以反應性離子蝕刻法研究砷化鎵及砷化鋁鎵之選擇性侵蝕

Abstract

對於砷化鎵(GaAs)以及砷化鋁鎵(AlGaAs)之反應性離子蝕刻，我們使用三 氯化硼(BCl3)以及六氟化硫(SF6)之混合氣 體，以及使用四氯化矽( SiCl4)與六氟化硫(SF6)之混合氣體，作選擇性侵蝕之研究，並將兩者的 實驗結果作個比較。我們發現使用BCl3/SF6和SiCl4/SF6對砷化鎵及砷化 鋁鎵之蝕刻速率有明顯的不同，這是因為矽原子和硼原子與砷化鎵及砷化 鋁鎵表面原子的化學反應難易不同所致。我們使用SiCl4/SF6混合氣體所 得的蝕刻速率結果，皆是砷化鎵大於砷化鋁鎵，而且當SiCl4/SF6 的比例 大於1 比1 時，兩者蝕刻速率的差距較大。在這種比例之下而且為低功率 時，我們可得到砷化鎵對於砷化鋁鎵選擇性蝕刻的實驗數據超過 200。在 本實驗中砷化鎵對於砷化鋁鎵的選擇性蝕刻，我們用 BCl3/SF6 混合氣體 可得最佳的值接近100。如果用SiCl4/SF6混合氣體的話，則可得到大 於200 的數據，這是此實驗做得最好的數值。由於硼原子比鋁原子容易與 氟原子反應，所以使用BCl3/ SF6 混合氣體無法做到像 SiCl4/SF6那樣好 的數值。正因為如此，我們可以做出砷化鋁鎵的蝕刻速率高於砷化鎵 兩 、三倍，這是過去沒有人做過的。 Reactive ion etch of GaAs and Al0.3Ga0.7As using BCl3 (boron trichloride) and SF6 (sulfur hexafluoride) gas mixture is described , and compared with the results using SiCl4 (silicon tetrachloride) and SF6 g-as mixture . There is obvious difference in etching rate for both GaAs and Al0.3Ga0.7As etch using BCl3/SF6 and SiCl4/SF6 gases. The effect of the variables such as power , pressure , and gas compositions on the etch rate and resulting etched surface morphology are studied . in theis study, the gas composition of BCL3/SF6 used is 9/1, at theis gas composition, the ethcing is nost effective. If SF6 ratio is too high, it's found that both GaAs and Al3 Ga0.7As have poor etch rage. When BCl3/SF6 ratio is 9/1 and low power, high GaAs to Al0.3Ga0.7As selectivity can be obtained. However, when etched at higher pressure, the etch rage of Al0.3Ga0.7As can be slightly faster than GaAs. In this thesis, the best eching selectivity between GaAs/AlGaAs is about 100 when Bcl3/SF6 are used and about 200 when SiCl4/SF6 are used. This is due to the fact that boron can react with fluoride easier than aluninum. This fact also results in higher AlGaAs to GaAs eching rete (selectivity>3), which is not observed when using SiCl4/SF6 as the etching gases.