Effect of hydrogenation of the leakage currents of laser-annealed polysilicon TFTs

Aoyama, Takashi; Koike, Y.; Okajima, Yoshiaki; Konishi, N.; Suzuki, Takaya; Miyata, Kenji

doi:10.1109/16.83729

Cited by 21 publications

(4 citation statements)

References 9 publications

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“…7. It is found that the I OFF increases with increasing LED, similar to two reports in the literature 14,19 but contradictory to another report. 17 It is well known that TFTs with high off-current degrade the contrast ratio of display because of the loss of video information before the frame is being refreshed.…”

Section: Resultssupporting

confidence: 53%

Correlation Between Electrical Characteristics and Oxide/Polysilicon Interface Morphology for Excimer-Laser-Annealed Poly-Si TFTs

Fan¹,

Chen²

2002

J. Electrochem. Soc.

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This work investigates the correlation between electrical characteristics and gate-oxide/polysilicon interface morphology for excimer-laser-annealed ͑ELA͒ poly-Si thin-film transistors ͑TFTs͒. The main feature of ELA poly-Si films is protrusion at grain boundaries that makes the film surface appear very rough. The surface roughness increases with increasing laser energy density and causes degradation of off-current and reliability for the ELA poly-Si TFTs. This degradation of the off-current is attributed to the lower channel resistance due to the increase in crystallinity of the poly-Si layer and the enhancement of localized electric field arising from the protrusions at the grain boundaries. In addition, the increase of localized electric field also degrades device reliability. Passivation of gate oxide/poly-Si channel by NH 3 -plasma treatment was found to be favorable in improving the performance and reliability of the ELA poly-Si TFTs.Low-temperature processed ͑LTP͒ polycrystalline silicon thinfilm transistors ͑poly-Si TFTs͒ are attracting much attention for use in active matrix liquid crystal displays ͑AMLCDs͒ because of their higher field-effect mobility and driving current compared to amorphous silicon TFTs currently used for large-area electronics. 1 Thus, integration of the AMLCD and its peripheral driver circuits on a single glass substrate is of great advantage for the LTP poly-Si TFTs. In order to fabricate LTP poly-Si TFTs on a glass substrate, all of the fabrication processes must be carried out at low temperatures of no more than 600°C.It is well known that excimer laser annealing ͑ELA͒ is a very promising scheme for the crystallization of amorphous silicon because the laser process heats thin silicon films to the melting point on several tens of nanoseconds that allows the films to melt and recrystallize without significantly heating the glass substrate. Moreover, it has been reported that ELA resulted in high-quality polysilicon films with very few intragrain defects, leading to significant improvement in the electrical characteristics of poly-Si TFTs. 2-5 However, during the phase transformation from liquid to solid in the laser crystallization, many protrusions are formed at the oxide/ polysilicon interface, causing a very rough surface of polysilicon. 6 The enhanced electric field arising from the asperities at the rough surface led to adverse effects on the electrical characteristics and also created reliability problems in the ELA poly-Si TFTs. 7,8 The surface roughness inherent to the ELA process has been a troublesome problem. In recent years, many investigations have been reported regarding the formation mechanism of protrusions and the reduction scheme of the surface roughness, 5,6,9-11 whereas little study has been made with respect to the correlation between device behavior and interface morphology for the ELA poly-Si TFTs. 12 In this study, correlation between electrical characteristics and oxide/ polysilicon interface morphology of the ELA poly-Si TFTs is investigated, in particular...

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Section: Resultssupporting

confidence: 53%

Correlation Between Electrical Characteristics and Oxide/Polysilicon Interface Morphology for Excimer-Laser-Annealed Poly-Si TFTs

Fan¹,

Chen²

2002

J. Electrochem. Soc.

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“…The effectiveness of hydrogen annealing has been widely reported for Si devices, for example, on decreasing the leakage currents of laser annealed polysilicon TFTs. 13) Improvement of ZnO film quality by hydrogendoping has already been reported; [14][15][16][17] for example, the role of hydrogen atoms in ZnO films was investigated for magnetron sputtering films grown in a hydrogen atmosphere, 18) but nothing has been reported about the hydrogen annealing of ZnO related sol-gel films.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Annealing of ZnMgO Sol–Gel Films

Abe¹,

Komiyama²,

Chonan³

et al. 2009

jjap

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ZnMgO films were formed on quartz substrates by a sol-gel technique using high (800 C) and low (500 C) temperature processes, followed by annealing in a hydrogen atmosphere at 420 C. Photoluminescence (PL) measurements indicate that, for the low temperature process films, hydrogen annealing decreases the green band (500 -565 nm) emission but it increases only slightly the near band edge (NBE) emission. For the high temperature process films, hydrogen annealing decreases the green band emission significantly and it also increases the NBE emission by three to four times. The effect of the hydrogen annealing on the PL property is explained by a conventional polycrystalline and grain boundary model. The above results indicate that the combination of the 800 C crystallization process and the 420 C hydrogen annealing process is very effective to obtain sufficiently strong NBE emission from the ZnMgO sol-gel films.

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“…1 Among several low-temperature fabrication techniques of poly-Si, the excimer laser annealing method seems to be the most promising one for the creation of large-area poly-Si. [2][3][4][5] Because of its extremely short duration ͑about 100 ns͒ 6 and shallow melting and regrowing process, relatively good poly-Si can be formed on the nonheat-tolerant glass substrate. Besides, due to its spatial selectivity, it is suitable for producing hybrid amorphous silicon ͑a-Si͒ and poly-Si devices in the neighboring regions.…”

Section: Introductionmentioning

confidence: 99%

Mechanism for pillar-shaped surface morphology of polysilicon prepared by excimer laser annealing

Shih

Meng

Lee

et al. 2000

Journal of Applied Physics

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Surface morphology of polycrystalline silicon prepared by excimer laser annealing has been investigated. It was found that when a thin amorphous Si film is irradiated by excimer laser, pillars are formed on the surface of the crystallized polysilicon. To find out the mechanism, various preparation parameters such as laser power densities, shot numbers and the thickness of the amorphous Si have been studied. Several intermediate patterns have been found which illustrate the sequential formation of pillars. A surface tension model is proposed to explain these patterns. This mechanism can be applied to prepare the self-assembled silicon quantum dots, whose average size and height are 14.2 and 3.7 nm, respectively.

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Effect of hydrogenation of the leakage currents of laser-annealed polysilicon TFTs

Cited by 21 publications

References 9 publications

Correlation Between Electrical Characteristics and Oxide/Polysilicon Interface Morphology for Excimer-Laser-Annealed Poly-Si TFTs

Correlation Between Electrical Characteristics and Oxide/Polysilicon Interface Morphology for Excimer-Laser-Annealed Poly-Si TFTs

Hydrogen Annealing of ZnMgO Sol–Gel Films

Mechanism for pillar-shaped surface morphology of polysilicon prepared by excimer laser annealing

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