Physical models for degradation effects in polysilicon thin-film transistors

Hack, M.; Lewis, A.G.; Wu, I‐Wei

doi:10.1109/16.210195

Cited by 128 publications

(51 citation statements)

References 14 publications

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“…A hydrogenation process has been utilized to reduce the trap states of poly-Si films to improve the device performance [2]. However, hydrogenated poly-Si TFTs suffer from a serious instability issue due to weak Si-H bonds, which will break easily under an electrical stress [3]. Using fluorine to passivate the trap states of poly-Si TFTs has been reported recently [4]- [6].…”

Section: P Olysilicon Thin-film Transistors (Poly-si Tfts)mentioning

confidence: 99%

A novel process-compatible fluorination technique with electrical characteristic improvements of poly-Si TFTs

Wang

Chang

et al. 2005

IEEE Electron Device Lett.

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A process-compatible fluorine passivation technique of poly-Si thin-film transistors (TFTs) was demonstrated by employing a novel CF 4 plasma treatment. Introducing fluorine atoms into poly-Si films can effectively passivate the trap states near the SiO 2 /poly-Si interface. With fluorine incorporation, the electrical characteristics of poly-Si TFTs can be significantly improved including a steeper subthreshold slope, smaller threshold voltage, lower leakage current, higher field-effect mobility, and better On/Off current ratio. Furthermore, the CF 4 plasma treatment also improves the reliability of poly-Si TFTs with respect to hot-carrier stress, which is due to the formation of strong Si-F bonds.

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Section: P Olysilicon Thin-film Transistors (Poly-si Tfts)mentioning

confidence: 99%

A novel process-compatible fluorination technique with electrical characteristic improvements of poly-Si TFTs

Wang

Chang

et al. 2005

IEEE Electron Device Lett.

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“…8 and 9, the on-current and the threshold voltage of TFTs were both degraded because dangling bonds were created due to the trapping of electrons at weak Si-Si and Si-H bonds. 19,20 Compared with that of conventional MIC-TFTs, the on-current degradation of DICCTFTs is greatly improved by F + implantation. DICC-TFTs also possess high immunity against the hot-carrier stress and thereby exhibit lower DV th and DI on /I on , compared with conventional MICTFTs.…”

Section: Resultsmentioning

confidence: 98%

Improved Electrical Performance and Reliability of Poly-Si TFTs Fabricated by Drive-In Nickel-Induced Crystallization with Chemical Oxide Layer

Lai

Chang

2011

Journal of Elec Materi

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Ni-metal-induced crystallization (MIC) of amorphous Si (a-Si) has been employed to fabricate low-temperature polycrystalline silicon thin-film transistors (TFTs). However, the Ni residues degrade the device performance. In this study, a new method for manufacturing MIC-TFTs using drive-in Ni-induced crystallization with a chemical oxide layer (DICC) is proposed. Compared with that of MIC-TFTs, the on/off current ratio (I on /I off ) of DICCTFTs was increased by a factor of 9.7 from 9.21 9 10 4 to 8.94 9 10 5 . The leakage current (I off ) of DICC-TFTs was 4.06 pA/lm, which was much lower than that of the MIC-TFTs (19.20 pA/lm). DICC-TFTs also possess high immunity against hot-carrier stress and thereby exhibit good reliability.

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“…It was reported that the hot-carrier stress induced degradation is attributed to the generation of gate-oxide/ poly-Si interface states and/or the breaking of the Si-Si and/or Si-H weak bonds in the poly-Si channel. 19,20 Thus, the introduction of fluorine into the active region by F ϩ implantation to an appropriate dose would result in the passivation of interface states and the formation of strong Si-F bonds in place of the weak Si-Si and/or Si-H bonds, 8,9 leading to ELA poly-Si TFTs of superior stability in comparison with those without a F ϩ implantation.…”

Section: Methodsmentioning

confidence: 97%

Performance Improvement of Excimer Laser Annealed Poly-Si TFTs Using Fluorine Ion Implantation

Fan

Chen

2002

Electrochem. Solid-State Lett.

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Significant improvement of device performance was observed for the excimer laser annealed ͑ELA͒ poly-Si thin film transistors ͑TFTs͒ by the incorporation of fluorine atoms using the ion implantation technique. This is presumably due to the relaxation of mechanical stress at the poly-Si/buffer-oxide interface and the passivation of trap-states in the poly-Si channel region and at the gate-oxide/poly-Si interface. We achieved high performance ELA poly-Si TFTs with a very low off-current of ϳ0.26 pA/m and a very high On/Off current ratio of about 10 8 . Moreover, the fluorine ion implantation also greatly improved the reliability of the ELA poly-Si TFTs with respect to the hot-carrier stress, presumably due to the formation of strong Si-F bonds.Excimer laser annealing ͑ELA͒ is a promising scheme for the crystallization of amorphous silicon in the fabrication of lowtemperature processed ͑LTP͒ poly-Si thin film transistors ͑TFTs͒ because the laser process can result in high-quality polysilicon films with very few in-grain defects. 1,2 However, a grain size of less than 100 nm as a result of extremely high solidification velocity inherent to the ELA process has been a troublesome problem. 2,3 Thus, the ELA polysilicon films usually contain a high density of grain boundaries, leading to lowered carrier mobility and degraded performance of the TFTs. Many techniques have been employed to reduce the detrimental effects of grain boundaries by either enlarging the grain size 4,5 or passivating the grain boundaries. 6,7 In addition, there is also a serious problem of mechanical tensile stress associated with the ELA process because of the large mismatch of thermal expansion coefficient between the molten polysilicon film and the buffer oxide layer of glass substrates. It is well known that the mechanical stress at the interface usually induces a large number of interface defect-states and thus deteriorates the electrical characteristics of the metal oxide semiconductor ͑MOS͒ devices. 8,9 Nevertheless, only a few studies have been reported regarding the effects of this mechanical stress on the performance of the ELA poly-Si TFTs. 5,10,11 In recent years, the incorporation of fluorine into gate-dielectrics of MOS devices by various processes has been used to induce the local strain relaxation and thus reduce the interface state density of MOS field-effect transistors ͑MOSFETs͒. 8,9 It was also reported that the defect states of the solid phase crystallized ͑SPC͒ LTP poly-Si TFTs can be passivated by fluorine ion implantation; 12 however, the SPC poly-Si TFTs have not experienced a large thermal expansion mismatch at the poly-Si/buffer-oxide interface because of the lack of laser irradiation process. Moreover, it was found that diffused fluorine spices from the SiO x F y dielectric can reduce the defect state density in the active channels of TFTs. 13,14 In this work, fluorine ions were implanted into the active regions before excimer laser irradiation for the fabrication of the high-performance ELA poly-Si TFTs. The implantatio...

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Physical models for degradation effects in polysilicon thin-film transistors

Cited by 128 publications

References 14 publications

A novel process-compatible fluorination technique with electrical characteristic improvements of poly-Si TFTs

A novel process-compatible fluorination technique with electrical characteristic improvements of poly-Si TFTs

Improved Electrical Performance and Reliability of Poly-Si TFTs Fabricated by Drive-In Nickel-Induced Crystallization with Chemical Oxide Layer

Performance Improvement of Excimer Laser Annealed Poly-Si TFTs Using Fluorine Ion Implantation

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