Novel high-performance TFTs fabricated by selectively enlarging laser x'tallizaion (SELAX) technology

摘要

We have developed a new crystallization technique using the pulse-like modulated CW-laser (LD-pumped Nd:YVO_4 SHG λ=532nm). Enlarging of lateral crystallization is attained by rapid laser-scanning on Si surface where the large (4μm x 0.5μm in average) columnar grains are uniformly obtained. Sequential and step-by-step scanning makes large crystallization areas. During the each scanning, the irradiation is frequently suspended by pulse-like modulation. By using this technique, in-plane tensile strain in the irradiated areas is relieved. The size and the crystal orientation ({110} normal to the substrate and {100} normal to the growth direction) of obtained grains are, therefore, rather homogeneous. We have developed the crystallization technique, which can obtain high crystal quality as well as large grains in the selected areas. We have fabricated TFTs (typically W/L=4μm/2-4μm, t_(ox)=100nm, t_(si)=50nm) in the irradiation areas on the glass-substrate. The field-effect mobility is 480 cm~2/Vs for n-channel devices and 130 cm~2/Vs for p-channel devices, respectively. The sub-threshold swing (S-value) is less than 0.2 V/dec for both types. This technology gives possibility to integrate electronic systems on the glass.