Functional Sub-micron Structure Array Fabricated On Silicon Surface By Dielectric Microsphere Assisted Laser Irradiation Followed By Chemical Etching

As one of the most important semiconductor materials, silicon with many advantages such as rich reserves, low cost, excellent thermal and mechanical property. Nowadays, silicon is still realized as the most fundamental material in electronic and information industry. The optics, electrics or magnetics properties of silicon can be improved by the preparation of functional micro patterning on the material surface. Therefore, it is significant to explore and utilize the special properties of silicon. In this paper a method based on laser irradiation of silica microspheres combined with chemical etching was proposed to fabricate microstructure arrays on silicon surface with excellent periodicity and homogeneity. The measurement results of reflectivity of the prepared samples prove that the controllability of surface optical property can be achieved by the controllable fabrication of such microstructure arrays on silicon surface.248 nm excimer laser and 355 nm picosecond laser were used respectively to irradiate or scanning irradiate on the silicon surface coated with a layer of microsphere array, in which different sizes of the microspheres were investigated. Hill-ring structure arrays(formed by excimer laser) and hole-ring structure(formed by picosecond laser) are achieved by the laser irradiation. Functional microstructures are obtained with following alkali etching. The technique takes advantage of the comprehensive superiority of dielectric microsphere assisted laser fabrication and chemical anisotropic etching of silicon. The effect of microsphere size, laser process parameters and alkali etching time on microstructure forming were studied. The mechanisms of the microstructure formation were analyzed by using finite-different time-domain(FDTD) simulation analysis method. The samples prepared by picosecond laser were further processed as SERS substrates. The SERS performance of the substrates caused by the distribution and morphology of microstructure was explored. In combination of the FDTD analysis, the mechanism of SERS enhancement was also investigated.Combination of the literature investigation and the experimental results, there are three significant research results were achieved:(1) Polyhedral cone microstructures with excellent periodicity and homogeneity were fabricated by integrating microsphere assisted laser fabrication and silicon chemical anisotropic etching. Superior controllability on morphology and distribution was achieved by controlling the size of microsphere, laser process parameters and alkali etching time during the process.(2) Forming processes of the functional surfaces patterned by laser assisted laser fabrication and chemical alkali were explained in terms of the results combined with experiments and FDTD simulation. It provides a scientific reference for the mechanism study on laser-chemical in fabrication of microstructure on silicon surface.(3)The reflectivity of the fabricated samples was measured and the fabrication of the silicon SERS substrates was also carried out further, which verified the superior functional properties of the microstructure arrays. In addition, the controllability of sample property was achieved by controlling the microsphere size, laser process parameters(laser fluence or power) and chemical etching time.The technique presented in the study can be processed in an open process environment with low cost. In addition, the controllability of this method is superior, which provide a novel way in fabrication of functional microstructure on silicon surface.