Metal Gate and Ge on Insulator Photodetector
Date Issued
2005
Date
2005
Author(s)
Lee, Cheng-Jiun
DOI
en-US
Abstract
In this thesis, the material properties of tantalum nitride (TaN) gate have been studied, such as proper work-function, thermal stability of the gate itself and also in contact with the dielectric underneath. Because the work function of a material depends on its crystalline structure, orientation, and composition. In our experiment, the work-function (Wm) variation and thermal stability of TaN are discussed as a function of nitrogen partial-flow rates and annealing temperature. The nitrogen partial-flow rates are increased in reactive sputtering, thus the thermal stability of TaN is decreased and work-function is increased.
Then the directly hydrophilic wafer bonding method is achieved by rapid thermal process and smart-cut process. Implanting hydrogen ions into the germanium wafer to from an in-depth weaken layer. The germanium (Ge) wafer is successfully bonded to silicon (Si) wafer capped with 600nm BPSG by the wafer bonding technology, thus thermal treatments and layer transfer taking place along the in–depth weaken layer (thin film Ge). The Ge-on-insulator (GOI) structure accomplished, and the thin film Ge surface observed very rough by atomic force microscopy (AFM). The GOI surface roughness is reduced by thermal rapid annealing with hydrogen gas in furnace, and hydrogen annealing is obvious and promising to reduce SOI and GOI surface roughness.
Finally, GOI fabrication is more suitability for low temperature splitting annealing. The low surface roughness is achieved by low temperature splitting annealing on thin film Ge. Since the ability of germanium to absorb in the near infrared makes it an interesting candidate for high-speed photodetector applications. Thus, the GOI MOS photodetectors are studied in this thesis. The leakage current at inversion bias is reduced by metal gate technique, and the oxide of GOI MOS photodetectors is deposited by liquid phase deposition (LPD) that carriers can tunnel through oxide via the assistance of multiple traps. In experiment, the novel GOI PMOS photodetectors have high responsivity and high quantum efficiency at 850nm. Therefore, the GOI photodetector can operate with 850nm, 1.3μm and 1.5μm lightwave and can be applied to the fiber optic communications.
Subjects
金屬閘極
絕緣層上鍺
光偵測器
氮化鉭
晶圓鍵結技術
Metal Gate
Ge on Insulator(GOI)
Photodetector
smart cut
tantalum nitride(TaN)
work-function
thermal stability
Type
thesis