Simulation And Fabrication Of Refractive Micro-Structures Based On Wet KOH Etching Characteristics Of Silicon

Silicon with special crystal orientation demonstrates an attractive anisotropic etching characteristics in KOH solution, and thus a number of aspherical or non-symmetrical refractive micro-optics structures can be fabricated in silicon according to the characteristics. Performing computer simulation of the anisotropic KOH:H2O etching of silicon, the needed technological parameters can be generated effectively and the final surface profile of target microstructures can be constructed.Based on the characteristics mentioned above, a model for describing the anisotropic wet etching of silicon leading to the destined functioned microstructures is created using VC6.0. According to the model, a variety of spherical and aspherical continuous profiles can be simulated and then the needed parameter configuration and technological data can be generated. The dynamic simulation of many 3-dimentional profiles can also be achieved through combining the OpenGL technology with them. The technological experiments show that the actual functioned microstructures fabricated according to the model are basically consistent with that simulated, and the surface roughness of microdevices can reach the requirements of optical mirror and also exhibits excellent optical performance.As demonstrated, the layout data determine the final surface profile etched by wet KOH solution. So, the most important procedure is the generation of the layout data for construction photolithography mask in both the computer simulation and the technological fabrication according to the method. In this Dissertation, a set of algorithms for generation microstructures is designed so as to create the layout of mask, which is originated from the basic idea of traditional greedy algorithm. Compared with conventional methods, this method can efficiently reduce designing and fabrication errors. The key design processes are as follows: (1) entering the expected profile and then setting a series of parameters and thus obtaining the layout data through algorithm program; (2) constructing a micro-opening map for photolithography mask according to the data acquired; and (3) fabricating desired continuous structure through a single step photolithography and a dual-step wet KOH etching. In this Dissertation, two types of refractive micro-structures including the concave refractive microlens arrays of 512×512 and a series of wavefront structures are designed and fabricated according to the algorithm constructed and the anisotropic KOH:H2O etching characteristics. The morphology and the surface roughness and further the common optical performances of the micro-structures fabricated, are measured and analyzed.