Real-time ellipsometry analysis and quality control of thin films
The challenge: Real-time ellipsometry analysis of complex materials
Ellipsometry is an optical technique used to characterise properties of thin films such as thickness, roughness, optical constants, composition, crystallinity, quality and concentration. In the study of mono-layered materials, these properties can be measured by fitting certain parameters, such as refractive indexes, into a model.
However, when studying complex multi-layered absorbing materials such as semiconductors, model analysis becomes challenging, computationally expensive and time-consuming.
In practice, real-time analysis of multi-layered thin films is limited to determining the thickness of the sample only, followed by intensive post-production quality testing. As a result, product defects are not identified until postproduction, causing high material wastage and process inefficiency.
The market: a competitive highly concentrated industry
The ellipsometer industry is a mature market, expected to grow at a CAGR of 5.5% until 2025. The growing interest in ellipsometry due to the need to measure nanometre-scale layers in a variety of industries is envisaged to drive the demand in the global ellipsometer industry.
Scientific advances in complex nanomaterials, in fields as varied as microelectronics, biology or medicine, are calling for further sophistication in ellipsometry instrumentation in an industry with increasing levels of competition.
Researchers at Oxford University have devised a quick, low-cost method to monitor dynamic changes and quality of multi-layered thin films during manufacture. The method enables in-situ, real-time analysis of spectroscopic ellipsometry data throughout each layer’s deposition.
The invention relies on a mathematical method to analyse raw data such as amplitude ratio (ψ) and phase difference (Δ), to extract parameters of interest representative of the refractive indices (n + j k) which are a measure of the quality of the layers.
Key advantages of the invention are:
- Changes in film properties and structure can be studied real-time during layer deposition and film growth, enabling in-situ quality control
- Spectroscopic data can be studied real-time
- Defects can be detected in real-time during manufacture, reducing wastage
- Energy-saving does not require computationally intensive modelling
- Time of analysis is reduced to milliseconds, compared to hours or even days required with computer modelling
- Highly useful for scientific research for examining quantum-level interactions
The method has applications in the analysis of a range of evolving systems such as thin film growth, surfaces, biomolecular interactions and electrochemical processes, among others.
Oxford University Innovation has filed a UK patent with the potential to be extended to international coverage and is looking for potential partners to aid in the commercialisation of the technology.
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