Taking the deep mesa etching of medium- and long-wave two-color InAs/GaSb type-II superlattice infrared detector as the research background, the relationship between the photolithographic solid-film process and the quality of the deep mesa sidewall is analyzed. The influence of different solid-film temperatures on the graphic transfer effect of the mesa pattern and the quality of the mesa sidewall forming is studied, and the best solid-film process is obtained through optimization. The superlattice medium- and long-wave two-color photosensitive chip with smooth sidewalls is interconnected with the readout circuit and packaged into the dewar; it is cooled to 77 K by liquid nitrogen, and then the component test is carried out. The experimental results show that the medium- and long-wave two-color superlattice material uses AZ4620 photoresist as a pattern mask, and after a gradient temperature increase to 140 °C for solid-film, a mesa junction device with smooth sidewalls is obtained by dry etching. The module test results show that the smooth sidewall can effectively reduce the noise equivalent temperature difference (NETD), blind pixel rate and non-uniformity of the module.