Dielectric function of amorphous tantalum oxide from the far infrared to the deep ultraviolet spectral region measured by spectroscopic ellipsometry
Dielectric function of amorphous tantalum oxide from the far infrared to the deep ultraviolet spectral region measured by spectroscopic ellipsometry
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DOI：
10.1063/1.1313784
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发表时间：
2000-11-01
影响因子：
3.2
通讯作者：
Frost, F
中科院分区：
文献类型：
--
作者：
Franke, E;Trimble, CL;Frost, F
用反应射频磁控溅射方法在[001]硅衬底上沉积了非晶态氧化钽薄膜。通过改变生长温度、氧分压和总气压来获得不同密度的薄膜。用X射线衍射仪、原子力显微镜和变入射角椭圆偏振光谱仪对薄膜进行了分析，测量了近红外至真空紫外区的光子能量E=1~8.5 eV和红外光区E=0.03~1 eV的光子能量。给出了非晶态氧化钽在E=0.03-8.5 eV(40微米-145 nm)范围内的椭圆偏振实验数据的线形分析所得的介电函数。在红外光谱区，对于光谱中观察到的每一种吸收模式，使用洛伦兹线形对椭圆偏振数据进行分析。利用Kim和Garland参数算法提取了非晶态氧化钽在近红外至真空紫外区的光学性质[C.C.Kim，Phys.Rev.B45，11 749(1992)]，以模拟由于材料的基本带隙而产生的吸收。我们考虑了薄膜的孔隙率，因此用一种有效的介质方法分析了实验椭圆偏振数据。我们获得了有关氧化钽的光学性质、空泡百分比和薄膜厚度的信息。空泡率的“光学”百分比对应于原子力显微镜测量的表面粗糙度，并取决于沉积参数。(C)2000年美国物理研究所。[S0021-8979(00)05821-7]。
Amorphous tantalum oxide thin films were deposited by reactive rf magnetron sputtering onto [001] silicon substrates. Growth temperature, oxygen partial pressure, and total gas pressure have been varied to obtain thin films with different densities. The thin films were analyzed by glancing angle-of-incidence x-ray diffraction, atomic force microscopy, and variable angle-of-incidence spectroscopic ellipsometry in the near infrared to vacuum ultraviolet spectral region for photon energies from E=1 to 8.5 eV, and in the infrared region from E=0.03 to 1 eV. We present the dielectric function of amorphous tantalum oxide obtained by line shape analysis of the experimental ellipsometric data over the range from E=0.03 to 8.5 eV (40 mu m-145 nm). In the infrared spectral region the ellipsometric data were analyzed using Lorentzian line shapes for each absorption mode observed in the spectra. Amorphous tantalum oxide optical properties in the near infrared to vacuum ultraviolet spectral region were extracted by using a Kim and Garland parameter algorithm [C. C. Kim , Phys. Rev. B 45, 11 749 (1992)] in order to model the absorption due to the fundamental band gap of the material. We consider thin film porosity, and therefore analyzed the experimental ellipsometric data by an effective medium approach. We obtain information on the tantalum oxide optical properties, a percentage of void fraction, and film thickness. The "optical" percentage of void fractions corresponds to surface roughness measured by atomic force microscopy and depends on deposition parameters. (C) 2000 American Institute of Physics. [S0021-8979(00)05821-7].