Indium tin oxide (ITO) deposition, patterning and Schottky contact fabrication

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Title: Indium tin oxide (ITO) deposition, patterning and Schottky contact fabrication
Author: Zhou, Jianming
Abstract: As a transparent conductive material, indium tin oxide (ITO) has been utilized as electrodes in liquid crystal displays, solar cells, heat reflecting films and gas sensors. In general, the desired properties are high conductance and transmission. However, due to the complexity of ITO, the film properties strongly depend on the deposition processes. In this study, the deposition conditions for ITO film were optimized to get both high conductivity and transmission. The emphasis was on investigating the effects of various deposition parameters, such as oxygen partial pressure, total gas flow, annealing conditions and power. These are the most critical parameters for ITO deposition. A mathematical model to describe the material properties as functions of these parameters for a CVC model 601 Sputterer was developed utilizing JMP IN software. Films with resistivity 3x10-4Ω-cm and transmittance above 90% were achieved on glass and silicon substrates with 20 hours of annealing. The processing window (power: 120-150W, oxygen ratio: 6-10%) is, to the author’s knowledge, the largest reported by literature. However, the ITO film properties (electrical and optical) variation between runs needs to be further reduced. Patterning of ITO was also investigated. High but controllable etch rates are desired. Both wet and dry etch processes were developed. The etch rate of 48nm/min was achieved by using HCL aqueous solution (4:1 HCl to DI water volumetric ratio, where HCl is the standard 37% HCl solution) with almost infinite selectivity between the ITO film and the photoresisit. For dry etch, the etch rate is 1nm/min with just argon as the working gas and the etching selectivity between the photoresist and the ITO film is 13.02. To etch 100nm ITO film, the photoresist needs to be at least 1.5um to serve as etching mask. This dry etch process still needs to be improved. A Schottky contact was successfully fabricated by using ITO as the metal. The electrical barrier height was calculated to be 1.01eV. The current-voltage characteristics were investigated as well.
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Date: 2006-04-24

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