3D microscopes based on white light interferometry (WLI) with vertical scanning have been widely used in many areas of surface measurements and characterizations for decades. This technology provides fast, non-contact, and full-field surface 3D measurements with vertical resolution as low as the sub-nanometer range. Its applications include measurements of step height, surface roughness, film thickness, narrow trench and via depths as well as other geometric and texture parameters. In order to assure the highest accuracy of the measurement, scanner linearity needs to be maintained or monitored so that the nonlinearity can be accounted for during the measurement. This paper describes a method that accounts for nonlinearities in real time without the need to store frame data; in addition this method is shown to be less sensitive to vibrations than previous methods described. The method uses an additional interferometer, a distance measuring interferometer to measure the actual scanner position at each scan step.
Increasing demand for high-brightness (HB) LEDs is prompting manufacturers to refine production methods and
improve performance of LED light sources. Achieving either of these requires high precision metrology tools that
are also fast and non-destructive. In particular, there is a need for the metrology for patterned sapphire substrates
(PSS) used in LED manufacturing to enhance light-extraction efficiency.
This article describes a gauge-capable metrology tool that is currently used for these purposes: the 3D optical
microscope based on white-light interferometer (WLI) which with special algorithms for fringe analysis can
specifically quantify the height, width and pitch for each individual PSS structure. We have measured a variety of
structures and their dimensions and compared them to SEM or AFM results. The white-light interferometer (WLI) is
a tool that better meets the needs of these applications because of the ease of its full field measurement and for faster
defects detection. 3D optical microscopes also provide excellent repeatability, especially when employing the
automated position calibration of the reference mirror position in the interferometric objective.
Conference Committee Involvement (2)
Optical Metrology and Inspection for Industrial Applications IV
12 October 2016 | Beijing, China
Optical Metrology and Inspection for Industrial Applications III