A method for forming a substrate module of a display device, comprising steps of: providing a substrate; and forming a plurality of recesses spaced apart from each other on a surface of the substrate to form a plurality of optical devices, wherein the step of forming the plurality of recesses comprises: forming a coating on the substrate and forming a plurality of through holes in the coating; and forming the plurality of recesses on the surface of the substrate through the plurality of through holes by etching, wherein the coating is formed as a black matrix of the display device, characterised in that the etching comprises: supplying an etching solution by a liquid supply device from an upper edge of the substrate in a state where a side of the substrate formed with the coating faces upwards and the substrate is obliquely placed or in a state where the substrate is substantially vertically placed, so that the etching solution flows downwardly from the upper edge of the substrate along the surface thereof, the liquid supply device controlling a concentration, a temperature, a supplying time of the etching solution, wherein the etching further comprises: injecting the etching solution toward the side of the substrate formed with the coating by a plurality of nozzles such that the etching solution in each through hole is subjected to a predetermined pressure to control a depth and a shape of the corresponding recess, wherein an injection direction of each of the plurality of nozzles is adjustable, to obtain recesses of desired shape, wherein the plurality of nozzles exert a lateral force to the substrate. providing a substrate; and forming a plurality of recesses spaced apart from each other on a surface of the substrate to form a plurality of optical devices, wherein the step of forming the plurality of recesses comprises: forming a coating on the substrate and forming a plurality of through holes in the coating; and forming the plurality of recesses on the surface of the substrate through the plurality of through holes by etching, wherein the coating is formed as a black matrix of the display device, characterised in that the etching comprises: supplying an etching solution by a liquid supply device from an upper edge of the substrate in a state where a side of the substrate formed with the coating faces upwards and the substrate is obliquely placed or in a state where the substrate is substantially vertically placed, so that the etching solution flows downwardly from the upper edge of the substrate along the surface thereof, the liquid supply device controlling a concentration, a temperature, a supplying time of the etching solution, forming a coating on the substrate and forming a plurality of through holes in the coating; and forming the plurality of recesses on the surface of the substrate through the plurality of through holes by etching, wherein the coating is formed as a black matrix of the display device, characterised in that the etching comprises: supplying an etching solution by a liquid supply device from an upper edge of the substrate in a state where a side of the substrate formed with the coating faces upwards and the substrate is obliquely placed or in a state where the substrate is substantially vertically placed, so that the etching solution flows downwardly from the upper edge of the substrate along the surface thereof, the liquid supply device controlling a concentration, a temperature, a supplying time of the etching solution, wherein the etching further comprises: injecting the etching solution toward the side of the substrate formed with the coating by a plurality of nozzles such that the etching solution in each through hole is subjected to a predetermined pressure to control a depth and a shape of the corresponding recess, wherein an injection direction of each of the plurality of nozzles is adjustable, to obtain recesses of desired shape, wherein the plurality of nozzles exert a lateral force to the substrate.