Optical gradients in a-Si:H thin films detected using real-time spectroscopic ellipsometry with virtual interface analysis
Optical gradients in a-Si:H thin films detected using real-time spectroscopic ellipsometry with virtual interface analysis
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使用实时光谱椭圆光度法和虚拟界面分析检测 a-Si:H 薄膜中的光学梯度
DOI：
10.1016/j.apsusc.2017.12.039
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发表时间：
2018
影响因子：
6.7
通讯作者：
N. Podraza
中科院分区：
文献类型：
--
作者：
Maxwell M Junda;L. K. Gautam;R. Collins;N. Podraza
采用虚拟界面分析（VIA）方法，对等离子体增强化学气相沉积（PECVD）过程中不同衬底上不同氢稀释液的氢化非晶硅（a-Si：H）薄膜生长过程中的真实的时间椭圆偏振光谱进行了测量。一个程序是开发用于优化VIA模型配置，通过调整采样深度到膜和分析的光谱范围，使模型符合尽可能低的误差函数实现。最佳的通孔配置被发现是不同的，这取决于氢稀释，衬底成分，和瞬时膜厚度。然后提取膜的光学性质中的深度分布，该深度分布由在沉积期间作为膜厚度的函数的参数a-Si：H模型中的光学吸收加宽参数的变化引起。以前确定的关系被用来链接这个加宽参数的光学特性的整体形状。观察到该参数在所有层的累积厚度达到约2000-3000 μ m后收敛，这意味着在足够的厚度后可以达到a-Si：H网络中的类似顺序。然而，在生长的早期阶段，从基板和处理引起的顺序导致的显着变化的扩大被检测和跟踪作为一个函数的体层厚度产生的光学性能的深度分布在最终的膜。最好的结果是实现与最简单的膜上基板结构，而局限性的情况下，膜已被沉积在更复杂的基板结构被确定。
Virtual interface analysis (VIA) is applied to real time spectroscopic ellipsometry measurements taken during the growth of hydrogenated amorphous silicon (a-Si:H) thin films using various hydrogen dilutions of precursor gases and on different substrates during plasma enhanced chemical vapor deposition. A procedure is developed for optimizing VIA model configurations by adjusting sampling depth into the film and the analyzed spectral range such that model fits with the lowest possible error function are achieved. The optimal VIA configurations are found to be different depending on hydrogen dilution, substrate composition, and instantaneous film thickness. A depth profile in the optical properties of the films is then extracted that results from a variation in an optical absorption broadening parameter in a parametric a-Si:H model as a function of film thickness during deposition. Previously identified relationships are used linking this broadening parameter to the overall shape of the optical properties. This parameter is observed to converge after about 2000–3000 Å of accumulated thickness in all layers, implying that similar order in the a-Si:H network can be reached after sufficient thicknesses. In the early stages of growth, however, significant variations in broadening resulting from substrate- and processing-induced order are detected and tracked as a function of bulk layer thickness yielding an optical property depth profile in the final film. The best results are achieved with the simplest film-on-substrate structures while limitations are identified in cases where films have been deposited on more complex substrate structures.