酸性溶液在氮化鎵磊晶層上蝕刻行為之研究

The study of etching on GaN epitaxial layer by acid solution

邱彥斌(Yen-Pin Chiu)

指導教授 ： 許世杰

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2018年)

https://doi.org/10.6846/TKU.2018.00389

摘要

本研究主要探討酸性溶液對於氮化鎵磊晶層之蝕刻行為，藉由三種不同的酸性溶液(硫酸、磷酸、硫磷酸)蝕刻藍寶石基板上的氮化鎵磊晶層，製造出表面粗糙化的氮化鎵結構。實驗中探討不同時間、不同蝕刻液對於表面形貌及蝕刻深度之影響，並使用SEM、AFM、XPS對蝕刻後的樣品進行分析。
實驗結果發現，經過酸性溶液的蝕刻，會在表面形成坑洞。根據不同的蝕刻液的選擇會產生不同的蝕刻形貌。硫酸蝕刻下，氮化鎵磊晶層的厚度並不會有明顯的改變，但會在表面產生倒六角椎的坑洞，並隨著時間增長而擴大、結合，最後會維持在蝕刻面(101 ̅5 ̅)；磷酸蝕刻下，氮化鎵磊晶層厚度隨著時間減少，蝕刻坑由倒六角椎形隨著時間轉變為六角柱形，並且坑洞隨著時間延長相互結合，坑洞的大小及深度會隨著時間增加而增加，整體的厚度也會隨著蝕刻時間的增加而減少；硫磷酸蝕刻下，氮化鎵磊晶層厚度隨著時間減少，蝕刻坑會由倒六角椎，漸漸轉為倒十二角椎的坑洞，最後的維持在約為9.3°之夾角。這些坑洞的產生，源於氮化鎵磊晶在藍寶石基板時，因為兩者晶格不匹配所導致的缺陷，而酸性溶液會由這些缺陷開始蝕刻並產生坑洞。
產物方面，在硫酸蝕刻的實驗組中，蝕刻過後可以發現Ga-OEx的峰值提升，且在169.1 eV處產生一硫化物之特徵峰，根據對應為產物Ga2(SO4)3；磷酸實驗中，蝕刻過後可以發現O 1s、P 2p的鍵結峰上升，可以證實磷酸根可能是影響蝕刻的主因；硫磷酸實驗下，反應後之鍵結能並沒有明顯之差異，因此在樣品的表面並沒有發現任何產物。

關鍵字

氮化鎵 ； 濕式蝕刻 ； 硫酸 ； 硫磷酸 ； 磷酸

並列摘要

This study aims at investigating the etching methods of acid solution to GaN epitaxial layer. It produced the surface roughening GaN structure by the GaN epitaxial layer on the sapphire which was etched by three different acid solutions, which were H2SO4, H3PO4, and H2SO4+H3PO4 (HH). The researcher investigated the influence of different time and etching etchant to surface morphology and etching depth and used SEM, AFM, and XPS to analyze the samples after etching.
The results show that the choice of different acid solutions will produce different etching morphologies. Under the H2SO4 etching, the thickness of the GaN epitaxial layer does not change significantly, but the pits of the inverted hexagonal pyramid are generated on the surface, and expand and combine with time, finally remain on the etched surface(101 ̅5 ̅); Under the H3PO4 etching, the thickness of the GaN epitaxial layer decreases with time, and the etch pit will change from inverted hexagonal pyramid to hexagonal prism over time, and the pits will be combined with each other, and the size of the pit and the depth will increase with time; Under the HH etching, the thickness of the GaN epitaxial layer decreases with time, and the etch pit will change from inverted hexagonal to dodecagonal pyramid over time, and finally maintained at an angle of about 9.3°. These etching pits are generated because of the dislocation. When GaN is growth on the sapphire substrate, A lattice mismatch between the two causes dislocation, and the acidic solution begins to etch and create pits from these defects.
For the product, the peak of Ga-OEx can be found to increase, and a characteristic peak of a sulfide is generated at 169.1 eV, corresponding product Ga2(SO4)3; in the experimental group of H2SO4 etching; in the H3PO4 experiment, the bonding peak of O 1s and P 2p was found to rise after etching, and it was confirmed that phosphate may be the main cause of etching; In the HH experiment, there was no significant difference in the bonding energy after the reaction, so no product was found on the surface of the sample.

並列關鍵字

GaN ； wet etching ； acid solution ； H2SO4 ； H3PO4

參考文獻

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