InSb is the mainstream material for the fabrication of mid-wave infrared detectors. Its photosensitive chip scale has undergone the development process from cell, multi-element, line array to area array. Due to the demand of market application, the fabrication technology of photosensitive chip is constantly updated. According to the development sequence, the fabrication technology of PN junction of InSb photosensitive chip is introduced, including thermal diffusion technology, ion implantation technology and epitaxy technology. At present, thermal diffusion technology is the mature technology of photosensitive chip formation in China. The main foreign manufacturers have mature technologies in thermal diffusion ion implantation and epitaxy technology and put them into actual production. The advantages and disadvantages of the three technologies and the design of the corresponding focal plane array structure are introduced emphatically.