The goal of this research is by using electrochemical etching to produce ultra-thin porous silicon layer. The layer can be used in the anti-reflection layer in the solar cell system. In the solar cell industry, the substrate can be divided to three different parts, which are single-crystal silicon, poly-silicon, and amorphous-silicon. The efficiency of the single-crystal silicon is the highest one. Therefore, we tried to use microwave (MW) technology to eliminate the defects of the porous-silicon. In this way, we can obtain a compact single-crystal silicon layer on the surface. The traditional way to recrystallization the layer should be process in high temperature above 1050 degree. Besides, it takes too much time and energy to do so. Therefore, in this experiment, we choose microwave to replace the traditional process, which can improve the quality of the layers and reduce the cost. After different periods of microwave process, we used SEM to observe the structure of the samples. Furthermore, X-ray diffraction results can show us the quality of the crystallization.