Background

Stress measurement for thin films is crucial in a variety of fields such as in semiconductor manufacturing, the optoelectronics industry, and biomedical science, among others. However, most measurement methods require surface treatment of the thin film.

Objective

A label-free measurement method for plane stress states in optical isotropic thin films based on spectroscopic ellipsometry analysis is proposed and verified in this paper.

Methods

The proposed method is based on the modulation of the stress-optic effect on reflected spectroscopic ellipsometry. A theoretical model is established to describe the relation between all components of the plane-stress state and the classic ellipsometric parameters (Ψ, Δ). An algorithm is developed to determine all components of a plane-stress state by fitting the model to the experiment data.

Results

In the verification experiment, we determined the plane stress state of a Cu film coated on a PI (polyimide) substrate. The results show a reasonable agreement between the experimental measurements from spectroscopic ellipsometry and the theoretical analysis based on the applied loading.

Conclusion

The results prove that our method can effectively measure the plane stress state of optical isotropic thin films.

中文翻译：

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光学各向同性薄膜平面应力状态的无标记光谱椭圆偏振测量方法

背景

薄膜的应力测量在半导体制造、光电子行业和生物医学等多个领域都至关重要。然而，大多数测量方法都需要对薄膜进行表面处理。

客观的

本文提出并验证了一种基于光谱椭圆光分析的光学各向同性薄膜平面应力状态的无标记测量方法。

方法

所提出的方法基于反射光谱椭圆光度术的应力光学效应的调制。建立了一个理论模型来描述平面应力状态的所有分量与经典椭圆参数（Ψ，Δ）之间的关系。开发了一种算法，通过将模型拟合到实验数据来确定平面应力状态的所有组成部分。

结果

在验证实验中，我们确定了PI（聚酰亚胺）基板上涂覆的Cu膜的平面应力状态。结果表明，椭圆偏振光谱仪的实验测量结果与基于施加载荷的理论分析之间具有合理的一致性。

结论

结果证明我们的方法可以有效测量光学各向同性薄膜的平面应力状态。