C-M Park

A Novel Excimer Laser Crystallization Method of Poly-Si Thin Film by Grid Line Electron Beam Irradiation

Excimer laser annealing technique is proposed to increase the grain size and controlling the microstructure of polycrystalline silicon (poly-Si) thin film. Our method is based on the lateral grain growth during laser annealing. Our specific grid ion beam irradiation method was designed to maximize the lateral growth effect and arrange the location of grain boundaries. We observed well-arranged poly-Si grains up to micrometer order by transmission electron microscopy (TEM).

27.4: Four-Terminal Poly-Si TFTs with Improved Reliability

We fabricate a novel poly-Si TFT, which employs counter-doped lateral body terminal in order to suppress kink effects and improve the device stability. The device also employs buried channel, which increase ON-current and operating frequency. The proposed poly-Si TFT exhibits superb dynamic reliability to conventional poly-Si TFT after AC stress.

4.4: A Novel Air‐Bridge‐Type Gate‐Data‐Line Crossover to Reduce Signal Delay for Large AMLCDS

A new TFT-LCD panel with an air-bridge type gate to data line inter-crossing has been proposed and its characteristics have been measured. The proposed structure has air-gap between gate and data line intercrossing. The new panel structure achieves 9 times faster signal delay compared with conventional panel. We have examined thermal and mechanical durability of new panel to verify capability for commercial AMLCD application.

A Novel Multi-Channel Poly-Si TFT Improving Hydrogen Passivation

We have fabricated a new multi-channel polycrystalline silicon thin film transistor (ploy-Si TFT), of which structure may be more effectively hydrogenated than conventional multi-channel poly-Si TFT. The new multi-channel TFT has stripe-cuts in gate electrode so that more hydrogen radicals penetrate into the gate oxide and passivate the active poly-Si layer. After 90 min. hydrogenation of the new device, the electrical characteristics such as threshold voltage and field effect mobility are improved more than those of conventional device. The new multi-channel poly-Si TFT, which receives more hydrogen radicals thorough gate oxide than the conventional multi-channel TFT, can be hydrogenated effectively in long channel devices. Besides the improvement of the device characteristics, our experimental results show that the dominant hydrogenation path is the diffusion though the gate oxide.

27.1: Excimer‐Laser Recrystallization of Poly‐Si Using Nucleation Seeds

We propose a new excimer laser annealing method with the artificial formation of nucleation seed. For the nucleation seed, we employed Si component incorporated in conventional sputter Al(aluminum) source target. By our method, the poly-Si grains were considerably enlarged up to five times and the electrical characteristics were much improved.

A Novel Lateral Field Emission Triode for Microwave Application

We propose a novel lateral field emission triode, which does not require any additional vacuum sealing process and exhibits superb field emitter triode performance. The purpose of this paper is to compare titanium polycide tip with polycrystalline silicon tip. A new experimental results of the device, such as variation of tip material, device stability experiment, measurement of the novel device in vacuum chamber in order to verify the proposed vacuum sealing process, and transconductance characteristics at each current level. The minimum turn-on anode to cathode voltage of titanium polycide tip is considerably decreased compared with polysilicon tip. The anode current measured in 10 −8 Torr vacuum chamber is similar to the anode current measured in atmospheric pressure, which shows that the proposed vacuum sealing process is reliable. The stable current of 300μΑ is maintained during 60 h.

Polycrystalline Silicon Single Electron Island by Excimer Laser Irradiation on a-Si Film

We propose a novel fabrication method for a room temperature operating single-electron memory using the size and location controlled poly-Si island by lithographic technique and excimer laser annealing. We have patterned tip shaped excimer laser windows and irradiated laser energy through windows for crystallizing amorphous silicon. As a result of laser energy, the poly-Si grains are growing from patterned window side so that the fine grain and isolated large poly-Si quantum dot are inherently formed by well-known ACSLG regime. The oxidation was then performed by RTP at 950 °C for 30 seconds in order to isolate quantum island and fine poly-Si grains for quantum dot. The peaks of the poly-oxide along the poly-Si grain boundaries were lowered during that oxidation and isolated the poly-Si grains and made oxide barriers.

A Dehydrogenation and Annealing Method of a-Si by Microwave

We propose a new method for selective crystallization of amorphous silicon and source/drain ion impurities activation by microwave annealing. We have measured FTIR to investigate hydrogen content variation in PECVD a-Si film and examined the poly-Si grain structure by SEM. We have also observed the Raman spectroscopy in order to investigate the grain growth mechanism during microwave annealing. In our experiment, a-Si layer between microwave absorbing layers was fully crystallized in 60 seconds and hydrogen content of a-Si under microwave reflective layer was not varied after 20 minutes microwave annealing. These results indicate that proposed method may be implemented for fabricating a-Si and poly-Si TFTs on the same glass substrate. We have fabricated the poly-Si and a-Si TFTs employing microwave annealing for active layer crystallization and source/drain activation by our method.

Improvement of Grain-Growth and Surface Roughness in Laser-Crystallized Polycrystalline Silicon Films

The effects of nitrogen-radical treated amorphous silicon (a-Si) films on laser-crystallization behavior have been studied for the improvement of the grain-growth and the surface roughness. The radical treatments were performed by the rf (13.56 MHz) plasma-enhanced-chemical-vapor-deposition (PECVD) system with N2 gas before the laser-crystallization. The grain-size of the laser-crystallized polycrystalline silicon (poly-Si) film with 600 seconds of radical-treatment time was remarkably increased by the relaxation of solidification process caused by the possible evolution of solid phase SiN x compounds which shows the low thermal conductivity. The electrical conductivity at 30 °C was rather lager value of 3×10 -5 Ω -1 cm -1 than 1×10 -5 Ω -1 cm -1 of poly-Si without radical treatment, while the highly resistive SiN x compounds were formed. From the SEM images, the surface roughness was also improved by the selective etching of the 5%-water-diluted hydrofluoric (HF) acid on the grain boundaries which the SiN x compounds were well segregated into during the laser-crystallization.