Hae-Yeol Kim

Kinetics of electric-field-enhanced crystallization of amorphous silicon in contact with Ni catalyst

Electric-field-enhanced crystallization of hydrogenated amorphous silicon in contact with nickel catalyst (Ni/a-Si:H) has been investigated. In order to elucidate the crystallization kinetics quantitatively, in situ conductivity measurement was used. With the change of Ni dose (4×1013∼1.3×1015 cm−2) and annealing temperature (550∼500 °C), crystallization rate varied drastically at the electric field of 33 V cm−1. The activation energy for the crystallization was found to be strongly dependent on the Ni dose, 85 kJ mol−1 for 1.3×1015 Ni cm−2, 243 kJ mol−1 for 6×1014 Ni cm−2, and 276 kJ mol−1 for 4×1013 Ni cm−2, respectively. The polycrystalline silicon films were composed of needle-like crystallites of ∼5 μm (long axis) and their thin-film transistors (TFTs) showed field effect mobility of 43 cm2 V−1 s−1.

Effect of Nitrogen Plasma Treatment on the Characteristics of AlN Thin Films

Aluminum nitride (AlN) thin films have been deposited on silicon (100) wafers by radio frequency reactive magnetron sputtering. The as‐deposited AlN films are less dense and have a higher dangling bonds percentage than AlN single crystals. In addition the surface of as‐deposited film is too rough to apply to electronic devices. In order to overcome those limitations, nitrogen plasma treatment (NPT), as a novel heat‐treatment, is used for the first time in this work. As NPT time increases, surface roughness is dramatically reduced and, at the same time, the Al‐N bonds in the films become stable. As a result, chemical stability of nitrogen‐plasma‐treated AlN films increases sharply in a strongly alkaline solution, 2 M KOH. Furthermore, the interactions between AlN films and nitrogen plasma result in the improvement of electrical properties of AlN films, i.e., the leakage current density measured by I–V method is reduced.

Low-temperature crystallization of amorphous silicon films in contact with palladium by hydrogen plasma heating

A new annealing process using hydrogen plasma heating was suggested for the fabrication of poly-Si (polycrystalline silicon) films. This fabrication process had the advantages of low processing temperature approximately 450 °C and a short processing time of 1 h. The a-Si (amorphous silicon) films and a-Si/Pd (palladium) bilayers were deposited by r.f. sputtering and subsequently annealed by conventional furnace heating and hydrogen plasma heating. It was found that the Pd layer, introduced to the surface of the glass substrate prior to deposition of the a-Si layer, enhanced the nucleation reaction of c-Si (crystalline silicon) during the annealing, and that hydrogen plasma heating enhanced the grain growth reaction effectively. These resulted in lowered processing temperature and reduced processing time, while the grain size in the poly-Si films annealed by hydrogen plasma heating was much larger than that in the films by conventional furnace heating. The grain size of the poly-Si films annealed by hydrogen plasma heating was approximately 0.3 μm.

Surface treatment effect on the poly-Si TFTs fabricated by electric field enhanced crystallization of Ni/a-Si:H films

Self-aligned, p-channel polycrystalline silicon thin-film transistors (TFTs) were fabricated by electric field enhanced crystallization of a-Si:H in contact with the Ni catalyst, where a chemical solution of 97.5% H/sub 2/O:1% HF:1.5% H/sub 2/O/sub 2/ was used for a surface treatment on polycrystalline silicon films. The wet surface treatment was found to remarkably improve the electrical properties of TFTs, especially the leakage current and subthreshold slope. The enhanced performance was confirmed to be from the removal of the Ni impurity remaining as defect states at the surface and also from the ameliorated surface roughness of the polycrystalline silicon films.