Surface micromachining of monocrystalline silicon wafer by wet etching procedures

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Supervisor:
Dr. Földváry-Bándy Eniko
Department of Electron Devices

In this thesis, I provide an insight into the surface etching processes of n-type <100> single-crystalline silicon with wet-chemical etching. My task was to review the steps of solar cell manufacturing, with emphasis on literature available about the effect of the saw-damage and saw-damage removal technologies.

Nowadays, the surface of the wafers after the ingot sawing technology is disadvantageous for the next technological steps of solar cell manufacturing, mainly due to the saw-marks and microcracks. Moreover, the damage of the as-cut surface creates recombination centers, which reduce the minority carrier lifetime and the overall efficiency of the solar cell.

The efficiency of single-crystalline silicon solar cells is greatly influenced by the quality and the optical properties of the surface, so it is essential to remove the

saw-damage and the match this technological procedure with the following manufacturing process steps.

During my experimental work, my primary purpose was to develop the saw-damage removal technology applicable to the single-crystalline as-cut wafer. Besides this my goal was to investigate the effect of the gained structure on minority carrier lifetime and examine the morphologies of the surface. Furthermore, based on experiments I have determined the adaptability of the surface texturing process to the surfaces gained at different saw-damage removal parameters. All of my etching experiments were performed by using metal ion free etchants, namely tetramethyl-ammonium-hydroxide. During my work I found several references that highlight the advantages of the metal ion free etching solutions. Also, considering that my experimental work was carried out the cleanroom of BME - Department of Electron Devices, it was important to avoid the pollution of the environment.

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