HYDROGEN PASSIVATION OF POLYSILICON THIN-FILM TRANSISTORS BY ELECTRON-CYCLOTRON-RESONANCE PLASMA

We have investigated the method of hydrogenation of polysilicon thin-f ilm transistors (TFT) by electron cyclotron resonance (ECR) plasma. It is found that with decreasing pressure (1.5 to 0.35 mTorr) of the hyd rogen plasma, the substrate temperature rises due to bombardment of hy drogen ions. At the same time, the amount of hydrogen supplied by the ECR plasma increases. Due to these two effects, the passivation procee ds more quickly under low pressure. The amount of hydrogen supplied by a low-pressure ECR hydrogen plasma is higher than that supplied by ot her means such as Al sintering or rf hydrogen plasma. When polysilicon TFTs are exposed to the ECR hydrogen plasma, the hydrogenation reduce s 75% of the electrically active defect states in 15 min. Polysilicon TFTs with an offset-drain structure reached an on/off current ratio of 8 decades after such ECR hydrogen passivation.