Reflectometry, as its name suggests, is a measurement technology that depends on analyzing the light reflected off a surface. The technique is used to characterize the properties and qualities of surfaces and surface coatings. Applications include thin film metrology, thin film optical properties, surface roughness, optical roughness, luminance, opacity, gloss, haze and other features of reflected light.

The basic technology is simple. A source of light is directed onto the sample surface, and the reflected light is detected. Subtleties in the measurements come from varying different parameters. The light source is typically a broad spectrum source, so that the reflectance can be measured at many different wavelengths, helping to build up a reflectance spectrum. The light wavelengths used are typically in the visible range, although reflectometers that reach into the IR and UV are common. Another parameter that may be of interest is the angle of incidence. While many reflectometers use normal incidence (i.e., perpendicular to the surface), many other possibilities exist. Some reflectometers will be fixed at a particular angle of incidence, while more flexible systems allow the angle to be varied.

One of the most common applications for reflectometry is in the characterization of thin films on semiconductor or optical substrates. Depending on the application, the instrument can be used to measure the film thickness, or certain optical properties of the thin film material, such as the index of refraction and the extinction coefficient. The accuracy of complex measurements, such as those of films made of several different layers, is often dependent on building up a mathematical model. These more challenging applications may be better suited to analysis using ellipsometry. However, for many common quality control applications, a simple reflectometer is often sufficient. Another broad class of applications is the analysis of paper and other packaging materials, and especially the inks, paints and coatings that are applied to them. Reflectometry is used to measure the gloss and luminance of these coatings, or to measure the optical roughness of the underlying paper materials. Some systems can also be configured to make transmission measurements.

There are a modest number of market participants, mostly very specialized firms involved in optical measurements like reflectometry and ellipsometry. Nanometrics is the market share leader, although much of its reflectometry business is in process tools. However, the firm does offer a lab system. SENTECH and Scientific Computing International (SCI) are the next most significant vendors. SENTECH is entirely focused on lab systems, while SCI offers both lab and process tools for reflectometry. Other market participants include Accurion, Angstrom Sun Technologies, Halma, Nano-View, Semilab, Surfoptic and WITec. Zehntner offers a very specialized portable system. The total 2013 market demand for lab reflectometry was about $10 million.

Reflectometry at a Glance:

Leading Suppliers

• Nanometrics

• SENTECH

• SCI

Largest Markets

• Thin Films

• Paper

• Paints/Coatings

Instrument Cost

• $10,000–$50,000