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Title: Very high frequency plasma enhanced chemical vapour depositions for thin film transistors
Author: Choi, Y. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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Hydrogenated amorphous silicon (a-Si:H) is increasingly being used in applications that require large-area, thin-film semiconductor. It can be deposited easily, at low temperature and low cost, on inexpensive substrates of almost any size by chemical vapour deposition methods. One of these applications of a-Si:H is the fabrication of thin-film transistors (TFTs) that are most often used in liquid crystal displays (LCDs). Plasma enhanced chemical vapour deposition (PECVD) is also called glow discharge deposition because of its visible luminosity of the plasma glow region, which is mainly the result of the de-excitation of emitting molecular and atomic species contained in the plasma. The field can be direct current (DC), radio frequency (RF), very high frequency (VHF), and microwave frequency. Deposition of a-Si:H employing the VHF-PECVD technique (typical frequency range 20-110 MHz) has been reported to yield an increase in deposition rate by one order of magnitude with respect to the conventional used frequency of 13.56 MHz, without adversely affecting material quality. The various electrical and optical properties of the VHF films were investigated as a function of main factors involved in the a-Si:H, SiNx, and n+ µc-Si layers deposition processes. The effects of the total pressure, the gases flow ratio, and the influence of VHF power have been intensively investigated to gain device-quality materials. Finally, a number of fabrication techniques and electrical testing were employed in order to realise high-performance thin film transistors with the optimised materials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available