負型砷化鎵基板形成含金多層歐姆接觸結構之研究

摘要由於通訊產業的蓬勃發展，而在常用基板材料中砷化鎵除了比矽元件有較高的電子遷移速度外，切換速度也很快，再加上元件尺寸小，所以在高頻通訊使用很廣泛。另外也具備抗輻射性，產品穩定度高，特別是可用於衛星通訊時曝露太空中所產生的輻射問題。所以砷化鎵的應用變得日漸重要。本文主要是以n型砷化鎵作為基板，利用Ni/Au及Ni/Ge/Au在n型砷化鎵上形成之歐姆接觸結構，再針對各種不同氣體、溫度及時間為回火變化條件來形成歐姆接觸，並且運用傳輸線模型法計算出歐姆接觸結構之特徵接觸電阻值，以找出最佳的特徵接觸電阻值及回火條件。而在經由實驗結果的驗證，我們以使用摻雜濃度為～1018cm-3之GaAs在以下條件可以做出良好的歐姆接觸：在N2氣體下，Ni/Au在溫度為375℃時回火一分鐘，可以得到1.27×10-4Ω-cm2為最低特徵接觸電阻值。Ni/Ge/Au則於350℃，回火一分鐘可以得到最佳接觸阻值為3.13×10-6 Ω-cm2；在H2氣體下，Ni/Au以350℃回火一分鐘之特徵接觸電阻值1.37×10-5Ω-cm2為最佳；Ni/Ge/Au則為350℃回火一分鐘的特徵接觸電阻值1.13×10-6Ω-cm2最佳。其中在包含Ge的結構下除了擁有較低的特徵接觸電阻值之外，其表面也較平坦。在本論文中也將會探討Ni/Au及Ni/Ge/Au在經過最佳條件回火之後，分別於溫度為 30℃、60℃、90℃及120℃的環境下進行變溫量測觀察特徵電阻值對於溫度之變化情況。且也會在250℃氣體流動環境下探討金屬結構的熱穩定度。

關鍵字

鎳；歐姆接觸；砷化鎵；鍺；金

並列摘要

Abstract Gallium Arsenic (GaAs) applications to devices have become increasingly critical due to the requirement for global communication industrial growth. In general, GaAs devices have the merit of the higher electric mobility than that of Si devices, fast switching speed and size of devices in miniature, therefore GaAs is used in wide range for high frequency communication. Otherwise, GaAs has anti-radiation and high reliability, so that is usually used for satellite to counteract high radiation problems in outer space. In this study, the substrate is n-type GaAs, and the ohmic contact was constructed by Ni/Au and Ni/Ge/Au. In order to find out the best annealing conditions achieving the lowest contact resistances, we intended to change annealing temperature, time duration and gas ambient. The contact resistances were measured in term of TLM and then the specific contact resistance ρc was calculated. The experimental result reveals that n-type GaAs with doping concentration ~1018cm-3 can get the lowest specific contact resistance under optimum annealing condition. In N2 ambient, Ni/Au metallurgical structure has the lowest contact resistance 1.27×10-4Ω-cm2 alloyed at 375℃ for 1min, and the contact resistance of Ni/Ge/Au is 3.13×10-6 Ω-cm2 at 350℃ for 1 min. Besides, the Ni/Au and Ni/Ge/Au has the lowest specific contact resistance for 1 min at 350℃ under H2, they are 1.37×10-5 Ω-cm2 and 1.13×10-6 Ω-cm2, respectively. The structures including germanium not only has the low specific contact resistance, but also has a more smooth surface morphology. Hence the best annealing condition has been found, the samples will be put onto the thermal pad to measure thermal variation under 30℃, 60℃, 90℃ and 120℃ to observe the thermal effect on specific contact resistance. And discuss thermal stability of metal contact fabricated at 250℃ in the H2 environment.

並列關鍵字

ohmic contact ； GaAs ； Ni ； Ge ； Au

參考文獻

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負型砷化鎵基板形成含金多層歐姆接觸結構之研究

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