The non-contact NT3300 features advanced automation and outstanding software for highly accurate, 3D surface topography measurements. The most advanced surface metrology system available, the NT3300 rapidly measures heights from Angstroms to millimeters, with vertical resolution to 0.1 nm. The NT3300 is ideally suited for quality inspection, failure analysis and rapid production measurement of MEMS, semiconductor packaging, medical devices, automotive systems and many other applications.
What is Interferometry?
Interferometry is a series of non-contact techniques, which use the interference of light to determine surface shape and transmission properties.
A light source is split into two beams, which reflect from a test and reference surface, recombining to form a pattern of interferences or "fringes." The test surface is scanned such that each point passes through focus. A series of fringe patterns, or "interferograms," are recorded, from which the height of each point on the surface can be mapped with subnanometer resolution.
In white light interferometry, or optical profiling, a white light source is employed to measure surface topography from 0.1 nm roughness to 8-millimeter step heights, as well as critical lateral dimensions.
In laser interferometry, a collimated laser beam is used to measure the surface shape and/or transmitted wavefront quality of optics and optical systems, as well as film thickness.
The Optical Profilometer utilizes two different measurement modes:
- VSI, or vertical scanning interferometry, uses the interference of light to map the surface of your sample. VSI is used for relatively rough surfaces (Ra greater than 0.1µm) or surfaces with discontinues or steps greater than 160nm (λ/4). In VSI, the optics physically scan through the focus of the objective while obtaining “snapshots,” called frames, from the camera inside the Integrated Optics Assembly (IOA). The frames are used to reconstruct a map of the surface of the sample.
- PSI, or phase shifting imterferometry, also uses the interference of light to produce information on the surface of a sample. PSI is used for extremely smooth samples like mirrors or optics. In PSI, a PZT (piezoelectric transducer) within the IOA head precisely shifts the interference pattern six times; each shift is captured to produce one frame of data. The frames are then reconstructed to form a topographical map of the measured surface. PSI is typically used to measure samples with Ra between 1Ĺ- 160nm.