Lithography aware overlay metrology target design method

Lee, Myungjun; Smith, Mark D.; Lee, Joonseuk; Jung, Mi-Rim; Lee, Honggoo; Kim, Young‐Sik; Han, Sangjun; Adel, Mike; Lee, Kangsan; Lee, Dohwa; Choi, DongSub; Liu, Zephyr; Itzkovich, Tal; Levinski, Vladimir; Levy, Ady

doi:10.1117/12.2218653

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…Using the angle-resolved pupil plane image (each pixel measuring its diffraction angle) allows the use of different weights to optimize the reported overlay. One of the main problems when measuring small targets is that light scattered from the edge of the target mixes with the desired signal and introduces noise [4]. Thus, our approach was to expand the illumination NA in the pupil to minimize the spot in the field plane and smooth the spot edges to avoid high spatial frequencies in the field plane.…”

Section: Measurement Systemmentioning

confidence: 99%

Scatterometry overlay (SCOL®) measurement of small cell target using pupil optimization

Gdor

Nagar

Yaziv

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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In semiconductor chip manufacturing, dedicated metrology targets are used for measuring overlay (OVL) between layers after the lithographic process step. Until recently, overlay targets have had typical dimensions of 20x20 microns, but have been reduced in size to allow for more critical product real estate. Reducing metrology target size, however, increases optical crosstalk and diffractions from the target’s edges which can introduce significant errors in the reported OVL values. In this work, we will evaluate the following parameters: 1. The beam spot shape on the metrology target 2. The best target design under size/wavelength constraints 3. Improved OVL extraction algorithm We will present the hardware and software optimizations for experimental measurements taken over a cascade of targets. While decreasing the target’s size, we quantified the OVL measurement performance via dynamic precision, tool-induced shift (TIS), and results through focus (Z position). We will demonstrate how these optimizations enable the measurement of targets as small as 6x6 microns without compromising throughput or measurement quality.

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Section: Measurement Systemmentioning

confidence: 99%

Scatterometry overlay (SCOL®) measurement of small cell target using pupil optimization

Gdor

Nagar

Yaziv

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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“…[10][11][12] There are also several research studies for evaluating and minimizing target noise. [13][14][15] This paper proposes a new overlay target to solve these two problems.…”

Section: Conventional Overlay Target Designmentioning

confidence: 99%

Image-based overlay target design using a grating intersection

Lee¹,

Chang²,

Shin³

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Background: An overlay target design is essential before performing overlay metrology and has a great impact on overlay performance. In addition, accurate overlay metrology is required to achieve high product yields in semiconductor manufacturing. When asymmetry of the overlay target occurs, it is necessary to increase the area of the pattern existing in the target and stabilize the optical aberration for stable measurement. For this reason, we propose an image-based overlay target design that can secure a larger area compared with the existing overlay target and stabilize the optical aberration by overlapping and exposing the upper and lower patterns of the overlay target.Aim: The effective area of the existing mark design is improved by proposing an overlay target and a measurement method used in image-based overlay measurement.Approach: The proposed overlay target design is configured by arranging different marks orthogonally to the upper and lower layers, and different two-dimensional information can be inserted in the same area. When necessary, single-dimensional information desired by the user can be obtained through a technique called projection, and it has the advantage of using a larger effective area than the existing overlay target.Results: Overlay can be measured using projected signal components, and the possibility and performance of the proposed target can be confirmed through simulation and test wafer. In addition, it was possible to bring about a 15% improvement in total measurement uncertainty performance compared with the existing advanced imaging metrology (AIM) target by taking a wider effective area.Conclusions: An overlay target design is proposed to solve the technical problems of the existing overlay target design. The proposed overlay target has a method that is capable of minimizing the size of the overlay target while maximally maintaining the signal density, a way of reducing the influence of aberration, and various other advantages.In addition, the proposed method provides a design rule that breaks the "lower pattern and upper pattern must not overlap" framework.

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