Projection Lens Wave-Front Aberration Measurement Method Based on Adaptive Aerial Image Denoising

提出了一种基于空间像自适应降噪的投影物镜波像差检测方法。通过对空间像进行统计分析,获取空间像的噪声模型和噪声标准差模型。以噪声标准差为权重因子,利用加权最小二乘法对空间像进行主成分分解,可以实现对空间像的自适应、无损降噪,从而得到更为精确的主成分系数和泽尼克系数。使用光刻仿真软件PROLITH的仿真结果表明,在相同的噪声水平下,0.1lambda像差幅值内,与基于空间像主成分分析的波像差检测技术相比,精度提高30%以上。在使用光刻实验平台测量Z_8调整量的实验中,该方法的精度更高。A wave-front aberration measurement method of lithographic projection lens based on adaptive aerial image denoising is proposed. Principal component analysis (PCA) and multivariate linear regression analysis are used for model generation. Weighted least-square (WLSQ) method based PCA is used to get the principal component coefficients that are used for extracting the actual Zernike coefficients. Both the noise model of aerial images and the standard deviation model of noises are obtained by statistical analysis of actually measured aerial images. The standard deviation of the noise is used as weighting factors of the weighted least-square method. Accurate principal component coefficients and Zernike coefficients can be calculated because of the adaptive and lossless denoising ability of this method. Compared with wave-front aberration measurement techniques based on principal component analysis of aerial images (AMAI-PCA), the new method can provide more accurate results. Simulations show that AMAI-WLSQ can enhance the accuracy by more than 30% when the range of wavefront aberration is within 0.1lambda. Experiments also show that AMAI-WLSQ can detect aberration shifts more accurately