In the fields of modern optoelectronics, semiconductors, and precision optics, a single thin film is no longer sufficient to meet complex functional requirements, and multilayer film stacking has become the norm. However, the thickness, uniformity, and control of interlayer interfaces of each layer of film pose severe challenges to measurement technology. The application of optical film thickness gauge in industrial field for multi-layer film analysis has become a core means to ensure device performance. As a professional provider of thin film measurement solutions, Unicon Technology Co., Ltd. (Yiying Technology)Optical film thickness gauge productsIt has demonstrated practical value in the analysis of multi-layer film stacking. This article will delve into its working principle and typical industrial applications.
1、 What are the difficulties in measuring multilayer films?
Unlike single-layer films, the measurement of multi-layer film stacking faces several main challenges:
Unknown optical constants: The refractive index (n) and extinction coefficient (k) of each layer material may vary with the process, and traditional single wavelength measurements are difficult to distinguish.
Interlayer interference is complex: incident light undergoes reflection and transmission at multiple interfaces, forming complex spectral superposition signals that require powerful algorithms for decoupling.
The thickness range spans from ultra-thin functional layers of a few nanometers to insulating layers of a few micrometers, requiring equipment to have a wide range and high resolution.
2、 Measurement principle and core advantages of optical film thickness gauge
To address the above challenges, the most widely used technology for optical film thickness gauges is spectral reflectance. The principle is that when a beam of broad-spectrum light (such as 380-1050nm) is vertically incident on the surface of a thin film, the reflected light from different interfaces will interfere, forming a spectrum with characteristic oscillations. By analyzing the oscillation frequency and amplitude of these spectra, and combining them with optical models in professional software such as FILMeasure, the thickness, refractive index, and extinction coefficient of each layer can be fitted at once.
The advantage of this method is that:
Non contact, non-destructive: No damage to soft or patterned wafers.
Information rich: Multiple layer thickness and optical constants can be obtained in one measurement.
Fast measurement speed: Single point measurement is usually completed within seconds, meeting the rhythm requirements of industrial site sampling or online monitoring.
3、 Analysis of Practical Application Scenarios in Industrial Sites
The application of optical film thickness gauge in multiple cutting-edge industrial fields has become very mature. Here are several typical practical cases:
Semiconductor manufacturing (such as STI shallow trench isolation, photoresist multilayer stacking):
In advanced manufacturing processes, photoresist often needs to be spin coated into a multi-layer structure to achieve better pattern transfer effects. Engineers can use Filmetrics F20 or the F50 series film thickness gauge that supports Mapping function to quickly measure the thickness distribution of multilayer films such as oxides/nitrides/photoresists on silicon wafers. Its precision of up to 0.02nm is sufficient to monitor changes in single atomic layer thickness, ensuring the accuracy of etching and deposition processes.
Optical coating (such as anti reflective film, high reflectivity film):
A typical anti reflective film may consist of 4-10 layers of alternating high and low refractive index materials (such as TiO ₂/SiO ₂). The application of optical film thickness gauge in this scenario not only monitors the physical thickness of each layer, but also calculates its optical thickness (n * d) in real time, which is a key parameter determining the final performance of the film system. By integrating into the coating machine, the F32 series online equipment can achieve closed-loop control, significantly improving product yield.
Display technology (such as OLED, ITO/organic layer in LCD):
In OLED devices, the total thickness of multi-layer organic thin films such as hole injection layers and electron transport layers may only be a few tens of nanometers. By using an optical film thickness gauge equipped with a micro spot (with a minimum of 1 micron, such as the F40 series), fixed-point measurements can be directly performed on glass substrates with precision circuits for non-destructive evaluation of film quality.
4、 Why choose the optical film thickness solution from Nikon Technology (Yiying Technology)?
The successful application of optical film thickness gauge relies on the integration of hardware, software, and services. As the general agent of Filmetrics in China, Younikon Technology Co., Ltd. (Yiying Technology) has obvious advantages in its solutions:
Rich material database: The FILMeasure software that comes with the device has built-in optical constants for thousands of commonly used thin film materials (such as SiNx, TiO2, ITO, photoresist, etc.), which can quickly establish analysis models.
Flexible multi-layer analysis capability: The software supports the construction of complex multi-layer film models and allows for unknown optical constants of some layers to be fitted together through algorithms, reducing the analysis threshold.
Professional application support: The team has over 10 years of industry experience and can provide customers with free sample testing services and one-on-one modeling guidance to ensure the smooth implementation of on-site applications.
5、 Conclusion
In summary, in the face of increasingly precise and complex measurement requirements for multi-layer film stacks, the application of optical film thickness gauges has shifted from being an "optional tool" in the laboratory to a "standard configuration" in industrial fields. It has become a reliable partner for engineers to monitor processes and improve yield rates, thanks to its non-contact, high-precision, and fast speed advantages.
Unicon Technology Co., Ltd. (Yiying Technology) is helping more and more industrial customers overcome the difficulties of multi-layer film measurement by providing stable optical film thickness gauges, powerful analysis software, and professional technical support. If you are facing similar application challenges, you may want to delve into their products and application solutions, and I believe you will gain some insights.
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