A method for manufacturing a semiconductor thick metal structure includes a thick metal deposition step, a metal patterning step, and a passivation step. In the thick metal deposition step, a Ti—TiN laminated structure is used as an anti-reflection layer to implement 4 μm metal etching without residue. In the metal patterning step, N2 is used for the protection of a sidewall to implement on a 4 μm metal concave-convex structure a tilt angle of nearly 90 degrees, and a main over-etching step is added to implement the smoothness of the sidewall of the 4 μm metal concave-convex structure. A half-filled passivation filling structure is used to implement effective passivation protection of 1.5 um metal gaps having less than 4 um of metal thickness. Manufacturing of the 4 μm thick metal structure having a linewidth/gap of 1.5 μm/1.5 μm is finally implemented.