Kari O'Rourke 0000-00-00 00:00:00
Microscopy Technology Results in Sharper Images New microscopy technology breaks the optical diffraction limit while delivering lateral resolutions that were previously unattainable. Released at the end of last year at the Materials Research Society (MRS) Fall 2010 Meeting in Boston, the AcuityXR from Bruker Nano Surfaces Business (Tucson, AZ), is an enhancedresolution microscopy technology available on select models of the ContourGTTM family of noncontact, three-dimensional (3-D) optical surface profilers. This innovative capability combines patent-pending hardware and software to determine what a part under test truly is while breaking the optical diffraction limit. As a result, blurred features turn out sharper and the heights of narrow structures are more accurately measured. The technology is an extension of Bruker’s interferometric microscope capability and mostly enables these systems to exceed the capability of other optical profilers. It also extends the lateral resolution of optical profiling closer to the realm of atomic force microscopy (AFM) measurements, which in some applications will allow manufacturers to measure their parts without resorting to slower and more complex technology. “AcuityXR increases the lateral resolution of select three-dimensional optical profilers by nearly a factor of three, allowing detection of features down to 130 nanometers in width on a wide variety of surfaces,” says Erik Novak, director, technology development optical products, Bruker Nano Surfaces Business. “This breakthrough technology therefore allows the fast measurement times, high vertical accuracy and repeatability of Bruker’s ContourGT optical profilers to be applied to measurement of narrower features, such as fine defects, small structures on MEMS devices, and structures in glass, semiconductors and polymers.” The company adds that the technology is not suitable for rough surfaces— those with surface roughness greater than 30 nanometers—but provides excellent capability for smooth surfaces, even those with large steps or other features. Surface defects often can affect function, performance, quality and manufacturing yields and are a concern to quality assurance and quality control (QA/QC) personnel. With this new technology, optical surface profiler systems can measure and resolve sample areas of interest under extreme magnification with zero or little stitched fieldsof- view, which improves ease of use. The higher pixel density from AcuityXR allows the resolution of nanometer-level features that have been impossible to resolve with conventional confocal or interferometric microscopy techniques. According to Novak, techniques based on microscopy in the visible range typically can only reliably image features down to about 500 nanometers in width, though most optical profilers claim capability down to the 300- to 400-nanometer range. In a study of line width metrology on 300-nanometer features, however, the AcuityXR improved the accuracy of the measurement by more than 25% and repeatability by more than a factor of five. Thus, reliable quantification is available on parts where before only a qualitative measure could be achieved. While the theory to increase lateral resolution of optical systems has been around for decades, and there has been great success with improved resolution in systems by the number of camera pixels available—such as in video or satellite images—Bruker was determined to extend the capability in a practical method to surface metrology, including when the resolution is curtailed by the optical diffraction limit. The technology has been in development for approximately two years, wherein a variety of approaches were tried and discarded before achieving a reliable method that worked on a wide range of samples under test. So far, the response has been positive. Novak says that the customers who saw the demonstrations claim that the images closely resembled those from Bruker’s AFMs. One customer in the energy storage industry decided to purchase their optical profiler with the AcuityXR immediately upon seeing the data and comparing it to scanning electron microscope images of the same surface. Uniformly, customers have been impressed with the lateral and vertical resolution provided by such measurements. SPECIFICATIONS Resolves features 130 nanometers in width Minimizes optical effects, providing true dimensions of narrow features Improves dimensional repeatability on nanoscale structures by a factor of 5X Allows wider field-of-view and higher pixel density than equivalent magnifications obtained with conventional means Improves sharpness, clarity and definition of scratches, defects and surface texture
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