Spectroscopic Reflectometry

Laboratory spectroscopic reflectometry is a niche market within the surface metrology market. Although it is heavily tied to the semiconductor and electronics industries, its has significant applications in other areas as well. The competitors in the market are generally small, and not particularly well known outside of the surface metrology market.

Spectroscopic reflectometry is used to measure the internal reflectance of thin films, from which the thickness and refractive index can be obtained. The technique is applicable to transparent or weakly absorbing thin films that are on top of reflective or absorbing substrates. Reflectometers measure the intensity of reflected light, usually at normal (90°) incidence to the sample. Nonpolarized light is typically employed and, while the visible spectrum is most commonly used, some instruments also make use of the ultraviolet and near infrared regions. Reflectance measurements can normally be made for single or stacked layers of thin films up to around 50 µm thick. Reflectivity, which is characteristic of thick materials, is different from reflectance.

Like most other surface metrology instrumentation, the largest industrial demand is from the semiconductor and electronics industries. Semiconductor chips are built up using many layers of thin films, making them a prime product for the application of reflectometry. Hard disk drives, LCDs and other electronics also make use of thin films, the thickness and quality of which are analyzed by reflectometry. Although such measurements are more often made using industrial inspection equipment, lab reflectometers play a key role in quality analysis and control and research applications.

Several other industries also use spectroscopic reflectometry. The thin film coatings on medical devices are critical to the devices’ lubricity and biocompatibility. Because many medical devices are reflective metal substrates, spectroscopic reflectometry can often be used. Also, antireflective optical coatings on glasses, windows and optical components are evaluated using reflectometry. The testing of sheet metal that is coated for corrosion, durability and appearance requirements is another application.

There are a number of vendors in the spectroscopic reflectometer market, but they are generally smaller companies and most offer only one instrument model. Some vendors combine reflectometry capabilities with spectroscopic ellipsometers as they are closely related techniques in terms of technology and applications.

Spectroscopic reflectometers are relatively simple instruments and, therefore, are inexpensive. The worldwide market for the technique was around $10 million in 2007. Because of the heavy tie to the semiconductor and electronics industries, which tend to be cyclical and are more directly affected by the consumer economy, demand for the technique is likely to decline in 2008. However, reflectometry should experience moderate average growth well into the future.

Spectroscopic Reflectometry

at a Glance:

Leading Suppliers

• Sentech

• NanoMetrics

• Angstrom Sun Technologies

Largest Markets

• Semiconductor

• Electronics

• Metals

Instrument Cost

• $10,000–$50,000

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