基于成像光强的光刻机像差原位检测理论与方法研究

发布时间：2018-06-05 01:46

本文选题：投影式光刻 + 部分相干照明　；参考：《华中科技大学》2016年博士论文

【摘要】：随着光刻技术不断发展,成像分辨率极限一再推进,投影物镜数值孔径越来越大,光刻机像差直接影响成像分辨率和工艺窗口,是评价光刻机成像最重要的参数。光刻成像系统可以抽象为部分相干成像系统,投影物镜像差需要在光刻机运行过程中实现原位、精确检测。基于成像光强的光刻机像差检测技术具有成本低、易于实现、误差来源少等优势,在原位检测中有很好的适用性。然而在实际应用中,该类技术仍然面临众多的技术难题：其一,现有技术缺乏严格的像差检测模型,难以实现整个光瞳面波像差的快速精确检测；其二,该类技术通常需要设计一组几十个掩模图形,同时需要离焦扫描测量光强,时间和经济成本较高；其三,在光刻机实际使用中,物镜热效应等因素会产生较大波像差,而目前的主流技术是基于建立线性的简化模型,不适用于较大波像差存在的情况；其四,随着数值孔径增大,偏振像差对成像质量造成空前的影响,现有的检测技术还没有实现完整的偏振像差检测。鉴于此,本学位论文从这四方面开展基于成像光强的光刻机投影物镜像差检测理论与方法研究,从像差与成像光强的内在联系机理出发,探索光刻机投影物镜像差原位检测新理论和新方法。本文具体内容包括：提出了基于光强传输方程的波像差原位检测方法,将传统光强传输方程扩展到了部分相干光成像中,建立了解析的像差模型。利用光刻机成像系统的远场衍射成像特性,将像面的振幅相位信息与光瞳面相位信息建立关系,从而将光强传输方程应用在了波像差检测中。该方法通过采集较小离焦处的成像光强信号,利用傅里叶变换,进行解析计算,实现波像差原位检测,在数值孔径小于0.6的光刻系统中,波像差检测精度高达mλ量级,有良好的适用性。提出了基于单帧光强提取的波像差原位检测方法,构建了波像差灵敏度矩阵解析模型,建立了波像差37级泽尼克系数快速重构算法。通过深入的理论推导,建立了光刻机成像模型,解析推导了泽尼克系数与成像光强之间的线性关系,从而定义了灵敏度矩阵,提出了掩模优化方法。配合采用优化设计的单个掩模图形,只需要测量单帧离焦成像光强,即可获得全部37级泽尼克系数,克服了离焦扫描的时间和成本问题。该方法在较大数值孔径(0.6NA0.85)下,对60m以内的波像差,检测精度高达mλ量级。提出了基于迭代求解的波像差原位检测理论与方法,解决了大波像差情况下高精度、原位检测难题。在解析线性模型的基础上建立了二次像差畸变模型,分析了不同泽尼克项之间的二次耦合关系,定义了光强基函数,调用解析计算的光强基函数,采用迭代算法,对37级泽尼克系数进行求解,从而实现较大波像差的原位检测。该方法在波像差高达150mλ时,泽尼克37级系数检测误差在0.1mλ量级,波像差检测精度仍然高达mλ量级。提出了基于解析灵敏度函数的偏振像差原位检测理论与方法。通过深入分析光刻机成像过程中光的偏振特性,建立了包含偏振的矢量成像模型,研究了不同类型偏振像差对成像畸变的不同影响。采用泡利泽尼克多项式对偏振像差进行表征,使用制作最为简易的二元光栅作为掩模图形,解析计算灵敏度函数,以成像光强的三维分布作为观测量,结合灵敏度矩阵,实现偏振像差原位检测。该方法对偏振像差琼斯光瞳的检测相对误差小于10-2,有效的对超大数值孔径(NA0.85)浸没式光刻机偏振像差进行了原位检测。本学位论文提出的一系列像差检测方法具有简便易行、低成本、高效率、高精度等诸多优点,为实际应用中所面临的技术难题提供了有效的解决方案,为光刻机投影物镜像差的原位检测、控制和补偿提供了新原理、新途径,极大丰富了现有的像差检测技术。
[Abstract]:With the development of photolithography, the imaging resolution limit has been pushed forward and the numerical aperture of the projection lens is more and more large. The aberration of the lithography machine directly affects the imaging resolution and the process window. It is the most important parameter to evaluate the image of the lithography machine. The lithography imaging system can be abstracted as a part of the phase dry imaging system, and the image difference of the projector needs to be in the lithography machine. In the process of operation, in situ, accurate detection. Based on the imaging light intensity, the lithography aberration detection technology has the advantages of low cost, easy realization, less error source and so on. In the actual application, this kind of technology still faces many technical problems: first, the existing technology is lack of strict aberration detection. It is difficult to realize the rapid and accurate detection of the whole pupil wavefront aberration. Secondly, this kind of technology usually needs to design a set of dozens of mask patterns, and needs to measure the intensity, time and cost of the focal scanning. Thirdly, in the actual use of the photolithography, the thermal effect of the objective lens will produce a larger wave aberration, and the present The mainstream technology is based on the establishment of a linear simplified model, which is not suitable for the existence of large wavefront aberrations. Fourthly, with the increase of the numerical aperture, the polarization aberration has an unprecedented impact on the imaging quality. The existing detection technology has not yet realized the complete polarization aberration detection. In view of this, this dissertation is based on these four aspects of imaging. The theory and method of the mirror image difference detection of the photolithography of the photolithography machine are studied. From the inner connection mechanism of the aberration and the imaging light intensity, a new theory and new method are explored for the mirror image difference in situ detection of the photolithography projector. The specific contents of this paper include: a method of in-situ detection of wavefront aberration based on the light intensity transmission equation is proposed, and the traditional light intensity transmission side is put forward. The analytical aberration model is established in the partially coherent optical imaging. Using the far-field diffraction imaging characteristics of the imaging system, the relationship between the amplitude phase information of the image surface and the phase information of the pupil surface is established, and the light intensity transmission equation is applied to the wavefront aberration detection. The method is used to collect the imaging light of the smaller defocus. Strong signal, using Fourier transform to carry out analytical calculation, the wavefront aberration in situ detection is realized. In the lithography system whose numerical aperture is less than 0.6, the accuracy of the wave aberration detection is up to m lambda, and it has good applicability. A wave aberration in situ detection method based on single frame light intensity extraction is put forward, and the analytical model of the wavefront aberration matrix is established. The fast reconstruction algorithm of the 37 stage Zernike coefficient of the wavefront aberration is developed. The imaging model of the photolithography is established through in-depth theoretical deduction. The linear relationship between the Zernike coefficient and the intensity of the imaging light is derived. The sensitivity matrix is defined and the mask optimization method is proposed. The intensity of single frame defocus imaging can obtain all 37 Zernike coefficients and overcome the time and cost of the defocus scanning. Under the large numerical aperture (0.6NA0.85), the accuracy of the wave aberration within 60m is up to m lambda. The theory and method of the in-situ detection of wavefront aberration based on iterative solution are proposed, and the large wave aberration is solved. The two aberration distortion model is established on the basis of the analytical linear model. The two coupling relations between different Zernike terms are analyzed. The light strong basis function is defined, the optical strong basis function of the analytic calculation is called, and the iterative algorithm is used to solve the 37 level Zernike coefficient, thus the larger wave image is realized. When the wavefront aberration is as high as 150m lambda, the Zernike 37 degree coefficient detection error is at the magnitude of 0.1M lambda and the accuracy of the wavefront aberration is still up to m lambda. The theory and method of polarization aberration in situ detection based on the analytic sensitivity function are proposed. The polarizing vector imaging model is used to study the different effects of different types of polarization aberrations on imaging distortion. The polarization aberrations are characterized by Pauli Zernike polynomials. The most simple two element grating is used as the mask pattern to calculate the sensitivity function. The three-dimensional distribution of the image intensity is measured and the sensitivity is combined to be sensitive. The polarization aberration in situ detection is realized by the degree matrix. The relative error of the polarization aberration Jones pupil is less than 10-2, and the polarization aberration of the ultra large numerical aperture (NA0.85) immersion lithography is in situ detection. A series of aberration detection methods proposed in this dissertation are simple and convenient, low cost, high efficiency and high precision. Many advantages, which provide an effective solution for the technical problems faced in the actual application, provide a new principle for the in-situ detection, control and compensation of the mirror image difference of the lithography projector, and a new way, which greatly enriches the existing aberration detection techniques.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP391.41;TN305.7

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