Silicon-hydrogen bonds in laser-crystallized polysilicon thin films and their effects on electron mobility

In this paper, we describe the behavior of H atoms in laser-crystallized poly-Si for thin-film transistors on liquid crystal display panels, where H atoms were introduced by plasma hydrogenation in order to improve mobility. Mobility was determined by the Hall effect measurement. Si-hydrogen bonds were analyzed by Raman scattering. By short-time hydrogenation, the introduced H atoms terminate the dangling bonds in the Si-H configuration mainly at the grain boundaries, which results in the improvement of mobility. With excessive hydrogenation, Si-H-2 bonds are generated simultaneously with the degradation of mobility. Si-H-2 bonds are mainly formed at the in-grain defects. Hydrogenation using the hot-wire method was also carried out and it was shown that plasma damage does not influence the hydrogenation effects. The relationship among Si-H-2, mobility and the amount of in-grain defects was discussed, based on impurity scattering and weak-bond models.