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標題: Fabrication of Patterned Sapphire Substrates by High-Density-Plasma Etching
作者: 白士峰
Pai, Shih-feng
關鍵字: sapphire;藍寶石;inductively coupled plasma (ICP);etch rate;etch profile;感應耦合式電漿;蝕刻速率;蝕刻角度
出版社: 材料工程學研究所
本論文係探討使用感應耦合式高密度電漿(ICP)蝕刻藍寶石基板,以其蝕刻出微形圖案之藍寶石晶圓,當改變腔體壓力、ICP 功率、下電極射頻功率以及氣體流量比例、不同的遮罩等參數,探討如何改變電漿特性以得到最佳蝕刻的效果。對於其電漿蝕刻的特性,我們使用掃描式電子顯微鏡來求其蝕刻的角度,使用原子力顯微鏡來量測其表面的粗糙度,對於不同的遮罩,我們增大BCl3在BCl3/Cl2混合氣中所佔的比例來提高其遮罩的選擇比,並且減小工作壓力來增加其蝕刻速率。由實驗中,蝕刻參數對於其蝕刻速率改變,其蝕刻速率由35 nm/min增加到280 nm/min,其粗糙度的變化量從0.2 nm到1.9 nm,其角度的變化更是從60°變化至79°,而在不同的遮罩實驗中,在我們的實驗範圍內,證明了Ni的蝕刻選擇比最好,而且,從以SiO2當遮罩的實驗中,我們可以衍生出其他不同的蝕刻角度,其角度可以從24°變化至35°,因此,對於我們所希望的圖案各種傾斜角度,可以利用遮罩的轉移方式,來蝕刻出我們所理想的角度、蝕刻速率與粗糙度等。

III-nitride compound semiconductors are recognized to be the key materials for optoelectronic devices, such as short-wavelength light-emitting diodes (LEDs) and laser diodes. In the conventional epitaxial process for GaN LEDs, threading dislocations are the most common defects, which make the carrier releasing energy without luminescence as a result of nonradiative recombination effect. The reduction of threading dislocations is very important if one wants to fabricate high-efficiency GaN LEDs. Recently, the patterned sapphire substrate was confirmed to be an efficient method to reduce the threading dislocations and to enhance the scattering the emission light from the active layer. Thus the external quantum efficiency of the GaN LED was improved.
In this thesis, the pattern etching process for the sapphire wafer by an inductively-coupled-plasma (ICP) etcher was described. The etch characteristics were investigated by varying the etching parameters, such as gas combination of Cl2/BCl3/Ar, chamber pressure, ICP power, and DC-bias voltage. The increase of BCl3 content (up to 66.7%) in the Cl2/BCl3 gas mixture increases the etch rate and improves the etch selectivity over Ni. In our experiments, the etch rate of sapphire can increase from 35 to 280 nm/min with a surface roughness from 0.2 to 1.9 nm, and the etch profile from 60 to 79. The etch selectivity over Ni can reach above 6 which is higher than the other mask materials (SiO2 or Cu). However, the SiO2 mask can offer the lower taper angle from 24 to 35 after ICP etching due to the faster etch rate of the SiO2 side wall. Thus one can utilize a suitable mask material to achieve the etching rate, taper angle, and roughness which are desirable for patterned sapphire substrates.
Appears in Collections:材料科學與工程學系

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