Nondestructive shape process monitoring of three-dimensional, high-aspect-ratio targets using through-focus scanning optical microscopy

Abstract

Low-cost, high-throughput and nondestructive metrology of truly three-dimensional (3-D) targets for process control/monitoring is a critically needed enabling technology for high-volume manufacturing (HVM) of nano/micro technologies in multi-disciplinary areas. In particular, a survey of the typically used metrology tools indicates the lack of a tool that truly satisfies the HVM metrology needs of 3-D targets, such as high aspect ratio (HAR) targets. Using HAR targets here we demonstrate that through-focus scanning optical microscopy (TSOM) is a strong contender to fill the gap for 3-D shape metrology. Differential TSOM (D-TSOM) images are extremely sensitive to small and/or dissimilar types of 3-D shape variations. Based on this here we propose a TSOM method that involves creating a database of cross-sectional profiles of the HAR targets along with their respective D-TSOM signals. Using the database, we present a simple-to-use, low-cost, high-throughput and nondestructive process-monitoring method suitable for HVM of truly 3-D targets, which also does not require optical simulations, making its use straightforward and automatable. Even though HAR targets are used for this demonstration, the similar process can be applied to any truly 3-D targets with dimensions ranging from micro-scale to nano-scale. The TSOM method couples the advantage of analyzing truly isolated targets with the ability to simultaneously analyze many targets present in the large field-of-view of a conventional optical microscope.

3D microscopy in industrial measurements

“…93,94 The method has promising application prospects for highaspect-ratio microstructure measurements. 95,96 The measurement method extracts the size information of the structure by matching the optical simulation data library and defocused images captured along the scanning direction. However, the actual measurement environment is susceptible to the interference of noise, the matching degree may be poor, resulting in large measurement errors.…”

“…Another nondestructive optical metrology technique, through‐focus scanning optical microscopy, is highly sensitive and suitable for nanostructure measurements 93,94 . The method has promising application prospects for high‐aspect‐ratio microstructure measurements 95,96 . The measurement method extracts the size information of the structure by matching the optical simulation data library and defocused images captured along the scanning direction.…”

Use of the Airy beam to extend the micro-hole measurement range of an OCT system

“…The depths and widths of the microholes affect the groove's filling effect [5], which in turn affects the quality and performance of three-dimensional chip integration. The commonly used micro-hole measurement techniques include coordinate measuring machines [6], length measuring machines [7], and non-contact detection instruments [8][9][10]. The first two methods have high measurement accuracy; however, their disadvantage is that the instrument probe scratches the surface when it contacts the aperture, causing large errors.…”

MEMS High Aspect Ratio Trench Three-Dimensional Measurement Using Through-Focus Scanning Optical Microscopy and Deep Learning Method

“…To date, various methods have been used to measure the HAR structures of MEMS [9,10]. Scanning electron microscopy (SEM) is a commonly used tool with high resolution and high magnification, but it is costly, inefficient, and not suitable for online real-time detection.…”