Hydrogen Passivation of Polysilicon Thin-Film Transistors by Electron Cyclotron Resonance Plasma

Abstract

We have investigated the method of hydrogenation of polysilicon thin-film transistors (TFT) by electron cyclotron resonance (ECR) plasma. It is found that with decreasing pressure (1.5 to 0.35 mTorr) of the hydrogen plasma, the substrate temperature rises due to bombardment of hydrogen ions. At the same time, the amount of hydrogen supplied by the ECR plasma increases. Due to these two effects, the passivation proceeds more quickly under low pressure. The amount of hydrogen supplied by a low-pressure ECR hydrogen plasma is higher than that supplied by other means such as Al sintering or rf hydrogen plasma. When polysilicon TFTs are exposed to the ECR hydrogen plasma, the hydrogenation reduces 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.

Defect Reduction in Polycrystalline Silicon Thin Films by Heat Treatment with High-Pressure H2O Vapor

“…For example, hydrogenation using a hydrogen plasma or a hydrogen radical has been widely investigated for defect reduction and device characteristic improvement. [1][2][3][4][5][6] Heat treatment with high pressure H 2 O vapor at approximately 300 C has also been developed. 7) Electrical active defects in polycrystalline silicon (poly-Si) and SiO 2 have been reduced by heat treatment.…”

Defect Reduction in Polycrystalline Silicon Thin Films at 150 °C

“…Hydrogenation using hydrogen plasma or hydrogen radicals has been widely investigated for defect reduction and improvement of device characteristics. [1][2][3][4][5][6] The density of defect states in polycrystalline silicon (poly-Si) films is well reduced by hydrogenation above 200 C. Heat treatment with high-pressure H 2 O vapor has also been developed. 7,8) Electrical active defects located in poly-Si and SiO 2 have been well reduced by heat treatment at approximately 260 C. The threshold voltage is reduced by decreasing the densities of trapped states and fixed oxide charges in SiO 2 as well as in SiO 2 /Si interfaces for poly-Si TFTs.…”

Heat Treatment with High-Pressure H2O Vapor of Pulsed Laser Crystallized Silicon Films

“…Redction of defects in silicon films at low temperatures is very important for fabrication of electronic devices, such as, thin film transistors (TFTs) and solar cells. [1][2][3] We have proposed a simple heat treatment with high-pressure H 2 O vapor for this purpose. 4) Reduction of the threshold voltage and increase of the effective mobility of polycrystalline silicon thin film transistors (poly-Si TFTs) have been observed by heat treatment with high-pressure H 2 O vapor.…”