Recently the nano-technology was rapidly developed. The demanding needs of nano-scale materials were required more and more in the industrial. Therefore, it is important to investigate the fabrication process and method of nano-structure materials. Owing to the nano-porous structure material has some unique physical characteristic, likes larger ratio of surface area and volume, adjustable energy gap and high sensitivity properties, thus the porous material is very suited to become the raw material of the optical-electric components and micro-sensors. In another hand, the porous diameter and depth of nano-porous structure material can be improved more effectively by way of adapting non-traditional machining in fabrication.
After researching and reviewing the references, we conclude that the generous research used for fabrication of porous structure are all adapt either in horizontal or vertical electro-chemical reaction tanks, both have shown some discrepancy were not able to precisely control the corrosion area, density of electrical current and the distance between silicon and electrode. In order to control more precisely the parameters of experiment and refer mentioned above about the advantage and discrepancy of both chemical reaction tanks, the “modified electro-chemical reaction tank”, made of PTFE material, is developed to be experienced and verified the effect of tightness, corrosion, and operation. The modified vertical chemical reaction tank not only can prevent the leakage of HF solution but also is capable of controlling the parameters of nano-porous structure experiment more precisely. Then, Taguchi Method L9 orthogonal array were employed to layout experiment arrangement, and placed the silica wafer in the HF solution with electric current flowed into the solution in order to observe the results of its chemical action. The silica wafer was developed to porous structure due to corrosive action in the anode pole and all relative results could be acquired by utilizing the micro-balance and SEM. After calculating the S╱N ratios under various factors and levels, response tables and diagrams were generated as well as the main influencing and the optimal combination of parameters in fabricating of porous structure by electro-chemical. Based on the results of ANOVA analysis, the variation, deviation, and degree of contribution of parameters were found. Finally the optimal combination of parameters must be confirmed by confirmation experiment.
Based on the results of experiment, the porous silicon was influenced by the machining parameters of electro-chemical machining. The different type porous silicon will be obtained under different machining parameters. The machining parameters of electro-chemical machining included of the concentration of HF solution, the density of current, the distance between electrode and silicon wafer and the resistance of work piece. The poor machining parameters of electro-chemical machining will be produced failure porous structure or induced electro-polishing. The porous silicon, made by electro-chemical machining, with high optical performance could use as the electrical-optical components. In this study, we use the modified electro-chemical reaction equipment to obtain the main influencing parameter with Taguchi method, and it is effect to save experimental time and cost.