A comparative study of wet and dry selective etching processes for GaAs/AIGaAs/lnGaAs pseudomorphic MODFETs
A comparative study of wet and dry selective etching processes for GaAs/AIGaAs/lnGaAs pseudomorphic MODFETs
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DOI：
10.1007/bf02670914
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发表时间：
1992
影响因子：
2.1
通讯作者：
M. Tong;D. Ballegeer;A. Ketterson;E. Roan;K. Cheng;I. Adesida
中科院分区：
文献类型：
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作者：
M. Tong;D. Ballegeer;A. Ketterson;E. Roan;K. Cheng;I. Adesida
研究了AlxGa_（1-x）As在柠檬酸/H_2O_2溶液和SiCl_4/SiF_4等离子体中的刻蚀特性。在20° C，柠檬酸/H_2O_2（4：1）溶液中，x = 0.3，x =0.45和x = 1.0时，GaAs/Al_xGa_（1-x）As的选择性分别为155，260和1450。GaAs在此溶液中的蚀刻速率被发现是独立的线宽和晶体取向的蚀刻深度高达1000埃。GaAs刻蚀剖面沿着[110]和[110]方向显示出不同的倾斜角，正如预期的那样。在90 mTorr和-60 V自偏压下，使用SiCl 4/SiF 4气体混合物的选择性反应离子刻蚀（SRIE）产生了200和500之间的选择性，x值范围为0.17至1.0。对于小于1000 μ m的蚀刻深度，GaAs的SRIE蚀刻速率相对恒定。在更大的蚀刻深度，蚀刻速率变化高达76%的线宽之间的0.3和1.0微米。选择性湿法刻蚀和干法刻蚀工艺都被应用于在具有嵌入式薄AlAs刻蚀停止层的异质结构上制造栅极长度为0.3至2.5 μm的赝晶GaAs/AlGaAs/InGaAs MODFFET。使用4：1柠檬酸/H2 O2溶液进行栅极凹陷，0.3 µ栅极长度MODFFET的阈值电压标准偏差为13.5 mV。该结果与使用SRIE获得的40 mV相比是有利的，并且比使用3：1：50 H3 PO 4：H2 O2：H2O的非选择性蚀刻获得的230 mV好得多上级。这表明，选择性湿法腐蚀使用柠檬酸/H2 O2溶液结合薄的AlxGa 1-xAs（x≥ 0.45）蚀刻停止层提供了一个合理的简单，安全，可靠的工艺，为假晶MODFFET的制造中的栅极凹陷。
The etching characteristics of AlxGa1-xAs in citric acid/H2O2solutions and SiCl4/SiF4plasmas have been studied. Using a 4:1 solution of citric acid/H2O2at 20° C, selectivities of 155, 260, and 1450 have been obtained for GaAs on AlxGa1-xAs withx =0.3,x =0.45, andx= 1.0, respectively. Etch rates of GaAs in this solution were found to be independent of line widths and crystal orientations for etched depths up to 1000Å. GaAs etch profiles along [110] and [110] directions displayed different slope angles as expected. Selective reactive ion etching (SRIE) using SiCl4/SiF4gas mixtures at 90 mTorr and -60 V self-biased voltage yielded selectivities between 200 and 500 forxvalues ranging from 0.17 to 1.0. SRIE etch rates for GaAs were relatively constant for etch depths of less than 1000Å. At greater etch depths, etch rates varied by up to 76% for line widths between 0.3 and 1.0µm. Both selective wet etch and dry etch processes were applied to the fabrication of pseudomorphic GaAs/AIGaAs/lnGaAs MODFETs with gate lengths ranging from 0.3 to 2.5 µm on heterostructures with an embedded thin AlAs etch stop layer. A threshold voltage standard deviation of 13.5 mV for 0.3 µ gate-length MODFETs was achieved using a 4:1 citric acid/H2O2solution for gate recessing. This result compares favorably with the 40 mV obtained using SRIE, and is much superior to the 230 mV achieved using the nonselective etch of 3:1:50 H3PO4: H2O2: H2O. This shows that selective wet etching using citric acid/H2O2solutions in conjunction with a thin AlxGa1-xAs(x≥ 0.45) etch stop layer provides a reasonably simple, safe, and reliable process for gate recessing in the fabrication of pseudomorphic MODFETs.