Flexus 2320

The Flexus 2320 determines wafer curvature by measuring the angle of deflection of a laser beam off the surface of the substrate. Film stress is determined by comparing the change in radius of curvature of the substrate, with and without the film. This means that the substrate and the film must be optically reflective in the wavelength used. Because semi-transparent films may absorb light (depending on the incident wavelength/angle and the film thickness/RI) the Flexus 2320 has two wavelengths (670 nm and 750 nm).