number of steps. The device comprises a gate electrode and a source wiring on an insulating surface, a first insulating layer on the gate electrode and on the source wiring, a semiconductor layer on the first insulating film, a second insulating layer on the semiconductor film, a gate wiring connected to the gate electrode on the second insulating layer, a connection electrode for connecting the source wiring and the semiconductor layer together, and a pixel electrode connected to the semiconductor layer.

Semiconductor Device and Method of Fabricating the Same

An object is to provide a method for manufacturing a semiconductor device, in which the number of photolithography steps can be reduced, the manufacturing process can be simplified, and manufacturing can be performed with high yield at low cost A method for manufacturing a semiconductor device includes the following steps: forming a semiconductor film; irradiating a laser beam by passing the laser beam through a photomask including a shield for shielding the laser beam; subliming a region which has been irradiated with the laser beam through a region in which the shield is not formed in the photomask in the semiconductor film; forming an island-shaped semiconductor film in such a way that a region which is not irradiated with the laser beam is not sublimed because it is a region in which the shield is formed in the photomask; forming a first electrode which is one of a source electrode and a drain electrode and a second electrode which is the other one of the source electrode and the drain electrode; forming a gate insulating film; and forming a gate electrode over the gate insulating film

Method for Manufacturing Semiconductor Device

This letter reports on the experimental findings, and provides a theoretical description of the super lateral growth (SLG) phenomenon observed in the pulsed laser‐induced solidification of amorphous thin Si films on SiO2. Experimentally, we report and elaborate on the isolated single‐crystal disk structure that is observed at the upper threshold of the SLG regime; the structure is revealed as an important microstructural feature for understanding the phenomenon. A theoretical discussion of the SLG phenomenon is provided in terms of the key factors that are suggested by our model—the interface response function of the solid, the nucleation kinetics of the solid, and a highly transient lateral‐thermal profile near the solid‐melt interface. Our model and analysis point out the important inadequacies associated with the vertical solidification rate/temperature gradient model, which is currently being utilized to explain the excimer laser crystallization of thin Si films on SiO2.

On the super lateral growth phenomenon observed in excimer laser-induced crystallization of thin Si films

Dependence of the sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques

By both numerical simulation and experimental investigation, we found it possible to enlarge the grain size (?3000 ?) of polycrystalline silicon (poly-Si) films by excimer laser annealing, using a new method to control the solidification process of molten Si - low-temperature (?400?C) substrate heating during laser annealing. Poly-Si thin-film transistors (TFTs) fabricated by this new excimer laser annealing method showed a high field-effect mobility of 230 cm2/V?s, and good uniformity of field-effect mobility (?10%) within the effective laser irradiation area.

https://iopscience.iop.org/article/10.1143/JJAP.30.3700/pdf

Enlargement of Poly-Si Film Grain Size by Excimer Laser Annealing and Its Application to High-Performance Poly-Si Thin Film Transistor

Lateral grain growth in nondoped poly-Si films was studied by using Si thin films (500 A) with different structures as a starting material for excimer laser crystallization. It was clarified that the lateral grain growth phenomenon (micron-size grains with strong (111) orientation) upon excimer laser annealing was strongly affected by both the microstructure and the orientation of the initial Si thin films. This result supports our previous speculation that the principal driving force of the lateral grain growth phenomenon is surface energy anisotropy. Poly-Si thin-film transistors using these films show a high field effect mobility of 440 cm2/Vs, achieved through a low-temperature process below 600° C. This excellent electrical characteristic is thought to be due to the large grain size of poly-Si thin film with controlled orientation, good crystallinity, and a smooth surface.

https://iopscience.iop.org/article/10.1143/JJAP.33.5657/pdf

Comprehensive Study of Lateral Grain Growth in Poly-Si Films by Excimer Laser Annealing and Its Application to Thin Film Transistors

Dramatic lateral grain growth of nondoped poly-Si films (maximum grain size: ~4.5 µm, film thickness: 500 A) with strong crystallographic (111) orientation on glass substrates has been achieved using an excimer laser annealing method, namely at low temperature below 400°C and in a processing time shorter than a second, for the first time. The surface morphology of these poly-Si films was very smooth and the crystallinity was excellent with minimal internal defects. These poly-Si films have monomodally distributed grain sizes, with an average grain size of around 1.5 µm. As a result of experimental study, we speculate that the basic driving force behind this lateral grain growth was surface free energy anisotropy, as the same mechanism was observed in high-temperature furnace annealing of doped poly-Si thin films.

Lateral Grain Growth of Poly-Si Films with a Specific Orientation by an Excimer Laser Annealing Method

A high-mobility (280 cm/sup 2//V-s), high-throughput poly-Si TFT (thin-film transistor) formed using a low-temperature process ( >

High mobility poly-Si TFT by a new excimer laser annealing method for large area electronics

Film uniformity is the main problem when applying laser-recrystallised poly-Si films to thin film transistors (TFTs) in giant micro electronics. However, this has been dramatically improved by a new excimer laser annealing method in which the solidification process of molten Si is controlled by low-temperature (400°C) substrate heating during excimer laser annealing. Poly-Si TFT fabricated around the laser irradiation overlap region exhibited a high field effect mobility uniformity of within ±8%.

Tomoyuki Nohda

Papers

Enlargement of Poly-Si Film Grain Size by Excimer Laser Annealing and Its Application to High-Performance Poly-Si Thin Film Transistor

Comprehensive Study of Lateral Grain Growth in Poly-Si Films by Excimer Laser Annealing and Its Application to Thin Film Transistors

Lateral Grain Growth of Poly-Si Films with a Specific Orientation by an Excimer Laser Annealing Method

High mobility poly-Si TFT by a new excimer laser annealing method for large area electronics

Improving the uniformity of poly-si films using a new excimer laser annealing method for giant-microelectronics