Mask manufacturing method and mask

A mask comprising:

• a substrate including a first substrate surface, a second substrate surface located opposite the first substrate surface, and at least one first opening extending through from the first substrate surface to the second substrate surface;
• a first metallic layer including a first metallic surface that overlaps the first opening in plan view and that partially faces the second substrate surface, a second metallic surface located opposite the first metallic surface, a plurality of second openings that extend through from the first metallic surface to the second metallic surface and that overlap the first opening in plan view, and a metallic outer wall surface located between the first metallic surface and the second metallic surface;
• and
• a first insulation layer including a first insulation surface facing the second substrate surface, a second insulation surface located opposite the first insulation surface, and an insulation wall surface that is located between the first insulation surface and the second insulation surface and that is in contact with the metallic outer wall surface.