Method of fabricating mask assembly

A method of fabricating a mask assembly, comprising:

• preparing an open mask having a plurality of first openings such that each first opening has an area;
• preparing a pattern mask having a plurality of second openings such that each second opening has an area relatively smaller than the area of each of the first openings;
• aligning the open mask and the pattern mask such that the second openings are disposed within an area bounded by the first openings;
• coupling a first side of the open mask to the pattern mask, the coupling of the open mask to the pattern mask including a first welding process, the first welding process including welding edges of the open mask to edges of the pattern mask, and a second welding process, the second welding process including binding together the open mask and the pattern mask at regions between the first openings of the open mask, the second welding process being carried out after the first welding process is completed;
• and
• coupling a second side of the open mask to a frame mask, the frame mask having a length and width each larger than that of the open mask,
• wherein the open mask is formed of a material having a thermal expansion coefficient that is lower than a thermal expansion coefficient of the pattern mask, and the open mask has a same size as the pattern mask.