Super-Resolution Optical Material Characterization

该项目需要研究一种方法，以确定有关纳米尺度的物体特征的信息，以及在环境不允许使用激光直接成像物体的情况下。该方法基于由相干光形成的结构化照明图案与物体或材料系统之间的相对运动，在该物体或材质系统中，以微小的精确空间步长扫描光线或物体。到目前为止，由于在没有先验信息的情况下，可实现的分辨率通常被限制在大约一半的光学波长内，因此在技术上提高空间分辨率或光学存储容量的方法一直是减小波长。这在向更短的波长转移方面面临着越来越多的挑战。另一方面，使用具有空间变化的光学强度的样品的相对运动提供关于样品的信息，该信息可用于远小于波长的特征的超分辨率成像。因此，检测半导体工业和显微镜中重要的微小结构应该成为可能。此外，一套材料检查和成像情况具有明显的背景杂乱，加剧了挑战。例如，目前很难或不可能检测到用于制造垂直固态存储器的三维半导体工艺步骤中的小缺陷，这将带来数十亿美元的市场后果。对于薄膜沉积后的激光检查，由于材料粗糙度引起的随机散射会产生斑点，这似乎会使情况变得更糟。在这个项目中，正在开发一种通过使用散斑来提取关于此类缺陷和其他物体的信息的检查和成像方法。更广泛地说，该方法允许使用光对隐藏在随机散射环境中的对象成像，例如雾或生物组织。相关研究构成了两名博士生论文的基础，该项目涉及本科生。正在为初中生创建一个数学学习模块。现有的光学检测方法无法充分检测三维半导体结构中的微小缺陷，如垂直记忆中的缺陷。该项目通过两个关键目标提供了一条寻找这种缺陷的途径：(I)数值模拟，以开发具有相对场运动的传感和成像；(Ii)以应用为导向的评估性实验。利用背景激光干涉条纹和随机散斑场的模拟被用来研究远亚波长材料几何变量与测量强度之间作为相对位置变化的函数的关系，为基于代价函数的反演提供物理正演模型，并辅助实验设计。正在研究两种类型的相干光学传感实验，以说明在感兴趣的(要表征的)对象和背景场之间的相对运动的技术应用。一种涉及随机散射介质产生的散斑和相关特征的统计提取。另一种是利用通过干涉条纹转换的薄膜，使用正演模型来确定相关参数。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project entails the study of a means to determine information about object features at nanometer length scales, and in situations where the environment does not allow direct imaging of the object, using laser light. The approach is based on relative motion between a structured illumination pattern, formed from coherent light, and the object or material system, where either the light or the object is scanned in small precise spatial steps. To date, because the achievable resolution is generally limited to about one half of the optical wavelength without prior information, the approach in technology to improve spatial resolution or optical memory capacity has been to reduce the wavelength. This faces increasing challenges in moving to shorter wavelengths. On the other hand, the use of relative motion of a sample with a spatially varying optical intensity provides information about the sample that can be used for super-resolution imaging of features far smaller than the wavelength. Consequently, it should become possible to detect small structures of importance in the semiconductor industry and in microscopy. Furthermore, a suite of material inspection and imaging situations have significant background clutter, exacerbating the challenges. For example, it is currently difficult or impossible to detect small defects in the three-dimensional semiconductor processing steps used in building vertical solid-state memory, with multi-billion-dollar market ramifications. With laser inspection following the deposition of films, random scatter due to material roughness produces speckle, and this seemingly worsens the situation. During this project, an inspection and imaging method for extracting information about such defects and other objects by using speckle is being developed. More broadly, the approach enables a means to image objects hidden in a randomly scattering environment such as fog or biological tissue using light. The associated research is forming the basis of theses for two Ph.D. students, and the project involves undergraduate research students. A mathematical learning module is being created for junior high school students.Existing optical inspection methods are incapable of adequately detecting small defects in three-dimensional semiconductor structures like those in vertical memory. This project offers a path to finding such defects through two key objectives: (i) Numerical modeling to develop sensing and imaging with relative field motion; and (ii) Evaluative application-oriented experiments. Simulations with background laser beam interference fringes and random speckle fields are being used to investigate the relationship between far-subwavelength material geometric variables and the measured intensity as a function of relative position change, to provide a physical forward model for cost-function-based inversion, and to aid in the design of experiments. Two types of coherent optical sensing experiments are being investigated to illustrate technology applications with relative motion between an object of interest (to be characterized) and the background field. One involves speckle generated from a randomly scattering medium and statistical extraction of the relevant features. Another utilizes membrane films translated through interference fringes, with the use of a forward model to determine the associated parameters.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.