5 minute read
Cutting Edge Applications Using Spectroscopic Ellipsometry
Since the 1960s, as ellipsometry developed to provide the sensitivity necessary to measure nanometer-scale layers used in microelectronics, interest in ellipsometry has grown steadily. Today, the range of its applications has spread to the basic research in physical sciences, semiconductor and data storage solutions, flat panel display, communication, biosensor, and optical coating industries.
Spectroscopic Ellipsometry is being used in all sorts of cutting edge applications. This widespread use is explained by increased dependence on thin films in many areas and the flexibility of ellipsometry to measure most material types: dielectrics, semiconductors, metals, superconductors, organics, biological coatings, and composites of materials.
Virtual and Augmented Reality
There is continued customer demand for integrated devices that provide increased situational awareness within the natural environment and that enable immersive experience for both technical and recreational purposes. Tech innovators are rapidly developing hardware that meet these demands ranging from headsets to integrated, wearable sensors. Ellipsometry is used in the development and production of many of these devices from detecting polarising effects such as birefringence and dichroism to characterisation of anti-reflection coatings, touchscreens, and flexible displays. We are excited to contribute to the development and production of such an exciting and rapidly growing field.
Architectural Glass
Thin film coatings have long been used to improve the thermal and optical properties of glass. Coatings on glass can be designed to change the visual colour of the glass for artistic design, commonly noticed on buildings and skyscrapers around the world. The consistency and uniformity of the coatings are critically important to ensure each pane of glass looks the same. Thin film coatings have also been used to improve the thermal efficiency of buildings. Passive approaches are designed to limit heat flow in or out by limiting the transmission of infrared light.
Active technologies are being used that control the transmissibility based on ambient lighting and other factors. Ellipsometers are used in the development of these new styles of coatings while also helping in production to ensure consistency and uniformity across each pane of glass.
Advanced Optics
The James Webb Space Telescope was recently launched into space and features gold-coated beryllium mirrors for imaging infrared signatures of galaxies too distant for Hubble to witness. To detect faint infrared signals, the thermal signature of the telescope must be reduced and thermal radiation from other sources must be blocked. A sunshield was developed to protect Webb from external sources of radiation. The sunshield is composed of a Kapton substrate coated with aluminium and doped-silicon films to reflect incident radiation back into space. Spectroscopic Ellipsometry was used to ensure the film properties meet design specifications for critical components like the sunshield. Ellipsometry is also used to ensure that the optical properties of these specialised coatings enable the telescope to transmit beautiful images back to earth for many years to come.
Biomedical Devices
Medical devices implanted or adhered to the body require specialised coatings to ensure biocompatibility, improve functionality, and increase the lifespan of the device within the body. Coatings are engineered to reduce inflammation caused by the device and therefore reduce the associated risk of infection. Thin-film coatings on these devices have also been designed to improve corrosion resistance caused by interactions with bodily fluids. Many different methods of deposition have been developed to optimise the coatings.
Ellipsometry is one form of metrology used in development and quality control of thin-film deposition on bio-implanted or adhered devices. Woollam technology is used to monitor the consistency of the coating as well as ensure its presence on the device.
Displays
Pure electrical insulators are highly transparent, but highly conductive metals are opaque. So what material can be used that is both transparent and conductive? We must find such a material to make our displays and touchscreens work.
Indium tin oxide (ITO) is both transparent and conductive ITO optical properties vary a lot with deposition conditions and annealing, so monitoring the quality of the ITO and its thickness is important. Ellipsometry is used for monitoring ITO film thickness and transparency at visible wavelengths while also being sensitive to absorptions in the ultraviolet, but it is very important for monitoring absorption in the infrared, which corresponds to the film’s electrical conductivity.
Improvements in display speed are critical for fast action in movies and sports. Imagine a baseball, golf ball, or hockey puck leaving a comet tail behind on the screen because the display cannot refresh fast enough.
Display pixel speed has been significantly enhanced using crystallised silicon films on the rear panel of the display. Ellipsometry is used to monitor the thickness and crystallinity of these deposited polysilicon films.
LCD displays used to be small, monochrome in color, and used in calculators, digital watches, etc. Modern displays are full colour, extremely fast, and very large. The coated films must be uniform over the entire panel size, and film uniformity has been a limiting factor in the size of displays for decades. With each new generation of larger displays, the film uniformity must be maintained. An ellipsometer can fly over the large panels as they move on a production line to monitor film quality.
SPECTROSCOPIC ELLIPSOMETRY
WORKSHOP AND SHORT COURSE 2025
Glasgow University – One A The Square
September 16, 2025
We are celebrating 25 years of Spectroscopic Ellipsometry workshops with our partners, J. A. Woollam.
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What’s your application?
We love to hear about your scientific challenges So, to discuss ellipsometry and your application, contact our Technical Director, Dr. Shayz Ikram, by email or call (01372) 378822
