Papers by Keyword: Poly-Si

Abstract: Tetramethylammonium hydroxide (TMAH) is a metal-free strong alkaline solution which can etch poly-Si. The concentration of dissolved gas as well as the concentration of TMAH affects etching rate of poly-Si. The detailed kinetics of poly-Si etching in TMAH solution is investigated in this study. The effect of water and TMAH concentration on the etching kinetics of poly-Si was investigated by using various concentrations of TMAH solution. It is found that H₂O in TMAH solution plays an important role in etching poly-Si. Presence of dissolved CO₂ and O₂ in TMAH solution tends to inhibit etching of poly-Si. The concentration of dissolved CO₂ and O₂ in TMAH were reduced by Ar bubbling, thereby the poly-Si etching rate increased.

Abstract: The failure mechanism of a SiC metal-oxide-semiconductor capacitor with a poly-Si gate electrode was investigated by time-dependent dielectric breakdown testing under a 200-nA constant current stress. The capacitor exhibited both hard and soft breakdowns. After dielectric breakdown in both cases, adjacent concaves were observed on the capacitor with a field-emission scanning electron microscope. Additional optical beam-induced resistance changes and photo-emission analysis of a capacitor after hard-breakdown located a failure point on the periphery of a group of adjacent concaves. Cross-sectional scanning transmission electron microscope observation revealed that a narrow, vertical defect had formed at this point on the SiC substrate.

Abstract: Amorphous silicon films with and without spin-coating aluminum-salt-solution are treated by 193nm ArF excimer laser with different laser energies. It is observed that the crystalline fraction increases along with the laser energy. By comparation, with the help of Al, higher crystalline volume fraction and lower in-plane stress can be achieved at the same laser energy (2.9mJ). Large grain size of 200~300nm and maximum crystalline fraction of 82.3% are obtained in Al-salt-solution spin-coated sample, which is treated with laser energy of 3.2mJ,and its carrier mobility is 56.3cm²/Vs.

Abstract: Solution-based nickel (Ni)-induced crystallization (S-MIC) of amorphous silicon (a-Si) films has been studied with a two-step annealing process. We especially introduced Ethyl cellulose (EC) into the Ni-salt solution, so the viscous Ni-salt solution can be uniformly spin-coated on the a-Si film prepared by plasma enhanced chemical vapor deposition (PECVD). The annealing temperature can be first set from room temperature (RT) to 400°C and kept at 400°C for 2 h in nitrogen ambience. And then, it is increased from 500°C to 550°C and kept for several hours in the following annealing. The correlations among crystallization, the concentrations of Ni-salt solution and annealing conditions can be discussed. The experimental results show that with the help of the two-step annealing, the a-Si films can be crystallized at a low temperature of 500°C. The crystalline fraction gets up to 81.2% after annealing at 520°C for 2 h and the grain size of the polycrystalline Si film is approximately 0.2 μm. Energy dispersive spectroscopy (EDS) analysis shows that very little Ni metal atoms reside in the crystallized Si film for S-MIC.

Abstract: A viscous Nickel (Ni) solution was applied on amorphous Si films by spin coating and its effect on the crystallization of amorphous Si films was investigated with a two-step annealing process. The experimental results show that with the help of the two-step annealing, the crystallization of the film can take place at 500oC. At the same time, the crystalline fraction gets up to 79.4% after annealing at a high temperature of 520oC and the grain size of the polycrystalline Si films is approximately 200 nm.

Abstract: For the system on panel applications, we fabricated and analyzed the polycrystalline silicon (poly-Si) silicon-oxide-nitride-oxide-silicon (SONOS) memory device on different buffer layer such as oxide or nitride. The threshold voltage (VT) and transconductance (gm) are extracted from each device and the X-Ray Diffraction (XRD) measurement is carried out to interpret these characteristics. The results show the device on oxide layer has higher mobility and lower VT than on nitride layer. From the XRD spectra, it can be explained by the fact that the grain size of poly-Si on oxide layer has larger than on nitride layer. The both devices show program/erase characteristics as the potential of SOP memory devices.

Abstract: Since Tetramethylammonium Hydroxide (TMAH) became widely used as a silicon etchant, e.g. the dummy gate removal for gate-last approach (RMG) [1, or Si fin formation on FinFET [, some careful preparations and optimizations have required implementation. These adaptations have involved not only chemical-related issues, but also hardware-related in order to satisfy the necessary process performance.

Abstract: This paper investigates a combination of Ni acetate solution induced crystallization and microwave induced crystallization of a-Si thin film. Ni acetate solution was coated over amorphous Si thin film for evenly spread of Ni metal source. The Ni inducing source was formed from Ni acetate powder dissolved in de-ionized water or ethanol. The crystallization using Ni acetate solution was a Ni-silicide mediated process, the same process used with Ni metal layer. Compared to Ni metal layer induced crystallization by conventional furnace annealing, it finds that the crystallization temperature was lowered to 450 °C and the time of crystallization was reduced. Using Ni acetate solution induced crystallization is propitious to big area crystallization. After the processing, the poly-Si grain size was found about 0.1-0.5μm. The crystallization of a-Si thin films was enhanced by applying microwaves and Ni acetate solution to the thin films. The technique that combines Ni solution induced crystallization with microwave annealing has potential applications in thin-film transistors (TFT’s) and solar cell.

Abstract: Metal-induced lateral crystallization (MILC) of patterned amorphous silicon(a-Si) thin film using Ni as a catalyst has been investigated. Ni-MILC grains are based on the growth of needle-like crystals due to the migration of NiSi2 precipitates, which located at the crystalline front, along the <111> directions. In the case where the needle-like crystallites collided at the a-Si pattern edge, not only “turn” or “branch” of the needle-like crystallites toward one of the possible <111> directions but also the growth along the pattern edge were observed. By limiting the growth area, the competitive growth of dendrite crystals that originated in needle-like crystallites was found to appear. This phenomenon resulted in the orientation alignment of MILC crystals in a wide area. Besides, the grain-filtering of MILC crystals was found to be possible by narrowing the pattern width.