Abstract:

Are you still worried about measuring the film thickness of your products? This article will help you solve the problem of film thickness measurement!

Film thickness measurement plays a key role in semiconductor, microelectronics, optics, display, new energy, automobile, aerospace and other industries. For example: photoresist and dielectric layers in chip manufacturing, functional films of MEMS devices, anti-reflection films of photovoltaic cells, functional layers of perovskite solar cells, etc.

The purpose of measuring film thickness in various industries is: quality control, cost control and technology research and development, to avoid the impact of film thickness on product functionality and safety, to accurately control cost reduction space at the nanometer level, and to break through the bottleneck of technology research and development.

So how to choose a suitable film thickness meter? Today, Dr. Atometrics provides you with selection tips!

Film Thickness Measurement instrument-Classification by Measurement Principle

1. Spectral reflection/light interference method

• Principle: Analyze the interference phenomenon between the film surface and the reflected light from the substrate, and calculate the thickness by combining the spectral reflectance and refractive index. For example: Atometrics AF series film thickness measurement instruments.

• Applicable scenarios: transparent/semi-transparent films such as semiconductor photoresists, liquid crystal display films, optical coatings, quantum dots, etc., with a thickness range of 1nm to 250μm.

Quantum dot chip measured by Atometrics AF series

• In theory, only films made of transparent/semi-transparent materials can be penetrated by light waves, so they can be measured by film thickness meters based on the principle of light interference. However, some opaque materials, such as metals, can also be measured under certain circumstances: when the metal film is only a few hundred nanometers or even a few nanometers thin, it can also be partially penetrated by light waves, and the thickness of the film can then be accurately measured.

Nickel film on Si wafer

2. Magnetic thickness measurement method

• Principle: Determine the thickness by measuring the change in magnetic resistance caused by the non-magnetic coating on the magnetic substrate.

• Applicable scenarios: non-magnetic coating on magnetic metal substrates, such as steel structure anti-corrosion layer, automotive spraying, etc.

3. Eddy current thickness measurement method

• Principle: Use high-frequency alternating current to generate an electromagnetic field in the coil, and the non-conductive coating on the conductive metal substrate will change the eddy current feedback signal to calculate the thickness.

• Applicable scenarios: non-conductive coating on conductive metal substrates, such as aerospace surfaces, aluminum oxide films, etc.

4. Fluorescent X-ray method

• Principle: X-rays are used to excite the material to release fluorescence, and the fluorescence energy and intensity are analyzed to determine the composition and thickness of the coating.

• Applicable scenarios: Non-destructive testing of multi-layer coatings or coatings with complex components, such as electronic component coatings, alloy materials, etc.

5. Ultrasonic thickness measurement method

• Principle: The thickness is calculated by using the time difference of ultrasonic wave reflection at the interface between the coating and the substrate.

• Applicable scenarios: Multi-layer coatings or occasions where magnetic/eddy current methods cannot be measured, but there are few applications in China.

6. Electrolytic Thickness Measurement Method

Principle: The coating is dissolved by electrolysis, and the thickness is calculated based on the current consumption. It is a destructive test.

Applicable scenarios: Coating analysis in laboratories with low accuracy requirements.

7. Radioactive Thickness Measurement Method

Principle: The thickness is measured by the attenuation of particles emitted by radioactive isotopes after penetrating the coating.

Applicable scenarios: Special industrial environments (such as high temperature and high pressure), but the cost is high.

Film Thickness Measurement Instrument - Classification by Film Thickness

Nanometer level  (1nm–100nm)

• Measurement technology: spectral ellipsometer, high-precision spectroscopic interferometer (such as Atometrics AF-3000 series), white light interferometry (such as Atometrics AM series).

• Application: semiconductor thin films (such as silicon nitride, photoresist), perovskite, quantum dots, etc.

Nanometer film measurement by AM series

Submicron level (100nm–1μm)

• Measurement technology: high-precision spectroscopic interferometer (such as Atometrics AF-3000 series), white light interferometer (such as Atometrics AM series).

• Application: optical coating, MEMS device thin film, etc.

Photovoltaic cell ink layer

Micron level (1μm–100μm)

• Measurement technology: magnetic method, eddy current method, high-precision spectroscopic interferometer (such as Atometrics AF-3000 series).

• Application: industrial anti-corrosion coating, printed circuit board plating, etc.

Microchannel

Millimeter level (>100μm)

• Measurement technology: ultrasonic method, high-precision spectroscopic interferometer (such as Atometrics AF-3000 series), spectral confocal technology (such as Atometrics AP-5000 series).

• Application: thick film coating, composite materials, etc.

AP sereis confocal displacement sensor

Combining the above two considerations: measurement principle and thickness magnitude, the range of measurement products suitable for the film to be measured can be greatly narrowed down. Then, the most suitable film thickness measurement method can be selected by combining measurement results, accuracy requirements, measurement efficiency and instrument cost.

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