Hybrid overlay control solution with CDSEM and optical metrology

Wu, Chengzhang; Xu, Duanfu; Yuan, Hua; Yu, Yinsheng; Zhao, Hongwen; Zhou, Wenzhan; Pu, Haifeng; Liu, Faquan; Pei, Jason; Song, Jinyan; Huang, Chung‐Che

doi:10.1117/12.2583804

Cited by 3 publications

(2 citation statements)

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“…Sensor miniaturization, distributed measurement systems, and complex measurement data processing algorithms are becoming inherent functionalities of modern measurement systems. This trend is also observed in optical metrology [ 1 , 2 ] and it is resulting in new application perspectives [ 3 , 4 , 5 ]. Applications of new technologies using integrated optical modules are also increasing in spectral metrology.…”

Section: Introductionmentioning

confidence: 82%

Micro-Electro-Mechanical Systems in Light Stabilization

Gilewski

2023

Sensors

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This article discusses application considerations in the micro-electro-mechanical system’s optical sensor. Furthermore, the provided analysis is limited to application issues occurring in research or industrial applications. In particular, a case was discussed where the sensor was used as a feedback signal source. Its output signal is used to stabilize the flux of an LED lamp. Thus, the function of the sensor was the periodic measurement of the spectral flux distribution. The application problem of such a sensor is the output analogue signal conditioning. This is necessary to perform analogue-to-digital conversion and further digital processing. In the discussed case, design limitations come from the specifics of the output signal. This signal is a sequence of rectangular pulses, which can have different frequencies, and their amplitude varies over a wide range. The fact such a signal must be conditioned additionally discourages some optical researchers from using such sensors. The developed driver allows measurement using an optical light sensor in the band from 340 nm to 780 nm with a resolution of about 12 nm; in the range of flux values from about 10 nW to 1 μW, and frequencies up to several kHz. The proposed sensor driver was developed and tested. Measurement results are presented in the paper’s final part.

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Section: Introductionmentioning

confidence: 82%

Micro-Electro-Mechanical Systems in Light Stabilization

Gilewski

2023

Sensors

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“…The Critical Dimension -Scanning Electron Microscope (CD-SEM) is a common tool to analyze the process at a local scale and is usually used for AEI overlay metrology. 7,8 CD-SEMs are very efficient when measuring indie dedicated targets, 2 however their application to target-free OPO measurement is not as intuitive. This paper proposes a way to enhance an existing CD-SEM tool fleet into measuring OPO using post-processing contour extractions.…”

Section: Introductionmentioning

confidence: 99%

High-spatial frequency on-device overlay characterization using CD-SEM contours

Bourguignon

Gratiet

Pradelles

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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The on-device and target-less overlay (OVL) measurement adds various challenges to the conventional target-based one.1 Most of the common solutions are based on the use of high voltage SEM to have a high resolution and see-through capabilities to see both layers entirely. To ensure repeatability and robustness the measurement is also generally realized on dedicated targets.2–4 Another approach is explored in this work : it consists of a direct measurement on the device itself, without any dedicated target and using a CD-SEM that do not have see-through capabilities. To avoid any damage on the final device and to ensure a partial vision of the bottom layer, the measurement is realized post etch. What can a true on-device, target-less, SEM overlay metrology reveal of the process? To answer this question, a custom design-based on-device CD-SEM overlay metrology was developed.5 It allows measuring the overlay on any bilayer 2D structure, even partially hidden, provided that sufficient edges are visible. Thanks to this post-processing capacity to measure on partially hidden patterns, the CD-SEMs from the current tool park can be used and non-transparent layers can be investigated. After demonstrating the capability of the previously mentioned solution on synthetic SEM images,6 by taking advantage of the versatility of the method and of an improved bilayer contour extraction algorithm, one product wafer was measured densely at different steps of the process on several patterns. These extensive measurements aim to reveal overlay signatures at different spatial frequencies: intra-field, intra-chip and even inside a random logic array. This paper details and interprets the observed overlay measurement with models while investigating the matching between the different measurement patterns and the mismatches with the optical overlay. To conclude, the contour-based metrology offers the capability to extract highly valuable information from CD-SEM images and represents a great opportunity for on-device overlay measurement. By measuring directly the products’ patterns, the developed metrology shows a mismatch between optical and SEM measurements up to a couple of nanometers. A hybrid model, mixing SEM and optical measurements reduced by 15% the on-product residuals. Additionally, the local overlay variability could be evaluated and low amplitude chip signatures have been observed. This new information will help process engineers to improve the process characterization, leading to a better process control that results in an improved reliability.

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