研究目的
Investigating the stability of p-channel low-temperature polycrystalline silicon thin-film transistors under positive bias stress, focusing on the degradation phenomena such as threshold voltage shifts and hump current behavior.
研究成果
The research concludes that under positive bias stress, p-channel poly-Si TFTs exhibit negative shifts in threshold voltage and elimination of hump current due to the creation and accumulation of positive charges in the gate oxide, outweighing electron trapping effects. The hump current is attributed to higher acceptor-like trap densities at channel edges, and its elimination is stable over time but shows slight degradation in subthreshold characteristics after prolonged periods.
研究不足
The study is limited to p-channel TFTs fabricated using MILC method; results may not generalize to other types of TFTs or fabrication processes. The mechanism proposed for hump current is based on specific experimental conditions and may require further validation.
1：Experimental Design and Method Selection:
The study involves applying positive bias stress to p-channel poly-Si TFTs to observe degradation in transfer curves, using theoretical models like Poole-Frenkel emission and electron trapping mechanisms.
2：Sample Selection and Data Sources:
Metal-induced lateral crystallization (MILC) poly-Si TFTs with top gate structure were fabricated on thermally oxidized Si wafers, with specific dimensions (e.g., channel width/length ratios).
3：List of Experimental Equipment and Materials:
Includes low-pressure chemical vapor deposition (LPCVD) systems for depositing a-Si and oxide layers, implantation equipment for doping, and annealing furnaces.
4：Experimental Procedures and Operational Workflow:
Fabrication steps involve depositing precursor a-Si, patterning, crystallization, gate dielectric deposition, gate formation, doping, activation, and stress application with Vgs=+20V at room temperature. Transfer curves are measured at Vds=-
5：1V. Data Analysis Methods:
Threshold voltage is extracted using linear extrapolation method; data analysis includes comparing shifts in Vth and hump current over stress time and temperature variations.
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