Kazutoshi Morikawa

33.3: Comparison of Poly-Si TFT Characteristics Crystallized by a YAG2ω Laser and an Excimer Laser

Poly-Si TFTs were fabricated by both a YAG2ω laser and an excimer laser annealing system using a same TFT manufacturing process, and the electrical characteristics of the TFTs were compared. As a result, it is found that a wider process window can be obtained with the YAG2ω laser annealing system. The possibility of overlapped irradiation is also shown.

Development of line-shaped optical system for YAG2omega laser annealing used in the manufacture of low-temperature poly-Si TFT

We have developed a new optical system that transforms the circle profile beam generated with near Gaussian intensity distribution by the YAG2ω laser (second harmonics of a Q-switched Nd:YAG laser) into a line-profile beam. This transformed bean has uniform distribution to within 5% in the longitudinal direction, and is about 100 mm long and 40 micron wide. For homogenization in the longitudinal direction, we employ a waveguide plate homogenizer. The laser beam is divided by waveguide plates, and the divided beams are overlapped on the surface of the works. We successfully reduced interference fringes by increasing the fixed optical pass difference beyond the inherent time and coherent length for every divided pair of adjacent beams under a controlled space coherent length. In the width direction, the laser beam is focused up to the limited M2 value.