Display device manufacturing method preventing diffusion of an aluminum element into a polysilicon layer in a heating step

A manufacturing method of a display device comprising:

• a polysilicon pattern forming step for forming a polysilicon layer by patterning on a background layer of an insulation substrate having the background layer on a surface thereof;
• a first insulation layer forming step for forming a first insulation layer which covers the polysilicon layer;
• a gate electrode forming step for forming gate electrodes on the first insulation layer;
• a second insulation layer forming step for forming a second insulation layer such that the second insulation layer covers the gate electrodes;
• a contact hole forming step for forming contact holes which penetrate the second insulation layer and the first insulation layer;
• and
• a source/drain electrode forming step for forming source/drain electrodes which are connected to the polysilicon layer through the contact holes and are formed on the second insulation layer;
• wherein
• the manufacturing method further includes a heat treatment step in steps which come after the source/drain electrode forming step, and
• the source/drain electrode forming step further includes:
• a barrier layer forming step for forming a barrier layer by sputtering molybdenum or a molybdenum alloy;
• an oxide nitride film forming step for forming an oxide nitride film on a surface of the barrier layer by performing a rapid heat treatment of the barrier layer in a nitrogen atmosphere;
• a conductive layer forming step for forming a conductive layer by sputtering aluminum or an aluminum alloy layer;
• and
• a cap layer forming step for forming a cap layer by sputtering molybdenum or a molybdenum alloy on the conductive layer.