TEM and EDX study of the Al2O3 ultra thin films

The ultra-thin layers of Al2O3 were deposited on a silicon substrates. The method of atomic layer deposition (Beneq TFS 200 ALD system) was chosen as the proper method of dielectric layer deposition. This method provides precise thickness control down to a single atomic layer. The precursors used were trimethylaluminum (Sigma-Aldrich) and purified water. The deposition of the atomic layer was carried out at 200 °C. Samples with a thickness of 2 and 8 nm of alumina were selected for the tests. A high-resolution transmission electron microscope TALOS F200X (HR TEM) equipped with an EDS detector was used for cross-section imaging and chemical composition analyzes. A thin layer of natural silicon oxides with a thickness of approx. 2 nm can be detected on the surface of the silicone substrate. The area with a mixture of oxygen, silicon and aluminum concentrations is also clearly visible. The thickness of the aluminum silicate phase boundary was calculated for approx. 1.7 and 4.5 nm for 2 nm and 8 nm films, respectively.

将超薄氧化铝（Al₂O₃）薄膜沉积于硅衬底之上。本研究选用原子层沉积（atomic layer deposition, ALD，Beneq TFS 200型ALD设备）作为介电层沉积工艺，该工艺可实现精确至单原子层的厚度调控。本次实验所用前驱体为三甲基铝（trimethylaluminum，Sigma-Aldrich）与去离子水，原子层沉积的实施温度设定为200℃。本测试选取氧化铝厚度分别为2 nm与8 nm的样品作为研究对象。采用搭载能谱仪（energy-dispersive X-ray spectroscopy, EDS）的高分辨透射电子显微镜（high-resolution transmission electron microscope, HR TEM）TALOS F200X对样品开展截面成像与化学成分分析。硅衬底表面可检测到厚度约2 nm的天然氧化硅薄层，同时可清晰观测到氧、硅与铝元素浓度混合的区域。经计算，对应2 nm与8 nm氧化铝薄膜的铝硅酸盐相界厚度分别约为1.7 nm与4.5 nm。