Thickness and birefringence of thin films assessed by interferometry using a low-cost spectrometer

Nemoto, Fumiya

doi:10.1080/00387010.2021.1991382

Cited by 2 publications

(2 citation statements)

References 34 publications

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“…Figure 1 shows a schematic of multiple interferences of the monolayer as illustrated elsewhere [35,36]. The incident light with an angle of θ 1 through the air media with a refractive index of n 0 was reflected at the surface with a reflection coefficient of r 01 and transmitted to the film media of n 1 with a transmission coefficient of t 01 .…”

Section: Basic Principlementioning

confidence: 99%

Large-Area Thickness Measurement of Transparent Films Based on a Multichannel Spectral Interference Sensor

Huang,

Tu,

et al. 2024

Applied Sciences

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Thickness measurement of thin films is essential for quality control in the manufacturing process of the semiconductor and display industries. Real-time monitoring of film thickness during production is an urgent technical problem to be solved. In this study, a method for large-area thickness measurement of transparent films based on a multichannel spectral interference sensor is proposed. The sensor simultaneously acquires multichannel spectral interference signals through a combination of fan-out fiber optic bundles, detection probes, and an imaging spectrometer. The spectral data are calibrated and transformed into the wavenumber dimension, and then the power spectral density estimation method is used to demodulate the data frequency to swiftly derive the film thickness. The thickness measurement capacity of the proposed system is successfully validated on two standard film samples with a relative deviation of less than 0.38% and a relative standard deviation of less than 0.044%. The total spectral acquisition and calculation time for a single multichannel measurement was approximately 7.5 ms. The experimental results on polyimide films show that the measurement efficiency of the system is at least 4 times higher than that of the traditional system, indicating the potential of the multichannel spectral interference sensor for online monitoring in film production.

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Section: Basic Principlementioning

confidence: 99%

Large-Area Thickness Measurement of Transparent Films Based on a Multichannel Spectral Interference Sensor

Huang,

Tu,

et al. 2024

Applied Sciences

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“…To the best of our knowledge, this is the first time the proposed sensors have been used for thin film measurements in an in situ small package device, as proposed in this research. Although Nemoto presented a work where one of the identified sensors was used for thin film thickness measurements, they were used in a microscope setup, which does not address the process scalability [19]. Additionally, the identified sensors have previously been used for applications such as measuring fruit ripeness, identifying wood defects and other hyperspectral imaging measurements [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

A Spectroscopic Reflectance-Based Low-Cost Thickness Measurement System for Thin Films: Development and Testing

Sánchez-Arriaga,

Tiwari,

Hutabarat

et al. 2023

Sensors

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The requirement for alternatives in roll-to-roll (R2R) processing to expand thin film inspection in wider substrates at lower costs and reduced dimensions, and the need to enable newer control feedback options for these types of processes, represents an opportunity to explore the applicability of newer reduced-size spectrometers sensors. This paper presents the hardware and software development of a novel low-cost spectroscopic reflectance system using two state-of-the-art sensors for thin film thickness measurements. The parameters to enable the thin film measurements using the proposed system are the light intensity for two LEDs, the microprocessor integration time for both sensors and the distance from the thin film standard to the device light channel slit for reflectance calculations. The proposed system can deliver better-fit errors compared with a HAL/DEUT light source using two methods: curve fitting and interference interval. By enabling the curve fitting method, the lowest root mean squared error (RMSE) obtained for the best combination of components was 0.022 and the lowest normalised mean squared error (MSE) was 0.054. The interference interval method showed an error of 0.09 when comparing the measured with the expected modelled value. The proof of concept in this research work enables the expansion of multi-sensor arrays for thin film thickness measurements and the potential application in moving environments.

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Thickness and birefringence of thin films assessed by interferometry using a low-cost spectrometer

Cited by 2 publications

References 34 publications

Large-Area Thickness Measurement of Transparent Films Based on a Multichannel Spectral Interference Sensor

Large-Area Thickness Measurement of Transparent Films Based on a Multichannel Spectral Interference Sensor

A Spectroscopic Reflectance-Based Low-Cost Thickness Measurement System for Thin Films: Development and Testing

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