Mechanical-free optical technology for nanostructures inspection

We present a novel all optical technology for precision nanoscale pattern inspection. The approach utilizes imaging system with the high value of axial chromatic aberration and a low-cost light source tunable in the ~30 nm wavelength bandwidth. Such combination allows us to capture defocused images in highly stable conditions without mechanical scanning of either tested sample or image sensor. Further processing of the diffraction images in the defocused planes gives one an ability to compare inspected objects and, using a library of preliminary measured data, define their geometrical parameters with nanoscale accuracy. The proposed method was tested with calibrated lines (height 50 nm, length 100 μm, width range 40-150 nm with 10 nm step) on top of monocrystalline silicon substrate. Measurement accuracy of the optical technology was estimated as ~1 nm.