Bidirectional reflection measurements of periodically microstructured silicon surfaces

Surface modifications have a great potential for selective emission and absorption for applications in photonics, energy conversion, and biosensing. Pattern-induced radiative property changes can be an important issue in the manufacturing and diagnostics of microelectronic devices. This work investigates the polarized diffraction of micromachined silicon wafers. Both one-dimensional (1-D) and two-dimensional (2-D) periodic microstructures are manufactured by plasma-assisted anisotropic etching. The rotating mask method is used to produce 2.25 × 10⁶ 2-D structures in a single sample (7.5 × 7.5mm²). Surface topography is characterized by using a scanning electron microscope (SEM). A bidirectional scatterometer with high accuracy and angular resolution measures the diffraction patterns from the microstructured silicon surfaces at a wavelength of 635 nm. The diffraction patterns follow the grating equation, which are caused by microstructures and their orientations. Predicted diffraction angles are in excellent agreement with the experimental results.