The fabrication of Si_0.7Ge_0.3 sub-10 nm nanochannels in gate-all-around devices requires a highly selective Si isotropic etching process. The etching of Si selectively to Si_0.7Ge_0.3 with CF₄/N₂/O₂ downstream plasma has been investigated using various morphological and surface characterization techniques. Conditions such as 400 W microwave power, 700 mTorr pressure, 25 °C chuck temperature, and 22% CF₄:22% N₂:56% O₂ feed gas mixture were found to be optimum for selectivity and etch rates. X-ray photoelectron spectroscopy showed that, during the etching process, a highly reactive 8 nm thick SiO_xF_y layer is formed on Si. Meanwhile, a 2 nm thick passivation layer is observed on SiGe. The latter is a mixture of SiO_xF_y and GeO_xF_y species that protected the alloy from etching. The process selectivity was improved by investigating different wet and dry oxidant treatments prior to etching. The dry oxidant treatment gives the best results in terms of selectivity. These results obtained on blanket wafers have been validated on pattern wafers. Scanning electron microscopy demonstrated that SiGe nanowires were fully released with a high selectivity after dry oxidation followed by the etching process.

中文翻译：

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选择性向Si0.7Ge0.3进行Si的各向同性干法蚀刻，以用于CMOS以下10 nm应用

在全方位栅器件中制造Si _0.7 Ge _0.3亚10纳米纳米通道需要高度选择性的Si各向同性蚀刻工艺。已经使用各种形态学和表面表征技术研究了用CF ₄ / N ₂ / O ₂下游等离子体选择性地将Si刻蚀成Si _0.7 Ge _0.3的方法。诸如400 W微波功率，700 mTorr压力，25°C卡盘温度和22％CF ₄：22％N ₂：56％O _2的条件发现进料气体混合物对于选择性和蚀刻速率是最佳的。X射线光电子能谱表明，在蚀刻过程中，在Si上形成了高反应性的8nm厚的SiO _x F _y层。同时，在SiGe上观察到2nm厚的钝化层。后者是SiO _x F _y和GeO _x F _y的混合物保护合金不受腐蚀的物种。通过在蚀刻之前研究不同的湿式和干式氧化剂处理，可以提高工艺选择性。就选择性而言，干氧化剂处理可提供最佳结果。在毯式晶圆上获得的这些结果已在图案晶圆上得到验证。扫描电子显微镜表明，SiGe纳米线在干法氧化之后经过刻蚀工艺以高选择性完全释放。